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Nuclear Safeguards Education Portal

Cf-252 Interrogation with Prompt Neutrons (CIPN)

Figure 29. (a) Horizontal cross section of CIPN; (b) Vertical cross section of CIPN. 

CIPN uses fission chambers in polyethylene in a Fork detector-like configuration with active interrogation from a Cf-252 neutron source to determine the total fissile content of a spent nuclear fuel assembly. Figure 29 shows a diagram with the horizontal cross section and vertical cross section of CIPN.  CIPN takes one measurement without the source and another measurement with the Cf-252 source.  The difference between the background and active count rates corresponds to the total fissile material content.  If a baseline measurement is taken prior to a partial defect diversion, CIPN has the capability to detect a partial defect of as little as 3 % of the total spent fuel mass (8 fuel rods from a 17 x 17 assembly).


  1. J. Hu, S.J. Tobin, H.O. Menlove, D. Henzlova, J. Gerhart, M.T. Swinhoe, and S. Croft, "Developing the Californium Interrogation Prompt Neutron Technique to Measure Fissile Content and to Detect Diversion in Spent Nuclear Fuel Assemblies," Journal of Nuclear Materials Management 40:3 (2012).