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Analysis of Salt Management Effects on the Molten Salt Research Reactor’s Operational Characteristics
Abstract
Due to the growing interest in advanced reactors such as molten salt reactors (MSRs), it is important to better understand some of their advantages. For example, a significant potential advantage of MSRs is their ability to refuel and remove waste without shutting down the reactor. This allows for a reduction in refueling outages and the ability to remove poisons such as Xe¹³⁵ and Sm¹⁴⁹ during operation. To support the Molten Salt Research Reactor (MSRR) project at Abilene Christian University, the impact of these advantages was studied.
The aim of this analysis was to evaluate how different methods of editing the fuel-salt composition can impact the ability of the MSRR to maintain criticality. These methods were broken into three operational approaches: adding UF₄, removing fission products, and a combination of the two. Several subcases were examined to better understand how fuel addition and/or fission product removal affects Keff, mean generation time, and the effective delayed neutron fraction. A Python script, designed to interface with MCNP input and output files, was created to simulate the online refueling aspect of MSRs. The various cases examined using this script and MCNP yielded the following results; 1) an upper bound for operation without refueling via fission product removal is approximately 6.5 years or 170% (not achievable with current fission product removal technology, but the potential benefits are significant), 2) an insertion of approximately 4.5% UF₄ added at year 3 and year 7 can conservatively extend the reactor lifetime to 10 years, 3) the mean generation time is sensitive to fuel insertion and can be influenced to a lesser degree by poison removal, and 4) negligible effects were observed on the effective delayed neutron fraction due to the utilized fuel management schemes.
Subject
MSRoperational lifetime
mean generation time
delayed neutron fraction
Keff
online refueling
online fission product extraction
operational parameters
nuclear
Citation
Valverde, John M (2023). Analysis of Salt Management Effects on the Molten Salt Research Reactor’s Operational Characteristics. Master's thesis, Texas A&M University. Available electronically from https : / /hdl .handle .net /1969 .1 /198964.