ALARP Principle Research Articles

The safety case for JET D-T operation

Formal approval was required to permit tritium operation of the JET machine to proceed and a safety case was prepared in order to justify this. The standards and the methodology used are summarised both for the Active Gas Handling System and for the torus systems. The main design safety principles are described and accident sequences are reviewed. Both deterministic and probabilistic analysis was carried out and the main results in terms of source terms, on-site and off-site doses are presented. It is shown that operation of JET with deuterium-tritium plasmas complies with the ALARP principle.

Offshore QRA and the ALARP principle

A discussion is presented of the use of QRA within a requirement, of the UK offshore safety case regime, to demonstrate that risks from offshore major accidents are ALARP. General considerations are given to uncertainties in failure and incident data, assumptions and consequence methodologies within the analysis element of offshore QRA. The validity of risk results arising from the analysis element is discussed in the context of such results being viewed on the basis of a classical interpretation of probability (the interpretation most often used for offshore QRA), and comments are made about the nature of results in relation to a distinction between objective knowledge and subjective ignorance. Consideration is given to a Bayesian interpretation of probability (rarely used for offshore QRA), and to the role that QRA may have when this interpretation is adopted against a background of some basic principles of engineering safety.

Risk Acceptance Criteria for Temporary Phases

Abstract The full life cycle approach to risk acceptance is proposed as the basis for establishing of acceptance criteria for the temporary phases, i.e., onshore and offshore construction as well as installation. The background for such criteria is discussed, as well as evaluations that may be used to formulate risk acceptance criteria in the construction and installation phases. The criteria are focused on personnel safety. Environmental spill protection and protection of assets are also addressed, but less extensively. FAR or AIR values are used to express tolerable personnel safety, whereas the acceptability of exposure of the investment is expressed in terms of acceptable probabilities of accidents with significant effect on the project time schedule, i.e., the possibility to delay significantly the start-up of the production phase. The approach is based on an ALARP principle.

A Framework for Offshore Risk Criteria

AbstractSome suggestions are put forward concerning a framework for offshore risk criteria. A proposal is made for general criteria based on group (societal) risk, formulated in a way that is consistent with criteria based on individual risk. The group risk criteria address Lord Cullen's suggestion that due regard should be had to risk aversion to major accidents. The criteria include tolerable levels of individual risk that reflect accident mortality data, and as such may accommodate the ‘real improvement in safety’ advocated by Lord Cullen. The framework is designed to make allowance for variations between offshore installations, and embraces a general application of the ALARP principle.

Routine Tritium Releases from JET

The JET tritium handling facilities have been designed to minimise tritium releases to the environment and to comply with the ALARP principle. However, it is not practicable to reduce such releases...

Experience on the application of the ALARP principle

The balance of importance to the decision-making process of individual dose and collective dose considerations is examined, based on experience at BNFL Sellafield over recent years. Appraisal of both shielding assessment techniques and effluent discharge assessments indicates that individual dose considerations usually dominate the decision-making process.