Gamma Transport Theory Analysis of the Three Mile Island Unit 2 Lower Head

The adjoint gamma transport theory method is used to analyze the postaccident gamma detector data from the Three Mile Island Unit 2 (TMI-2) reactor lower head. It is concluded that there are two layers of materials at position L-11 of the TMI-2 reactor lower head. The lower layer contains predominantly nonfuel materials and the upper layer contains predominantly fuel. It is also concluded that ¹³⁷Cs, ^137mBa, ⁶⁰Co, and ¹⁵⁴Eu have the highest contribution to the detector signal. Finally, it is shown that the detector field of view is very small; hence, further evidence is needed to generalize these results to the remainder of the TMI-2 lower head.