Dose Rate Calculations Research Articles

The Study of Radioactive Fallout Source of Low-Equivalent Nuclear Bursts Based on Nuclear Cloud Simulation Using the CFD-DPM

The activity-height distribution of radioactive particles in the stabilization cloud of a nuclear burst plays a crucial role in the radioactive fallout prediction model, serving as the source for transport, diffusion, and dose rate calculation modules. A gas-particle multiphase flow solver was developed using the OpenFOAM Computational Fluid Dynamics (CFD) library and discrete phase method (DPM) library under a two-way coupling regime to simulate the U.S. standard atmosphere of 1976 with good stability. The accuracy of the numerical model was verified through low-equivalent nuclear weapons tests, including RANGER-Able and BUSTER-JANGLE-Sugar, depicting reasonable spatio-temporal changes in cloud profiles. The initialization module of the Defense Land Fallout Interpretative Code (DELFIC) and activity-size distribution, which considered fractionation, were employed for nuclear fireball and radioactive particle initialization. Simulations indicated that the activity-height distribution of the stabilization cloud mainly concentrated on the lower third of air burst cloud caps, while settling near the burst center for surface or near-surface bursts. This study has confirmed the effectiveness of the gas-particle flow solver based on the CFD-DPM method in simulating low-equivalent nuclear clouds and enriching research on radioactive fallout prediction models.

AniMAIRE‐A New Openly Available Tool for Calculating Atmospheric Ionising Radiation Dose Rates and Single Event Effects During Anisotropic Conditions

AbstractAniMAIRE (Anisotropic Model for Atmospheric Ionising Radiation Effects) is a new model and Python toolkit for calculating radiation dose rates experienced by aircraft during anisotropic solar energetic particle events. AniMAIRE expands the physics of the MAIRE + model such that dose rate calculations can be performed for anisotropic solar energetic particle conditions by supplying a proton or alpha particle rigidity spectrum, a pitch angle distribution, and the conditions of Earth's magnetosphere. In this paper, we describe the algorithm and top‐level structure of AniMAIRE and showcase AniMAIRE's capabilities by analyzing the dose rate maps that AniMAIRE produces when the time‐dependent spectra and pitch angle distribution for Ground Level Enhancement (GLE) 71 are input. We find that the dose rates AniMAIRE produces for the event fall between the dose rates produced by the WASAVIES and CRAC:DOMO models. Dose rate maps that evolve throughout the event are also shown, and it is found that each peak in the input pitch angle distribution generates a dose rate hotspot in each of the polar regions. AniMAIRE has been made available openly online so that it can be downloaded and run freely on local machines and so that the space weather community can easily contribute to it using Github forking.

Shutdown dose rate calculation for fission reactors: An application of the MS-CADIS method to OPAL

There have been considerable advances of shutdown dose rate (SDDR) calculation methods for fusion related problems, however applications of these methods in the fission reactor field have hitherto been sparse. The present study attempts to bridge this gap by investigating the applicability of SDDR calculation methods for fission reactor problems. Specifically, we aim to assess and validate whether recent advances in SDDR methods can be successfully applied in fission research reactors. To this end, we estimate the shutdown dose rate distribution at the Open Pool Australian Light water reactor (OPAL) using the rigorous two step (R2S) computational method, and we compare the calculated results with the experimental data. This method utilizes a 3D reactor model implemented in the Monte Carlo N-Particle (MCNP) transport code, the AutomeD VAriaNce reduction Generator (ADVANTG) code for geometry discretization and variance reduction calculations, and the Oak Ridge Isotope GENeration (ORIGEN) inventory code for activation calculations. To ensure robustness, we employ two variance reduction techniques, Forward Weighted Consistent Adjoint Driven Importance Sampling (FW-CADIS) and Multi-Step Consistent Adjoint Driven Importance Sampling (MS-CADIS). To the best of our knowledge, this is the first MS-CADIS method implementation for fission reactor problems. The SDDR is estimated at ten locations within the experimental hall, all situated more than 4 m away from the reactor core.The paper shows that, the experimental observations are within the lower and upper bounds of the simulation results for 4 out of 10 locations, while the remaining observations are within a factor of 7, with one significant outlier. The calculated average dose rate is within 5% of the nominal values of the experimental observations for 3 locations. The computational results are within statistical uncertainty by using two different variance reduction techniques, with significant computational advantage of MS-CADIS over FW-CADIS for SDDR calculations. The results indicate that the combination of SDDR distribution maps, estimated dose rate energy dependance, and activation information are powerful tools in identifying the radioisotopes and reactor components dominating the SDDR. These results can contribute to better radiation safety practices in contaminated areas, by enabling the minimal dose path planning or by improving radiation shielding.

