MULTISPHERE SPECTROMETRY AND ANALYSIS OF TEPC AND REM METER RESULTS AROUND A HEAVY-WATER MODERATED REACTOR

The NRU reactor is a vertically oriented, heavy water moderated and co oled research reactor. Water and iron shielding above the core permit only a small amount of leakage neutrons through the top deck plate. Tw o leakage neutron spectra determined using a multisphere, or Bonner sp here, system are reported here. The spectra are used to analyse measur ements made with a moderator-type neutron dose equivalent meter (i.e. a rem meter) and a tissue-equivalent proportional counter (TEPC) syste m. Rem meter readings are not reproduced by folding the response funct ion of the instrument with the fluence spectra. Based on TEPC and Bonn er sphere data, ambient dose equivalents are found to be 30 and 17 mu Sv.h(-1) (+/-25%), in the two locations investigated, for a reactor po wer level of 107 MW(t).