Design study of long-life small modular sodium-cooled fast reactor

Abstract

Summary This paper presents a new design for a small modular sodium‐cooled fast reactor core with an optimized lifetime and reactivity swing through the analysis of various breed‐and‐burn strategies and its neutronic analyses in terms of active core movements, isotopic mass balance, kinetic parameters, and inherent safety. The new core design aims at a power level of 260 MW with a long lifetime of 30 years without refueling and a reactivity swing smaller than 1000 pcm. Starting from five initial candidate cores with various breed‐and‐burn strategies, an optimum core was selected from a combination of the two candidates that shows a proper breeding behavior with the optimized uranium enrichment in the low‐enriched uranium region and the optimized size of the blanket region. The depletion analysis of the new core provides various reactor design parameters such as the core multiplication factor, breeding ratio, heavy metal mass change, power distribution, and summary of neutron balance. In addition, the perturbation analysis provides the reactor kinetic parameters and reactivity feedback coefficients for the inherent safety analysis of the core. The integral reactivity parameters of the quasi‐static reactivity balance analysis demonstrate that the new core is inherently safe in cases of unprotected loss of flow, unprotected loss of heat sink, and unprotected transient over power. Copyright © 2016 John Wiley & Sons, Ltd.

Core design of long‐cycle small modular lead‐cooled fast reactor

“…Finally, the nodal diffusion and depletion calculations are carried out by REBUS‐3 using these broad‐group cross sections. Figure shows the fast reactor analysis flow.…”

“…The core type considered in this paper is the onion zoning core. It is proved by Park et al that this approach improves the core breeding capability and can lead to a breed and burn (B&B) reactor . In SMLFR, the main nuclear fuel cycle is a uranium cycle, with 235 U the fissile material and 238 U the fertile material.…”

“…As a result of previous sensitivity analyses, two types of core were selected, with different numbers of driver and reflector assemblies. The core configuration was selected as the best performance for the breed and burn concept and for achieving an active core diameter less than the maximum value of 1.7 m. The radial and the axial fuel arrangements of the two core candidates (TYPE I and TYPE II, referred with modification from Park et al 260 MW SMSFR and UCFR‐1000 proposed by Tak et al) are shown in Figure , and Table summarizes the core parameters of the two core candidates proposed for optimization study. The two candidates are analyzed in the next section in terms of k eff and core breeding ratio trends during depletion for different values of enrichment in the LEU region.…”

“…By applying the QSRB method, the self‐controllability and inherent safety for LFR core are ensured if the following criteria are satisfied: A , B , and C are all negative, which guarantees the power and temperature control in the core. A / B < 1, which guarantees control of the asymptotic temperature rise under ULOF condition. 1 < C Δ T c < 2, which guarantees an appropriate balance between ULOHS and the chilled inlet temperature (the opposite circumstance to the loss of heat sink event, in which the secondary coolant system removes heat more efficiently than it was designed to) and maintains the balanced state of a plant. Δ ρ TOP /| B | < 1 to ensure the reactivity control in UTOP scenarios, where Δ ρ TOP is the ratio of the reactivity that control systems need to compensate for the number of operation control assemblies in the reactor core. …”

“…Numerous LFR concepts have been developed to satisfy these requirements. Park et al has proposed the 260 MW long‐life fast reactor for a 28.5‐year operation without refueling and a small burnup reactivity swing by utilizing the breed and burn (B&B) concept . The 2600 MW ultralong‐cycle fast reactor (UCFR‐1000) proposed by Tak et al can operate for 60 years without refueling and also adopts the B&B strategy .…”