Fast Reactors and Accelerator Driven Systems Knowledge Base

Conference Article: Core physics performance of recycled LWR discharge TRU oxide fuel in a GT/AD-MHR

T.A. Taiwo, Y. Gohar, P.J. Finck

Abstract

The core physics performance of recycled LWR-discharge-transuranic (TRU) oxide fuel in a gas-cooled and accelerator driven (GT/AD-MHR) system has been assessed for the U.S. DOE accelerator transmutation of waste (ATW) program. This activity is part of preliminary design studies being performed at ANL and LANL to define and compare candidate ATW systems. The studies have focused primarily on the blanket component of the overall system, since the choice of blanket technologies is an important technical decision faced in designing an ATW system. The gas-cooled system point design is a 600 MWt hybrid system operated in the critical mode for three cycles and in a subcritical accelerator-driven mode for a subsequent single cycle. The transmuter contains both thermal and fast spectrum transmutation zones. The thermal zone is fueled with the “fresh” LWR-discharge TRU oxide fuel (encapsulated as TRISO-coated particles); the fast zone is fueled with TRU-oxide fuel that has been burned in the thermal region for three critical cycles and one additional accelerator-driven cycle. The fuel loaded into the fast zone is irradiated for four additional cycles. This design ensures the high consumption of the high thermal-neutron-cross-section Pu isotopes in the thermal spectrum zone, and the relatively enhanced consumption of minor actinides in the fast-spectrum zone. Single batch and three-batch fuel loading schemes for the GT/AD-MHR system have been evaluated using Monte Carlo and deterministic codes to determine the feasibility of achieving high consumption levels without exceeding reactivity and power density limits. The studies revealed the potential for high consumption of Pu-239 (97%), total Pu (71%), and total TRU (64%) in the system. These consumption levels are however lower than values obtained in previous studies in which weapons-grade plutonium is employed as fuel, because the latter fuel is more reactive and hence permits a longer cycle length at the same operating power. The higher consumption levels in the gas-cooled system, relative to say a fast system is due to the relatively lower fuel inventory required in the gas-cooled system. Our evaluation also confirmed the need for burnable absorber, most likely Er-167, for both suppressing the initial excess reactivity and ensuring a negative temperature coefficient under all operating conditions. Additionally, current results suggest that it may be preferable to use a double strata thermal critical system and fast subcritical system to achieve nearly complete destruction of the TRU oxide fuel.

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key words: Fast Neutron Spectrum Systems, Nuclear Technology
Reference:
Proceedings of a Committee Meeting (TCM) on “Core Physics and Engineering Aspects of Emerging Nuclear Energy Systems for Energy Generation and Transmutation” held in Argonne, Illinois, U.S.A., 28 November - 1 December 2000
International Atomic Energy Agency, Vienna (Austria)
IAEA-TECDOC--1356, pp:120-133