CATHENA Model of the End Shield Cooling System for Point Lepreau Generating Station

Abstract

Failures in the shield cooling system (i.e. loss of circulation, loss of heat sink and loss of end shield inventory) cause the metal components in the end shield assembly to heat up. These components, particularly the inner and outer tubesheets, heat up at different rates. Thermal loading of the tubesheets in this manner causes them to deform and possibly lead to distortion of the calandria assembly and exert extra load on the fuel channels. This in turn may jeopardize the integrity of the fuel channels and/or operation of the shutdown systems.This paper discusses the CATHENA thermalhydraulic model of the end shield cooling system used in Point Lepreau. The thermalhydraulic response of the system following different Point Lepreau Generating Station transients and the predicted system temperature are also presented.The thermalhydraulic response of the system following shield cooling system failures and the temperature profile of the inner and outer calandria tubesheets can be obtained using this model. Such tubesheet differential temperatures are normally used as input to assess the integrity of the calandria assembly following postulated end shield cooling system failures.