to the Log of the Activity of Fe3+ Versus pH (lA), and Plot of the Log AP/K Versus pH for Alunite (lB). 54 Plot of the Log AP/K Versus Sulfate Concentration for Gypsum (2A) and Celestite (2B) 58 TABLES Characterization of the Morton Ranch Clay Liner and Overburden Materials from the Morton Ranch, Dawn, and Lucky Me Mills •

Tritium is a potentially important environmental contaminant originating from the nuclear industry, and its behaviour in the environment is controlled by that of hydrogen. Animal food products represent a potentially important source of tritium in the human diet and a number of transfer coefficient values for tritium transfer to a limited number of animal products are available. In this paper we present an approach for the derivation of tritium transfer coefficients which is based on the metabolism of hydrogen in animals. The derived transfer coefficients separately account for transfer to and from free (i.e. water) and organically bound tritium. A novel aspect of the approach is that tritium transfer can be predicted for any animal product for which the required metabolic input parameters are available. The predicted transfer coefficients are compared to available independent data. Agreement is good (R2=0.97) with the exception of the transfer coefficient for transfer from tritiated water to organically bound tritium in ruminants. This may be attributable to the particular characteristics of ruminant digestion. We show that tritium transfer coefficients will vary in response to the metabolic status of an animal (e.g. stage of lactation, diet digestibility etc.) and that the use of a single transfer coefficient from diet to animal product is inappropriate. It is possible to derive concentration ratio values from the estimated transfer coefficients which relate the concentration of tritiated water and organically bound tritium in an animal product to their respective concentrations in the animals diet. These concentration ratios are shown to be less subject to metabolic variation and may be more useful radioecological parameters than transfer coefficients. For tritiated water the concentration ratio shows little variation between animal products ranging from 0.59 to 0.82. In the case of organically bound tritium the concentration ratios vary between animal products from 0.15 (goat milk) to 0.67 (eggs).

Regulatory models for atmospheric releases of tritium approved by the Environmental Protection Agency (CAP88, AIRDOS-PC, and COMPLY) calculate doses only from tritiated water (HTO) taken into the body. They do not deal with dose from emissions of tritiated hydrogen gas (HT) and conversion of HT to HTO in the environment, nor do they address the dose from ingesting tritium incorporated into organic compounds. A simple model (NEWTRIT) is proposed that accounts for all pathways to dose from atmospheric releases of HT and HTO. The model is formulated in terms of the tritium-to-hydrogen ratio in each environmental compartment. With each transfer, a small reduction in the ratio is introduced to reflect the dilution that occurs in nature. Conversion of HT to HTO in the environment is modeled using the latest experimental data. Concentrations of organically bound tritium are calculated in foodstuffs based on amounts of hydrogen in proteins, fats, and carbohydrates. Concentrations in foodstuffs and doses calculated by NEWTRIT are consistent with the predictions of existing regulatory models. In addition, the HTO component of NEWTRIT is tested using public bioassay data and the HT component is tested using results from a model intercomparison study for a hypothetical HT release. Although tritium doses probably have not been underestimated by regulatory models that account only for HTO (due to the high degree of conservatism built into these models), the explicit treatment of HT and organically bound tritium proposed here will make the dose assessments more comprehensive, defensible, and scientifically acceptable. Because NEWTRIT includes all pathways to dose and predicts conservative doses, it is a suitable model to replace the tritium models currently used for compliance.

DCART (Doses from Chronic Atmospheric Releases of Tritium) is a spreadsheet model developed at Lawrence Livermore National Laboratory (LLNL) that calculates doses from inhalation of tritiated hydrogen gas (HT), inhalation and skin absorption of tritiated water (HTO), and ingestion of HTO and organically bound tritium (OBT) to adult, child (age 10), and infant (age 6 months to 1 year) from routine atmospheric releases of HT and HTO. DCART is a deterministic model that, when coupled to the risk assessment software Crystal Ball ® , predicts doses with a 95% confidence interval. The equations used by DCART are described and all distributions on parameter values are presented. DCART has been tested against the results of other models and several sets of observations in the Tritium Working Groups of the International Atomic Energy Agency's programs, Biosphere Modelling and Assessment and Environmental Modeling for Radiation Safety. The version of DCART described here has been modified to include parameter values and distributions specific to conditions at LLNL. In future work, DCART will be used to reconstruct dose to the hypothetical maximally exposed individual from annual routine releases of HTO and HT from all LLNL facilities and from the Sandia National Laboratory's Tritium Research Laboratory over the last fifty years.iv This page intentionally left blank.v

Based on annual tritium release rates from the five sources of tritium at Lawrence Livermore National Laboratory and the Tritium Research Laboratory at Sandia National Laboratory, the regulatory dispersion and dose model, CAP88-PC, was used to predict tritium concentrations in air at perimeter and offsite air surveillance monitoring locations for 1986 through 2001. These predictions were compared with mean annual measured concentrations, based on biweekly sampling. Deterministic predictions were compared with deterministic observations using predicted-to-observed ratios. In addition, the uncertainty on observations and predictions was assessed: when the uncertainty bounds of the observations overlapped with the uncertainty bounds of the predictions, the predictions were assumed to agree with the observations with high probability. Deterministically, 54% of all predictions were higher than the observations, and 96% fell within a factor of three. Accounting for uncertainty, 75% of all predictions agreed with the observations; 87% of the predictions either matched or exceeded the observations. Predictions equaled or exceeded observations at those sampling locations towards which the wind blows most frequently, except those in the hills. Under-predictions were seen at locations towards which the wind blows infrequently when released tritium was from elevated sources. When a high fraction of tritium was from area (diffuse) sources, predictions matched observations.