Experimental Study of Upper Core Quench in PWR Reflood Phase

Abstract

The present study investigates experimentally the characteristics of quench phenomena, top quench and bottom quench, in the upper part of the core during reflood phase in a PWR-LOCA. The characteristics of quench phenomena in the upper part of the core have not been predicted well even by a best estimate safety analysis code such as TRAC. The following are revealed from the experiment. (1) Quench phenomena in the upper part of the core are classified into three types; 1 top quench of heated rods, 2 top quench of non-heated rods, and 3 bottom quench of heated rods, with respect to the relation of quench velocity vs. quench temperature. (2) Top quench of heated rods is influenced by the falling water film on the adjacent non-heated rod. (3) Top quench velocity of heated rod rises with an increase of quench temperature; this is a tendency opposite to the prediction by the existing theory. (4) Top quench of non-heated rods has the same tendency as the existing theory.

The effects of system pressure and coolant flow rate are also investigated.

KEYWORDS:

• PWR-type reactors
• reflood phase
• slab core tests
• upper core
• top quench
• heated rod
• non-heated rod
• water film
• parameter effects
• bottom quench
• quench velocity
• quench temperature
• loss of coolant
• temperature dependence