APPLICATION OF THE JSIR2S CODE PACKAGE FOR SHUTDOWN DOSE RATE CALCULATIONS ON JET

In this paper we present a computational exercise for shut-down dose rate calculations for the JET tokamak using the in-house developed JSIR2S code package as part of its validation. The computation is performed in two parts: neutron transport and transport of secondary gamma radiation. In order to calculate neutron activation reaction rates with sufficiently low variance, hybrid variance reduction techniques using the ADVANTG code have been utilized. Probability based sampling of secondary source particles was performed. Calculated gamma dose rates after shut down are compared with dose rate measurements performed on site using ionization chambers. The C/E agreement for 1st octant is between 0.8 to 1 while statistically meaningfull results for the 2nd octant are yet to be obtained.

EVALUATION OF THE DOSE LEVELS IN THE IRRADIATION CHANNELS OF PU-BE NEUTRON SOURCES STORAGE DEVICE BY USING NEUTRON ACTIVATION ANALYSIS AND MCNP6 MODELLING

PuBeneutrons sources of Educational Neutron Laboratory in the Center for Physical Sciences and Technology are used in several activities including neutron activation for educational purposes and laboratory irradiation experiments. In this work we address the dose rate estimation in the irradiation channels of reconstructed PuBe neutron sources storage device in the particular positions dedicated for neutron irradiation experiments using neutron activation analysis (NAA) and MCNP6 modelling.The results on neutron activation of V2O5, MnO2, Al and Na2CO3were analyzed and compared with MCNP6 model prediction results. The conclusions on the actual neutron flux energy distribution and model corrections are drawn. The absolute neutron intensity at dedicated irradiation points as well as neutron and gamma dose rates are obtained.

Spatial distribution of natural and artificial radioactivity concentrations in soil samples and statistical approach, Nevşehir, Turkey

The concentrations of 226Ra, 232Th, 40K and 137Cs radionuclides in soil samples collected from 323 different regions of Nevşehir province were determined by using a gamma spectrometer with an HPGe detector. The mean gamma activity concentrations (ranges) of 226Ra, 232Th, 40K and 137Cs for districts were determined as 49.45 (7.40–193.90), 54.08 (<2.8–122.50), 698.43 (37.67–1370.20) and 8.26 (0.10–52.60) Bq kg−1, respectively. The mean activity concentrations of 226Ra, 232Th and 40K were higher than the world mean value. According to Kolmogorov–Smirnov test, distributions of 226Ra, 232Th and 137Cs show log-normal distributions. Whereas, 40K shows normal distribution. The mean radium equivalent activity was 181.68 Bq kg−1 which is lower than the recommended maximum value of 370 Bq kg−1. The mean external terrestrial gamma dose rate was found to be 85.12 nGy h−1. The calculated external hazard value was 0.49 and within the acceptable limit which is less than unity (Hex ≤ 1). Thermo Scientific RadEye NBR detector was used to determine environmental gamma dose rates. The gamma dose rates were measured at 445 points at a height of 1 m from land surface. The mean outdoor gamma dose rate (range) was found as 150.13 (50–480) nGy h−1. This mean value was found higher than world mean value. The fact that most of the Nevşehir province is based on volcanic rocks explains why the gamma dose rates are high.

Vertical distribution of the radon concentration at Batu Pahat district, Johor, Malaysia

This study investigated the vertical distribution of radon, 222Rn concentrations in soil gas for different soil types and found the relation between the measured gamma dose rates and radon concentrations. The 222Rn concentrations in soil gas were measured at depth of 20 cm, 60 cm, 80 cm and 100 cm using semiconductor detector (RAD7) coupled with soil gas probe. The overall activity concentrations of 222Rnin soil were ranged from Minimum Detectable Activity (MDA)to 54000 ± 3000 Bq m−3 in Batu Pahat District. The results showed that the overall highest concentration of 222Rn was recorded at 40 cm depth for most of the soil types, which could be the most reliable for taking the radon measurements than other depths. Soil type 32 (Dystric Nitosolse Orthic Ferrasols-Rengam Jerangau) has the highest radon concentration, which was 12,462 ± 5237 Bq m-3. The gamma dose rates (GDR) above 1 m were measured using portable survey meters (Ludlum 19). A good relationship between radon concentrations in soil gas and the measured gamma dose rates was observed using Pearson Correlation. The results of 222Rn concentration in soil gas obtained from this study were in agreement with results reported by other researchers.

