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Title: MODELING ATMOSPHERIC RELEASES OF TRITIUM FROM NUCLEAR INSTALLATIONS

Abstract

Tritium source term analysis and the subsequent dispersion and consequence analyses supporting the safety documentation of Department of Energy nuclear facilities are especially sensitive to the applied software analysis methodology, input data and user assumptions. Three sequential areas in tritium accident analysis are examined in this study to illustrate where the analyst should exercise caution. Included are: (1) the development of a tritium oxide source term; (2) use of a full tritium dispersion model based on site-specific information to determine an appropriate deposition scaling factor for use in more simplified, broader modeling, and (3) derivation of a special tritium compound (STC) dose conversion factor for consequence analysis, consistent with the nature of the originating source material. It is recommended that unless supporting, defensible evidence is available to the contrary, the tritium release analyses should assume tritium oxide as the species released (or chemically transformed under accident's environment). Important exceptions include STC situations and laboratory-scale releases of hydrogen gas. In the modeling of the environmental transport, a full phenomenology model suggests that a deposition velocity of 0.5 cm/s is an appropriate value for environmental features of the Savannah River Site. This value is bounding for certain situations but non-conservative compared tomore » the full model in others. Care should be exercised in choosing other factors such as the exposure time and the resuspension factor.« less

Authors:
Publication Date:
Research Org.:
SRS
Sponsoring Org.:
USDOE
OSTI Identifier:
908927
Report Number(s):
WSRC-STI-2007-00027
TRN: US0703799
DOE Contract Number:
DE-AC09-96SR18500
Resource Type:
Conference
Resource Relation:
Conference: ANS Conference
Country of Publication:
United States
Language:
English
Subject:
08 HYDROGEN; 11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS; ACCIDENTS; DEPOSITION; DOCUMENTATION; ENVIRONMENTAL TRANSPORT; HYDROGEN; NUCLEAR FACILITIES; PARTICLE RESUSPENSION; SAFETY; SIMULATION; SOURCE TERMS; TRITIUM; TRITIUM COMPOUNDS; TRITIUM OXIDES; VELOCITY

Citation Formats

Okula, K. MODELING ATMOSPHERIC RELEASES OF TRITIUM FROM NUCLEAR INSTALLATIONS. United States: N. p., 2007. Web.
Okula, K. MODELING ATMOSPHERIC RELEASES OF TRITIUM FROM NUCLEAR INSTALLATIONS. United States.
Okula, K. Wed . "MODELING ATMOSPHERIC RELEASES OF TRITIUM FROM NUCLEAR INSTALLATIONS". United States. doi:. https://www.osti.gov/servlets/purl/908927.
@article{osti_908927,
title = {MODELING ATMOSPHERIC RELEASES OF TRITIUM FROM NUCLEAR INSTALLATIONS},
author = {Okula, K},
abstractNote = {Tritium source term analysis and the subsequent dispersion and consequence analyses supporting the safety documentation of Department of Energy nuclear facilities are especially sensitive to the applied software analysis methodology, input data and user assumptions. Three sequential areas in tritium accident analysis are examined in this study to illustrate where the analyst should exercise caution. Included are: (1) the development of a tritium oxide source term; (2) use of a full tritium dispersion model based on site-specific information to determine an appropriate deposition scaling factor for use in more simplified, broader modeling, and (3) derivation of a special tritium compound (STC) dose conversion factor for consequence analysis, consistent with the nature of the originating source material. It is recommended that unless supporting, defensible evidence is available to the contrary, the tritium release analyses should assume tritium oxide as the species released (or chemically transformed under accident's environment). Important exceptions include STC situations and laboratory-scale releases of hydrogen gas. In the modeling of the environmental transport, a full phenomenology model suggests that a deposition velocity of 0.5 cm/s is an appropriate value for environmental features of the Savannah River Site. This value is bounding for certain situations but non-conservative compared to the full model in others. Care should be exercised in choosing other factors such as the exposure time and the resuspension factor.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Wed Jan 17 00:00:00 EST 2007},
month = {Wed Jan 17 00:00:00 EST 2007}
}

Conference:
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  • The Chernobyl accident released a large amount of highly fractionated radioactive debris, including approximately 89 PBq of /sup 137/Cs. We calculated the resulting collective dose commitment to the Northern Hemisphere via the pathways of external exposure and ingestion of radionuclides withd food. We developed a rural/urban model of external dose and we used the PATHWAY model for ingestion. The results are a collective dose commitment of 630,000 person-Gy over the first year and 1,200,000 person-Gy over 50 years. 13 refs., 1 tab.
  • Burial sites for low-level radioactive wastes are situated on the Oak Ridge National Laboratory (ORNL) reservation. Releases of radioactive material from these sites into the ground- and surface waters, thus affecting nearby residents, has long been a concern. Such releases are considered the primary pathway of concern from low-level burial sites in humid regions. However, recent publications indicate that the atmospheric pathway, through which tritiated water vapor, /sup 14/C, /sup 85/Kr, /sup 222/Rn, and possibly other gases are emitted the trenches, dispersed downwind, and inhaled, may be an important impact from some low-level burial sites. This paper represents an attemptmore » to estimate the atmospheric contribution from the ORNL burial grounds, specifically the Solid Waste Storage Areas (SWSAs), to the total dose commitment resulting from ORNL burial ground operations. The results of this study indicate that tritium released from the ORNL SWSAs is not a significant contributor to the offsite dose received as a result of ORNL operations. The assumptions used in this study are conservative, but some additional work may be required before the problem can be dismissed. 8 refs.« less
  • A general model and corresponding computer code were developed to calculate personnel dose estimates from chronic releases via aqueous pathways. Potential internal dose pathways are consumption of water, fish, crustacean, and mollusk. Dose prediction from consumption of fish, crustacean, or mollusk is based on the calculated radionuclide content of the water and applicable bioaccumulation factor. 70-year dose commitments are calculated for whole body, bone, lower large intestine of the gastrointestinal tract, and six internal organs. In addition, the code identifies the largest dose contributor and the dose percentages for each organ-radionuclide combination in the source term. The 1974 radionuclide releasemore » data from the Savannah River Plant were used to evaluate the dose models. The dose predicted from the model was compared to the dose calculated from radiometric analysis of water and fish samples. The whole body dose from water consumption was 0.45 mrem calculated from monitoring data and 0.61 mrem predicted from the model. Tritium contributed 99 percent of this dose. The whole body dose from fish consumption was 0.20 mrem calculated from monitoring data and 0.14 mrem from the model. Cesium-134,137 was the principal contributor to the 70-year whole body dose from fish consumption.« less
  • Knowledge of particulate or gaseous removal from the atmosphere is becoming increasingly important for more realistic assessment of the risk involved with hazardous atmospheric releases. In transport models, this removal at the air-surface interface, exclusive of that due to precipitation (rain or snow), is often termed dry deposition. Uncertainties exist with respect to the values of the deposition velocity and to the accurate computation of deposition even if the deposition velocity were known. The purpose in this paper is to present a correlation to the deposition velocity and to examine the accuracy of a computational model proposed by Giorgi inmore » which the size distribution is broken into three sections (groups).« less