نشریه سنجش و ایمنی پرتو
سال دوازدهم شماره 3 (پیاپی 47، پاییز 1402)

Platinum agents continue to be the main chemotherapeutic agents used in the treatment of cancer. Cisplatin agents labeled with platinum-195m theranostic radionuclide can potentially be a useful tool to determine the patient's dose and also assist in the investigation of the mechanism of Cis-platinum’s action and its metabolism in the human body. 195mPt radionuclide with suitable nuclear properties can be easily used in the synthesis of platinum-based cytotoxic compounds. In this study, production calculations of platinum-195m in the Tehran Research Reactor (TRR) were performed through the simultaneous solution of differential equations of the decay chains for natural platinum and natural iridium targets using MATLAB software. Natural platinum and iridium targets were irradiated in the TRR and after the radiochemical process, the experimental value of activity of 195mPt resulting from the irradiation of the natural platinum target was compared with the theoretical values. The results showed that there is good compatibility between the measured values experimentally and the results of the theoretical calculations. The results of this research can be used in studies of Cis-platinum labeling with platinum-195m.

In current study, the relative biological effectiveness (RBE) values relevant to the various Iodine radioisotopes, have been assessed to compare the performance of the MCSD and GEANT4-DNA Monte Carlo codes at low energy regions. After the calculation of the Auger electrons energy spectrum, obtained from the Iodine radioisotopes including 123I, 124I, and 125I through the GEANT4 Monte Carlo code, the calculation of the RBE values was performed through the GEANT4-DNA extension by considering the B-DNA model. In addition, the RBE values were also estimated by the MCDS code in completely aerobic conditions. The results of this study showed that employing the GEANT4-DNA-option4 physics by GEANT4-DNA extension in the physical stage provides near results in comparison with MCDS code for the radiobiological assessments and RBE estimation. The obtained highest difference values in this study were related to the use of GEANT4-DNA-option2 physics which varies from 22.30% to 24.60% for the studied radioisotopes. Since double strand damages along the DNA molecule can eventually lead to the cell death, and due to the appropriable agreement between the calculated results of RBEDSB values through the MCDS and GEANT4-DNA codes, it can be deduced that the MCDS code provides accurate results for the radiation induced DNA damage.

There are several methods to measure the reactor power. Since the power is directly related to the neutron flux in a reactor, the usual way to measure the power is to detect the neutron flux in the reactor core. The miniature neutron source reactor (MNSR) uses two fission chamber (FC) neutron detectors connected to computer and console control systems to determine the reactor power. These instruments are indicators of power, therefore the output of them has a significant role in reactor safety and needs to be calibrated. Importantly, the calibration measurements should be performed in a neutron-gamma environment very similar to the environment in which they will be used later. The aim of this study is to calibrate the fission chamber detectors in the core of the reactor by using the solid-state nuclear trace detector (SSNTD). The calibration factors of the FC detector related to the computer and control systems are equal to 1.02 and 0.88, respectively.

In this paper, we have tried to provide details about possible radioactive wastes produced in the fission molybdenum-99 production process using LEU uranium targets in the country and how to manage them throughout the production process. Potential solid, liquid, and gaseous wastes are a combination of low-level (LLW), and medium-level (ILW) wastes that contain enriched uranium and other fission products and actinides. Based on the results of radiation calculations and heat generated by the radionuclides in each waste package, it seems that no high-level waste (HLW) is generated from the 99Mo production facility, as this waste contains long-lived or alpha-emitting radionuclides with more activity of 400 Bq/g which their heat generation is not more than 2 kW/m3. The economic aspects of 99Mo-related waste management are important and can substantially influence the final price of 99Mo and by-products. In the fission 99Mo production process, the recovery of unburnt uranium is highly recommended, preferably the uranium should be segregated from the waste streams within the production facility.

One of the most important limitations of gas detectors is the phenomenon of polymerization. This factor can disrupt the overall performance of the detector. The occurrence of this phenomenon has been observed and proven in wired detectors. In this paper, the polymerization phenomenon on thick gas electron multiplier detectors (THGEM) in self-quenching streamer (SQS) mode has been investigated using a 137Cs gamma source with 3.95µCi(1.46×105Bq) activity. In the presence of an approximate amount (10%) of a hydrocarbon gas such as methane, which is used as a quencher in the P10 gas composition, it is observed that after three days the detector is used an average of three to four hours per day. Sudden changes in the counting rate and also electrical sparks are seen. According to the images and observations, the harmful effects of hydrocarbon gas polymerization, which is one of the main factors of this phenomenon, have been proven in THGEM detectors, and suggestions have been made to improve and extend the life of the system.