HTGR Knowledge Base

Conference Article: Advanced gas-cooled reactor design approach to safety

Ingham, E.L. (AGR Systems Reliability, National Nuclear Corp., Ltd., Knutsford (UK))

Abstract

The AGRs currently under construction at Heysham II and Torness in the United Kingdom are the first to be designed and assessed against the specific probabilistic safety criteria adopted in Britain. The paper discusses the impact of these design criteria on the development of the AGR system and examines the design approach taken to satisfy probabilistic and other safety requirements. The paper concentrates on the influence of the criteria on the definition, specification and assessment of the protective features and systems in so far as these are fundamental to achieving an adequate level of safety. The paper discusses the systematic approach that has been adopted by which all potential initiating faults and hazards which could affect the safe operation of the plant are recognised and classified. It goes on to describe how the provision and arrangement of the main protection systems has been devised to ensure that in the event of any of these faults or hazards occurring there is sufficient redundancy and diversity to ensure that the potential risk of a significant radiological release is sufficiently small. The methods of fault detection, reactor shutdown and post shutdown heat removal are described showing the principal features of the relevant systems, in which conservative and proven component design and segregation against hazards are used to achieve an adequate standard. Finally the methods and results of the assessment of the design against the probabilistic criteria are discussed showing how the complementary aspects of the probability analysis, the design specification and the assessment of the performance of the plant in fault conditions combine towards ensuring that the overall safety requirements are met.

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key words: after-heat removal; agr type reactors; failed element detection; failure mode analysis; safety analysis; safety engineering; scram; specifications; detection; enriched uranium reactors; gas cooled reactors; graphite moderated reactors; reactor shutdown; reactors; shutdown; system failure analysis; systems analysis
Reference:
Specialists' meeting on safety and accident analysis for gas-cooled reactors. Oak Ridge, TN (USA). 13-15 May 1985
International Atomic Energy Agency, Vienna (Austria)
IAEA-TECDOC--358, pp:133-154