This is a pre-print of the following chapter: Arvind W. Kiwelekar, Sanil S
Gandhi, Laxman D. Netak, Shankar B Deosarkar, Use cases of blockchain
technology for humanitarian engineering, published in Information and
Communication Technologies for Humanitarian Services,2020, edited by Muhammad
Nazrul Islam, 2020, publisher IET. The authenticated version is available on
publisher site

Cite this chapter as: Arvind W Kiwelekar, Sanil Gandhi, Laxman D Netak and
Shankar B Deosarkar Use-cases of Blockchain Technology for Humanitarian
Engineering in Information and Communication Technologies for Humanitarian
Services(pp143-163) Publisher: IET Publication. Editor Muhammad Nazrul Islam,

# Use-cases of Blockchain Technology for Humanitarian Engineering

Arvind W. Kiwelekar, Sanil S. Gandhi, Laxaman D. Netak,
Shankar B. Deosarkar Department of Computer Engineering, Dr. Babasaheb
Ambedkar Technological University, Lonere-402103, Raigad(M.S.), India.

## Abstract

Humanitarian Engineers need innovative methods to make technological
interventions for solving societal problems. The emerging blockchain
technology has the enormous potential to provide effective interventions in
various developmental sectors, including Agriculture, Education, Health, and
Transportation. In these sectors, mediators have been considered as one of the
impediments for developmental work. Blockchain technology facilitates peer-to-
peer business transactions, thus eliminating the role of mediators. Hence, the
blockchain technology is emerging as an alternative to conventional mediator-
centred solutions adopting client-server based Internet technologies.

A combination of blockchain technology with other technologies can be used to
address domain-specific challenges. For example, the combination of blockchain
technology and Internet-of-Thing (IoT) has the potential to monitor the usage
of scarce resources such as the level of ground-water and amount of energy
consumption.

The aims of this chapter are twofold. Firstly, it describes the primary
building blocks of blockchain technology. Secondly, it illustrates various
use-case scenarios of blockchain technology in the fields of Agriculture,
Energy Health and others.

##  1 Humanitarian Engineering: An Example

The goal of Humanitarian Engineering is to help underprivileged and
marginalized people. It does so by designing and implementing technology-based
solutions to address the challenges faced by such people. The Jaipur foot [1]
is one of the best examples of humanitarian engineering products. The Jaipur
foot is an artificial leg designed to help people with below-knee leg
amputation. It uses a new material of that time called polyurethane to develop
near-natural but artificial leg. Since the last fifty years, the Jaipur foot
has been assisting thousands of physically challenged people to compete with
ordinary people, bringing a smile on their faces. Durability, flexibility and
convenience of use are some of the critical factors behind the successful and
widespread use of Jaipur foot which was the result of innovative use of
material technology.

The example of Jaipur foot illustrates two significant aspects of humanitarian
engineering. First one is the use of technology, i.e. material technology in
case of Jaipur foot and the second one is relieving pain or grief of
underprivileged people.

The focus of this chapter is on blockchain technology, one of the emerging
Information and Communication Technologies. The objective of this chapter is
to illustrate how blockchain technology has promising applications to address
the diverse needs of various developmental sectors as envisaged by the United
Nations (UN) sustainable development program.

Sr. No. |  Development
Agencies |  Activities
---|---|---
1 |  UNDP |  United Nations Development Program (UNDP) is one of the subunits of the United Nations headquartered in New York City. The primary role of the UNDP is to formulate policies, set priorities, and sponsor development programs to address the challenges faced by humanity. It does so by proactively working with all the member nations of United Nations Organizations (UNO)[2].
2 |  UNWFP |  United Nations World Food Program (UNWFP) is a branch of UNO raising the war against hunger and malnutrition. It provides food assistance to member countries so that the nutritional needs of the people leaving in poverty can be met. It aims to reduce child mortality, improve maternal health and to fight against diseases [3].
3 |  WHO |  World Health Organization (WHO) is a subsidiary of UNO dealing with matters of public health at the international level. It articulates policies for ensuring the highest possible health for individuals by identifying social and economic factors affecting health. It closely works with national government agencies and monitors the effective implementation of health policies [4].
Table 1: International Development Agencies and Their Role

##  2 A Framework for understanding Humanitarian Engineering

Before delving into details of technological alternatives for realizing
humanitarian engineering, let us develop a framework to understand the
dynamics of humanitarian engineering as a discipline. The three main pillars
of humanitarian engineering are: (1) Stakeholders (2) Goals (3) Sectors for
humanitarian engineering.

Figure 1: Sustainable Development Goals

###  2.1 Stakeholders for Humanitarian Engineering

The main stakeholders for humanitarian engineering projects are the people and
organizations that play a critical role in the development of underprivileged
communities. These are also known as development agencies. These agencies
operate at different geographical levels from global to local level.

The first kinds of development agencies are international development
agencies. Their primary function is to address the problems faced by
humankind. These agencies set the agenda for development programs, identify
the problems, monitor and evaluate the performance of development programs,
collect data and evidence to study the impact of development programs and to
fund the developmental activities in various countries.

Table 1 describes the role of three leading international development
agencies. Besides this, the World Bank and Asian Development Banks (ADB) are
some of the other international development agencies which sponsor
developmental projects.

Category |  SDGs |  Description
---|---|---
People |  (SDG 1) No Poverty, (SDG 2) Zero Hunger, (SDG 3) Good Health and Well-being, (SDG 4) Quality Education, (SDG 5) Gender Equality. |  End poverty and hunger in all their forms and dimensions, ensure all human beings can fulfil their potential in dignity, equality and healthy environment.
Prosperity |  (SDG 8) Decent Work and Economic Growth. |  Enjoy prosperous and fulfilling lives, economic, social, and technological harmonic progress.
Peace |  (SDG 10) Reducing Inequality, (SDG 16) Peace, Justice, and Strong Institutions. |  Foster peaceful, just and inclusive societies, free from fear and violence.
Partnership |  (SDG 17) Partnerships for the Goals. |  Revitalized global Partnership, the participation of all countries, stakeholders and people.
Planet |  (SDG 6) Clean Water and Sanitation, (SDG 7) Affordable and Clean Energy, (SDG 9) Industry, Innovation, and Infrastructure, (SDG 11) Sustainable Cities and Communities, (SDG 12) Responsible Consumption and Production, (SDG 13) Climate Action, (SDG 14) Life Below Water, (SDG 15) Life On Land. |  Protect degradation through sustainable consumption, production, natural resource management, stakeholders and people.
Table 2: Sustainable Development Goals

Many countries in the world have development agencies at the national level to
formulate country-specific development policies, align it with policies
formulated by UNDP, and implement developmental projects. For example, in
India, the National Initiative for Transforming India (NITI) Aayog, is one
such organization.

Also, there are some regional development agencies whose primary role is to
implement the developmental projects in coordination with national and
international agencies. In a few countries, universities and academic
institutes are slowly emerging as a regional knowledge centre to provide
information necessary to get insights about the local developmental needs [5].

###  2.2 Sustainable Development Goals

The Sustainable Development Goals (SDG) shown in Figure 1.1 capture the
expectations and aspirations of people to live in a prosperous society without
compromising on the needs of future generations. These SDGs are a set of
ambitious goals put forward by the UN in the Year 2015 for the entire
development of humanity [6, 7]. These set of goals are linked to specific
targets to be achieved by the end of the Year 2030. Table 2 list out all
seventeen goals categorized into five labels, namely People, Prosperity,
Peace, Partnership and Planet [8].