Determining beta radiation doses from Y-90 microsphere for the treatment of hepatic tumors by using Monte Carlo and analytical methods

The very short range of beta radiation is a potential radiation treatment for tumor, which can preserve sensitive structures. However, due to the limited range of beta radiation, practical dosimetry of beta sources may be a point of concern, and theoretical dosimetry methods play an important role. A resin microsphere loaded with the Yttrium-90 (Y-90) radionuclide can be applied in the radioembolization of hepatic tumors. In this work, we present initial calculations of dose rates around a microsphere loaded with the Y-90 radionuclide uniformly distributed on its exterior surface. Two approaches were used to carry out the estimations: the first one by means of Monte Carlo simulations using the PENELOPE code and the second one by means of the beta-point dose function formalism. A Fortran code was developed to handle with the various quantities necessary to perform the numerical integration of the beta-point dose function. A comparison between results obtained by means of both methods indicated a maximum difference of ~5% up to the 0.3 cm distance from the center of the sphere.

Assessment of the skin contamination dose coefficients for 252Cf radionuclide: Monte Carlo approach

Handling the 252Cf radionuclide source poses a potential hazard of skin surface contamination in case of an unexpected occurrence. Consequently, there is a growing need to establish precise dose conversion coefficients tailored to each type of emitted primary particle and various radionuclides. Nevertheless, the current body of literature does not provide specific data or methodologies for evaluating skin contamination dose and its associated coefficients, particularly with regard to the 252Cf source. Thus, this study aims to quantify the dose rate received by the skin and its associated coefficients after contamination scenario. Utilizing the established MCNPX environment, the Equivalent dose rate and Absorbed dose, along with Skin contamination dose coefficient (SCDC), have been calculated within the skin tissue. Two methodologies, specifically Watt Fission distribution and the Doppler Effect, are proposed to analyze particle spectra within skin phantom, enabling the calculation of Equivalent dose rate. In accordance with ICRP recommendations regarding the optimal depth for assessing skin doses, the designated scoring volume within the skin is located between depths of 50–100 μm. This volume is tasked with evaluating the dose. The SCDC results were entirely consistent with previously published data from MCNPX, with statistical uncertainties of less than 15%, demonstrating the efficacy of the methodologies employed in this study. This research presents an innovative method for generating data related to skin contamination doses. The novel outcomes in the current research facilitate the assessment of skin dose contamination for the targeted radionuclides and radiotherapy purposes due to staff oversight and radiobiological effects.

Radiological assessment of radon in groundwater of the northernmost Kashmir Basin, northwestern Himalaya.

This study investigates the radon concentration in groundwater in Kupwara, the northernmost district of the Kashmir valley. It further assesses the annual effective dose experienced by the district's diverse population-infants, children, and adults-attributable to both inhalation of airborne radon released from drinking water and direct ingestion. In addition to this, the calculation of gamma dose rate is also carried out at each of the sampling site of radon. A portable radon-thoron monitor and a portable gamma radiation detector were respectively employed to estimate the activity concentration of radon in water samples and to measure the gamma dose rate. The radon concentration was found to exhibit variability from a minimum of 2.9BqL-1 to a maximum of 197.2BqL-1, with a mean of 26.3 BqL-1 and a standard deviation of 23.3BqL-1. From a total of 85 samples, 10.6% of the samples had radon activity concentrations exceeding the permissible limits of 40BqL-1 set by the United Nations Scientific Committee on Effects of Atomic Radiations as reported by UNSCEAR (Sources and effects of ionizing radiation, 2008) and only 1.2% of the samples have radon activity concentration exceeding the permissible limits of 100BqL-1 set by the World Health Organization as reported by WHO (WHO guidelines for drinking-water quality, World Health Organization, Geneva, 2008). The mean of the annual effective dose due to inhalation for all age groups as well as the annual ingestion dose for infants and children, surpasses the World Health Organization's limit of 100μSvy-1 as reported by WHO (WHO guidelines for drinking-water quality, World Health Organization, Geneva, 2008). The observed gamma radiation dose rate in the vicinity of groundwater radon sites ranged from a minimum of 138nSvh-1 to a maximum of 250nSvh-1. The data indicated no significant correlation between the dose rate of gamma radiation and the radon levels in the groundwater. Radon concentration of potable water in the study area presents a non-negligible exposure pathway for residents. Therefore, the judicious application of established radon mitigation techniques is pivotal to minimize public health vulnerabilities.

