Nuclear facilities, like plants, laboratories, and other involved in the storage and transportation of fissile material, must evaluate and prepare for a wide range of catastrophic events. The ISO 27467 was released in 2009 to provide such facilities with a way to identify and analyze such possible criticality accidents in all nuclear facilities with the exception of nuclear power reactor cores. It defined the areas to study and review, so that organizations can make sure that they do all the things necessary to prevent such occurrences. Now ISO 16117 provides specific guidance for how to estimate a reasonably maximal value of the number of fissions of a postulated criticality accident.
Titled “Nuclear Criticality Safety – Estimation of the Number of Fissions of a Postulated Criticality Accident,” the new ISO 16117 gives you the information you need for more accurate assessments of the number of fissions involved in any projected scenario.
Why a standard on just this topic alone? Most of the other issues involved in the analysis of potential accident risk depend on getting the estimate of the potential number of fissions as correct as possible. You cannot develop credible contingency plans without credible estimates of the consequences of any given accident scenario.
In most situations, there are a number of factors to be considered when estimating the radiation doses and radioactive materials that may be released. So getting the assumptions correct will affect the outcomes of the estimates.
The ISO 16177 discusses two different “routes” to estimating the number of fissions used in these models. One is the calculation tools route and one is the simplified models route (which should be considered first). Guidance is given on each of these along with a discussion of the calculation tools that are relied upon during this process.
Four Annexes complete the standard:
- Annex A, Flow diagram of a criticality accident analysis,
- Annex B, Characteristics of criticality accidents that occurred during process operation,
- Annex C, Experimental results, and
- Annex D, Simplified formulae.
The 7-page bibliography contains 146 separate references for further information on this topic.
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