Achieving these goals is an enormous task. Development agencies need to devise
social, legal, financial and technological interventions. A development
engineer responsible for technological interventions should know these SDGs so
that project objectives and outcomes can be aligned with the SDGs. Knowledge
of these SDGs is also essential for any engineer to become conscious of
societal needs and environmental responsibilities.

###  2.3 Sectors for Humanitarian Engineering

The set of SDGs described in the last section aims for the overall development
of humanity. The three main sectors which directly capture the needs of the
human being responsible for achieving SDGs are Economic systems, Social
systems and Environmental systems. However, some additional institutes and
sectors are responsible for laying the operational and legal framework
necessary for business transactions. A legal system which enacts the laws
protecting the environment is one such example. This section reviews such
business sectors responsible for achieving the target indicators set for each
SDGs.

  1. 1.

Agriculture The agriculture sector is the most crucial sector for sustainable
development. The SDGs like End Poverty and Zero Hunger are directly related to
agricultural production. Feeding the ever-growing population with sufficient
food and nutrient is a huge task. As most of the rural population depends on
income from agricultural produce, the goal of ending poverty is also
correlated with agriculture. The sustainable agricultural production is
constrained by factors like growing population, water shortages, declining
soil fertility and climate change [8]. Recently scientists have been exploring
technologies such as Wireless sensor technologies[9] and ICT[10] for
Sustainable agricultural production

  2. 2.

Banking and Finance Banking and financial markets drive economic development.
It provides capital to start new businesses. It provides various avenues for
income growth and wealth accumulation [11]. The number of banks and non-
banking financial institutes present in the community is one of the indicators
of economic development. Trust in financial institutes, efficiency of
processing business transactions (e.g., remittances, payment made to farmers
on selling upon crops), diversity of financial instruments (e.g., crop
insurance, loans, micro-credits) are some of the factors necessary for decent
work and economic growth. Emerging technologies such as cryptocurrencies have
to play a significant role in making business transactions simpler.

  3. 3.

Education Education brings changes in behaviour. Education makes people more
knowledgeable and skilful to get decent jobs. Education brings awareness about
the environment, and once social responsibility. It also has an indirect
impact on the health of an individual, reduction in the rate of population
growth. The task providing education to all is becoming more challengable
because of a shortage of trained teachers, difficulties in providing better
learning experiences to students on account of a shortage of playground in
urban areas and oversized classrooms. Educators are gradually adopting
technologies to overcome some of these challenges.

  4. 4.

Energy The goal of affordable and clean energy (SDG 7), is directly related to
the Energy sector. This sector also drives industrial development and economic
growth. The demand for energy is increasing exponentially because of
increasing population and wide-spread use of electro-mechanical devices to
carry out routine works. Conventional energy generation methods that use
natural resources such as coal and fossil fuels fail to meet this increasing
energy demand. Hence use of non-conventional and renewable energy sources need
to be increased on a large scale for sustainable development. In this context,
it is required to provide technological solutions that would reduce energy
demand, techniques for efficient energy production and replacement of
conventional energy sources[12].

  5. 5.

E-Governance E-governance is the use of Information and Communication
Technologies (ICT) into day-to-day government processes. It is aimed to bring
effectiveness in administration, transparency in the services provided by the
government, and increasing participation of citizens in implementing
government policies. The sector of E-governance is directly linked to Goal 16
and Goal 17. This sector plays a critical role in building accountable
institutes necessary for enforcing peace and justice in societies (Goal 16).
It also lays the technological infrastructure necessary to strengthen
partnership at the global level required to implement various SDGs (Goal 17)
[13, 14].

Sr. No. |  Emerging Technologies |  Benefits of the technology
---|---|---
1 |  Bioplastic, Bio-degradable plastic and Sustainable plastic |  To Protect from climate change and prevent degradation of natural resources (SDG 13)
2 |  Renewable Energy Sources (e.g., Wind, Solar, and biofuels) |  prevents degradation of natural resources, clean and green energy (SDG 7)
3 |  Electric Vehicle |  Effective fuel consumption and pollution-free automobiles (SDG 7 and SDG 13)
4 |  Artificial Intelligence and Machine Learning |  Personalized Medicine, outcomes-based public health and diagnosis of cancer, pneumonia and other diseases (SDG 3)
5 |  Communication Technologies (e.g., Mobile communication, Wireless communication, Smartphone, Internet) |  Dissemination of knowledge between doctors, patients and caretakers (SDG 3)
6 |  3D Printing |  Lowers cost of personalized medicine and organ transplant (SDG 3)
7 |  Genetic Technology |  Facilitates precision medicine (SDG 3)
8 |  Digital Financial Technologies (e.g., Cryptocurrencies and Blockchain) |  Supports micro-payments, create a trustworthy environment for business transactions (SDG 8 & SDG 17)
Table 3: Emerging technologies for Sustainable Development

  6. 6.

Environment Science and Engineering The policymakers formulating the
developmental goals have realized the drawbacks of uncontrolled development
that took place in the last century. The economic growth that pollutes air and
water that reduces the portion of forest and agricultural land, never satisfy
the needs of the future generation. Hence the SDGs such as the provision of
clean water and sanitation (SDG 6), actions for regulating climate change (SDG
13), and protecting life below water and on land (SDG 14 & SDG 15) are
directly linked to environmental science and engineering. Newer clean and
green technologies need to be developed and adopted, especially in the areas
of civil engineering, construction, water management, urban development, and
for maintaining biodiversity [15].

  7. 7.

Health To provide good health and well being are the sustainable goals which
are directly linked to the health sector. Besides the lack of primary health
care mechanisms, there exist many factors which affect the health and wellness
of individuals. Some of these are the byproducts of uncontrolled development.
For example, industrialization and modern urban centred life are causing
stress and respiratory system-related diseases. Technologies such as
information and communication, genetic engineering have been found useful in
preventing, monitoring and diagnosis of diseases[16].

##  3 Technological Perspective of Humanitarian Engineering

The sustainable development goals listed in the previous section are ambitious
in terms of number, scope, and indicators used to measure the attainment of
these goals. One of the effective ways to achieve the set targets is through
innovative use of existing and emerging technologies. Table 3 lists some of
the emerging technologies that will have a positive impact on sustainable
development.

These technologies can help to combat climate change, degradation of natural
resources, achieve good health and well being, to speed up economic growth and
promote all-inclusive and equitable social development.

Data is one of the common threads across all the technologies listed in Table
3. It has been envisaged that in the coming decade, data will drive
sustainable development. At the same time, data-driven development is
continuously raising many issues, such as security of information, privacy,
and ethical concerns.

In the following sections, we discuss and evaluate one the emerging technology
called blockchain technology in this context.

##  4 A Blockchain Primer

The necessity of blockchain technology can be understood through the knowledge
of potential and pitfalls of the Internet as a platform for business.

The Internet has introduced an information-centric model of business, and it
has revolutionized the way people transact online. For example, the emergence
of e-commerce sites (e.g., Amazon) has been attributed to the growth and
widespread presence Internet.

The Internet has bridged the information gap that exists between a service
provider and service consumer by creating a third-party for information
exchange called intermediaries or agents or service providers. These agents
which are e-commerce sites, hold the information about who sells what, i.e.
seller’s information and who wants what, i.e. buyers profile and their needs —
thus bringing together consumers of services or goods with that of producers.

The advantages of doing online business are that it simplifies the process of
business transactions, reduces the time required for businesses, and as a
result, it has brought prosperity in the society.