Testing the applicability of standardised growth curves for chemically heterogeneous single-grain feldspars from the Atacama Desert, Chile

The Atacama Desert is generally considered the driest non-polar desert on Earth and is therefore an ideal study area for exploring the water and biota free endmember of Earth's Critical Zone (ECZ). Single grain (SG) luminescence dating has successfully identified processes in the ECZ. However, SG luminescence dating of Atacama Desert feldspars is challenging and time consuming since only a small fraction of grains emits sufficient luminescence and their potassium (K) contents, needed for internal dose rate calculations, are highly variable. Here we present an adaption of the standardised growth curve (SGC) method adjusted to the conditions of Atacama Desert sediments and a correlation of single-grain geochemistry and luminescence properties.To evaluate if SGCs are suitable for our study site and to determine the influence of the K-content on our luminescence age calculations, we used a set of five samples from the Atacama Desert and five chemically and structurally different feldspar sediment extracts from various geological origins worldwide. We performed a dose recovery test (DRT) using a post-infrared infrared stimulated luminescence (pIRIR) protocol and measured nine major element concentrations, including K, on a single grain level using a scanning electron microscope (SEM) with energy-dispersive X-ray spectroscopy (EDX). The DRT dataset was then used to test the application of SGCs. The accuracy of Atacama feldspar pIRIR measurements fitted onto SGCs frequently suffers from odd values in single measurement cycles, since the SGC approach developed for SG feldspar luminescence (Li et al., 2015b) uses one Lx/Tx measurement to project the Ln/Tn values onto a SGC. We investigate the influence of calculating a synthetic regenerative signal (sR) for SGC fitting, to reduce the effect of those odd values on individual grain measurements. Furthermore, we reduced the regenerative cycles used for our sR approach, to test if shorter protocols would result in equivalent dose (De) estimates in agreement with longer protocols. We then calculated Spearman rank correlations between the results obtained with our modified SGC and the SAR protocol, luminescence signal intensities, and the geochemical dataset.Finally, we present a new method of fitting data onto a SGC which significantly decreases measurement time, without risking the inclusion of outliers. We furthermore show that the luminescence signal intensities, the De values and their dose recovery ratios obtained with our SGC method and a SAR protocol, are independent of the sample geochemistry.

Shutdown dose rate calculations in high-temperature gas-cooled reactors using the MCNP-ORIGEN activation automation tool

Background High-temperature gas-cooled reactors (HTGRs) have many distinct features from the current light water reactor (LWR) fleet, and potential decommissioning strategies should take them into consideration. The proper characterization of the shutdown dose rates can establish a suitable strategy. Methods This article introduces a new shutdown dose rate calculation capability that relies on the MCNP-ORIGEN activation automation tool and the MCNP repeated structures to explicitly model the TRistructural ISOtropic (TRISO) particles as decay radiation sources. Results Three exercises are conducted with this capability, and their results discussed. The first two exercises verify and demonstrate the workflow. The third exercise proposes a decommissioning strategy for a high-temperature gas-cooled microreactor and studies its feasibility from the shutdown dose rate standpoint. The calculations yield a dose rate map above at the reactor citadel after a three month cool-down, showing values above 40 mSv/h. Conclusions The findings imply that the decommissioning strategy based on placing the reactor in a safe shutdown state and allowing it to cool down for three months before removing various components and extracting the fuel assemblies, may not be sufficient to minimize unnecessary exposure of personnel.

Accuracy of patient-specific I-131 dosimetry using hybrid whole-body planar-SPECT/CT I-123 and I-131 imaging

