An evaluation method on the integrated safeguards based on fuzzy theory

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Abstract

Many countries concluding comprehensive safeguards agreements with the International Atomic Energy Agency (IAEA) are currently going to agree a new additional protocol (INFCIRC/540). The protocol will make them provide more information to the IAEA. The expanded framework is expected to establish stronger and more efficient IAEA safeguards system, which we call “Integrated Safeguards”. However, there seems to be no evaluation method that enables inspectorate to derive a final evaluation from the information collected through the Integrated Safeguards Implementation. Evaluation of safeguards-effectiveness should be to estimate a degree of assurance to what extent the objective is attained. In this case, the assurance-degree of the following proposition should be given, “No nuclear material in a country is used for manufacture of nuclear explosive devices”. In this paper, a simple method is proposed to calculate the assurance-degree of non-manufacture of nuclear explosive devices. The method uses a simple logic tree and fuzzy linguistic variables as its inputs. In addition, the method is shown to be useful for considering the efficient implementation of safeguards. For example, case-studies by the method show that conventional safeguards inspection efforts relevant to low enriched uranium and spent fuels can be reduced to half by introducing the integrated safeguards activities relevant to highly enriched uranium and plutonium.

Introduction

Many countries concluding comprehensive safeguards agreements (INFCIRC/153 type) with the International Atomic Energy Agency (IAEA) are currently going to agree a new additional protocol (INFCIRC/540 type). The protocol will make them provide more information to the IAEA. The expanded framework is expected to establish stronger and more efficient IAEA safeguards system, which we call “Integrated Safeguards”. (See the paragraphs 2 and 23 of [1].) However, there seems to be no evaluation method that enables inspectorate to derive a final evaluation from the information collected through the Integrated Safeguards Implementation. In this paper, the authors try to make the fundamentals clear and propose a method to evaluate the effectiveness of Integrated Safeguards Implementation. In addition, the method is shown to be useful for the planning to improve the efficiency.

Section snippets

Objective of the evaluation

Objective of the comprehensive safeguards is described in INFCIRC/153. Evaluation of the safeguards-effectiveness should be to estimate a degree of assurance to what extent the objective is attained. In this case, the assurance-degree that “no nuclear material in a country is used for manufacture of nuclear explosive devices” should be estimated.

Definition of nuclear material types

Manufacture of nuclear explosive devices will need many steps. However, the final step before weaponisation will be a step to acquire “Highly enriched

Representation by “Fuzzy linguistic variables”

In case of semi-quantitative evaluation, “Fuzzy linguistic variables” will be useful because they can represent human judgement of evaluation naturally. In the application here, they will represent different levels of assurance-degrees. Concretely, the authors propose the definitions of five fuzzy linguistic variables; “nearly one”, “high”, “medium”, “low” and “completely zero”. They are defined by their corresponding membership functions on the interval of [0,1]. Their forms are depicted in

Considerations

(1) Especially in the fields of fuzzy logic applications, various kinds of definitions similar to our definitions of “and” and “or” have been proposed. Many of them are divided into three groups: “t-norms”, “t-conorms” and “mean operators”. Among them, “t-norms” are often used to represent the meaning of “and” in various applications. But, for example, when we assume that the input–assurance-degrees are 0.6 and 1, the output is 0.6 according to the definitions of “t-norms” (see [4]). On the

Conclusions

(1) Effectiveness of safeguards implementation can be evaluated by the method proposed in this paper. Its evaluation logic trees are given by Fig. 1, Fig. 2. Definitions of “and” and “or” needed to calculate the logic trees are given by Section 2.2.

(2) From the case-studies using the above evaluation method, implementation of integrated safeguards only to HU and PU is shown to be able to attain high efficiency. As the consequence, the conventional safeguards activities relevant to LU, SF and FF

References (4)

  • IAEA General Conference, Strengthening the effectiveness and improving the efficiency of the safeguards system and...
  • A. Kaufmann et al.
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