Monitoring the critical radiation exposure pathways at a BWR nuclear power station

Iodine-131 in milk and gamma radiation from radionuclides in air in the environment of a 3-unit nuclear power station were measured at the levels predicted for airborne effluent. These measurements were part of a modified environmental radiological monitoring program to confirm the population doses computed from radionuclide release rates and environmental transfer models. The limits of detection were lowered relative to conventional monitoring programs by analyzing 21 L samples of milk for 131I and by determining external gamma radiation with a system that combined use of thermoluminescent dosimeters, pressurized ionization chambers, and NaI(T1) survey meters. For monitoring periods slightly longer than 6 months, during a time when fallout from atmospheric nuclear tests contributed very little, the average measured 131I concentration in milk was 0.1 pCi/L for cows on a nearby pasture and 0.02 pCi/L for cows at a more distant control location, compared to predicted values of 0.07 and 0.02 pCi/L, respectively; the average radiation exposure from airborne radionuclides measured at 16 nearby dosimeter locations was 7 mR, compared to the average of predicted values of 4 mR.