a b s t r a c tA TRISO-coated fuel thermo-mechanical performance study is performed for the fusion-fission hybrid Laser Inertial Fusion Engine (LIFE) to test the viability of TRISO particles to achieve ultra-high burn-up of Pu or transuranic spent nuclear fuel blankets. Our methodology includes full elastic anisotropy, time and temperature varying material properties, and multilayer capabilities. In order to achieve fast fluences up to 30 Â 10 25 n m À2 (E > 0.18 MeV), judicious extrapolations across several orders of magnitude of existing material databases have been carried out. The results of our study indicate that failure of the pyrolytic carbon (PyC) layers occurs within the first 2 years of operation. The particles then behave as a single-SiC-layer particle and the SiC layer maintains reasonably-low tensile stresses until the end-oflife. It is also found that the PyC creep constant, K, has a striking influence on the fuel performance of TRISO-coated particles, whose stresses scale almost inversely proportional to K. Conversely, varying the geometry of the TRISO-coated fuel particles results in little differences in terms of fuel performance.Ó 2010 Elsevier B.V. All rights reserved.
MotivationThe hybrid version of Laser Inertial Fusion Engine (LIFE) provides an attractive pathway to burn fissile materials such as excess weapons-grade Pu (WG-Pu) or transuranics from processed spent nuclear fuel, which can be burnt up to 99% fraction of initial metal atoms (FIMA) in less than a decade of operation [1]. The LIFE concept being pursued at Lawrence Livermore National Laboratory (LLNL) consists of a point source of 14-MeV neutrons produced by an inertial-confinement fusion engine enveloped by a Be neutron multiplier and a sub-critical fuel blanket. A schematic view of the LIFE engine configuration is shown in Fig. 1. Details about the geometry and the neutronic and thermal-hydraulic performance of the reactor have been given by Abbott et al. [2,3].The type of fuel to be used in the hybrid LIFE engine is still open to debate, including whether it should be in a liquid or solid form. The nominal engine design calls for 2-cm-diameter graphite pebbles containing %1-mm-diameter TRISO (TRI-structural ISOtropic) fuel particles suspended in liquid Li 2 BeF 4 ('flibe') [2]. A TRISO particle consists of an internal fuel kernel surrounded by a low-density pyrolytic carbon (PyC) buffer layer to moderate fission product recoils. The buffer layer is coated successively by an inner high-density PyC layer (iPyC), a thin SiC film, and an outer PyC (oPyC). The configuration of a TRISO particle, with its constituent layers is shown in Fig. 2. The preliminary fuel composition for the WG-Pu engine consists of 20% of Pu oxycarbide (PuCO) embedded in a ZrC matrix (80%). The main objective of this paper is to model TRISO-coated fuel particles under LIFE's conditions using the state-of-the-art in fuel performance modeling, and assess the feasibility of TRISO-coated fuel for LIFE's WG-Pu engine. Next, we review the TRISO-coated fuel perfor...