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ISO 16117:2013 pdf free

ISO 16117:2013 pdf free.Nuclear criticality safety – Estimation of the number of fissions of a postulated criticality accident
The input data needed for the simplified models or the calculation tools (geometry, external environment, media characteristics, etc.) shall be taken from assumptions considered for the accident scenario and the accident evolution. When the accident scenario and the accident evolution do not set necessary input data, these should be measured or calculated or estimated from the international literature.
NOTE Depending on the way estimates are made, the type and the number of input data needed may vary.
The selected input data sensitivities (linked to uncertainties and possible variations pointed out in 3.1) should be studied for the chosen route(s) of estimate (4.3 and/or 4.4). This study will provide a better understanding of the uncertainties associated with the estimated number of fissions. This study may be one possible basis for the nuclear criticality safety specialist to appropriately select a maximal estimate. Otherwise, further justifications should be made as to the applicability of the result.
Account shall be made for parameters that could vary significantly for the criticality accident duration.
WARNING一Care should be taken when using the criticality accident calculation tool results for the estimation of the number of fissions. In particular, a complete validation of a criticality accident calculation tool is presently difficult, mainly due to the complexity of models and paucityof criticality experiment and precise information from past criticality accidents.
The calculation tool used shall be documented, including the verification of the adequate implementation of the different models (for example, neutron physics, thermal transfer, bubbles behaviour).
When it is possible, comparison between the calculation tool results and experiments/accidents close to the chosen assumptions of the postulated criticality accident should be documented.
When a calculation tool is used, the consistency of its area of applicability with the chosen assumptions ofthe postulated criticality accident shall be justified and documented. In case ofinconsistency, the calculation tools may still be used; however, justification for its use shall be documented.
Free evolution of the system during the accident duration shall be accounted for. Resulting assumptions used in the calculation should lead to a maximal evaluation of the number of fissions.
To estimate the number of fissions, the calculation tool results should be associated with the sensitivity study performed (4.2.2) and with other available elements (for example, results obtained from comparison with experiments, complexity of models, possible penalizing hypothesis in the models).ISO 16117 pdf download.

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