ASSESSMENT OF RADIATION DOSE RATE LEVELS AND RADIATION RISK AT THE COBALT -60 UNIT, KOMFO ANOKYE RADIOTHERAPY CENTER, GHANA.

Purpose: A study was conducted to estimate the Annual Effective Dose Equivalent (AEDE) and Excess Lifetime Cancer Risk (ELCR) caused by the presence of an artificial cobalt-60 radioactive source producing ionizing radiation levels within the radiotherapy facility at Komfo Anokye Teaching Hospital (KATH) in Ghana. This study validated the safety of cobalt-60 radioactive sources, as well as the notion of calculating the Annual Effective Dose Equivalent (AEDE) and Excess Lifetime Cancer Risk (ELCR), which contributed to reducing occupational and public exposures inside the facility. Methodology: The investigation was carried out with the use of a portable OD-01 Ionization Chamber Survey Meter. The absorbed dose rate (ADR) in air was changed between 5 m and 40 m, with measurements taken inside and around the cobalt 60 bunker, as well as at sixteen other sites within the radiation facility. Findings: From 5 m to 40 m surrounding the Cobalt-60 source, the estimated Absorbed Dose Rate in air inside the cobalt-60 bunker ranged from 0.299 0.001 to 0.977 0.005 Sv/h, with an average of 0.498 0.005 Sv/h. The estimated Annual effective dose equivalent varied from 1.100 mSv/yr to 3.595 mSv/yr around the cobalt-60 source inside the Co-60 bunker. Radiation exposure levels ranged from 0.268 0.008 Sv/h to 0.678 0.005 Sv/h, with an average of 0.440 0.004 Sv/h observed around the fifteen sites chosen. Excess Lifetime Cancer has values ranging from 3.85 10-3 to 12.58 10-3 and 3.45 10-3 to 8.73 10-3. Risks were evaluated for the cobalt and the sixteen places inside the plant. The absorbed dose values at 5 m, 10 m, and 15 m inside the Co-60 bunker and the location Co-60 bunker as part of the facility exceeded the ICRP-recommended limit of 0.57. The AEDE and ELCR levels were within the ICRP's acceptable limits. The AEDE and ELCR statistics acquired indicate that the Cobalt-60 unit and its surroundings are radiation safe, although the likelihood of employees contracting cancer from the absorbed dose and background ionizing radiation is significant over a lifetime. Recommendation: However, it is recommended that absorbed dose level monitoring and evaluation of the Radiation Therapy Technologist (RTT) and other workers surrounding the unit be monitored on a regular basis. It is also recommended that Occupational Staff, such as RTTs, spend as little time as possible in the bunker

Radiological urban threat due to special protective actions from security forces

The neutralization of suspicious objects by a conventional explosion in public places seems to be an option often considered by security forces. A radiological dispersive device (RDD) uses a radioactive material coupled to an amount of conventional explosive in order to contaminate an area. Extremist groups may take advantage of such protocol by leaving the radioactive material in public places to provoke suspicion, thus leading to the neutralization by an explosion, which in turn creates a RDD event. This work aims to discuss the influence of such a protocol in the radiological threat by means of computational simulation. The total maximum effective dose equivalent (TEDE Max), the Pasquill–Gifford atmospheric stability classes (PG classes), and the potentially affected population size were evaluated. The results consider two radionuclides Cs-137 and Sr-90. The findings allow us to infer that TEDE Max and surface contamination are strongly dependent on the PG classes. In addition, the affected population size depends on the plume size, which seems to be independent of the radionuclide, but not of the PG classes. Therefore, PG classes play a key role in the radiological threat. The findings may be of value to support decisions when facing an event.

Impact of Lockdown during COVID-19 on Annual Effective Dose Equivalent values of Natural Gamma Radiation

The study aimed to find the impact of COVID-19 on values of Annual Effective Dose Equivalent of the natural Gamma dose rate from Balod, Durg and Bemetara districts of Chhattisgarh (India). COVID-19 is a severe problem for many countries and to control and prevent the spread of this problem implemented the lockdown approach in many countries, including India. In this lockdown situation, almost all people are staying at home for 24 hours. Due to the present status of COVID-19, the Indian government also fixed the 67 days lockdown and one day was already successfully done as Janta Curfew, which worked the same as a lockdown. The value of indoor gamma dose rates was reported higher in most places as compared to the outdoor gamma dose rate, but in this pandemic situation, occupancy factor values are not applicable as recommended by UNSCEAR for calculation of Annual Effective Dose Equivalent (AEDE). Therefore, the present study introduces the new equations, which can measure the extra AEDE value during the lockdown for adults, children and infants.

