Abstract
Specific research reactors are capable of reproducing reactivity injection accidents in order to study the behavior of the nuclear fuel pins in accidental situations. In the CABRI research reactor, the fuel pin to be examined (test pin) is placed in the center of the core in a dedicated test loop. It is then subjected to a power transient, obtained by the fast depressurization of the 3He neutron absorber gas from the transient rods located in the core. One of the central parameters of the experiment is the energy deposition in the test pin, which is currently not measured during a transient. Instead, it is assumed that the relative energy distribution between the core and the test pin is constant regardless the operational state of the reactor. Currently, this correlation is measured in steady state. As such, the impact of the variations in the neutron flux, fuel and moderator temperatures during the transient is assumed equivalent on the energy deposition in the core and in the test pin. The goal of this work is to improve our knowledge on the mechanisms involved in the transient energy deposition. The aim of this paper is to present a methodological approach for the energy deposition estimation during a CABRI transient, based on static Monte Carlo calculations. The results suggest that the transient energy deposition rate is mainly dependent on the helium pressure and the Doppler feedback, and the relative energy distribution between the core and test pin changes during the transient.
Highlights
The term Reactivity Initiated Accident (RIA) refers to nuclear accidents involving a sudden and unexpected reactivity increase in the core
The aim of this work is to improve our knowledge of the mechanisms involved in the energy deposition and relative energy distribution during a transient with static Monte Carlo calculations
The reactor core is accurately modeled with a 3D native TRIPOLI-4 geometry, and the initial core configuration corresponds to the critical state of the CABRI reactor at 100 kW with a helium pressure of 11.4 bar in the transient rods
Summary
The term Reactivity Initiated Accident (RIA) refers to nuclear accidents involving a sudden and unexpected reactivity increase in the core. It is characterized by an extremely rapid power excursion with a significant energy deposition in the fuel assemblies surrounding the perturbation. In order to minimize the possibility of fuel failure and its consequences (such as the fuel dispersal in the primary circuit), the fuel safety criterion associated with this kind of accident is defined as a limit on the energy deposited in fuel pins [1]. Specific research reactors are capable of reproducing reactivity injection accidents in order to study the behavior of the nuclear fuel pins in accidental situations. The main parameters of the power pulse such as the peak power, the pulse length and the total energy deposition, depend on the operational characteristics of the reactor and are adjustable by experimental design
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