In the context of SDGs, the Internet as a platform for business has created
various opportunities for decent work and economic growth. The Internet as a
platform for communicating information has reduced the impact of natural
disasters such as cyclones and spread of epidemics by timely disseminating
useful information. The Internet as a learning platform has increased the
accessibility of education fostering the goal of education to all.

Despite the various benefits of the Internet, it has always remained an
unreliable platform to share valuable personal information because of its
mediator-centric or client-server model for information exchange. As shown in
Figure LABEL:fig:sub1, personal information is exchanged through mediators or
servers. A server or mediator may be a payment gateway or an e-commerce site.
The information shared with such sites is always susceptible to breach of
security and privacy attacks.

|
---|---
(a) Client Server System | (b) Decentralized Systems
Figure 2: Client-Server versus Decentralized Systems

The emerging blockchain technology removes these pitfalls by laying a trust
layer on top of the existing Internet technology. It replaces the mediator-
centric model of information exchange with the peer-to-peer model or
decentralized model, as shown in Figure LABEL:fig:sub2 of information
exchange. It transforms the Internet into a trustworthy platform for doing
business when transacting parties do not trust each other. It eliminates the
role of mediator responsible for authenticating the identities of transacting
parties. Table 4 differentiates the client/server and decentralized model of
interactions.

|  Client/Server Architecture |  Decentralized Architecture
---|---|---
Mode of Communication |  Client and Server communicate through each other via Inter-networking protocols |  Peer-to-Peer communication via inter-networking protocols.
Components |  Nodes, Server, Communication Links |  Nodes, Communication Links
Architecture Style |  Layered |  Object-based
Availability |  Need to achieve high availability |  No need to achieve high availability
Servers |  Only single server is present to serve clients |  Servers are distributed in a system.
Privacy |  It is easy to determine who is handling the content |  Difficult to determine who is handling the content
Failure |  Bottleneck as the sever fails down |  No bottleneck as services can be provided through other nodes in case of failure.
Cost |  Implementation cost is high |  Implementation cost is negligible
Table 4: Difference Between Client/Server and Decentralized Architecture

Initially emerged as a platform to exchange digital currency over the
Internet, now the blockchain technology gradually emerging as a general-
purpose platform for doing business over the Internet. Due to potential
applications of blockchain technology in various Fields, UN has included it as
one of the frontier technologies to realize SDGs [17].

This section provides an overview of essential elements of blockchain and how
it achieves the various quality attributes that make it as one of the
promising technology. The blockchain technology can be understood at the
conceptual level and specific instance level. The Bitcoin, Ethereum, and
Hyperledger are a few common examples of specific blockchain. This section
reviews the blockchain technology at the conceptual level. The four
fundamental concepts common across the blockchain implementation are [18]: (i)
Distributed Ledger, (ii) Cryptography, (iii) Consensus Protocols, and (iv)
Smart Contracts

###  4.1 Distributed Ledger

In a conventional sense, ledgers are the registers or logbooks employed for
account-keeping or book-keeping operations. Similarly, in the context of a
blockchain-based information system, ledgers are the databases storing up-to-
date information about business transactions. These are distributed among all
the nodes participating in the network. In a blockchain environment, ledgers
are not stored at a central place. They are distributed among all the nodes.
So multiple copies of a ledger exist in a business network. Hence these are
referred to as distributed ledgers. When a node in a network updates its local
copy, all other nodes synchronize their copy with the updated one. Hence, each
copy is consistent with each other.

These ledgers are used to store information about valuable assets. In the
Bitcoin implementation, the first blockchain-based system, ledgers are used to
store digital currencies. It may be used to store information about other
valuable assets such as land records, diamonds, student’s academic credentials
and others.

In a blockchain-based information system, records in a distributed ledgers are
arranged in a chain-format, as shown in Figure 3 for storage purpose. Here,
multiple transactions related to an asset are grouped in a block. The
$(n+1)^{th}$ block in the chain links to the $n^{th}$ block and the $n^{th}$
block links to the $(n-1)^{th}$ block and so on. The first block in a chain is
called a genesis block or the root block. Due to this peculiar storage
arrangement, the distributed ledgers are also known as Blockchain. Here it is
worth to note that all blockchain-based systems contain distributed ledgers
but not all distributed ledgers employ blockchain-based storage mechanism. The
blockchain data structure permits only append of new records. Updating and
deletion of records are not permissible.

Figure 3: Blockchain

The most critical design feature of blockchain-based information system is the
use of hash pointers instead of physical memory based pointers to link blocks
in a chain. A hash pointer is a message digest calculated from the information
content of a block. Whenever a node attempts to tamper the information
content, a small change in the information leads to a ripple effect of changes
in hash-pointers — making it impossible to change the information once it has
been recorded in the blockchain.

Facilitating mediator-less business transactions and supporting immutability
of stored information are the two significant quality attributes associated
with blockchain-based information systems. These quality attributes are
derived from replicating ledgers on all the nodes in a network and linking
blocks in a chain through hash pointers.

Typically, blockchains are of two kinds based on how blockchains are accessed,
i.e. private and public blockchains. In a public blockchain, any node can join
and leave the network and validate the business transactions. While in the
case of private blockchain, the network is small and requires permission to
join and leave the network. Hence private blockchains are also known as
permissioned blockchain, and public blockchain is known as permission-less
blockchain. For example, Bitcoin is a public blockchain, and Hyperledger is an
example of private blockchain.

###  4.2 Cryptography

Blockchain technology makes heavy use of cryptographic functions to assure
trust among the users transacting over a blockchain-based business network. A
typical business network includes many un-trustworthy elements. In a
conventional banking domain, an agent issuing the check without having
sufficient balance in the account, or an agent forging a signature are typical
examples. In a digitized economy, these challenges are aggravated because of
information transfer over an unreliable communication medium. Hence,
cryptographic functions, a set of mathematical functions, are used to encode
messages to assure the security of information in a network containing
malicious or untrustworthy agents. These cryptographic functions address
various purposes. Some of them are:

1) Authenticating the identity of agents involved in a business transaction:
Blockchain-based systems use a kind of asymmetric key cryptography. These
protocols use two different keys called public and private keys. The public
keys are open and used as addresses for performing business transactions while
private keys are secret and used for validating the transactions. SHA-256
(e.g., Bitcoin) and ECDSA (e.g., Hyperledger) are some of the cryptographic
protocols used for this purpose. The private blockchain use another service
called membership service, which authenticates the identity for business
transactions.

2) Ensuring Privacy: Maintaining the privacy of transactions is a challenge,
especially in public blockchains (e.g., Bitcoin). In such systems,
transactions are possible to trace to real-life identities. Advanced
cryptography-based techniques such as cryptographic mixers (e.g., Zerocoin)
and Zero-Knowledge proof (e.g., Zerocash) have been found useful to address
this challenge.

Cryptographic functions such as digital signature are also used to
authenticate a particular transaction.

###  4.3 Consensus Protocols

In decentralized systems, agreeing upon the global state of the transaction is
a challenge. In a centralized system, this is not an issue because only one
copy of transaction history is present at the central authority (e.g., Banks
main Server machine). Blockchain being a decentralized system, holds multiple
replicas of transactions at several nodes. Agreeing upon the unique state of
the transaction is an issue which is solved by executing a consensus process
involving all the nodes in the system. This process is typically carried out
in three stages. In the first phase, a node is elected/selected as a leader
node to decide upon a unique state. In the second stage, transactions are
validated. In the third stage, transactions are committed. A variety of
consensus algorithms exists in blockchain-based system. These are often
compared based upon how scalable the algorithm is and several malicious nodes
it tolerates. The Proof-of-Work (PoW) algorithm used in Bitcoin is one example
of the consensus protocol. It selects the leader node responsible for deciding
upon a global state by solving a cryptographic puzzle. It takes about 10
minutes for solving the puzzle requiring extensive computational work and much
electric energy. It can work in the presence of 50% of malicious nodes in the
network. The Proof-of-Stake (PoS) is another consensus protocol in which a
leader is selected with the highest stakes in the network. It has been found
as scalable as compared to PoW, and it also works in the presence of 50% of
malicious nodes in the network.

