The radiation fields in nuclear power plants consist of a mixture of photons and neutrons of various energies. A detector is usually constructed to respond to one type of radiation only and is usually useful in a limited energy range . .This is especially so for neutrons. Accurate descriptions of the radiation envirorunent are therefore very complicated to obtain. During the last decade great effort has gone into improving of instruments suitable for this 'kind of measurement. However, their usefulness in practical field measurements is still not fully explored. In some areas such as inside the containment building of a reactor, the temperature is well above normal room temperatue (up to 45 C) and the acoustic and electromagnetic noise level may be very high. Such envirorunental conditions could influence a dosemeter reading.
Over the last decade the ICRU .has introduced the operational dose equivalent quantities for radiation monitoring. The idea is that their numerical values should never be below those of the effective dose equivalent as defined by the ICRP. As this committee in 1990 suggested increased risk factors for neutrons and changed the definition of the risk quantity, the safety margin is unclear.