Neutronic Assessment of Accident-Tolerant Cladding Concepts for Civil Nuclear Marine Propulsion Cores. Part I: Reactivity and Spectral Hardening

Abstract

In this reactor physics study, we examine the neutronic performance of accident-tolerant fuel (ATF) claddings - austenitic type 310 stainless steel (310SS), ferritic Fe-20Cr-5Al (FeCrAl), advanced powder metallurgic ferritic (APMT), and silicon carbide (SiC)-based materials - as alternative cladding materials compared with Zircaloy-4 (Zr) cladding. The cores considered in this study use 18% and 15% 235U enriched micro-heterogeneous ThO2-UO2duplex* and homogeneously mixed all-UO2fuels, respectively, loaded into 13x 13 pin arrays. A constant cladding coating thickness of 655 μ was assumed throughout this study. We use the WIMS reactor physics code to analyse the associated reactivity, achievable discharge burnup and spectral variations to compare the different neutronic cases for candidate cladding materials. The results show that candidate fuels with 310SS cladding exhibit a ∼13% discharge burnup penalty compared to Zr due to the presence of a very high nickel (Ni) concentration; Ni has a thermal neutron absorption cross-section about twice that of iron (Fe). In addition, the high neutron absorption cross-sections of Fe in the FeCrAl and APMT claddings also lead to a ∼10% discharge burnup penalty. The fuels with SiC cladding can achieve a ∼ 1 % higher discharge burnup compared to Zr cladding due to the low thermal neutron absorption cross-sections of its constituents along with the presence of a softer neutron spectrum. Furthermore, duplex fuel yields a softer spectrum than the UO2fuel with the candidate claddings, which improves neutron economy and thus discharge burnup. Finally, it can be concluded from this study that, when modeling SiC, a standard cladding thickness could be implemented with marginally less enriched uranium. On the other hand, in order to overcome the burnup penalty while using an iron-based alloy cladding, it is recommended to reduce the cladding thickness and slightly increase the fuel enrichment in order to match the cycle length achieved with Zr.

Department(s)

Nuclear Engineering and Radiation Science

Keywords and Phrases

Accident-tolerant cladding; Achievable discharge burnup; Reactivity; Soluble-boron-free (SBF) design; Spectral hardening

International Standard Book Number (ISBN)

978-171380851-0

Document Type

Article - Conference proceedings

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 2024 Curran Associates Inc., All rights reserved.

Publication Date

01 Jan 2018

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