Whole-body Counters in Routine Monitoring

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Abstract
Work with radioactive materials should be properly planned and controlled so that the activities entering the bodies of workers are very small. The principal use of wholebody counters in routine monitoring for body radioactivity, therefore, should be to detect those occasional accidental intakes of radioactive material which are greater than significant levels. A significant activity, A μCi, is taken to be one-tenth the quarterly limit on intake resulting from continuous exposure to MPCw or MPCa recommended by ICRP. A figure of merit related to the gamma-rays escaping from the body and the difficulty of measuring them, is derived which is equal to the product of A and the number, N, of gamma-rays emitted with energies greater than 100 keV per disintegration of the radionuclide, i.e. AN gamma-ray μCi. About 85 per cent of the 111 radionuclides considered have values of AN which are greater than 0.1 gamma-ray μCi, many greatly in excess of this value. Activities in the body of this magnitude may be measured by quite simple equipment. This is fortunate because many of these radionuclides have short residence times in the body and monitoring must, therefore, be done at frequent intervals, preferably at the place of work. It is concluded that there is scope for the development of a simple whole-body counter for routine use and that there are few radionuclides for which the setting up of high sensitivity whole-body counters is justified. The use of high sensitivity equipment is best limited to a few specialist centres having the necessary qualified personnel and facilities which are required to make best use of the equipment.