Disruptive Event Biosphere Dose Conversion Factor Analysis

Abstract

This analysis report, ''Disruptive Event Biosphere Dose Conversion Factor Analysis'', is one of the technical reports containing documentation of the ERMYN (Environmental Radiation Model for Yucca Mountain Nevada) biosphere model for the geologic repository at Yucca Mountain, its input parameters, and the application of the model to perform the dose assessment for the repository. The biosphere model is one of a series of process models supporting the Total System Performance Assessment (TSPA) for the Yucca Mountain repository. A graphical representation of the documentation hierarchy for the ERMYN is presented in Figure 1-1. This figure shows the interrelationships among the products (i.e., analysis and model reports) developed for biosphere modeling and provides an understanding of how this analysis report contributes to biosphere modeling. This report is one of the two reports that develop biosphere dose conversion factors (BDCFs), which are input parameters for the TSPA model. The ''Biosphere Model Report'' (BSC 2003 [DIRS 164186]) describes in detail the conceptual model as well as the mathematical model and lists its input parameters. Model input parameters are developed and described in detail in five analysis report (BSC 2003 [DIRS 160964], BSC 2003 [DIRS 160965], BSC 2003 [DIRS 160976], BSC 2003 [DIRS 161239], andmore » BSC 2003 [DIRS 161241]). The objective of this analysis was to develop the BDCFs for the volcanic ash exposure scenario and the dose factors (DFs) for calculating inhalation doses during volcanic eruption (eruption phase of the volcanic event). The volcanic ash exposure scenario is hereafter referred to as the volcanic ash scenario. For the volcanic ash scenario, the mode of radionuclide release into the biosphere is a volcanic eruption through the repository with the resulting entrainment of contaminated waste in the tephra and the subsequent atmospheric transport and dispersion of contaminated material in the biosphere. The biosphere process model for this scenario uses the surface deposition of contaminated ash as the source of radionuclides in the biosphere. The initial atmospheric transport and dispersion of the ash as well as its subsequent redistribution by fluvial and aeolian processes are not addressed within the biosphere model. The analysis was performed in accordance with the TWP (BSC 2003 [DIRS 163602]). The biosphere model considers features, events, and processes (FEPs) applicable to the Yucca Mountain biosphere (DTN: MO0303SEPFEPS2.000 [DIRS 162452]). The disposition of these FEPs in the TSPA is through the BDCFs which are the direct input to the TSPA model. The disposition of the included FEPs within the biosphere model is documented in the ''Biosphere Model Report'' (BSC 2003 [DIRS 164186]). Specifically, the consideration of the included FEPs in the conceptual model is shown in Table 6.2-1, relationships among the biosphere-related FEPs, the biosphere conceptual model, and the exposure scenarios are more fully examined in Section 6.3, and the disposition of the included FEPs within the mathematical model, and their relationship to the model equations and input parameters is presented in Table 6.7-1 of the ''Biosphere Model Report'' (BSC 2003 [DIRS 164186]). In addition to producing the BDCFs for the volcanic ash exposure scenario, this analysis develops the values of dose factors for calculation of inhalation exposure during a volcanic eruption. The FEPs that were considered in the development of dose factors are listed in Table 1-1. The disposition of these FEPs in TSPA is through the dose factors that are the input to the TSPA model.« less