NEA/CSNI Workshop on

Safety Assessment of Fuel Cycle Facilities – Regulatory Approaches and Industry Perspectives

Toronto, Canada, 27-29 September 2011

Introduction

Organisation and host

The CSNI Workshop on Safety Assessment of Fuel Cycle Facilities – Regulatory Approaches and Industry Perspectives will be held by the OECD Nuclear Energy Agency and hosted by Canadian Nuclear Safety Commission (CNSC) from 27-29 September 2011 in Toronto, Canada. The Workshop is planned for 3 days.

Objectives

The objective of this workshop is to review the various approaches of national regulators, and their technical support organizations (TSO), in the Safety Assessment of Fuel Cycle Facilities (FCFs) and the experience of their industry in providing safety justification for their facilities. It will address the present situation in various NEA member countries (MC) and will concern both initial safety assessment of new facilities and reassessment of existing ones (periodic safety review). It will also consider trends of future improvement of safety assessment techniques.

The objective of the Working Group on Fuel Cycle Safety (WGFCS) is to advance the understanding for both regulators, and their TSO, and operators of relevant aspects of nuclear fuel cycle safety in member countries.
 
For the various FCFs types and processes, and age, special emphasis will be given to the identification of initiating events, the determination of release limits, justification on chemical safety and the various risk assessment techniques used for FCF safety.

Safety authorities, and their TSO, and FCF operating organisation are invited to share information on their approaches, practices and current development.

Background

Nuclear fuel is produced, processed, and stored mainly in industry scale facilities where uranium (U) ores are processed and refined. Uranium is converted and then enriched, nuclear fuel is fabricated (U fuel and U/Pu fuel for the close cycle option); and spent fuel is stored and reprocessed (close cycle option). Facilities dedicated to the research and development of new fuel or new processes are also considered as FCFs.

The nuclear renaissance will require the set-up of new FCFs and the modernization of existing ones as extension of operational life and increase of capacity.

The general trend of the safety assessment of nuclear facility is often led by the methodology and techniques initially developed for Nuclear Power Plants (NPPs). Consequently the workshop intends to share experience and limits on this direction.

Scope, content and outline

Fuel cycle facilities cover a wide diversity of installations. This activity will focus on: facilities dedicated to conversion, enrichment, fuel manufacturing, interim spent fuel storage, spent fuel reprocessing, radioactive waste conditioning, on-site interim storage of radioactive waste.

Specificities related to the diverse facility age, from 60 years old to those currently in design/ construction will be addressed. Nevertheless the safety assessment of decommissioning of FCF would be out of scope; as WGFCS shall take into account the limits of its human resources for achieving tangible results.

For the same reason, in the field of waste management, this activity is proposed to focus only on national regulatory methodologies and the industrial practices related to waste conditioning (resulting in liquid/aerial discharges or conditioned solid waste) and waste storage (with exception of legacy waste management and final disposal).

Particular assessment themes have been identified by the 2009 WGFCS meeting, and revised and finalized at the October 2010 meeting:

• Identification of initiating events – Due to the diverse nature of the radiological and chemical challenges of FCFs there are a number of methods by which events causing chemical or radiological releases can be identified. Threshold below which events are screened out of consideration should be also discussed;
• Determination of release limits – Radioactive or chemical release from an FCF can generate harm to both workers and the public but also in certain instances can generate significant public concern even when harm does not exist. Sharing methodologies for fixing the regulatory limits on routine releases of both hazardous chemicals and radioactive materials in the various countries is useful  as well as sharing on how events that do not generate harm but are of public concern can be dealt with early or negated by clear transparent communication;
• Justification on chemical safety – This theme recognises that public concern associated with the nuclear industry can be affected by events in the low radiological chemical facilities (e.g. Uranium fluorination plants) and that many nuclear facilities have major chemical hazards associated with them as well as radiological. Different countries have different regulations associated with chemical hazards (including fire and explosion) and exploration of how they are applied in nuclear facilities is important to establish
• Bounding accident, DSA, PSA, Integrated risk informed decision making – There is a clear consensus that the severe accident corresponds to the core damage accident for power reactors. On the other hand, for FCFs, there is no clear consensus on what is the accident to assess the safety in the region of beyond design basis, or what is the accident which has very low probability but large consequence. Risk management is often used as a justification where a hazard cannot be reasonably designed out deterministically. It is also often used as a justification to underpin the extension of the operation of a facility beyond its original design life and where deterministic approaches cannot be followed. Some questions to be consider are:
  • What kind of accidents should be chosen as bounding accidents?
  • How could PSA be used to focus attention on the most risk-significant structures, systems, components, and operator actions, by both the operator and the regulator?
  • What are the international approaches to the use of PSA in justifying facility extension beyond design life?
  • What could be an integrated assessment that combines nuclear safety, radiation safety, chemical safety (...) through deterministic considerations (defence in depth, safety margins), probabilistic considerations, organisational considerations (management systems, operational experience), standards, good practices, economic factors…?

Format

The organisation of the Workshop is divided into three parts: Opening Session; Technical Sessions; and a Final Summary Session. All the participants are expected to take part in the discussion and in the formulation of conclusions in the final session.

Last reviewed: 26 May 2011