Unannounced interim inspections: do false alarms matter?

Unannounced Interim Inspections (UIIs) in nuclear facilities of the European Union have recently attracted major attention by the International Atomic Energy Agency (IAEA) and by European Atomic Energy Community (EURATOM)in the context of the IAEA/EURATOM Partnership Approach. Therefore, a research project had been organized by the Joint Research Centre in Ispra in collaboration with the Universität der Bundeswehr München in the framework of which the assumptions have been classified which are necessary for a quantitative analysis and a few variants have been studied in detail. In that project only so-called Attribute Sampling Procedures were considered which means that only errors of the second kind (no detection of the illegal activity), but not those of the first kind (false alarms), where taken into account. It was the purpose of the work presented here to investigate the impact of errors of the first kind on UIIs which may occur if so-called Variable Sampling Procedures are used. Two kinds of planning UIIs are considered: in the sequential one both players, the inspector and the operator of the facility, decide step by step to inspect resp. to start the illegal activity – if there is one. In the hybrid-sequential one the inspector decides at the beginning of the reference time interval where to place his UIIs, whereas the operator acts again sequentially. For two UIIs during the reference time interval equilibria are determined, which generalize the results of the above mentioned research project. It turns out that in both cases, the sequential and hybrid-sequential one, the equilibrium strategies of the inspector and the equilibrium payoffs to both players are the same, but not the equilibrium strategies of the operator. We try to present a plausible explanation for this surprising result

Optimal Scheduling of Inspections: Models and Approaches

A facility is considered the operations of which are subject to agreed rules. Since the Operator of this facility may have an interest in violating these rules, an Inspectorate verifies the Operator´s adherence to these rules. A mathematical analysis of the conflict between the Operator and the Inspectorate requires assumptions concerning the inspection philosophy, timing, planning and more. In this paper, we first introduce the four dimensions which can be used to classify inspection games over time. Thereafter, two inspection games are analyzed in which the Operator’s illegal activity needs to be detected within a critical time. Both inspection games differ only by one assumption and its consequences on the optimal inspection strategies are shown. Finally a quantitative assessment of effectiveness and efficiency is presented, and some problems of implementing optimal inspection schedules are discussed

Unannounced Interim Ispections

In this study unannounced interim inspections are analyzed in general, and specifically in view of the recently defined IAEA/EURATOM Partnership Approach. In particular the following aspects are addressed: A general discussion of the problem of unannounced interim inspections which includes an identification and description of all the types of assumptions which are necessary to be made for a quantitative treatment, an outline of the general methods identified and proposed for the solution of problems of that kind, the identification of two examples for a detailed analysis to be carried out with the general method identified in the previous steps, and lessons learned and reflections aiming at identifying also practical recommendations on the matter of unannounced interim inspections. As a major result, for a specific facility and a given number of inspections per reference time, e.g., one year, optimal inspection strategies are determined. Whereas for the case that inspection are perfect the results can be guessed, this does not hold anymore for imperfect inspections, e.g., limited sample sizes of seals to be checked. Also, together with the optimal inspection strategies, optimal expected detection times are determined as functions of the parameters of the model, namely number of inspections per reference time interval and probability of not detecting an illegal activity during an inspection.JRC.DG.G.8-Nuclear securit

Inspection Games over Time Fundamental Models and Approaches

Having worked for so many years in the field of modelling inspections, in particular in inspections over time, we felt a need for writing a monograph on this subject for basically two reasons. In the last thirty years a large number of game theoretical models have been developed and analysed, which describe similar or related inspection problems. As a consequence it has become increasingly difficult to maintain an overview on what exists already, how these models are related to each other and where possible gaps might exist. More than that are in many cases the assumptions for these models not documented very well, to say the least, which means that in particular for practitioners, who wants to use the results of the analyses of these models, it is very difficult to decide whether or not they describe their inspection problems and procedures properly. This monograph tries to solve these two kinds of problems. Most of the inspection models presented here, but not all of them, have been published already elsewhere, sometimes in conference proceedings, sometimes as PhD dissertations or just as technical reports which means, not easily accessible. Also, as indicated above, underlying assumptions were not complete or lacking at all, and references to related work was missing. But of course there are also publications in which assumptions, analyses and results are so carefully described that we simply, with due reference, used their wording. Beyond the collection of published inspection models over time we present $\textit{nine}$ new inspection models which close obvious gaps and - this we consider most important - we structure the material: We develop a hierarchy of assumptions for all models, and we describe equivalences, relations and differences between game theoretical models and their solutions. When talking about mathematical models, the question of their applicability will be raised immediately. Without discussing this issue here in detail - this will be done in the main text - it should be answered already here that indeed most of the inspection models have their origin in a practical problem, but that they range from those which lend themselves to immediate application to those which have been developed primarily for theoretical purposes. In the introductory first chapter we will say more about this central issue. Here we just express our hope that both practitioners and theoreticians will become interested into our work which we performed with so much enthusiasm for the subject

Inspection games over time: Classification of inspection schemes and resulting models

An inspection game is a mathematical model of a situation where a person or an organization, in the following called Inspectorate, verifies that another party, maybe a person, an organization or even a State, and in the following called Operator, adheres to certain agreed or legal rules. The Operator may, however, have an interest in violating these agreed rules. Typically, the Inspectorate's resources are limited so that verification can only be partial. A mathematical analysis helps in designing an optimal inspection scheme, where it must be assumed that an illegal activity is planned strategically. This defines a game theoretical problem between the two players, Operator and Inspectorate.Generally, inspection games over time, i.e. games in which timing aspects are the basis for the objective function, can be characterized along four dimensions: Inspection philosophy (playing for time vs. critical time), timing of interim inspections (discrete time vs. continuous time), planning aspects (non-sequential vs. sequential decision making), and statistical sampling (consideration of statistical errors), leading to 36 inspection games over times.The aim of this paper is twofold: First, the four dimensions and their consequences on the inspection models are discussed. Second, the situation in which the Operator’s illegal activity needs to be detected within a critical time is analyzed, and the sensitivity of the optimal inspection strategies depending on the model assumptions is demonstrated

Considerations on the large-scale deployment of the nuclear-fuel cycle

In papers by Häfele, Manne and Schikorr, strategies for a transition from fossil to nuclear fuels are considered for a model society of 250 M people with an asymptotic energy consumption of 10 kW thermal per capita. In the final state, a purely nuclear energy production system, based on only two reactor types, was assumed to cover all electric and non-electrical energy demands of the model society. It is the purpose of this paper to evaluate the whole nuclear fuel cycle belonging to the asymptotic nuclear energy-production system. In order to achieve this, all normal operational and accidental risks connected with the nuclear material throughputs are analyzed. Thus, an idea of the relative importance of the different hazards is obtained; furthermore, the basis for a comparison of the nuclear option with alternative options (which is the subject of forthcoming work) is given. With this purpose in mind, only orders of magnitude are considered throughout the paper; in addition, the argumentation is restricted to the level of expected values. Following the introduction, the mass flows of nuclear material through the nuclear fuel cycle are analyzed. The methodology used is then developed. The normal operation releases of radioactivity are considered and possible modes of accidental radioactive releases are analyzed; the problem of a final waste storage is treated separately because of its unique nature. Different kinds of sabotage and blackmail, including the construction of a nuclear explosive device, are next analyzed; finally, all calculations are summarized. In conclusion, a number of decision-oriented assessments are identified that must be made when the large-scale deployment of nuclear energy is considered