Measurement of Neutron Dose Equivalent Close to a Supposedly Stuck Transport Cask with Spent Reactor Fuel

The individual doses received during normal handling of spent fuel in transport casks are at or below 3 mSv per annum. At these low exposure levels it is sufficient to ascertain that the individual dosemeters show conservative values and to complement this with monitoring of the workplace. If a transport cask with spent fuel must be maintained without water shielding for long periods of time it becomes necessary to reduce the degree of conservatism offered by the dosemeters in normal use. Estimations of the personal dose equivalent at a few positions close to a transport cask are described. The estimation is based on measured neutron energy and angular distributions and on algorithms for combining the reading of two dosemeters. The new (ICRP 60) Q(L) function and new stopping powers (ICRU 49) are used. For the tested irradiation conditions (calculated as well as measured) the personal dose equivalent gives a slightly conservative estimate of E (100% to 140%). To reach this agreement only one dosemeter is needed for irradiation towards the anterior, right or left sides of the body while for irradiation towards the posterior side of the body two dosemeters (front and back) are needed. (author)