Nodalization effects on RELAP5 results related to MTR research reactor transient scenarios

Abstract

The present work deals with the anal y sis of RELAP5 results obtained from the evaluation study of the total loss of flow transient with the deficiency of the heat removal system in a research reactor using two different nodalizations. It focuses on the effect of nodalization on the thermal-hydraulic evaluation of the re search reactor. The analysis of RELAP5 results has shown that nodalization has a big effect on the predicted scenario of the postulated transient. There fore, great care should be taken during the nodalization of the reactor, especially when the avail able experimental or measured data are insufficient for making a complete qualification of the nodalization. Our analysis also shows that the research reactor pool simulation has a great effect on the evaluation of natural circulation flow and on other thermal-hydraulic parameters during the loss of flow transient. For example, the on set time of core boiling changes from less than 2000 s to 15000 s, starting from the beginning of the transient. This occurs if the pool is simulated by two vertical volumes in stead of one vertical volume

Thermal-hydraulic modeling of reactivity accidents in MTR reactors

“…The anal y sis of the tran sient be hav ior of research re ac tors has re ceived great at ten tion since Wood ruff [1], till Mir za et al, [2], Nasir et al, [3], and Housiadas [4], be cause of its in abil ity to de ter mine the lim its of clad melt ing tem per a ture. In fact, so far, re search re ac tor safety anal y sis has been per formed us ing con ser va tive com pu ta tional tools [5][6][7][8][9]. In terna tional ther mal-hy drau lic codes, cur rently in use for re search re ac tors, are ca pa ble of sim u lat ing most re ac tor tran sients, but these com puter codes are not ac ces si ble to a lot of re search ers.…”