EFFECTS OF LOCAL BUILDING MATERIALS ON INDOOR GAMMA DOSES AND RELATED RADIOLOGICAL HEALTH RISKS, AYVACIK, ÇANAKKALE/TURKEY

In situ indoor gamma dose rate measurements were held in 79 dwellings by NaI(Tl) scintillation probe connected portable dose rate meter. For the building materials and impurities (nodules), spectrometric gamma analysis was applied by a high-resolution HpGe detector. For Ahmetçe and Nusratlı villages in Ayvacik/Çanakkale (Turkey), the measured in situ indoor gamma dose rates and related indoor annual effective dose equivalents (AEDEin) were 3 and 3.3 times, and indoor excess lifetime cancer risks (ELCRin) were 4.25 and 4.68 times higher than those of the world averages, respectively. The used local rocks were mostly ignimbrite and dacitic–rhyolitic tuffaceous (Arıklı tuff), and wall plasters were made of local soil. The highest in situ indoor gamma dose rates of the region belonged to Nusratlı village due to the intense impurities (nodules) and hydrothermal alterations in Arıklı tuff. Spectrometric gamma results revealed that 40K has an important effect on the indoor gamma doses.

Release rate estimation of both long- and short-lived radionuclides for the Fukushima Daiichi nuclear accident based on local-scale observations

&lt;p&gt;Many efforts have been devoted to estimate the release rate of the radionuclide emission in the Fukushima Daiichi nuclear accident using regional scale observations. Because of the radioactive decay, regional scale observations may not provide information of short-lived radionuclides, which contributes the majority of radiation exposure in the early stage. In this study, the local-scale gamma dose rates data were used to estimate the atmospheric release rates of both long- and short-lived radio nuclides.The proposed method uses reactor physics to obtain an a priori radionuclide composition and a reverse source term estimate as an a priori release rate. A weighted additive model is developed, which uses the local-scale gamma dose rates to handle the conflicts between the two priors and to simultaneously incorporate them into the source inversion. The proposed method is validated against both the local-scale gamma dose rates and the regional concentration measurements of Cs-137. The results prove that the retrieved a posteriori source term combines the advantages of both priors and substantially improves the predictions of the on-site gamma dose rates. Given a detailed priori release rate, this approach also improves the regional predictions of both airborne and deposited Cs-137 concentrations.&lt;/p&gt;

AT HIGH BACKGROUND RADIATION AREAS THE RELATIONSHIP BETWEEN IN SITU INDOOR GAMMA DOSE RATES AND BUILDING MATERIALS: A CASE STUDY FROM ARIKLI VILLAGE (AYVACIK/ÇANAKKALE/TURKEY)

This study measured in situ indoor gamma dose rates in Arıklı village situated near a uranium mineralisation region, evaluated the risks of radiological health hazards and established a hypothetical relationship between these values and building materials using statistical tools. Eberline brand portable type ESP-2 model Na (I) scintillation probe connected detector was used for the measurements in 45 dwellings. Statistics revealed two groups. The first group consists of the dwellings made of bricks or mixed materials both plastered by cement, while the second group represented the dwellings made of Arıklı tuff plastered with soil (modified Arıklı tuff) or cement. For the first and second groups, respectively, the medians of the indoor gamma dose rates were 188.79 and 261.87 nGy/h; for indoor Annual Effective Dose Equivalents (AEDEin) they were 0.93 and 1.28 mSv/h; and for Excess Lifetime Cancer Risks (ELCRin) they were 3.69 and 5.12, respectively. All the values were higher than those of the world averages.