SYSTEM BY NEUTRON AND GAMMA-RAY DOSIMETRY

Neutron and gamma-ray dosimetry are being used for nondestructive assessment of the fuel distribution throughout the Three Mile Island Unit 2 (TMI-2) reactor core region and primary cooling system. The fuel con­ tent of TMI-2 makeup and purification Demineralizer A has been quantified with Si(Li) continuous gamma-ray spectrometry and solid-state track recorder (SSTR) neutron dosimetry. Results obtained from these gamma­ ray and neutron dosimetry experiments were 1.3 + 0.6 kg and 1.7 + 0.6 kg, respectively, for the fuel content of TMI-2 Demineralizer A. For fuel distribution characterization in the core region, results from SSTR neutron dosimetry exposures in the TMI-2 reactor cavity (i.e., the annular gap between the pressure vessel and the biological shield) will be presented. These SSTR results are consistent with the presence of a significant amount of fuel debris, equivalent to several fuel assemblies or more, lying at the bottom of the reactor vessel.