Abstract
Several concepts of new reactors use graphite. Some of them use graphite as a moderator, some of them as a reflector. There are at least two concepts of these graphitetype reactors under development in the Czech Republic. Both reactors use graphite as the reflector. An in-core measurement might be impossible to use because of various reasons, for instance, high temperature or aggressive environment. Therefore, this article focuses on ex-core neutron flux measurement system placed in the graphite reflector and the optimization of ex-core detector position. A set of experiments were performed at LR-0 reactor. The LR-0 is a light water reactor with a well-defined neutron field, which can be used for different material insertion tests and testing of its influence on criticality. Several modifications of LR-0 cores were modelled in Monte Carlo codes Serpent and KENO. A set of calculations were performed for verification of the criticality and neutron flux course in the reactor core and graphite reflector. Further investigation was focused on the influence of the presence of a graphite reflector on the neutron distribution in the reactor core. The LR-0 graphite experiments were also used to verify the calculations. Based on the results of this article, the optimal position of ex-core detectors in the graphite reflector is proposed.
Highlights
IN the context of global interest in small modular reactors and new 4th generation reactors, the Czech Republic thinks about their utilization in its own energy sector
A graphite prism was prepared and a set of experiments were carried out in the LR-0 reactor. These experiments serve as a source of experimental data for the validation of neutron flux models, which were created in the Monte Carlo codes Serpent and SCALE-KENO [2,3]
These reactor concepts need to be equipped with a neutron flux instrumentation to control the reactor power and to ensure the safety functions
Summary
IN the context of global interest in small modular reactors and new 4th generation reactors, the Czech Republic thinks about their utilization in its own energy sector. Czech researchers propose a few designs of small reactor concepts. This paper focuses mainly on ex-core neutron flux instrumentation in reactors with the graphite reflector. This work presents the following research of the optimal detector position in the graphite reflector. The positioning of the detectors has to be determined with respect to the axial and radial neutron flux distribution and the whole reactor core design. A graphite prism was prepared and a set of experiments were carried out in the LR-0 reactor These experiments serve as a source of experimental data for the validation of neutron flux models, which were created in the Monte Carlo codes Serpent and SCALE-KENO [2,3]. The performed calculations investigate the optimal position of the ex-ore detectors in the graphite prism and a neutron flux distribution
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