Abstracts and Available Papers Presented at the
1999 International RERTR Meeting

Conversion of the BER II

A Status Report

(H. Krohn, C.-O. Fischer, K. Haas)

Introduction

The BER II is a swimming pool reactor and mainly used for neutron scattering experiments. The BER II has been operating since 1973, and was upgraded from 1985 to 1991 to increase the neutron flux. Hereby, the power was increased from 5 to 10 MW. In addition the core size was decreased and was then encompassed by a beryllium reflector. Finally, a Cold Source was installed.

When the reactor restarted 1991 with HEU-fuel, we applied for a license to convert to LEU-fuel, which was granted in 1993. However, we still had to solve the problem of getting rid of our spent LEU-fuel assemblies. At that time, we also had about 30 HEU-assemblies on storage. This was the main reason why we only started conversion after August, 1997, when our HEU-fuel was used. At this point, we signed a contract with US-DOE dealing with the return of the spent fuel assemblies to the USA.

Since then, at each refueling, we have exchanged 2 to 5 HEU-fuel assemblies by LEU-assemblies. Each time we had to perform several measurements to ensure for the necessary safety requirements.

These measurements and their results are presented in the following paper.

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