Year
1992
Abstract
An underwater video inspection of the Three Mile Island Unit 2 ,TMI-2, Reactor Vessel, RV,internals resulted in an approximate inventory of fuel. Uncertainties could not be determined for the video inspection requiring a different method to complete the assay. The preceeding paper, Ref. 1, described the passive neutron method and counting equipment used for the assay. This paper deals with the measurements and analysis used to determine the amount of residual fuel in the RV. The video inspection listed 30 locations that contained fuel. Lowering a simple counting system into the dry RV could only provide a fuel value that would be proportional to the original inventory. This technique would improve the assay, but a significantly better method was used. The measurement resolving power was enhanced by making neutron measurements during staged draining of the RV. This technique allowed the water to serve as a shadow shield. Using staged drain-down and passive neutron measurements, the total residual fuel in the TMI-2 RV was about 1320 kg UOj. At one standard deviation, the uncertainty was about 165 kg.