Precision method of measuring heat release in critical assemblies

Abstract

The compact arrangement of the primary loop equipment of fast reactors, such as the BN-600, complicates the design of the thermal shield which is placed between the core and the heat exchangers and is one of the principal elements of the integral arrangement. The heating of the shield is important in the thermal behavior of the assembly. The study of gradients of the volumetric heat-release rate at boundaries between regions with different material compositions is of particular interest from the technological point of view. The methods available for calculating such composites are not accurate enough, and it is necessary to study the distribution of the volumetric heat-release rate in mock-ups. At the present time the most widely used methods of studying the total volumetric heat-release rate in critical assemblies are the calorimetric method [I, 2] and a method using thermoluminiscent dosimeters [3]. These methods either are not direct, or the detectors are large and complex and perturb the temperature and neutron distributions in the reactor. We propose a method based on the measurement of the dynamics of temperature distributions in various parts of the critical assembly as a function of the reactor power. The heat-release rate at the center of the volume under study is measured with a temperature sensing device which makes reliable thermal contact with the structural elements. the rate of change of temperature is measured at zero power, the reactor is brought up to power, and the time rate of change of temperature is measured at constant reactor power. In this case the volumetric heat-release rate Q is