The Practical Byzantine Fault Tolerant (PBFT) is the third example of
consensus protocol which has been found scalable and works in the presence of
66% (2/3) malicious nodes in the network.

###  4.4 Smart-Contracts

Smart-contracts are the most significant element in the blockchain-based
system because it provides configuring the behaviour of such systems.
Blockchain programmers can customize the working of blockchain systems by
writing programs called Smart-Contract. The smart contracts are scripts which
are executed when a specific event occurs in a system. For example, in the
context of Bitcoin, a coin may be released when more than one signatures are
validated, or when miners solve a cryptographic puzzle.

These scripts can be written in a native language provided by blockchain
systems or general-purpose programmable language. For example, Bitcoin
provides a simple and less expressive native language to write a smart
contract while Ethereum provides a Turing complete native language called
Solidity to write smart contracts. In Hyperledger, blockchain programmers can
write a smart contract in a general-purpose language such as Java/Go.

##  5 Sectoral Applications of Blockchain Technology

###  5.1 Blockchain Technology in Agriculture:

Numerous business factors motivate the adoption of blockchain technology in
Agriculture sector.

First and the topmost key-factor behind the adoption of blockchain technology
in agriculture is to eliminate bad actors and poor processes involved in the
food supply chain. For example, AgriDigital ($agridigital.io$) is a cloud-
based platform that is designed using blockchain technology to provide an
efficient interface for the agriculture supply chain.

The second key factor is to create trust among consumers and retailers about
the originality and authenticity of food products. For example, $ripe.io$ is
an organization which provides a blockchain-based platform with this sole
purpose.

Blockchain technology has the potential to open up new market areas for food
producers, specifically farmers from the developing nations. For example,
AgriLedger ($agriledger.io$) adopts the distributed ledger technology to open
up new market areas for the farmers.

We broadly classify the typical use-cases of blockchain technology in the
agriculture sector as below:

  1. 1.

Crowd-funding for the development of agricultural products Entrepreneurs and
start-up organizations have been increasingly using blockchain as crypto-
currencies or digitized tokens to raise capital for their entrepreneurial
ventures. This mode of application is generally known as Initial Coin
Offerings (ICO) [19].

The ICOs are a type of digitized financial instruments which can be monetized
through crypto-currencies or fiat currencies. The $NagriCoin$ ($nagricoin.io$)
is one such application, which has raised capital to develop smart fertilizers
that stimulate plant growth.

  2. 2.

Development of agricultural supply chain management Various business factors
drive the use of blockchain technology for the agricultural supply chain
management. First, paying the farmers their due share in food production is
the key motivating factor behind the adoption of blockchain technology for the
food supply chain. The second most important factor is to address the concerns
about food safety in the minds of consumers. For example, the $AgriDigital$ is
a cloud-based supply chain management platform primarily supporting the supply
chain for grains.

The objective of such platforms is to effectively connect the various
operators in the supply chain such as farmers, distributors, storage
operators, retailers and consumers.

Creation of digital assets representing physical products, recording and
tracking their flow within the supply chain are the main functionalities
offered by such platforms. They implement it by providing a set of smart-
contracts executing over a blockchain implementation such as Ethereum.

  3. 3.

Tracking and Traceablity Assuring about the quality of food products and
agricultural commodities is one of the main challenges faced by agriculture
and food processing industries [20]. Consumers expect authenticity about food
products in terms of composition, origin, and purity. These expectations are
valid when the food-products are costly, consumed at a distant place far from
its origin, and they are directly linked to the health and safety of
consumers.

Providing accurate and verifiable information about the composition and origin
of the food product is one of the solutions to address this challenge. The
blockchain technology plays this role precisely while tracking and tracing the
origin of food production.

The blockchain-based solutions to address this problem are typically built
around the immutability feature of the blockchain along with other
technologies such as DNA marking, RFID tagging, QR coding, and isotope
testing.

  4. 4.

Blockchain-based financial products for farmers Conventional financial
institutes such as banks, insurance companies and cooperative credit societies
face the challenge of including small-farmers in the mainstream financial
sectors. This situation leads to undue exploitation of farmers by illegal
money lenders and traders.

Blockchain, as a technology initially emerged as a payment system through
digital currencies (e.g., Bitcoin) can be used to provide financial products
specially designed for farmers.

The $AgriWallet$ is one such example of saving scheme designed and implemented
by COIN22 ($coin22.com$) for smallholder farmers to manage the risk associated
with droughts, floods and low-yield of crops [21].

Also, the use of blockchain technology is currently being explored by many
companies and government agencies to provide agriculture insurance, micro-
credit and subsidy transfer [22].

Mapping of the physical commodity to the digital artefact is one of the
challenges faced while designing such platforms. This challenge can be
addressed by using the Internet-of-Things (IoT) and various sensors along with
blockchain technology. The sustainable goal of ensuring zero hunger (SDG 2)
and no poverty (SDG 1) is indirectly supported by extensive adoption
blockchain technology in the agriculture sector.

###  5.2 Blockchain for Financial Services:

The factors such as to eliminate the role of mediators between two transacting
parties, to reduce transaction time, and to simplify the transaction process
motivates the use of blockchain in providing financial services.

In such scenarios, blockchain technology mainly plays the role of validating
transactions. It helps to reduce the transaction charges by offering an
efficient and secure way to transfer the funds either within a country or
between two different countries.

The use-cases of blockchain technology in finical sectors belong mainly to two
categories, first, in the area of payment and transfer, and other record-
keeping and verification.

For example, the Mojaloop ($mojaloop.io$) is one of the examples of the block-
chain-based payment transfer platform developed for Gates Foundation
($gatesfoundation.org$) to connect financial service-providers and customers
from all over the world. In addition to offering efficient payment mechanism,
blockchain technology reduces the possibilities of frauds such as corruption
during the disbursement of funds.

Secondly, the features of blockchain technology, such as distributed ledger
and smart contracts, have been in use for effective aid distribution. Each
step involved during the aid distribution from donation to receipt of the
amount can be tracked and monitored using distributed ledgers. Donations are
released upon meeting specific criteria and occurrence of pre-specified events
encoded in the smart contracts. For example, $Amply$ [23] is a blockchain-
based protocol developed by IXO Foundation which links the release of
government subsidies to the attendance of children in a school.

Applications of blockchain technology in the banking and finance sectors
enable the attainment of sustainable development goals such as SDG 1, SDG 9, &
SDG 8. For example, the World Food Program (WFP) used the blockchain
technology to provide food assistance to refugees from Syria.

###  5.3 Blockchain in Education:

The information and communication technologies have revolutionized the mode of
delivering education. It has realized the goal of open education to all and
created multiple ways to equip oneself and upgrade the skill set. The
blockchain technology is now providing value-added services in the education
sector, which includes credit transfer, issuing a transcript, digital
certificates, and payment for online courses.

We use the following categories to classify the uses of blockchain technology
in the education sector.

  1. 1.

Record Verification and Validation In this mode, developers have been using
blockchain as distributed ledgers which store and verify academic credentials
of students. For example, $BlockCert$ ($https://www.blockcerts.org/$) is a set
of tools that provides the functionality to create, store and validate
blockchain-based digital certificates.

