Occupational dose assessment for radiation staff at nuclear reactor research centre, 2011 – 2015 (prior to core conversion)

Abstract

Radiation absorbed dose data of staff at the Nuclear Reactor Research Centre (NRCC) of Ghana Atomic Energy Commission, from 2011 to 2015, was analyzed to evaluate the performance of personnel monitoring program prior to the reactor core conversion, and to set baseline criteria for compliance after the core conversion. Personnel radiological deep dose data Hp (10) and surface dose data Hp (0.07) of three radiation workgroups, each of 4 wor-kers were extracted from Thermolumiscent Dosimeters (TLDs). The reactor dose rate data from coolant water was used as control factor influencing radiation absorbed by the staff. The mean dose rate values were respectively, 0.56 mSv and 0.48 mSv for H_p(10) and H_p (0.07), which were very low compared to the annual occupational limit of 20 mSv/year averaged over any 5-year period set by the International Commission on Radiological Protection. Statistical analyses were performed using Repeated Measure Analysis of Variance, Multivariate Analysis and Mauchly test. Significant differences were found in both Hp (10) (F_{(11, 36)} = 7.45, p < 0.05) and Hp (0.07) (F_{(11, 36)} = 4.51, p < 0.05) per year, however, no significant differences were found among the three workgroups. The dose data showed reduction in personnel radiological dosage over the five-year period, indicating either effec-tiveness of radiological protection program, reduction in reactor power due to burn out of nuclear fuel after 20 years of operation or reduced staff workload.

Keywords: Occupational Dose, Thermolumiscent Dosimeter, Effective Dose, Personnel Monitoring, Analysis of Variance