A passive neutron dose equivalent meter for environmental and aera monitoring in the low dose range

For the purpose of long-term monitoring of the natural neutron radiation background in the dose range above 1 μSv the passive neutron dose equivalent meter makes use of track etch detectors and TLDs in the center of a 30 cm polyethylene sphere. Makrofol polycarbonate foil in contact with two (n,α) radiators as well as 6LiF/7LiF serve as thermal neutron detectors. The track detector is etched electrochemically and the track density is counted in a single field of 0.6 cm2 using a microfiche reader/printer. The design and holder of the neutron detectors as well as the evaluation technique for both detector types have been standardized. The total dose range has been found to be 5 μSv to 10 mSv for track etch detectors with two (n,α) radiators of different sensitivity and 0.1 mSv to 10 Sv for TLD detectors. Electrochemically etched Makrofol shows practically no fading. The passive neutron dose equivalent meter has been applied for long-term neutron monitoring in the environment of nuclear facilities allowing to estimate the natural neutron radiation background with a random error of 20% after monitoring periods of half a year