  2. 2.

Information Sharing Universities need to share and transfer the academic
credentials of a student when a student migrates from one university to
another. In this mode of application, blockchain technology enables effective
transfer of academic information between two universities. For example, in
[24] describes the design of one such platform called $EduCTX$ that enables
credit transfer among institutes.

  3. 3.

Identity Management Online learners use multiple applications and services
such as Coursera, Google Classroom, and note-taking apps (e.g., Keep).
Securely sharing and authenticating identity credentials across the
applications remain a big challenge. Blockchain technology addresses this
challenge by providing a unique identifier accessible and verifiable across
the applications. For example, $BlockStack$ ($https://blockstack.org/$) one
such cloud-based identity management service.

These applications of blockchain technology have realized the goal of
providing equal learning opportunities to everyone i.e. (SDG 4).

###  5.4 Blockchain in Energy Sector:

The energy sector worldwide is undergoing structural as well as functional
changes. The decentralized network of renewable energy generators have been
gradually expanding, which is currently dominated by the conventional
centralized grid structure. The functionalities of the conventional power grid
are also not only limited to the functions of power generation and
distribution but providing additional services such as analyzing the data
generated through the deployment of smart devices and offering intelligent
services to consumers.

The blockchain technology is the driving force behind all these changes. The
features of blockchain, namely distributed ledger and smart contracts, are
being increasingly used to provide additional services. Andoni M, Robu V,
Flynn D, et al. present a comprehensive survey of such services in [25]. Some
of these services are:

  1. 1.

Wholesale Energy Trading and Supply The technologies such as distributed
ledgers and smart contract are used to simplify the business processes
involved in energy trading and supply. In this context, developers use
blockchain technology primarily for record-keeping, autonomous agents
executing business logic, and for payment and transfers. Elimination of
intermediaries and reduced transaction times are the benefits gained by
adopting the blockchain-based approach.

  2. 2.

Imbalance Settlement It is a process executed by grid operators. It aims to
remove discrepancies between energy units sold by energy suppliers and the
energy sold by distributors to the consumers. Blockchain technology provides
an efficient solution to this problem which normally takes months for
settlement. Here also, distributed ledgers are used to keep track of energy
generation and consumption.

  3. 3.

P2P Trading Peer-to-Peer (P2P) trading is a form of trading in which energy
providers or generators directly sell the energy units to consumers. Thus
eliminating the role of energy distributors. Here blockchain technology is
used as a platform that facilitates energy trading in-exchange of digital
currencies.

Providing affordable access to reliable and modern energy (SDG 7) is one of
the sustainable goals that blockchain technology realizes through the use-
cases, as mentioned above. Further blockchain technology is providing an
effective platform for energy trading in micro-grids and community-owned
energy systems.

###  5.5 Blockchain for E-Governance:

Government agencies face the challenge of providing transparent and citizen-
centric services. These agencies are looking at blockchain technology as a
medium to improve the quality of their service. These agencies have been
adopting blockchain for multiple application areas. Some of which are listed
below:

  1. 1.

A Platform for offering integrated services The government of Estonia has been
using blockchain as a platform to provide more than a thousand services to its
citizen. Here, the distributed ledgers are used for logging and auditing each
transaction of citizens with the government. The government of Estonia has
issued digital-ID and signatures to all citizens for this purpose. The use of
blockchain has brought transparency and trust in the services offered by the
Estonian government.

  2. 2.

E-voting Democratic societies face the challenge of conducting free and fair
elections. Conventional ballot-paper based elections are prone to be rigged
and manipulated. Blockchain technology is currently being explored as an
alternative to address this challenge. The $Votem$ is a cloud service that
uses blockchain to securely cast votes by mobile or remote users. The system
uses distributed ledger technology to record and verify the votes.

  3. 3.

Land Records Recording the information of landholding and ownership is one of
the obvious usages of blockchain technology. The recording of such information
in the immutable registry and for archival purpose is essential to avoid land-
related frauds. Some countries, such as India and Sweden, have initiated the
use of blockchain technology for land records. In cities such as Chicago,
civic administrators have been using blockchain technology to automate the
complete workflow involved in land registry.

The blockchain technology, in some cases, have been directly realizing the
goal of Peace, Justice, and Strong Institutions (SDG 16). While in other
cases, it has been indirectly supporting the goal of equitable development
(SDG 5).

###  5.6 Applications of Blockchain in Environment and Climate Change:

Developers have started thinking about innovative applications of blockchain
technology in the areas of environmental protection and climate change. Some
of these novel applications include:

  1. 1.

Incentive Mechanism for Recycling Project The blockchain technology is useful
in rewarding digitized tokens or crypto-currencies for joining in the
recycling project. A digital token can be exchanged for the deposit of plastic
wastage.

  2. 2.

Enforcing Environmental Treaties Government agencies face the challenge of
enforcing environmental obligations while sanctioning developmental project.
Developers have started applying the feature of the smart contract embedded in
various blockchain platforms for this purpose.

  3. 3.

To implement Carbon Tax The carbon footprint is a measure used for assessing
carbon-dioxide emission caused by an individual, event or an organization. The
blockchain technology is useful to track and record the carbon footprint.
Further, it can levy a tax based on carbon footprint or build a reputation
system to provide incentives for low carbon footprint products and services.

These applications illustrate the potential of blockchain technology in
protecting the environment and ensure responsible consumption and production
(SDG 12 and SDG 13).

###  5.7 Blockchain in Health Sector:

The applications of blockchain technology in health sector belong to the
following categories.

  1. 1.

Record keeping and ensuring confidentiality of information The use of
blockchain technology in the health sector is driven by the motive to overcome
the negligence of health-related documents and privacy of these documents
(e.g., medical prescriptions, and health reports). Preserving this information
is not only useful to an individual but in carrying out research related to
genetic diseases. All such documents are valuable to medical researchers,
health care providers, public health authorities and health insurance
providers.

Blockchain technology provides secure access to store existing medical
reports. These reports are made available on-demand through various blockchain
platforms. One of the typical applications is MedRec[26], which stores
Electronic Medical Records (EMRs) on blockchain. This information is
accessible in a secure way to various stakeholders, such as medical
researchers and public health authorities.

  2. 2.

Drug Supply Chain and Traceability In the supply chain of drugs and medicinal
products, it needs to track the initial details of medical products while it
is in transit. The Modum.io, a European company, has implemented a hardware
sensor-based technology to monitor the temperature of drugs in pharmaceutical
supply-chain. In such applications, drug-related information exchanged between
drug manufacturers, wholesalers, pharmacists, and the patients are recorded
and tracked to authenticate the originality of the drug. The features like a
distributed ledger and smart contracts are used to implement these
functionalities.

The combination of technologies such as Artificial Intelligence, Blockchain
and Internet-of-Things are providing various solutions and products to realize
the goal of smart technologies for a healthy life (SDG 3).

##  6 A Cost-Benefit Analysis of Adopting Technology

The blockchain technology is an emerging technology. It is yet to reach the
level of maturity of many internet-based technologies such as web applications
and mobile applications. In this scenario, it becomes essential to know the
costs and benefits associated with the deployment of blockchain-based
solutions. From the humanitarian engineering point of view, it becomes more
vital because it offers numerous opportunities to realize SDGs and will have
an impact on all aspect of development.

The strengths of blockchain technologies include:

  1. 1.

It provides a platform to build trustworthy services Many government and
development agencies face the challenge of creating trust offered by their
services which may include aid transfer. Blockchain technology addresses this
challenge and enables the strengthening of institutes and services.

