API Publication 7105:1997 pdf download.Probabilistic Estimates of Dose and Indoor Radon Concentrations Attributable to Remediated Oilfield Naturally Occurring Radioactive Material NORM).
3.0 EXPOSURE SCENAIUOS AND PATHWAYS
Dose assessment requires characterization of the exposure. Doses from radium arise from numerous pathways but, depending on the particular scenario, the contribution to oral dose can be dominated by one or two pathways.
This chapter describes the potential exposure pathways chat were considered and describes a screening level assessment that indicated that gamma radiation and indoor radon arc, by far, the primary exposure pathways. These two exposure pathways and the methodology for estimating exposures from source term scenarios are described.
3.1 SCREENING PATHWAYS ASSESSMENT
The potential doses to users of remediated sites are critically dependent upon the exposure frequency and duration. Therefore, the potential doses to residents living in homes built on remediatcd oil field sites would exceed corresponding doses from any other forsecabte use. The largest contributors to the incremental dose to residents who may live on the remediated oil field sites were identified by a screening assessment. Pathways illustrated in Figure 3.1, were included in the screening evaluation:
external gamma radiation; inhalation of resuspended dust; ingestion of dust and dirt ingestion of well water; consumption of vegetables from a backyard garden; and, consumption of beef, milk, es and poultry mesc.
The pathways and dose calculations were based on models recommended by the US Nudear
Regulatory Commission (NRC 1992). The mathematical models and calculations are provided in
Appendix C. Parameter values were also taken from NRC (1992) and tend to overestimate the
predicted doses.
The results of the screening calculations show that the external gamma dose typically comprises more than 80% of the total incremental dose (exduding radon). The dose from consumption of well water (which was assumed to have percolated through the remcdracd soil) and from consumption of garden produce grown in the remediated soil, each contributed less than 10% to the incremental dose. Under almost all exposure scenarios, the external gamma pathway will contribute to and dominate total dose. Many residents will not have wells nor backyard gardens and these exposure pathways may not always contribute to total dose. Thereftire, it was conduded that the remainder of the assessment would focus on a more detaild evaluation of only the external gamma radiation and radon pathways.
API Publication 7105:1997 pdf download
