Burn-up characteristics of ADS system utilizing the fuel composition from MOX PWRs spent fuel

doi:10.1016/S0306-4549(02)00033-6

Annals of Nuclear Energy

Volume 29, Issue 18, December 2002, Pages 2173-2186

https://doi.org/10.1016/S0306-4549(02)00033-6 Get rights and content

Abstract

Burn-up characteristics of accelerator-driven system, ADS has been evaluated utilizing the fuel composition from MOX PWRs spent fuel. The system consists of a high intensity proton beam accelerator, spallation target, and sub-critical reactor core. The liquid lead–bismuth, Pb–Bi, as spallation target, was put in the center of the core region. The general approach was conducted throughout the nitride fuel that allows the utilities to choose the strategy for destroying or minimizing the most dangerous high level wastes in a fast neutron spectrum. The fuel introduced surrounding the target region was the same with the composition of MOX from 33 GWd/t PWRs spent-fuel with 5 year cooling and has been compared with the fuel composition from 45 and 60 GWd/t PWRs spent-fuel with the same cooling time. The basic characteristics of the system such as burn-up reactivity swing, power density, neutron fluxes distribution, and nuclides densities were obtained from the results of the neutronics and burn-up analyses using ATRAS computer code of the Japan Atomic Energy research Institute, JAERI.

Introduction

Since early 1990s, management of high level wastes (HLW) has become one of the top priority issues with the rise of development and utilization of nuclear energy. The Japan Atomic Energy Research Institute, JAERI has carried out research and development (R&D), on a new technology for partitioning and transmutation, (P–T), of MAs contained in HLW. The R&D was mainly dedicated to improve the design of an accelerator-driven system, ADS. Here, the ADS has been proposed as a priority candidate for self-consistence of wastes management and disposal of the nuclear energy system. Although the ADS has been selected as the most probable choice for a transmutation system of HLW, it still must be studied intensively and carefully. So far no experience relating to such a system exists.

The ADS comprises of a high intensity proton accelerator, a spallation target, and a sub-critical core region. Neutrons produced by means of a spallation reaction of a liquid Pb–Bi target drives the sub-critical core (Takizuka et al., 2000). Most researchers have developed the target and coolant materials (Tsujimoto et al., 1998, Sasa et al., 1999), but only view researches were conducted on the characterization of burn-up and related aspects. It is important to study the burn-up characteristics using the fuel composition from light water reactors (LWRs), spent fuel.

This paper report the studies of burn-up characteristics of ADS using spent fuel composition of mixed oxide (MOX), obtained from pressurized water reactors (PWRs). The objectives of the system are to destroy or to minimize the long-lived radionuclide wastes and to improve the long-term safety assurance in the management of HLW in order to develop the available transmutation system covering the future nuclear power plant based on PWRs technology. The main long-lived radionuclide to be transmuted are minor actinide isotopes, MA, consisting of neptunium, Np, americium, Am, curium, Cm, and plutonium, Pu.

The schematic diagram of the core calculation model of ADS is shown in Fig. 1. The liquid lead–bismuth as spallation target was at the center of the core region. The neutrons generated from spallation reactions were used to drive the sub-critical reactor core containing MAs+Pu introduced surrounding the target region. Different fuel compositions coming from different PWRs spent fuels together with nitride, N-15, enriched fuel were studied in order to see the performance of burn-up characteristics of ADS. The fast energy region was obtained by means of ADS, in which the MAs have fission threshold suitable for transmutation of MA isotopes. The configuration of the ADS core design in this neutronic calculation is given in Fig. 1.

In this calculation, the radii of the spallation target and the fuel in the core regions were set to 25 and 122 cm, respectively, while the core height was 100 cm. Thermal power generated in the core was 657.53 MWt with the energy of incident proton 1.5 GeV. The basic parameters of the system were obtained from the results of the neutronics and burn-up analyses, using actinide transmutation system, ATRAS Code System, of JAERI.

Section snippets

Transmutation characteristics

Design study of the transmutation system concerned was a full-scale power level system of 657.53 MWt sub-critical reactor for an accelerator-driven transmutation system. The liquid Pb–Bi was used both as spallation target material and coolant, aiming some advantages compared to sodium coolant. Moreover, it has a possibility to achieve a hard neutron energy spectrum, which avoids a positive void reactivity coefficient, to allow much lower system operating temperatures, and is favorable for

Effects of de-contamination factor of rare earth elements in pyro-chemical process to burn-up reactivity swing

Burn-up reactivity swing is one of the most important characteristics in the design of either a critical or sub-critical reactor in relation to the safety performance. In a sub-critical reactor, which is driven by an accelerator, effects of the initial fuel composition coming from several kinds of PWRs spent fuels related to the safety parameters should be well understood in order to get an advantage in the design. In this work, the evaluation on the effect of the fuel composition to the

Conclusions

Burn-up characteristics of the ADS system are mostly dependent upon the spent fuel compositions such as MOX fuel. The dependencies to the burn-up reactivity swing and the transmutation ratio result from the accumulation of several nuclides in MOX fuel caused by the following:

1.
Decontamination factor of rare earth (RE) in the pyro-chemical process could affect the negative burn-up reactivity swing. The effect of RE should be considered in the requirement of related safety parameter analysis (by

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