  2. 2.

It provides a platform for open market As observed in Section 5.1, blockchain
technology is creating an open platform to sell and buy products without any
mediators. Thus it has the potential to bring small producers in the
mainstream global market leading to multiple avenues for prosperity and
growth.

  3. 3.

It simplifies business processes and transactions The feature of smart-
contract in blockchain technology allows to code the business logic and
execute it upon the occurrence of a specific event. For example, the release
of payment upon successful delivery of goods. Smart-contracts are an effective
mechanism to implement business logic when business processes are well
defined, and it involves multiple business operators crossing the
organizational boundaries.

The following risks associated with the blockchain-based services need to be
considered while implementing services on top of it.

  1. 1.

No Central Authority means greater responsibility on users A blockchain
system, by its design, is a decentralized system. It means there is no central
authority to contact in case of loss of public keys or loss of passwords.
Hence restoring users credentials becomes impossible in such events. Also, the
data entered in a system is immutable one and needs to be entered carefully.
The implications of all these architectural elements put a greater
responsibility on users to be careful.

  2. 2.

High Energy Requirement of some Consensus Protocols blockchain-based systems
use a consensus protocol to validate a business transaction. Some consensus
protocols such as Proof-of-Work (PoW) used in Bitcoin have been found
ineffective in terms of energy consumption. It needs a high amount of electric
power to validate a business transaction. Hence this cost needs to be
considered when one selects a public blockchain for implementation.

  3. 3.

Maturity of code to replace business logic Blockchain-based systems use smart
contracts to encode business logic and well-defined business rules. These
contracts are automatically executed, and it replaces the need for human
interventions. However, the smart contracts thus implemented need to be tested
rigorously and formally verified. Otherwise, it will lead to a situation
called hard-fork of blockchain i.e. replacement of older code with newer code
for the smart contract, which is a costly affair.

  4. 4.

Legislation related to data privacy In most of the countries, the use of
public blockchain such as Bitcoin is legally prohibited for payments systems
because of lack of provision to trace the identity of transacting parties.
Also, blockchain-based systems use immutable distributed ledgers which means
they are write-once- never-forget systems. Such systems violate the privacy
principle of right-to-forget. Such legal and ethical concerns need to be
considered before adopting a blockchain-based approach.

##  7 Conclusion

The Chapter reviews the existing and potential applications of blockchain
technology for humanitarian engineering. The scope of humanitarian engineering
is vast. It includes every aspect of humanity, from agriculture to finance.
Information and Communication Technologies (ICT) have played a vital role to
address the challenges in these sectors by sharing and exchanging information.
However, many of the challenges need to be addressed, such as information
privacy and security, which require more effective solutions. Humanitarian
engineers are looking towards blockchain technology as a potential solution to
address many of these challenges.

The Chapter defines the scope of humanitarian engineering actions in terms of
achieving the Sustainable Development Goals (SDG) formulated by UNO. It
identifies seven sectors crucial for the attainment of SDGs. The Chapter
further describes the challenges in these sectors, which can be addressed by
the use of blockchain technology.

In general, across all these sectors, blockchain technology provides an
effective mechanism to track and record information exchanged in a chain of
business transacting entities. It automates the business workflow by reducing
human intervention. It opens up new global market opportunities by creating a
sound digital payment system crossing the boundaries of nations.

Blockchain being a technology yet to achieve the maturity level of web and
mobile technologies, the deployment of blockchain-based solutions come with
risks and adverse consequences. The Chapter briefly illustrates such
implementation risks by doing cost-benefit analysis from a humanitarian
engineering point of view.

Two main contributions of the Chapter include: (1) Identifying the scope of
human humanitarian engineering in terms of SDGs and sectors responsible for
the achievement of these goals. (2) A functional evaluation of blockchain
technology by describing potential and existing applications of blockchain for
achieving SDGs.

The functional evaluation presented in the Chapter highlights the promising
role for blockchain technology to build a global society free from hunger,
deceases, and with equal opportunities for growth and decent work. However,
for more theoretical and foundational role of technologies and Engineers in a
society one can refer [27].

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[1]

[cor1]Corresponding author

# Stochastic modeling of a neutron imaging center at the Brazilian
Multipurpose Reactor

LP de Oliveira<EMAIL_ADDRESS>APS Souza  FA Genezini  A dos Santos
Instituto de Pesquisas Energéticas e Nucleares, IPEN/CNEN, Av. Prof. Lineu
Prestes, 2242 – Cidade Universitária – CEP 05508-000 São Paulo – SP – Brazil
Idaho National Laboratory, INL, 1955 N. Fremont Ave. Idaho Falls, ID 83415,
United States of America

###### Abstract

Neutron imaging is a non-destructive technique for analyzing a wide class of
samples, such as archaeological or industrial material structures. In recent
decades, technological advances have had a great impact on the neutron imaging
technique, which has meant an evolution from simple radiographs using films
(2D) to modern tomography systems with digital processing (3D). The 5 MW
research nuclear reactor IEA-R1, which is located at the Instituto de
Pesquisas Energéticas e Nucleares (IPEN) in Brazil, possesses a neutron
imaging instrument with $1.0\times 10^{6}$ $n/cm^{2}s$ in the sample position.
IEA-R1 is over 60 years old and the future of neutron science in Brazil,
including imaging, will be expanded to a new facility called the Brazilian
Multipurpose Reactor (RMB, Portuguese acronym), which will be built soon. The
new reactor will house a suite of instruments at the Neutron National
Laboratory, including the neutron imaging facility, viz., Neinei. Inspired by
recent author’s works, we model the Neinei instrument through stochastic Monte
Carlo simulations. We investigate the sensitivity of the neutron imaging
technique parameter ($L/D$ ratio) with the neutron flux, and the results are
compared to data from the Neutra (PSI), Antares (FRM II), BT2 (NIST) and DINGO
(OPAL) instruments. The results are promising and provide avenues for future
improvements.

###### keywords:

Neutron Imaging Monte Carlo MCSTAS

##  1 Introduction

The Brazilian Multipurpose Reactor (RMB) project inaugurates a new era of
research on nuclear science and technologies in Brazil. Besides
radiopharmaceutical feedstock production, the reactor will allow the study of
irradiation in materials and the use of neutron beams to investigate the
structures of materials in low dimensions [1, 2]. The RMB project has a suite
of 15 instruments that use thermal and cold neutrons, allowing the
investigation of structures at a wide range of micro- and nanoscales [2]. The
Instituto de Pesquisas Energéticas e Nucleares (IPEN), in São Paulo - Brazil,
houses the 5 MW research reactor IEA-R1. The correspondent reactor research
center possesses a neutron radiography/tomography instrument that has made a
great contribution to the Brazilian scientific community, since its creation
in 1987 [3]. It has gone through recent upgrades that keep it in the select
group of international instruments with a high thermal neutron flux at the
sample position ($1.0\times 10^{6}$ $n/cm^{2}s$) and, consequently, excellent
spatial resolution [4, 5]. Even considering such excellence, we must consider
that the IEA-R1 reactor is over 60 years old, which naturally makes RMB a
successor facility that will bring many benefits to Brazilian society.

