RESULTS OF SURVEYS AT UNITED STATES PULP AND PAPER MILLS FOR THE PRESENCE OF SCALES AND PRECIPITATES CONTAINING NATURALLY OCCURRING RADIOACTIVE MATERIAL (NORM).

Field surveys were carried out at sixteen pulp and paper mills in the United States—seven kraft process, two sulfite process, and seven recycling process mills—for the presence of naturally occurring radioactive material (NORM) in precipitates and scales. NORM was detected at three of the kraft mills, one sulfite mill, and none of the recycling mills. At one of the kraft mills, the NORM was associated with a commercial aluminum sulfate ("alum") slurry used on the paper machines and in intake water treatment. The maximum activity level of this alum scale was 252,000 Bq kg[sup -1] (6,800 pCi g[sup -1]) [sup 228]Ra. At two kraft mills, NORM was associated with precipitates in the bleach plant. The measured NORM activity in samples of these scales was approximately 44,400 Bq kg[sup -1] (1,200 pCi g[sup -1]) [sup 226]Ra. Where NORM was detected at a sulfite mill, the NORM deposits were found adhering tightly to the surfaces of brownstock washers. Although samples were not removed for radionuclide analysis, survey readings at the drum surface were 26 nC kg[sup -1] h[sup -1] (100 µR h[sup -1]) with a scintillation counter and 2,200 cpm with a Geiger-Muller counter. At all mills, exposure rate measurements and risk assessment calculations indicated that it would be highly unlikely for any worker's annual exposure to exceed 1 mSv (100 mrem) (the Nuclear Regulatory Commission limit for untrained workers) due to exposure to these materials. [ABSTRACT FROM AUTHOR]