Small modular high temperature reactor optimisation part 2: Reactivity control for prismatic core high temperature small modular reactor, including fixed burnable poisons, spectrum hardening and control rods



Atkinson, S ORCID: 0000-0001-7434-6686, Litskevich, D ORCID: 0000-0002-3207-3058 and Merk, B
(2019) Small modular high temperature reactor optimisation part 2: Reactivity control for prismatic core high temperature small modular reactor, including fixed burnable poisons, spectrum hardening and control rods. PROGRESS IN NUCLEAR ENERGY, 111. pp. 233-242.

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Abstract

This article investigates a high temperature prismatic core small modular reactor concept based on the U-Battery. To achieve a long operational time without reloading of the fuel, a high fissile fuel load is required, to provide the required excess reactivity which needs to be compensated to allow safe operational states in all stages of the life of the core. This is achieved through the means of reactivity control methods. In this article we deploy a design methodology for controlling the reactivity in a design based on the U-Battery. The initial excess reactivity within the core was 2000 pcm, implying that the reactivity control systems were required to bring this to unity. To reduce this reactivity, we investigated three main reactivity control methods. Initially the control rod designs which is kept constant. Then a full range of fixed burnable poison designs are evaluated. The final reactivity control method investigated the process of flux spectrum hardening by changing the moderation within the core. This work managed to identify that maximum full power days without any reactivity control as 1364 days. The fixed burnable poisons deployed reduced this lifetime by 62 days due to a reduced neutron economy. However, by removing part of the central reflector the flux spectrum hardens (increases the proportion of fast neutrons) this provides additional bred plutonium provided an additional 62 full power operating days. The meant that the overall design saw no lifetime reduction due to reactivity control devices, without including the use of control rods. Due to the implemented reactivity control systems, the highest point of reactivity has been identified as 1.03, this meant that the control rod position required to reduce this reactivity is limited to the maximum of 50% insertion. Identifying the power profile at this position showed additional loading at the fuel below this point, where additional thermal distribution work will be undertaken.

Item Type: Article
Uncontrolled Keywords: Small modular reactor, Reactivity control, Criticality, neutronics, fuel cycle, core design
Depositing User: Symplectic Admin
Date Deposited: 28 Nov 2018 11:25
Last Modified: 19 Jan 2023 01:11
DOI: 10.1016/j.pnucene.2018.11.001
Related URLs:
URI: https://livrepository.liverpool.ac.uk/id/eprint/3029143