Reassessment of the generic assumptions applied to the conventional analysis of the reactivity insertion accident in the MTRs using a novel coupled code

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In this study, a novel coupled-code developed according to the concept of “predictive simulation” is modified and employed to analyze a reactivity insertion accident in Tehran Research Reactor (TRR) as a typical Material Test Reactor (MTR). The modified coupled-code is named RRASK (Research Reactor Advanced Simulation Kit). The PARET code was used in Safety Analysis Report (SAR) of TRR to model this design basis accident with a conservative approach. First, conservative conditions of SAR and limitations of the PARET code are applied to the RRASK and results are compared to verify the new code for this application. Then, the conditions and limitations are removed in order to assess their effects. Results demonstrate considerable consequences of the limitations. The crucial fact is that most of these limitations cannot be resolved even if source of the conventional code is available to be modified because the limitations have roots in the basic methodology. Removing the limitations, combined with the capability of the RRASK in providing detail-orientated, three-dimensional data on the real geometry of the reactor (instead of the homogenized one used by the PARET code) results in achieving an accurate estimation of the positions which are vulnerable to the accident, thereby proposing informed modifications in order to mitigate the consequences. A matter, which will not be possible if a conventional code such as the PARET or Relap 5 is employed to analyze the accident. Providing a practical example to demonstrate advantages of using the concept of predictive simulation for accident analysis, over the conventional codes is a primary objective of this study.