Like the other RMB instruments, the neutron imaging instrument (radiography
and tomography) has been named after a bird of the Brazilian fauna. Neinei
(scientific name = Megarynchus pitangua) is a bird found in Brazil and belongs
to the Tyrannidae family. Neinei will be located on the south face of RMB N01
building, where the proximity to the reactor pool (see Figure 1) will allow a
better use of $1.0\times 10^{14}$ $n/cm^{2}s$ thermal neutron flux in the
core. RMB has six times the power of IEA-R1, i.e, $30$ MW. Therefore, Neinei
will enable research in hydrogenous substances [5], cultural heritage [4] and
other materials that are analyzed using the traditional X-ray imaging
technique [6].

Neutrons are spin $1/2$ neutral fermions that have great penetration into the
matter because of their slight interaction with most chemical elements.
However, neutrons interact strongly with a small group of light elements and
distinguish isotopes of the same element. The use of polarized beams and spin
projection, which is governed by the magnetic field of the nuclei that compose
the sample, can reveal details of the structure of magnetic materials [7]. The
neutron imaging technique uses neutronic properties to study materials in $2D$
(radiography), and in $3D$ (tomography). Neutron imaging is a non-destructive
technique that has been used to investigate metallic materials, ceramics,
rocks and industrial material structures [4, 6, 7]. A disadvantage that
neutron beam techniques posses in comparison to the X-ray technique is that
nuclear facilities have high cost of design and construction. In this
scenario, Monte Carlo simulations through the MCNP [8] and McStas [9] codes
are essential to allow the development of instruments and optical components
designs [10, 11, 12, 13].

The absence of other instruments nearby the Neinei Neutron imaging, according
to the design stage of the RMB, brings the advantage of free assembly without
spatial constraints, relying only on the physical limitation of the N01
building. The proximity to the reactor face allows the use of short lengths of
neutron guides (for collimation purposes only) or tubes. According to
Schillinger et al. [14], neutron guides alone are not a good choice for a
radiography setup because of the high divergence at the end of the guide
($L/D$ = 70 to 115, where $L$ is the distance between the slit, of diameter
$D$, and the detector). According to the authors, the only way to obtain a
parallel neutron beam is to use a slit and a long flight tube. If the beam
area is to be covered, the arrangement can be followed by a neutron guide that
carries the reactor flux within the acceptance angle of the guide. Recently,
in the DINGO imaging instrument design project for the OPAL reactor, Garbe et
al. used an in-pile collimator to obtain a homogeneous neutron beam for two
different configurations, at the end of a guide system (TG1) and beam port
position (HB-1/2) for $L/D$ = $250$ and $1000$ [12, 13]. The design chosen for
implementation in the project was HB-$1/2$, due to the flux of $4.75\times
10^{7}$ $n/cm^{2}s$ in the detector position for $L/D$ = $250$, although the
intensity distribution with the McStas software reveals inhomogeneous spatial
distribution [12]. The uniformity of the beam incident on the sample directly
affects the quality of the imaging technique [7, 11]. The unexpected
inhomogeneous spatial distribution phenomenon, which always appears in the
neutron radiography facilities installed at the end of the neutron guide, was
investigated by Wang et al. [11]. The authors report that the phenomenon
observed is related to the spacing gaps in the guide transmission system and
can be mitigated by decreasing the distances between the source and the guide
entrance, increasing the guide length and source size, decreasing the guide
cross-section [11]. The techniques for neutron radiography and tomography have
improved in the last decades and the development of new instruments can be
guided by all the knowledge presented in the literature [7, 15, 16, 17, 18].

In this spirit, the proposal of this work is the conception of the basic
design of the Neinei instrument in RMB. Inspired by the works of Garbe et al.
[12], Wang et al. [12] and Schillinger et al. [14], we propose a basic
configuration for Neinei using the McStas software [9]. In this proposal, we
have investigated the uniformity and flux of the neutron beam at the detector
position for $L/D$ ratios $=100$, $500$ and $1000$. The results are compared
to DINGO at OPAL [12, 13], Neutra at PSI [19], ANTARES at FRM-II [14] and BT2
at NIST [20]. Our results will have a direct impact on the Neinei instrument
design project at more advanced stages.

Figure 1: Side-view sketch of the RMB and Neinei instrument. The remaining
shutters and the neutron beam hall are on the west face of the reactor and are
not shown to not overload the figure.

##  2 Monte Carlo Simulations of the RMB core

The RMB reflector tank was modeled using the MCNP6 code, and a section along
the Z-axis is shown in Figure 2. Highlighted in this scheme are the entrances
of the thermal (TG) and cold (CG) neutron guides, the core reactor, the cold
neutron source (CNS) and the neutron imaging entrance. The reactor core is
composed of a 5x5 assembly of $U_{3}Si_{2}$ (19.75 wt percent) fuel elements,
made up of 21 parallel plates framed by Aluminum $6061$ alloy. The simulations
were carried out in the Nuclear Engineering Center (CEENG-IPEN), which has 200
processing nodes. Information about the distribution of neutrons such as
position, velocity, spin vectors and their respective statistical weights are
obtained from of PTRAC card [8].

Figure 2: Z-axis section of the RMB reflector tank modeled by MCNP6 code.

The PTRAC file, which is an output from MCNP6, is used as an input file of the
software McStas (Monte Carlo Simulation of Triple Axis Spectrometers) [9], in
which we read the neutron beam through a virtual detector. We modeled the
detector with an area of 100 $cm^{2}$ (10 cm x 10 cm) and a resolution of 2000
bins in order to obtain the intensity distribution found in Figure 3. There,
the black dots represent the MCNP6 results, while the red curve is a
Maxwellian fit,
$\phi(\lambda)=(\eta/\lambda^{5}T^{2})exp(-\gamma/T\lambda^{2})$, with
parameters $\eta=(3.84056\pm 0.00834)\times 10^{15}$
$n/cm^{2}sK^{2}\mathring{A}^{5}$, $T=(286.70239\pm 0.4479)$ $K$,
$\gamma=933\mathring{A}^{2}K$ and $R^{2}=0.99772$. The Maxwellian
$\phi(\lambda)$ is a function that describes the neutron distribution after
thermal equilibrium with a material medium at temperature T [8]. Obtaining
$\phi(\lambda)$ is a fundamental step in the design of nuclear facilities, as
it allows evaluating the efficiency of neutron transport.

Figure 3: Intensity of the neutron beam at the entrance to the neutrongraphy
capture tube.

##  3 Basic Neinei Design and McStas Simulations

The basic design of the Neinei instrument is shown in Figure 4. Inspired by
the DINGO instrument at OPAL, the neutron source for the instrument features
an in-pile collimator in the primary shutter to homogenize the high-flux beam
at the reactor face. To circumvent the inhomogeneous spatial distribution
phenomenon, we have used a short neutron guide length according to the work of
Wang et al. [11] and Schillinger et al. [14]. In Monte Carlo simulations, two
values for guide length ($l_{g}$ $=0.5$ m and $1.0$ m) and section of $50$ mm
x $300$ mm are used to evaluate the beam divergence before it enters the
instrument slit. In another configuration of guides for neutron transport, the
use of a collimation length (extra guide) proved to be fruitful [10]. A slit
selector allows the adoption of 3 different diameters, $D=$ $5$ mm, $10$ mm
and $50$ mm, which allow obtaining $L/D$ ratios $100$, $500$ and $1000$, for
$L=5$ m, which is the same value adopted in the imaging instrument of IEA-R1
[4]. A rotating table with a stepper motor is used to obtain different angles
of the sample in front of the incident neutron beam. The sample rotation
adjustment will be determined according to the resolution of the CCD camera
and the image storage system. The neutrons transmitted by the sample sensitize
the scintillator (e.g., Li/ZnS), which generates 2D images captured by the CCD
camera [5]. To avoid direct exposure of the CCD chip to radiation, a plane
mirror reflects the image to the camera, which is installed at 90 degrees to
the incident beam, as shown in Figure 4.

