Investigation of irradiated soil byproducts.

The high dose irradiation of windblown soil deposited onto the surface of spent nuclear fuel is of concern to long-term fuel storage stability. Such soils could be exposed to radiation fields as great as 1.08 x 10(-3) C/kg-s (15,000 R/hr) during the 40-year anticipated period of interim dry storage prior to placement at the proposed national repository. The total absorbed dose in these cases could be as high as 5 x 10(7) Gy (5 x 10(9) rads). This investigation evaluated the potential generation of explosive or combustible irradiation byproducts during this irradiation. It focuses on the production of radiolytic byproducts generated within the pore water of surrogate clays that are consistent with those found on the Idaho National Engineering and Environmental Laboratory. Synthesized surrogates of localized soils containing combinations of clay, water, and aluminum samples, enclosed within a stainless steel vessel were irradiated and the quantities of the byproducts generated measured. Two types of clays, varying primarily in the presence of iron oxide, were investigated. Two treatment levels of irradiation and a control were investigated. An 18-Mev linear accelerator was used to irradiate samples. The first irradiation level provided an absorbed dose of 3.9 x 10(5)+/-1.4 x 10(5)Gy (3.9 x 10(7)+/-1.4 x 10(7) rads) in a 3-h period. At the second irradiation level, 4.8 x 10(5)+/-2.0 x 10(5)Gy (4.8 x 10(7)+/-2.0 x 10(7) rads) were delivered in a 6-h period. When averaged over all treatment parameters, irradiated clay samples with and without iron (III) oxide (moisture content = 40%) had a production rate of hydrogen gas that was a strong function of radiation-dose. A g-value of 5.61 x 10(-9)+/-1.56 x 10(-9) mol/J (0.054+/-0.015 molecules/100-eV) per mass of pore water was observed in the clay samples without iron (III) oxide for hydrogen gas production. A g-value of 1.07 x 10(-8)+/-2.91 x 10(-9) mol/J (0.103+0.028 molecules/100-eV) per mass of pore water was observed in the iron (III) oxide containing clay samples for hydrogen gas production. This value was noticeably larger when the samples were spiked with both KCl and KNO3 salts. The ratio of oxygen to nitrogen gas was observed to increase as a function of absorbed dose particularly in the presence of both KCl and KNO3 salts. The creation of radiolytic byproducts produced an observable but small increase in headspace pressure. Temperature increases during irradiation were not observed. Additionally, KCl and KNO3 salts added to the clays enhanced nitrite production as a function of radiation-dose and the type of clay considered. The addition of aluminum to these samples had no statistically discernable impact at the alpha = 0.05 level. Generation of the irradiation products, hydrogen peroxide and hydrogen gas also depended upon the type of clay irradiated and the presence of both KCl and KNO3 salts and the total dose received.

A Monte Carlo investigation of electron backscattering.

Kearsley's, Haider's and Frujinoiu's cavity expressions depend upon the existence of reliable data on electron backscattering in different media. These data are not available in the literature. By using MCNP, backscatter distributions and their saturation values were obtained for electron beams with energies between 0.1 MeV and 9 MeV traversing different materials such as polyethylene, solid water, lithium fluoride, aluminium, copper and lead. The data obtained using MCNP show that electron backscatter probability most strongly depends on the scatterer's effective atomic number and electron energy. Backscatter probability becomes less dependent on energy and is mostly a function of the effective atomic number of the scatterer for electron energies below 0.5 MeV. For low atomic number materials MCNP data suggest that the backscatter saturation values are distributed linearly with the effective atomic number of the scatterer for all energies investigated.

An evaluation of 222Rn concentrations in Idaho groundwater.

Factors potentially correlated with 222Rn concentrations in groundwater were evaluated using a database compiled by the U.S. Geological Survey. These included chemical and radiological factors, and both well depth and discharge rate. The 222Rn concentrations contained within this database were examined as a function of latitude and longitude. It was observed that the U.S. Geological Survey sample locations for 222Rn were not uniformly distributed throughout the state. Hence, additional samples were collected in southeastern Idaho, a region where few 222Rn in water analyses had been performed. 222Rn concentrations in groundwater, in Idaho, were found using ANOVA (alpha = 0.05) to be independent of the chemical, radiological, and well parameters thus far examined. This lack of correlation with other water quality and well parameters is consistent with findings in other geographical locations. It was observed that an inverse relationship between radon concentration and water hardness may exist.