Neutron dose equivalent rates in the vicinity of waste containers containing TRU

Abstract

The Transuranic Waste Processing Center is charged with treating, packaging and shipping TRU waste for disposal in a safe and efficient manner. The nature of TRU waste, i.e. it contains radionuclides which spontaneous fission and emit alpha particles which can lead to the production of (α,n) neutrons, can lead to neutron dose equivalent rates of radiation protection concern. Neutron dosimetry measurements were performed at the TWPC facility in locations where neutron dose equivalent rates of significance had been observed using neutron survey instruments. These measurements provide an assessment of the dosimetric properties of neutron fields that are deemed to be typical at the TWPC. The neutron measurements were performed at four locations using a Bonner sphere spectrometer which provides a low resolution spectrum that yields a good estimate of the neutron dose equivalent rate and the fluence rate. A tissue equivalent proportional counter dose equivalent measurement was performed at one location. Based on the Bonner sphere measurements, over 90% of the ambient dose equivalent is delivered between approximately 100 keV and 7.4 MeV.