WASTE CRATE ASSAY SYSTEM (WCAS): ASSAY SOLUTIONS FOR VERY LARGE REMOTE HANDLED CRATES Page: 2 of 16
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WASTE CRATE ASSAY SYSTEM (WCAS): ASSAY SOLUTIONS FOR VERY LARGE
REMOTE HANDLED CRATES
H. O. Menlove, P. M. Rinard, and T. K. Li
Los Alamos National Laboratory
Los Alamos, New Mexico 87545
M. Romero and J. B. Franco
BNFL Instruments, Inc.
Santa Fe, NM
K. Hiruta and S. Nasuno
An advanced passive neutron counter has been designed and fabricated to measure the plutonium content
in large remote handled (RH) waste crates. The waste crate assay system (WCAS) was developed under
an agreement between Los Alamos National Laboratory, Japan Nuclear Fuel Limited (JNFL), and BNFL
Instruments Inc. (BII) to measure the plutonium content in the waste generated in the Rokkasho
reprocessing facility. The primary goal of the design was to produce an assay system for large waste
containers. The system also includes 200-L drum pallet assay capability. The measurements are based on
neutron-time correlation counting of the passive neutron emissions from the 240Pu, and the plutonium
isotopic ratios are used to calculate the total plutonium. The system is designed for both RH waste and
low-activity plutonium waste. The system permits the measurement of the singles, doubles, and triples
rates and the multiplicity mode analysis is used together with the "add-a-source" method to correct for the
matrix materials in the crates. In the multiplicity analysis, the efficiency for counting the neutrons
emitted from the crate is directly calculated from the three measured rates. For improved detectability
limits, advanced methods have been incorporated in the WCAS-A to reduce the cosmic-ray neutron
backgrounds. These methods include statistical filters and truncation of high-multiplicity events. The
paper describes the WCAS-A design, performance, and calibration.
Los Alamos National Laboratory (LANL) was contracted by Japan Nuclear Fuels Limited (JNFL)
in 1998 to develop two nondestructive assay systems for the spent fuel reprocessing plant under
construction at Rokkasho, Japan. LANL teamed with BNFL Instruments Inc. (BII) to fabricate and
deploy these systems, which can accommodate a maximum crate whose volume is about forty 200-L
drum equivalents. The WCAS systems (named A and B) are targeted at making both domestic and
international safeguards related measurements on dry, reprocessing waste. The WCAS-A system was
designed to work in high radiation fields up to 1.1 Gy/h (110 R/h) for RH debris, with an average 240Pueff
content of 40%; the WCAS-B system was designed to measure only low-activity non-RH waste. This
paper will focus on the WCAS-A system for the RH wastes.
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MENLOVE, H. O.; RINARD, P. M. & AL, ET. WASTE CRATE ASSAY SYSTEM (WCAS): ASSAY SOLUTIONS FOR VERY LARGE REMOTE HANDLED CRATES, article, October 1, 2001; New Mexico. (digital.library.unt.edu/ark:/67531/metadc719682/m1/2/: accessed September 25, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.