The 250-MW, boiling-water Gundremmingen reactor KRB-A in the Federal Republic of Germany (FRG) has been decommissioned. A joint USA/FRG/UK study, conceived by the U.S. Nuclear Regulatory Commission (NRC), is underway to evaluate material removed from the vessel for a critical assessment of power reactor versus test reactor environment effects. The vessel operated at ∼288°C; the inner-wall fluence estimate at decommissioning was about 1 × 10 19 n / cm 2 , E > 1 Me V .

This report describes test reactor irradiation assessments of a forging segment believed to be archive material from the KRB-A vessel fabrication. Charpy-V ( C v ), compact tension (CT), and tension test specimens were evaluated in five as-irradiated conditions and two postirradiation annealed conditions. With 288°C irradiations, the elevation in 100 MPa · m^1/2 temperature was found to match the elevation in 41-J temperature within 12°C. The latter elevation was predicted well by NRC's Regulatory Guide 1.99.

The L-C orientation data for the archive material versus the vessel trepans suggest a fluence-rate effect. However, the C-L orientation data do not. A test orientation dependence of radiation embrittlement sensitivity, described by the trepan material, but not the archive material, is responsible and is anomalous.