Global environmental transport models for tritium

Conference · Tue Jan 01 04:00:00 EST 1985

OSTI ID:5619178

Killough, G G; Kocher, D C

In this paper we discuss some of the obstacles to the construction of credible models of global tritium transport for use in dose assessments. We illustrate these difficulties by comparing model predictions of environmental tritium levels with measurements. Monitoring of tritium has shown that specific activities in precipitation over land are typically higher by a factor of three to four than those in precipitation over the oceans. Experience with modeling CO/sub 2/ turnover in the oceans has led to the conclusion that two-box reservoir models of the ocean often give unsatisfactory representations of transient solutions. Failure to consider these factors in global models can lead to distorted estimates of collective dose and create difficulties in validation of the model against real data. We illustrate these problems with a seven-box model recommended by the National Council on Radiation Protection and Measurements in which we forced the atmospheric compartment to reproduce an exogenous function based on historic observations of HTO in precipitation at 50/sup 0/N. The fresh water response underestimates data from the Ottawa River by a factor of about five, and the ocean surface response overestimates tritium data from the surface waters of the Northern Pacific by nearly an order of magnitude. Revision of the model to include (1) separate over-land and over-ocean compartments of the atmosphere and (2) a box-diffusion model of the subsurface ocean brings the discrepant responses into good agreement with the environmental data. In a second exercise, we used a latitudinally disaggregated model and replaced a tropospheric compartment in the northern hemisphere by historic precipitation data. The model's response greatly underestimates the tritium specific activity in the southern hemisphere. These exercises lead us to doubt that a proper global transport model for tritium is available at present for collective dose assessment. 12 refs., 3 figs.

• Research Organization: Oak Ridge National Lab., TN (USA)
• DOE Contract Number: AC05-84OR21400
• OSTI ID: 5619178
• Report Number(s): CONF-850405-7; ON: DE85011437
• Country of Publication: United States
• Language: English

Related Subjects

500300* -- Environment
Atmospheric-- Radioactive Materials Monitoring & Transport-- (-1989)
510301 -- Environment
Terrestrial-- Radioactive Materials Monitoring & Transport-- Soil-- (-1987)
520301 -- Environment
Aquatic-- Radioactive Materials Monitoring & Transport-- Water-- (1987)
54 ENVIRONMENTAL SCIENCES
ATMOSPHERIC PRECIPITATIONS
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
DATA
EARTH ATMOSPHERE
ECOLOGICAL CONCENTRATION
ENVIRONMENTAL TRANSPORT
EXPERIMENTAL DATA
GLOBAL ASPECTS
HYDROGEN ISOTOPES
INFORMATION
ISOTOPES
LIGHT NUCLEI
MASS TRANSFER
MATHEMATICAL MODELS
NUCLEI
NUMERICAL DATA
ODD-EVEN NUCLEI
RADIOECOLOGICAL CONCENTRATION
RADIOISOTOPES
RADIONUCLIDE MIGRATION
SOILS
SURFACE WATERS
TRITIUM
YEARS LIVING RADIOISOTOPES