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DNFSB spots possible bottleneck in Hanford’s waste vitrification
Workers change out spent 27,000-pound TSCR filter columns and place them on a nearby storage pad during a planned outage in 2023. (Photo: DOE)
While the Department of Energy recently celebrated the beginning of hot commissioning of the Hanford Site’s Waste Treatment and Immobilization Plant (WTP), which has begun immobilizing the site’s radioactive tank waste in glass through vitrification, the Defense Nuclear Facilities Safety Board has reported a possible bottleneck in waste processing. According to the DNFSB, unless current systems run efficiently, the issue could result in the interruption of operations at the WTP’s Low-Activity Waste Facility, where waste vitrification takes place.
During operations, the LAW Facility will process an average of 5,300 gallons of tank waste per day, according to Bechtel, the contractor leading design, construction, and commissioning of the WTP. That waste is piped to the facility after being treated by Hanford’s Tanks Side Cesium Removal (TSCR) system, which filters undissolved solid material and removes cesium from liquid waste.
According to a November 7 activity report by the DNFSB, the TSCR system may not be able to produce waste feed fast enough to keep up with the LAW Facility’s vitrification rate.
Mathew W. Swinney, Charles M. Folden III, Ronald J. Ellis, Sunil S. Chirayath
Nuclear Technology | Volume 197 | Number 1 | January 2017 | Pages 1-11
Technical Paper | doi.org/10.13182/NT16-76
Articles are hosted by Taylor and Francis Online.
A terrorist attack using an improvised nuclear device is one of the most serious dangers facing the United States. The work presented here is part of an effort to improve nuclear deterrence by developing a methodology to attribute weapons-grade plutonium to a source reactor by measuring the intrinsic physical characteristics of the interdicted plutonium. In order to demonstrate the developed methodology, plutonium samples were produced from depleted uranium dioxide (DUO2) surrogates irradiated in a fast-neutron environment. In order to replicate the neutron flux in a fast-neutron-spectrum reactor and obtain experimental samples emulating weapons-grade plutonium produced in the blanket of a fast breeder reactor, DUO2 samples were placed in a gadolinium sheath and irradiated in the High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory. Previous computational work on this topic identified several fission products that could be used to distinguish between reactor types (fast and thermal reactors), specifically: 137Cs, 134Cs, 154Eu, 125Sb, 144Ce, 85Rb, 147Pm, and 150Sm along with the plutonium isotopes. Simulations of the fast neutron irradiation of the DUO2 fuel surrogates in the HFIR were carried out using the Monte Carlo radiation transport code MCNPX 2.7. Comparisons of the predicted values of plutonium and fission product concentrations to destructive and nondestructive assay measurements of neutron-irradiated DUO2 surrogates are presented here. The agreement between the predictions and gamma spectroscopic measurements in general were within 10% for 134Cs, 137Cs, 154Eu, and 144Ce. Additional experimental results (mass spectroscopy) agreed to within 5% for the following isotopes: 85Rb, 147Pm, 150Sm, 154Eu, 148Nd, 144Ce, and 239Pu. Two indicator isotopes previously suggested to differentiate between the reactor types were ruled out for use in the attribution methodology; 125Sb was ruled out due to the difficulty in accurately predicting its concentration, and 242Pu was ruled out because of its low content in weapons-grade plutonium.
