Donald McEachern

Deep-Burn: making nuclear waste transmutation practical

Abstract In the Deep-Burn concept, destruction of the transuranic component of light water reactor (LWR) waste is carried out in one burn-up cycle, accomplishing the virtually complete destruction of weapons-usable materials (Plutonium-239), and up to 90% of all transuranic waste, including the near totality of Neptunium-237 (the most mobile actinide in the repository environment) and its precursor, Americium-241. Waste destruction would be performed rapidly, without multiple reprocessing of plutonium, thus eliminating the risks of repeated handling of weapons-usable material and limiting the generation of secondary waste. There appears to be no incentive in continuing the destruction of waste beyond this level. An essential feature of the Deep-Burn Transmuter is the use of ceramic-coated fuel particles that provide very strong containment and are highly resistant to irradiation, thereby allowing very extensive destruction levels (“Deep Burn”) in the one pass, using gas-cooled modular helium reactor (MHR) technology developed for high-efficiency energy production. The fixed moderator (graphite) and neutronically transparent coolant (helium) provide a unique neutron energy spectrum to cause Deep-Burn, and inherent safety features, specific to the destruction of nuclear waste, that are not found in any other design. Deep-Burn technology could be available for deployment in a relatively short time, thus contributing effectively to waste problem solutions. Extensive modeling effort has led to conceptual Deep-Burn designs that can achieve high waste destruction levels (70% in critical mode, 90% in with a supplemental subcritical step) within the operational envelope of commercial MHR operation, including long refueling intervals and the highly efficient production of energy (approximately 50%). To the plant operator, a Deep-Burn Transmuter will be identical to its commercial reactor counterpart.

Project Deep-Burn: Development of Transuranic Fuel for High-Temperature Helium-Cooled Reactors

The helium-cooled, graphite-moderated Very High Temperature Reactor (VHTR) has become the centerpiece of the U.S. Department of Energy’s (DOE) Next Generation Nuclear Plant (NGNP) program. The NGNP program aims to construct a VHTR prototype, with the participation of industry, by the year 2021.Copyright

The Bench-Scale Facility for Fabrication of TRISO-Coated Plutonium Fuels

The program to develop the GT-MHR [1] and its coated particle fuel for disposal of excess Russian weapons plutonium is being carried out by Russian nuclear labs and industrial organizations shown in Table 1 with support from US specialists at General Atomics and Oak Ridge National Laboratory. Rosatom of Russia and the U. S. National Nuclear Security Agency each provide 50% of the funds for the program.Copyright

The Analysis of the Thorium-Fueled Modular Helium-Cooled Reactor

The potential of thorium fertile fuel has been evaluated for a graphite-moderated MHR (Modular Helium Reactor) from the perspective of a self-sustainable U233-Th fuel cycle in the MHR. The 3-D core analyses have been performed with the thermal-hydraulic-coupled computer code systems (HELIOS-MASTER). The feasibility of a self-sustainable U233-Th fuel cycle in MHR was evaluated for a simplified equilibrium fuel cycle. A mixed oxide fuel (ThO2 -UO2 ) was used. Whole-core analysis was performed with the MASTER code for various core configurations. In the core analysis, a 3-batch radial fuel shuffling scheme was adopted to find an equilibrium fuel cycle. Three types of fuel blocks were considered: a homogeneous fuel arrangement and two seed-blanket arrangements. It was found that a near self-sustainable U233-Th fuel cycle (conversion ratio = 0.95∼0.97) is feasible for the MHRs with the appropriate U-233 and Th-232 loadings. To achieve a high conversion ratio while maintaining a long cycle length, it is essential to maximize the thorium loading (∼30 tons) and at the same time soften the neutron spectrum to achieve sufficient reactivity. In order to achieve conversion ratios over 0.95 and an 18-month cycle length, the moderator volume needs to be increased with respect to the regular MHR design. Also, removing the inner graphite reflectors increases noticeably the core performance in terms of the conversion ratio and cycle length. A special seed-blanket block configuration (ISB, with seed and blanket fuels in the inner and outer regions of a block, respectively) provides a superior conversion ratio with respect to a homogeneously fueled block, whereas reversing the placement of seed and blanket in the ISB block configuration (with seed fuels in the outer zone) results in a worse performance. In the case of the U233-Th fuel cycle, the fissile (U233+U235) fraction in the discharged fuel is almost 90%. Denaturing of the uranium vector in the self-sustainable U233-Th fuel was investigated by adding 10% LEU in the fuel, to make the initial fissile fraction ∼20.5%. Neutronic analysis of the operation with denatured fuel reveals that the conversion ratio is substantially reduced and the available cycle length is much shorter.© 2008 ASME

A Distributed Fiber Optic Sensor Network for Online 3-D Temperature and Neutron Fluence Mapping in a VHTR Environment

Robust sensing technologies allowing for 3D in-core performance monitoring in real time are of paramount importance for already established LWRs to enhance their reliability and availability per year, and therefore, to further facilitate their economic competitiveness via predictive assessment of the in-core conditions.