Impact of thermal spectrum small modular reactors on performance of once-through nuclear fuel cycles with low-enriched uranium

Abstract

Small modular reactors (SMRs) may offer potential benefits relative to large light water reactors, such as enhanced flexibility in deployment and operation. However, it is vital to understand the holistic impact of SMRs on nuclear fuel cycle performance. The focus of this paper is the fuel cycle impacts of light water SMRs in a once-through fuel cycle with low-enriched uranium fuel. A key objective of this paper is to describe preliminary neutronics and fuel cycle analyses conducted in support of the US Department of Energy, Office of Nuclear Energy, Fuel Cycle Options Campaign. The hypothetical light water SMR example case considered in these preliminary scoping studies is a "cartridge type" one-batch core with slightly less than 5.0% enrichment. The high-level issues identified and preliminary scoping calculations in this paper are intended to inform decision makers regarding potential fuel cycle impacts of one-batch thermal-spectrum SMRs. In particular, this paper highlights the impact of increased neutron leakage and a reduced number of batches on the achievable burnup of the reactor. Fuel cycle performance metrics for the simplified example SMR analyzed herein are compared with those for a conventional three-batch light water reactor (LWR) in the following areas: nuclear waste management, environmental impact,

Nuclear waste from small modular reactors

“…Since the NuScale iPWR components discussed will consist of stainless steel with a composition similar to that of a PWR (i.e., type 304/304L stainless steel) ( 8 , 19 ), these long-lived LILW estimates are not sensitive to differences in the steel composition and associated neutron absorption cross-sections.…”

“…Non-LWR SMRs will generate a similar array of radioisotopes for disposal but will employ fuels with markedly different bulk chemistries. Lacking fuel cladding, the liquid fuel envisioned for molten salt reactors will release gaseous fission products—including isotopes of Xe that decay to high-activity or long-lived isotopes of Cs—to an off-gas system, forming an HLW stream ( 8 , 53 ). Noble metal fission products, on the other hand, will precipitate throughout the reactor structures ( section 3.3.2 ).…”

“…Rather, the safety and the cost of managing a nuclear waste stream depend on its fissile, radiological, physical, and chemical properties ( 6 ). Reactor type, size, and fuel cycle each influence the properties of a nuclear waste stream, which in addition to HLW, can be in the form of low- and intermediate-level waste (LILW) ( 6 – 8 ). Although the costs and time line for SMR deployment are discussed in many reports, the impact that these fuel cycles will have on nuclear waste management and disposal is generally neglected ( 9 – 11 ).…”

Parametric neutronics analyses of lattice geometry and coolant candidates for a soluble-boron-free civil marine SMR core using micro-heterogeneous duplex fuel

“…The smaller core (500 MWth) will lose 7%, If the latter (3500 MWth) loses 3.5%. Furthermore, a recent SMR neutronic study by Oak Ridge National Lab (Brown et al, 2017) showed that ∼400 MWth SMR exhibits 6-8% leakage depending on the core loading patters and other input parameters.…”

Small modular reactor core design for civil marine propulsion using micro-heterogeneous duplex fuel. Part II: whole-core analysis

“…The smaller core (500 MWth) will lose 7%, If the latter (3500 MWth) loses 3.5%. Furthermore, a recent SMR neutronic study by Oak Ridge National Lab (Brown et al, 2017) showed that ⇠400 MWth SMR exhibits 6-8% leakage depending on the core loading patters and other input parameters. Since WIMS calculations assume an infinitely-large core and a small core is prone to larger leakage, we have assumed 7.5% leakage in this study.…”