Technical Assistance Request, Westinghouse Electrical Company, Evaluation of Residual Contamination
See the memorandum from J. E. Glenn to R. R. Bellamy dated May 18, 1992.
This memo responds to a technical assistance request from Region I, dated April 14, 1992 (Enclosure 1), for confirmation of their interpretation of the Branch Technical Position (BTP) for evaluation of residual concentrations of processed uranium on the Bloomfield, NJ site and generic applicability to other remediated facilities with processed uranium waste. The interpretation of Region I is correct (Enclosure 2) and is applicable to other remediated sites. For unenriched uranium, with no decay products of uranium-234 (U-234) present, the applicable values in the BTP are those for depleted uranium.
Westinghouse Electric Company's Bloomfield Lamp Plant is currently being remediated to remove thorium and processed uranium waste and contamination resulting from past operations from the facility. The Branch Technical Position for Disposal or Onsite Storage of Thorium and Uranium Wastes from Past Operations (BTP) provides guidance on acceptable concentration limits for various types of materials for five disposal options. While the BTP provides numerical guidance for thorium (natural thorium), there is no criteria for processed uranium.
The Branch Technical Position (46 FR 52061-52063) describes five options for disposal of certain uranium or thorium wastes. For each option, a disposal methodology is described and a concentration limit for each of four various kinds of material is tabulated. For Option 1, these values are as follows: natural thorium (Th-232 plus Th-228) if all daughters are present and in equilibrium, 10 picocuries per gram (pCi/g); depleted uranium, 35 pCi/g; enriched uranium, 30 pCi/g; and natural uranium ores (U-238 plus U-234) if all daughters are present and in equilibrium, 10 pCi/g. For other options, higher concentrations apply. One problem with the BTP is that there is no stated disposal option nor concentration limit for processed uranium; i.e., waste materials containing uranium, in which the uranium is neither enriched nor depleted and is not natural uranium ore with all daughters present and in equilibrium. There is a need for a concentration limit for disposal of this type of material in order to evaluate the remediation that has been performed at this site and other sites contaminated with material of this kind.
The concentration limits for wastes containing processed uranium should be the same as that tabulated for depleted uranium since processed uranium most closely resembles the radiological characteristics of depleted uranium; i.e., U-235 makes up only about 0.7% of natural uranium, and based on Section II.B of Enclosure 3 to the Branch Technical Position, the U-235 decay chain is generally unimportant compared with the U-238 chain. For Disposal Option 1, the appropriate concentration limit for processed uranium would thus be 35 pCi/g.
NMSS agrees with that interpretation. The basis is the contribution of U-238 to the inhalation and ingestion doses relative to that of U-234. For both natural and depleted uranium, the U-238 contributes a substantial fraction of the radioactivity; whereas, for enriched uranium, the radioactivity is completely dominated by the U-234, with regard to inhalation and ingestion doses.
Regulatory references: None
Subject codes: 5.8, 9.0