Impact of Lockdown during COVID-19 on Annual Effective Dose Equivalent values of Natural Gamma Radiation

The study aimed to find the impact of COVID-19 on values of Annual Effective Dose Equivalent of the natural Gamma dose rate from Balod, Durg and Bemetara districts of Chhattisgarh (India). COVID-19 is a severe problem for many countries and to control and prevent the spread of this problem implemented the lockdown approach in many countries, including India. In this lockdown situation, almost all people are staying at home for 24 hours. Due to the present status of COVID-19, the Indian government also fixed the 67 days lockdown and one day was already successfully done as Janta Curfew, which worked the same as a lockdown. The value of indoor gamma dose rates was reported higher in most places as compared to the outdoor gamma dose rate, but in this pandemic situation, occupancy factor values are not applicable as recommended by UNSCEAR for calculation of Annual Effective Dose Equivalent (AEDE). Therefore, the present study introduces the new equations, which can measure the extra AEDE value during the lockdown for adults, children and infants.

Assessment of Radiation Exposure Level from Some Scrap Metal Dumpsites in Nasarawa State, Nigeria

In this study, the radiation exposure rate emanating from the scrap metals dumpsite was assessed using an Interceptor Spectroscopic personal radiation detector (SPRD). Sixteen (16) scrap metal dumpsites were selected at random across four Local Government Areas (Nasarawa, Lafia, Akwanga, and Keffi) of Nasarawa State, Nigeria. The gamma activity level in µrem/hr on three (3) randomly selected points on each of the scrap metal dumpsites was determined. A reading was taken on point 100 m away from each of the scrap metal dumpsite. Results show that the highest annual effective dose equivalent was observed in Akwanga (AKW4) scrap metal dumpsite with an annual effective dose equivalent of 0.2167 mSv/yr. The scrap metal dumpsite with the lowest annual effective dose equivalent was observed in Lafia (LAF3) and (LAF4) with an annual effective dose equivalent of 0.0613 mSv/yr. The excess lifetime cancer risk of 0.7585 × 10-3 was the highest value recorded in AKW4, while the lowest value was found to be 0.2146 × 10-3 in LAF3 and LAF4. The control radiation exposure level, 100 m from scrap metal dumpsites, shows the value of gamma activity level and annual effective dose equivalent obtained is ranged between 13 µrem/hr and 0.1594 mSv/yr respectively on location KEF1 to 3 µrem/hr and 0.0368 mSv/yr on locations LAF2 and LAF3 respectively. The annual effective dose equivalent values obtained were below the ICRP dose limit of 1 mSv/yr, indicating that, the environments around these scrap metal dumpsites are safe. The excess lifetime cancer risk value (ELCR) obtained in some locations is higher than the world average value of 0.29 × 10-3. Therefore, we recommend that scavengers, workers at the scrap dumpsites are to minimise the period of their stay within the dumpsites, and also the residential homes are to maintain a distance of 500 meters around the scrap metal dumpsites so as to minimise the risk of developing any health problem relating to cancer in future.

Radiological Safety Analysis for a Hypothetical Accident of a Generic VVER-1000 Nuclear Power Plant

Atmospheric dispersion modelling and radiological safety analysis have been performed for a postulated accident scenario of a generic VVER-1000 nuclear power plant using the HotSpot Health Physics code. The total effective dose equivalent (TEDE), the respiratory time-integrated air concentration, and the ground deposition concentration are calculated considering site-specific meteorological conditions. The results show that the maximum TEDE and ground deposition concentration values of 3.69E – 01 Sv and 3.80E + 06 kBq/m2 occurred at downwind distance of 0.18 km from the release point. This maximum TEDE value is recorded within a distance where public occupation is restricted. The TEDE values at distances of 5.0 km and beyond where public occupation is likely to be found are far below the annual regulatory limits of 1 mSv from public exposure in a year even in the event of worse accident scenario as set in IAEA Safety Standard No. GSR Part 3; no action related specifically to the public exposure is required. The released radionuclides might be transported to long distances but will not have any harmful effect on the public. The direction of the radionuclide emission from the release point is towards the north east. It is observed that the organ with the highest value of committed effective dose equivalent (CEDE) appears to be the thyroid. It was followed by the bone surface, lung, red marrow, and lower large intestine wall in order of decreasing CEDE value. Radionuclides including I-131, I-133, Sr-89, Cs-134, Ba-140, Xe-133, and Xe-135 were found to be the main contributors to the CEDE.