PurposeThis study aimed to assess the accuracy of patient-specific absorbed dose calculations for tumours and organs at risk in radiopharmaceutical therapy planning, utilizing hybrid planar-SPECT/CT imaging.MethodsThree Monte Carlo (MC) simulated digital patient phantoms were created, with time-activity data for mIBG labelled to I-123 (LEHR and ME collimators) and I-131 (HE collimator). The study assessed the accuracy of the mean absorbed doses for I-131-mIBG therapy treatment planning. Multiple planar whole-body (WB) images were simulated (between 1 to 72 h post-injection (p.i)). The geometric-mean image of the anterior and posterior WB images was calculated, with scatter and attenuation corrections applied. Time-activity curves were created for regions of interest over the liver and two tumours (diameters: 3.0 cm and 5.0 cm) in the WB images. A corresponding SPECT study was simulated at 24 h p.i and reconstructed using the OS-EM algorithm, incorporating scatter, attenuation, collimator-detector response, septal scatter and penetration corrections. MC voxel-based absorbed dose rate calculations used two image sets, (i) the activity distribution represented by the SPECT images and (ii) the activity distribution from the SPECT images distributed uniformly within the volume of interest. Mean absorbed doses were calculated considering photon and charged particle emissions, and beta emissions only. True absorbed doses were calculated by MC voxel-based dosimetry of the known activity distributions for reference.ResultsConsidering photon and charged particle emissions, mean absorbed dose accuracies across all three radionuclide-collimator combinations of 3.8 ± 5.5% and 0.1 ± 0.9% (liver), 5.2 ± 10.0% and 4.3 ± 1.7% (3.0 cm tumour) and 15.0 ± 5.8% and 2.6 ± 0.6% (5.0 cm tumour) were obtained for image set (i) and (ii) respectively. Considering charged particle emissions, accuracies of 2.7 ± 4.1% and 5.7 ± 0.7% (liver), 3.2 ± 10.2% and 9.1 ± 1.7% (3.0 cm tumour) and 13.6 ± 5.7% and 7.0 ± 0.6% (5.0 cm tumour) were obtained for image set (i) and (ii) respectively.ConclusionThe hybrid WB planar-SPECT/CT method proved accurate for I-131-mIBG dosimetry, suggesting its potential for personalized treatment planning.

Quantitative, real-time scintillation imaging for experimental comparison of different dose and dose rate estimations in UHDR proton pencil beams.

Ultra-high dose rate radiotherapy (UHDR-RT) has demonstrated normal tissue sparing capabilities, termed the FLASH effect; however, available dosimetry tools make it challenging to characterize the UHDR beams with sufficiently high concurrent spatial and temporal resolution. Novel dosimeters are needed for safe clinical implementation and improved understanding of the effect ofUHDR-RT. Ultra-fast scintillation imaging has been shown to provide a unique tool for spatio-temporal dosimetry of conventional cyclotron pencil beam scanning (PBS) deliveries, indicating the potential use for characterization of UHDR PBS proton beams. The goal of this work is to introduce this novel concept and demonstrate its capabilities in recording high-resolution dose rate maps at FLASH-capable proton beam currents, as compared to log-based dose rate calculation, internally developed UHDR beam simulation, and a fast point detector (EDGE diode). The light response of a scintillator sheet located at isocenter and irradiated by PBS proton fields (40-210 nA, 250 MeV) was imaged by an ultra-fast iCMOS camera at 4.5-12 kHz sampling frequency. Camera sensor and image intensifier gain were optimized to maximize the dynamic range; the camera acquisition rate was also varied to evaluate the optimal sampling frequency. Large field delivery enabled flat field acquisition for evaluation of system response homogeneity. Image intensity was calibrated to dose with film and the recorded spatio-temporal data was compared to a PPC05 ion chamber, log-based reconstruction, and EDGE diode. Dose and dose rate linearity studies were performed to evaluate agreement under various beam conditions. Calculation of full-field mean and PBS dose rate maps were calculated to highlight the importance of high resolution, full-field information in UHDRstudies. Camera response was linear with dose (R2 = 0.997) and current (R22 = 0.98) in the range from 2-22 Gy and 40-210 nA, respectively, when compared to ion chamber readings. The deviation of total irradiation time calculated with the imaging system from the log file recordings decreased from 0.07% to 0.03% when imaging at 12 kfps versus 4.5 kfps. Planned and delivered spot positions agreed within 0.2 0.1 mm and total irradiation time agreed within 0.2 0.2 ms when compared with the log files, indicating the high concurrent spatial and temporal resolution. For all deliveries, the PBS dose rate measured at the diode location agreed between the imaging and the diode within 3% 2% and with the simulation within 5% 3% CONCLUSIONS: Full-field mapping of dose and dose rate is imperative for complete understanding of UHDR PBS proton dose delivery. The high linearity and various spatiotemporal metric reporting capabilities confirm the continued use of this camera system for UHDR beam characterization, especially for spatially resolved dose rateinformation.

