Environmental radiation monitoring

Monitoring of the external radiation exposure rate was continued at the Chester site with recording high pressure ionization chambers (HPIC) and LiF thermoluminescence dosimeters (TLD). An annual in situ gamma spectral measurement is used to determine the status of individual natural and any fallout radionuclides in the soil. The average daily exposure rates measured by the ionization chamber system are listed. The average exposure rate for the entire period shown was 14.6 μR/h with a standard deviation of the 0.52 μR/h. The range of daily values was 11.1 to 15.7 μR/h. The monthly TLD data are presented; the HPIC data were averaged over the same time periods and are shown for comparative purposes. These two sets of measurements differ by 3.5% when averaged over the year which is within the estimated systematic error of either system. Similarly, the agreement for each monthly period, 3.8% on average, is consistent with the expected precision of the measurements. The variation in the exposure rate observed over this period can be traced to natural phenomena