Software verification, model validation and hydrogeologic modelling aspects in nuclear waste disposal system simulations : a paradigm shift

G.M. Sheng

Research output: Thesisexternal PhD, WU

Abstract

<p>This work (1) reviews the current concept ad~ internationally on the disposal of highlevel nuclear wastes; (2) discusses some of the major challenges facing this disposal technology; (3) presents an evaluation of the Canadian performance assessment work as a case study; and (4) introduces a new paradigm within which to site an underground. disposal facility that offers many significant advantages over the existing concept.<p>Chapter 1 explains the setup of the work and forms the "General Introduction" to the subject material.<p>Chapter 2 describes the current internationally-accepted concept of underground disposal in stable, terrestrial, geologic media using a multi-barrier system of engineered (man-made) and natural barriers to prevent or retard the movement of radionuclides from depth to man's environment at the surface. Various aspects of the research and development work being conducted internationally to demonstrate the efficacy of this technology are described with emphasis paid to the Canadian Nuclear Fuel Waste Management Program (CNFWMP).<p>Chapter 3 examines some of the technical challenges of the current disposal concept including (a) the present focus on the lithologic aspects of the geologic/geotechnic research; (b) the unsatisfactory situation in attempts at "validating" models used in computer simulations to forecast very long-term future conditions; and (c) the unsatisfactory state of software quality assurance in such computer simulations. The collection of papers in this chapter points out these problems and presents some of the software engineering tools and techniques used for software verification and quality assurance. Paper 3.4 introduces a comprehensive and systematic approach with which a rigorous process of validating models can be applied.<p>Chapter 4 presents a review of some aspects of the Canadian performance assessment code, its models, as a case study to illustrate the application of principles, and tools and techniques described in Chapter 3. As such, various widely-recognized ANSI/IEEE software engineering standards were used to carry out the evaluation. This review is the first m-depth evaluation done externally and will likely serve, m part, as a basis for the ultimate judgement as to the quality and credibility of the Canadian performance assessment work.<p>Chapter 5 introduces a completely new approach, called the Regional Recharge Concept (RRC), to the siting of underground waste repositories. The emphasis of this new concept is on achieving understanding of regional groundwater flow patterns so as to exploit such knowledge to locate a repository in an area where escaping contaminants will be carried by the groundwater into "stagnant zones" or on a flow trajectory long enough to render decaying radionuclides harmless if and when they do ever surface. The theoretic basis of the RRC is developed in this chapter and the many advantages of the concept are shown through a modelling exercise. Because of the "passive safety" philosophy inherent in this new concept, as well as the move away from the current international focus on lithologic studies (where experience has shown the great difficulties in characterizing fractures and predicting their future behaviour), the RRC being advocated in this work represents a true paradigm shift from the current concept of nuclear waste disposal.<p>Chapter 6 summarizes the results from previous chapters in the form of conclusions relevant to future work in this area.
Original languageEnglish
QualificationDoctor of Philosophy
Awarding Institution
Supervisors/Advisors
  • Elzas, M.S., Promotor, External person
Award date22 Jun 1994
Place of PublicationS.l.
Publisher
Publication statusPublished - 1994

Keywords

  • nuclear power stations
  • hazards
  • storage
  • nuclear energy
  • radionuclides
  • radioactive wastes
  • waste disposal
  • municipal refuse disposal
  • waste disposal sites
  • landfills
  • refuse tips
  • computer simulation
  • simulation
  • simulation models
  • computer software
  • applications
  • groundwater flow
  • programming
  • software engineering

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