Hiroyuki Umeki

Knowledge management for radioactive waste disposal: moving from theory to practice

The exponential growth in the knowledge base for radioactive waste management is a cause for concern in many national programmes. In Japan, this problem is exacerbated by a volunteering approach to siting of a deep geological repository, which requires particular flexibility in the tailoring of site characterisation plans, repository concepts and associated Performance Assessments (PAs). Recognition of this situation led, in 2005, to initiation by Japan Atomic Energy Agency (JAEA) of an ambitious project to develop an advanced Knowledge Management System (KMS) aimed to facilitate its role as the supplier of background R&D support to both regulators and implementers of geological disposal. The paper will review progress to date in this work, with emphasis on tailoring of existing Knowledge Engineering tools and methods to radioactive waste management requirements, and outline future developments and challenges.

Key Aspects of the H12 Safety Case

In Japan, as outlined in the overall high-level radioactive waste (HLW) management program defined by the Japanese Atomic Energy Commission (AEC, 1994), HLW from reprocessing of spent nuclear fuel will be immobilized in a glass matrix and stored for a period of 30 to 50 years to allow cooling. It will then be disposed of in a deep geological formation. Pursuant to the overall HLW management program, an organization with responsibility for implementing HLW disposal will be established around the year 2000. This will be followed by site selection and characterization, demonstration of disposal technology, establishment of the necessary legal infrastructure, relevant licensing applications and repository construction, with the objective of starting repository operation by the 2030s and no later than the mid 2040s. The HLW disposal program is currently in the research and development (R&D) phase and the Japan Nuclear Cycle Development Institute (JNC) has been assigned as the leading organization responsible for R&D activities. The aim of the R&D activities at the current stage is to provide a scientific and technical basis for the geological disposal of HLW in Japan and to promote understanding of the safety concept not only in the scientific and technical community but also by the general public. One of the features of the R&D program is that its progress is documented at appropriate intervals, with a view to clearly determining the level of achievement of the program and to promote understanding and acceptance of the geological disposal strategy by the general public. As a major milestone, the Power Reactor and Nuclear Fuel Development Corporation (PNC, now JNC) submitted a first progress report, referred to as H3 (PNC, 1992), in September 1992.

A Challenge on Development of an Advanced Knowledge Management System (KMS) for Radioactive Waste Disposal: Moving from Theory to Practice

In recent years there has been much discussion on the topic of knowledge management in many areas of nuclear science, particularly associated with the nuclear renaissance and the evident shortage of skilled manpower (e.g. Yanev, 2008). More generally, however, the exponentially expanding capacity of computer systems parallels an explosion in the documentation and databases supporting nuclear projects. This is nowhere more evident than in the field of radioactive waste management, characterised, as it is, by the extremely wide range of disciplines involved and very long project timescales (e.g. Kawata et al., 2006; Umeki et al., 2008; Umeki et al., 2009). Although this may not yet be universally accepted, there is increasing evidence that the rapid rate of growth of material supporting complex technical projects – which we will term ‘knowledge’ – is rapidly reaching, if not passing, the point where conventional management systems show signs of collapse. Although tried and tested over millennia, the type of Knowledge Management System (KMS) developed to handle written documents is proving inherently incapable of being simply modified to cope with the present flood of electronic material. Although Moore’s Law of expansion of data transfer speeds and storage capacity means that some of the simpler tasks involving document collation and archiving can be handled, there has been little progress in addressing the more difficult problems of how the huge volumes of documentation being produced can be critically reviewed/quality assured, synthesised, integrated and communicated to all the interested stakeholders in a form that they can understand. A common blockage to progress is that, while many of the component problems (symptoms) may be acknowledged, it is not easy for organisations to perceive the magnitude of the approaching catastrophic system collapse and hence to implement the paradigm shift needed to introduce effective solutions. Indeed, it is a classic Catch-22 situation: the breakdown of conventional approaches means that those involved lack the overview required to see that their KMS is becoming increasingly dysfunctional. The exponential growth in the knowledge base for radioactive waste management is a cause for concern in many national programmes. In the Japanese radioactive waste disposal field,

The JNC Generic URL Research Program - Providing a Knowledge Base to Support both Implementer and Regulator in Japan

In accordance with the R&D framework specified by the Atomic Energy Commission of Japan in 2000 for the implementing phase of HLW disposal, the Japan Nuclear Cycle Development Institute (JNC) continues to be responsible for R&D activities aimed at enhancing the reliability of disposal technologies and safety assessment methodologies and associated databases. JNC has thus been actively promoting technical R&D with a view to contributing to both the implementation of disposal and the formulation of safety regulations. One of JNCs key roles is to establish and demonstrate site characterization methodologies based on investigations in two purpose-built generic URL (underground research laboratory) projects: one at Mizunami in crystalline rock and the other at Horonobe in sedimentary rock. Through the surface-based investigations in the Mizunami and Horonobe projects (phase 1), integration of work from different disciplines into a “geosynthesis” has been illustrated and is planned to be developed further in the underground facilities at these sites (phases 2 and 3). These projects also serve for developing and testing the tools and methodologies required for site characterization. Further know-how will be gained through participation in foreign underground laboratory projects, transfer of experience from these projects to Japan and tailoring it to Japanese conditions and requirements. This experience represents an important knowledge base, which is obviously important for the implementer but is also needed by the regulator, in order to assess how key site characteristics are derived and what uncertainties are associated with this process.

Radionuclide migration analysis using a discrete fracture network model

This paper describes an approach for assessing the geosphere performance of nuclear waste disposal in fractured rock. In this approach, a three-dimensional heterogeneous channel-network model is constructed using a stochastic discrete fracture network (DFN) code. Radionuclide migration in the channel-network model is solved using the Laplace transform Galerkin finite element method, taking into account advection-dispersion in a fracture network, matrix diffusion, sorption in the rock matrix as well as radioactive chain decay. Preliminary radionuclide migration analysis was performed for fifty realizations of a synthetic block-scale DFN model. The total radionuclide release from all packages in the repository was estimated from the statistics of the results of fifty realizations under the hypothesis of ergodicity. The interpretation of the result of the three-dimensional network model by a combination of simpler one-dimensional parallel plate models is also discussed.