International Topical Meeting on Nuclear Research Applications and Utilization of Accelerators

4-8 May 2009, Vienna

Precisions Improvement of Dynamic Calculation Code for Accelerator Driven System

M. Suzuki¹, T. Iwasaki¹, N. Aizawa¹, T. Sugawara², and T. Sato¹

¹Tohoku University, Sendai, Japan
²Japan Atomic Energy Agency Japan

Corresponding Author: naoto aizawa021@neutron.qse.tohoku.ac.jp

An Accelerator Driven System (ADS) has been widely studied for transmuting Minor Actinide
(MA) and Long-Lived Fission Product (LLFP) in High Level Waste (HLW). An ADS has high efficiency for transmuting those. There are many R&D (Research and Development topics about ADS. Dynamics of ADS is one of the topics. However, it has been studied few since there are no dynamics calculation codes which are able to treat dynamic changes of spallation neutron source and accelerator parameters (beam intensity, energy, diameter, etc.).

The ADS dynamics calculation code DSE (Dynamics calculation code system for Sub-critical system with External neutron source) was developed in our laboratory. The DSE code consists of a neutronics calculation module and a thermal-hydraulics calculation module. The DSE code can calculate time variations of thermal power, neutron flux, fuel temperature, cladding temperature and coolant temperature distributions by treating the dynamic changes of the accelerator parameters directly.

The improvement of precisions is needed to study dynamics in more detail. The purpose of this study was to improve precisions of each module. For the purpose of this study, some improvements were conducted. In the neutronics calculation, the transport code was employed instead of diffusion one to consider angular distributions of neutron flux. The transport code is efficient to improve the precision of neutronics calculations. In the thermal-hydraulics calculation, databases of the temperature correlations for thermal properties of core structures (Pb-Bi, etc.) were improved. They are useful to improve the precision of thermal-hydraulics calculations.

Calculation results by the improved DSE code were evaluated using experimental results and the other calculation results. The results of a sub-critical transient experiment at TRACY (TRAnsient experiment Critical facilitY) were compared to verify neutronics calculations. The OECD/NEA dynamics benchmarks about beam-trip transients on 80 MWt XADS were also compared to verify thermal-hydraulics calculations. As a result, calculations agreed well with each comparison data. These results indicate that precisions of calculations are improved in each module.

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