A NEW NEUTRON MULTIPLICITY COUNTER FOR THE MEASUREMENT OF IMPURE PLUTONIUM METAL AT WESTINGHOUSE SAVANNAH RIVER SITE

Year
1998
Author(s)
D.G. Langner - Los Alamos National Laboratory
Steven D. Salazar - Los Alamos National Laboratory
Martin R. Sweet - Los Alamos National Laboratory
Kenneth E. Kroncke - Los Alamos National Laboratory
Abstract
A new neutron multiplicity counter has been designed, fabricated, characterized, and installed to assay impure plutonium metal buttons from the FB-line at the Westinghouse Savannah River Site (WSRS). This instrument incorporates the performance characteristics of the Pyrochemical or Inplant Multiplicity Counter with the package size of the Plutonium Scrap Multiplicity Counter. In addition, state-of-the-art features such as the derandomizer circuit and separate ring outputs have been added. The counter consists of 113 71-cm active length 3He tubes in a polyethylene moderator. Its efficiency for 252Cf is 57.8%, the highest of any multiplicity counter to date. Its dieaway time is 50.4 ms and its deadtime is 50 ns. In this paper, we will present the characterization data for the counter and the results of preliminary metal measurements at WSRS. We will also discuss the new challenges the impure metal buttons from FB-line are presenting to the multiplicity counting technique.