A comprehensive appraisal of {sup 241}Am in soils around Rocky Flats, Colorado

Journal Article · Sun Sep 01 04:00:00 EDT 1996 · Health Physics

DOI:https://doi.org/10.1097/00004032-199609000-00012· OSTI ID:380955

Litaor, M I ^[1]; Allen, L ^[2]

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1. Univ. of Colorado, Boulder, CO (United States)
2. Mine Reserves Associates, Inc., Wheat Ridge, CO (United States)

Soils east of Rocky Flats Plant (RFETS) near Golden, Colorado, were contaminated with actinides because of accidental release of oils laden with plutonium isotopes. Consequently, these soils were contaminated by {sup 241}Am due to radioactive decay of {sup 241}Pu (t{sup {1/2}} = 14.4 y). A spatial analysis of {sup 241}Am activity in soils east of RFETS was conducted to elucidate the magnitude and the mode of {sup 241}Am dispersion in the soil environment. {sup 241}Am activity of 178 soil samples ranged from 0.037 Bq Kg{sup {minus}1} to 10,004 Bq kg{sup {minus}1} with a mean of 214 Bq kg{sup {minus}1}, median of 7.28 Bq kg{sup {minus}1}, standard deviation of 942 Bq kg{sup {minus}1}, and a coefficient of variation of 4.3. Spatial analysis of {sup 241}Am in soils around RFETS was conducted using indicator kriging, which is a nonparametric technique especially suitable to model a conditional cumulative distribution function (ccdf) of highly skewed environmental data such as {sup 241}Am. The (ccdf) was used to generate an E-type (mean of the conditional cdf) surface. The resulted surfaces were consistent with the hypothesis that the westerly winds were the dominant mechanism of americium dispersal. The spatial distribution and dispersal mechanisms of {sup 241}Am were similar to those of {sup 239+240}Pu. The ccdf was also used to construct probability of exceedence maps of {sup 241}Am in soils. For the purpose of this report two threshold values for the probability maps were selected: (1) the mean measured background activity of {sup 241}Am (0.4 Bq kg{sup {minus}1}), and (2) the programmatic preliminary remediation goal for residential occupancy scenario (87.7 Bq kg{sup {minus}1}). The probability-of-exceedance maps provide estimates of spatial uncertainty associated with each threshold. The E-type maps in conjunction with the probability-of-exceedance maps provide a robust framework for future cleanup options and land use decisions. 34 refs., 7 figs., 4 tabs.

• Sponsoring Organization: USDOE
• OSTI ID: 380955
• Journal Information: Health Physics, Journal Name: Health Physics Journal Issue: 3 Vol. 71; ISSN HLTPAO; ISSN 0017-9078
• Country of Publication: United States
• Language: English

Related Subjects

05 NUCLEAR FUELS
54 ENVIRONMENTAL SCIENCES
ACTINIDES
AMERICIUM
AMERICIUM 241
CONTAMINATION
ENVIRONMENTAL EFFECTS
LAND USE
PLUTONIUM
RADIOECOLOGICAL CONCENTRATION
ROCKY FLATS PLANT
SOILS
SPATIAL DISTRIBUTION