S. Saavedra, W. Charlton, A. Solodov, and M. Ehinger,
"Using NDA Techniques to Improve Safeguards Metrics on Burnup Quantification and Plutonium Content in LWR SNF,"
Proceedings of the 2010 Annual Meeting of the Institute of Nuclear Materials Management
, Baltimore, MD, July 11-15, 2010.
Globally, there exists a long history in reprocessing in
evaluation of the shipper/receiver difference (SRD) on
spent nuclearfuel (SNF) received and processed. Typically, the
declared shipper's values for uranium and plutonium in SNF (based
on calculations involving the initial manufacturer's data and
reactor operating history) are used as the input quantities to the
head-end process of the facility. Problems have been encountered
when comparing these values with measured results of the input
accountability tank contents. A typical comparison yields a
systematic bias indicated as a "loss" of 5 - 7 percent of the
plutonium (Pu) and approximately 1 percent for the uranium (U).
Studies suggest that such deviation can be attributed to the
non-linear nature of the axial burnup values of the SNF. Oak Ridge
National Laboratory and Texas A&M University are
co-investigating the development of a new method, via
Nondestructive Assay (NDA) techniques, to improve the accuracy in
burnup and Pu content quantification. Two major components have
been identified to achieve this objective. The first component
calculates a measurement-based burnup profile along the axis of a
fuel rod. Gamma-ray data is collected at numerous locations along
the axis of the fuel rod using a High Purity Germanium (HPGe)
detector designed for a wide range of gamma-ray energies. Using two
fission products, 137Cs and 134Cs, the burnup is
calculated at each measurement location and a profile created along
the axis of the rod based on the individual measurement locations.
The second component measures the U/Pu ratio using an HPGe detector
configured for relatively low-energy gamma-rays including xrays.
Fluorescence x-rays from U and Pu are measured and compared to the
U/Pu ratio determined from a destructive analysis of the sample.
This will be used to establish a relationship between the measured
and actual values. This relationship will be combined with the
burnup analysis results to establish a relationship between fission
product activity and Pu content. It is anticipated that this new
method will allow receiving facilities to make a limited number of
NDA, gamma-ray, measurements to confirm the shipper declared values
for burnup and Pu content thereby improving the SRD.
Associated Project(s):Development of Advanced Safeguards Measurement Techniques Using the Coupled End-to-End (CETE) Demonstration at ORNL