Research On Simulation And Phenomena Identification Ranking Table(PIRT) Quantification Of The EBR-Ⅱ Fast Reactor Loss Of Flow Accident Based On System Code FRTAC

The Fast Reactor Transient Analysis Code(FRTAC),developed by China Institute of Atomic Energy,can be used to calculate normal fast reactor operation and accident conditions.In the process of code validation and verification,comparison calculation based on real reactor data is an important part of code verification.EBR-Ⅱ fast reactor loss of flow condition is one of the real reactor experiments conducted by Argonne National Laboratory in the United States with relatively rich measured data.In order to ensure that FRTAC code can be used in fast reactor design and accident condition analysis,it is necessary to select EBR-Ⅱ benchmark test to preliminatively confirm the effectiveness of the code.At present,most studies on the loss of flow accident conditions of EBR-Ⅱ fast reactor at home and abroad are aimed at the verification of the code itself and the comparison of the code calculation model,and the identification and ranking of the important phenomena of the loss of flow accident itself are not involved.Phenomenon identification ranking table(PIRT)is a table used to identify and rank important phenomena in reactor thermal engineering.This table is often used for software development and experimental modeling.It is generally determined based on experience and qualitative analysis,and quantitative research is rarely carried out.On the premise of verifying the accuracy of FRTAC code.this paper carries out the identification and ranking of important phenomena in the transient state of loss of flow accident,and puts forward the quantization index of PIRT parameters for the first time,and obtains the quantization range of importance,which can provide data support for the subsequent comparison of different PIRTs and PIRT formulation.In the EBR-Ⅱ loss of flow transient calculation,the protected loss of flow test SHRT-17 and the unprotected loss of flow test SHRT-45R were selected as the benchmark tests for validation.The reactor model of the EBR-Ⅱ was established.and transient condition calculations were carried out.SHRT-17 was a protected loss of flow accident condition where the reactor was stopped synchronously while the pump was idling.The response characteristics of key parameters in the primary loop system were compared,and the maximum relative error between the calculated and experimental values were 2.07%for main pump flow rate.1.26%for core inlet temperature.6.8%for core outlet temperature,and 8.31%/6.08%for temperature in the top region of channel XX09/10.SHRT-45R was an unprotected loss of flow accident condition where the reactor relied entirely on reactivity feedback to stop after the pump was stopped.The response characteristics of key parameters in the primary loop system were compared,and the maximum relative error between the calculated and experimental values were 1.93%for relative fission power,0.89%for main pump flow rate,and 8.32%/5.71%for temperature in the top region of channel XX09/10.The results preliminarily verified the accuracy of the FRTAC code,which can be used for accident condition analysis in fast reactors.Based on the accident processes of SHRT-17 and SHRT-45R,20 PIRT identification phenomenon index parameters were proposed,including fuel rod heat transfer,pump idling,heat transfer tube heat conduction in the intermediate heat exchanger,and reactivity feedback.The quantitative range of the performance index parameter ε corresponding to H,M,L,and N were determined to be greater than 1%,0.5-1%,0.05-0.5%,and less than 0.05%,respectively.According to the results,the functional modules of the FRTAC code were selected.