No abstract

In the present study, measurements of alpha/beta contamination and gamma dose rates measurements were carried out in scrap yard contaminated by spillage of sludge contained 238U at Al-Tuwaitha Nuclear Site. Alpha/beta surface soil contamination levels were directly measured in the field at January 2016 using RadEye SX monitor. Gamma dose rates measurements were conducted using RadEye PRD. The results showed that alpha/beta surface soil contamination levels varied from 0.1 for uncontaminated areas and reach 2.8 Bq/cm2 for contaminated areas, with an average value of 0.8 Bq/cm2, which is more than 6 times the local natural background level. Results of dose assessment indicate that, the potential radiation doses to on-site workers from site contaminants were estimated to be in the order of 0.036 mSv/y, which was considered within the occupational dose limit of 20 mSv/y recommended in the International Atomic Energy Agency (IAEA) GSR Part 3 (2014). However, the mean dose rate reaches 4.5 times the background level, indicating that remediation of site contaminants is recommended to ensure environmental safety.

In the present study, the scrap yards (located within the latitudes 33o 21’ 613” to 33o 21’ 290” North, and longitudes 44o 51’ 299” to 44o 50’ 904” East) at Al-Tuwaitha nuclear site were scanned for the period from January to February 2016 using hand-held radiation detectors with the intent of locating radioactive sources thrown within piles of scrap material. Only one 137Cs radioactive source has been found with an estimated activity of 6.3×108 Bq, which was found to be considerably less than the “dangerous quantity” D-value of 1×1011 Bq. Assessment of the potential radiological consequences arising from exposure to the source during normal conditions has been conducted using Rad Pro Calculator Version 3.26 (2009). The potential radiological dose arising from normal occupational exposure situation was estimated to be 139 mSv/y at 1 meter distance from the source, which was considerably higher than the occupational dose limit of 20 mSv/y recommended in the International Atomic Energy Agency (IAEA) GSR Part 3 (2014), indicating that this source must be removed and treated as radioactive waste.

In the present study the radon concentration was measured in indoor places by the RAD7 (radon detector) was in some locations at Al-Tuwaitha nuclear site and some surrounding areas for the duration from 13/10/2016 to 2/1/2017 and the measurement of the indoor radon concentration ranged from (4.96±4.4 to 102±25) Bq/m3. The high value of radon has been found at decommissioning directorate /emergency room, which is lower than the action value recommended by the Environmental Protection Agency (EPA) which is (148 Bq/m3) while the lowest value has been founded in central laboratories directorate \ models room. These values were used to calculate the annual effective dose and the health risks for cells bronchial which caused by the inhalation of radon. The values of the annual effective doses were calculated and ranged from (0.1249 to 2.5704) mSv/y these results are lower than the value of (10 mSv/y) recommended by the International Commission Radiological on Protection (ICRP). The results from this study shows that the region has background radioactivity levels within the natural limits.

The specific activity of 29 soil samples collected from FuelFabrication Facility FFF at AL-Tuwaitha site, 20 km south ofBaghdad were determined using HPGe detector in a low backgroundconfiguration, it's relative efficiency of 40%, and resolution of 2keVfor the 1332 keV gamma ray emission of 60Co. The range of activityconcentrations of 226Ra, 232Th and 40K were between (12.56-31.96),(10.2-18.4) and (47.47-402.1) Bq/kg respectively. In order to assessany radiological hazard to human health, the absorbed gamma doserate D in air at 1m above the ground surface was calculated in therange (18.87 to 36.46) nGy/h; the outdoor annual effective doseequivalent AEDE was evaluated to vary from 0.0039 to 0.0076mSv/y with the mean value 0.0059 mSv/y, this value comparable tothe worldwide effective dose 0.48mSv/y. The Radium EquivalentRaeq for all samples were evaluated and were lower than the acceptedsafety limit value of 370 Bq/kg. The results indicated that theradiation of hazards from primordial radionudlides in all samples inthis study is not significant.