Monte Carlo simulations are performed using McStas ray tracing software [9]. A
file containing the neutron distribution at the primary shutter position is
generated through the PTRAC function of the MCNP code [8] for the RMB core.
The neutron distribution is used by McStas as a source for the instrument to
be designed. For this purpose, we have optical components arranged along the Z
axis in the following sequence: `Source_gen()`, `Collimator_radial()`,
`Guide_simple()`, `Slit()`, `Absorber()`, `PSD_monitor()`, and `Monitor_nD()`.
All components and parameters used for the simulations are listed in Table 1.

The simulations have been performed, and the results correspond to data
collected in the detector at the end of the long flight box (absorber). Such
data are the flux and the intensity of thermal neutrons, as a function of
planar dimensions ($x$ and $y$), and are presented and discussed in the next
section.

Figure 4: Basic Neinei Design. Table 1: Simulation parameters of Neinei instrument. Components | Parameters
---|---
Source |  | RMB thermal beam, Intensity = $2.3\times 10^{18}$; nps = $79909340$;
---
Collimator |  | Section (width x height) = 5 cm x 30 cm;
---
Length = 0.3 m; Divergence = 30’;
Neutron guide |  | Section (width x height) = 5 cm x 30 cm;
---
Length = 0.5 m and 1.0 m;
Curvature = infinity;
Supermirror indexes: $M_{out}=3$, $M_{top}=3$, $M_{bottom}=3$, $M_{in}=3$;
Slit |  | Diameters = 5 mm, 10 mm and 50 mm;
---
Absorbent box |  | Section (width x height) = 20 cm x 30 cm;
---
Length = 5.0 m;
Detector |  | Section (width x height) = 5 cm x 30 cm;
---

##  4 Results

The neutron imaging technique is sensitive to several parameters, including
the $L/D$ resolution. A simple derivation allows us to obtain the beam
divergence, given by $d=l/(L/D)$, where $l$ is the distance between the sample
and the detector. Therefore, for the given detector resolution $C$, the other
parameters must be adjusted by the constraint $C>l/(L/D)$ [17].

In Figures 5-10, we present the beam intensities as a function of the spatial
coordinates for $l_{g}=0.5$ m, $1.0$ m, and $L/D=$ $100$, $500$, and $1000$.
We can see that the results reveal the effects of collimation by verifying a
high neutron signal at the center of the detector. We found that the results
for the guide length of $1.0$ m (Figures 8-10) provide the best neutron flux
values in the detector. Therefore, we selected the results for $l_{g}=$ $1.0$
m for a comparative analysis presented in Table 2. We can observe that the
results have excellent agreement with the instruments of other facilities if
we compare the usual values for $L/D=$ $500$ and $1000$. Additionally, for
testing purposes, we provided the value corresponding to the $L/D$ ratio = 100
only as an upper limit, finding a promising result that was physically
expected. We have observed that even with the use of an in-pile collimator and
an auxiliary neutron guide, before the slit, the neutron beam still presents
inhomogeneity along the detection plane, as was observed by Garbe et al. [12].
As pointed out by Wang et al., we observed a better distribution of the beam
in the $L/D=$ 100 ratio in view of a larger slit opening and, consequently,
better neutron sampling. If we compare it to the DINGO instrument from OPAL,
the reference reactor for the RMB, we observe a difference of only $4$ percent
in neutron flux for the high-resolution configuration. We also verified that
all the results of our simulations show an expected decrease in intensity with
an increase in the resolution of the instrument. The neutron imaging technique
is sensitive to several parameters, including the $L/D$ resolution. A simple
derivation allows us to obtain the beam divergence, given by $d=l/(L/D)$,
where $l$ is the distance between the sample and the detector. Therefore, for
the given detector resolution $C$, the other parameters must be adjusted by
the constraint $C>l/(L/D)$ [17].

A set of simulations reveals the behavior of the neutron flux in the
instrument detector as a function of resolution (Figure 11). We can also
observe that there is a decrease in the neutron flux of two orders of
magnitude, which can be adjusted by the curve
$\phi(L/D)=10^{12.48921}\times(L/D)^{-1.81594}$. It is observed that the
values obtained are found in intervals in which the parameters of the imaging
instruments of the other installations are located, including the DINGO-OPAL.
As an initial study, the simulations have proven to provide guidelines for
future, more in-depth studies where we will improve the instrument design.

Table 2: Calculed flux compared with measured flux of neutron imaging instruments at OPAL, PSI, FRM2 and NIST $(n/cm^{2}s)$. $L/D$ | Neinei (RMB) | DINGO (OPAL) | Neutra (PSI) | ANTARES (FRM2) | BT2 (NIST)
---|---|---|---|---|---
$100$ | $7.20\times 10^{8}$ | $-$ | $-$ | $-$ | $-$
$500$ | $3.64\times 10^{7}$ | $4.75\times 10^{7}(L/D=250)$ | $3.96\times 10^{6}(L/D=550)$ | $9.4\times 10^{7}(L/D=400)$ | $5.9\times 10^{7}(L/D=400)$
$1000$ | $1.10\times 10^{7}$ | $1.15\times 10^{7}$ | $NA$ | $2.5\times 10^{7}(L/D=800)$ | $1.0\times 10^{6}(L/D=1200)$

Figure 5: Calculated intensity distribution for $l_{g}=0.5$ m and $L/D=1000$
at the location of the detector, x-position (above) and y-position (below).

Figure 6: Calculated intensity distribution for $l_{g}=0.5$ m and $L/D=500$ at
the location of the detector, x-position (above) and y-position (below).

Figure 7: Calculated intensity distribution for $l_{g}=0.5$ m and $L/D=100$ at
the location of the detector, x-position (above) and y-position (below).

Figure 8: Calculated intensity distribution for $l_{g}=1.0$ m and $L/D=1000$
at the location of the detector, x-position (above) and y-position (below).

Figure 9: Calculated intensity distribution for $l_{g}=1.0$ m and $L/D=500$ at
the location of the detector, x-position (above) and y-position (below).

Figure 10: Calculated intensity distribution for $l_{g}=1.0$ m and $L/D=100$
at the location of the detector, x-position (above) and y-position (below).
Figure 11: Neutron flux in the detector as a function of Neinei resolution.
The $L/D$ range covers all neutron imaging instruments compared.

##  5 Conclusions

The beam intensities found are in agreement with the results of other neutron
imaging instruments [12, 14, 15, 20]. Additionally, we provide the results
referring to a low-resolution configuration, which provides excellent signal
intensity, as physically expected. It is worth mentioning that the presented
model still shows an inhomogeneous neutron beam, even after a collimation
system formed by an in-pile collimator and an auxiliary neutron guide.
However, this phenomenon is found in the literature and is associated with
spatial gaps between the components of the imaging instrument [11], although
there are other geometric constraints that can cause beam divergence [14].

In general, our results are promising and indicate important directions for
the continuity of the project. In terms of equipment shielding, it must be
pointed out that the McStas software cannot estimate the dose of gamma
radiation, both in the region of the detectors and in the vicinity of the
primary shutter. Therefore, a more detailed study with the MCNP code should be
carried out for details of shielding the Neinei instrument. The sensitivity of
the camera’s CCD chip requires special care, and the use of filters (e.g.,
bismuth) in the beam path can be very important.

## Acknowledgement

L.P. de Oliveira also would like to thank National Nuclear Energy Commission
(CNEN) for financial support, Process SEI 01341011049/2021-22.

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