New chronology of K-feldspar isochron optical dating (iIRSL) in the late Pleistocene coastal aeolian deposits of Southeast China

Old red sand (ORS), which developed during the late Pleistocene, is widely distributed along the coasts of the western Pacific and Indian Ocean.The Optically Stimulated Luminescence (OSL) dating technology have primarily determined its sedimentary age. However, in tropical and subtropical regions, chemical weathering can impact the calculation of environmental dose rates, potentially leading to age biases whose magnitude remains uncertain.Recently, advance in the OSL dating technique, the new K-feldspar isochron dating method (iIRSL), have determined its depositional age. This approach effectively enhances the accuracy of age data by accounting for variations in past dose rates caused by chemical weathering and changes in water content during sample burial. This study used the iIRSL method to conduct infrared stimulated luminescence signal tests on ORS samples from the Haitan Island, south China. Five grain sizes of K-feldspar grains were extracted from each sample during experimentation. The single aliquot regenerative dose method (SAR) was utilized to determine the equivalent dose for each grain size and calculate age using the isochron method (iIRSL). Furthermore, it compared the iIRSL ages with quartz age (SAR). The results indicate that: (1) This study obtained four iIRSL ages, which are consistent with the ages obtained from quartz (SAR) within a reasonable range, ranging from 62.13 ± 4.85 to 39.44 ± 4.85 ka BP. (2) Comparison of the simulation results of different weathering degrees using the iIRSL method and K-feldspar two-step IRIR methods indicates that the iIRSL method can effectively mitigate the impact of chemical weathering on age determination, giving more reliable iIRSL ages. (3) The ORS along the southern coast of China mainly deposited during Marine Isotope Stages 5, 4, and 3, exhibiting relatively higher deposition rates during MIS 5 and MIS 3 at approximately 30 cm/ka and 15 cm/ka respectively. This suggests that the ORS was predominantly deposited during periods of elevated sea levels. However, it is important to note that the data from MIS 5 may have been influenced by the absence of samples from this particular stage and limitations in dating methods, resulting in a lower frequency-density of deposition ages during MIS 5 and creating an “illusion” of sediment interruption.

Absorbed dose rates and biological consequences of discrete alpha-emitting particles embedded in tissue

This study calculates dose rate in Gy y-1 for individual dust, soil, and sediment particles that contain significant amounts of alpha-emitting uranium or thorium. When inhaled or ingested, these particles deliver radiation dose to organs where they embed. The presented method uses X-ray microscopy to measure alpha emitting elements in environmental microparticles, followed by calculation of dose rates delivered to the targeted volume of tissues that surround embedded microparticles. The example calculations use a real-world, 89% uranium house dust particle.

Calibration of buried NaI(Tl) scintillator detectors for natural radionuclide measurement based on Monte Carlo modelling

Measurements of naturally occurring concentrations of 40K, and of the decay series of 238U and 232Th, are of interest in the earth sciences in general, and in particular, scintillator-based gamma spectrometers can be used for the low cost determination of burial dose rates in natural geological samples. We are currently developing a robust, portable, wireless detector specifically intended for field measurement of natural radionuclide concentrations and hence, the calculation of dose rates. One of the challenges in developing and applying such an instrument is reliable calibration. Most calibrations of field instruments depend on access to non-finite matrices of known K, U, Th activity concentrations, in either a 4π or 2π geometry; these are only available at a few facilities around the world. Here we investigate an alternative approach, based on the measurement of small samples containing well-known activity concentrations of only K or U or Th, and Monte-Carlo radiation transport modelling to convert the observed spectra into those expected from specific activity concentrations in a non-finite 4π geometry. We first validate our modelling procedure by simulating these observed spectra. The non-finite matrix calibration spectra are then predicted, and least-squares fitted to the spectrum observed at the centre of a 1 m3 of granite chips; the resulting predicted U, Th and K activity concentrations are compared with independently known values.

Relevance of radon progeny measurements for the assessment of inhalation doses in groundwater utilities

The high radon concentrations measured in the indoor air of groundwater facilities and the prevalence of the problem have been known for several years. Unlike in other workplaces, in groundwater plants, radon is released into the air from the water treatment processes. During the measurements of this study, the average radon concentrations varied from 500 to 8800 Bq m–3. In addition, the indoor air of the treatment plants is filtered and there are no significant internal aerosol sources. However, only a few published studies on groundwater plants have investigated the properties of the radon progeny aerosol, such as the equilibrium factor (F) or the size distribution of the aerosol, which are important for assessing the dose received by workers. Moreover, the International Commission on Radiological Protection has not provided generic aerosol parameter values for dose assessment in groundwater treatment facilities. In this study, radon and radon progeny measurements were carried out at three groundwater plants. The results indicate surprisingly high unattached fractions (fp = 0.27–0.58), suggesting a low aerosol concentration in indoor air. The corresponding F values were 0.09–0.42, well below those measured in previous studies. Based on a comparison of the effective dose rate calculations, either the determination of the fp or, with certain limitations, the measurement of radon is recommended. Dose rate calculation based on the potential alpha energy concentration alone proved unreliable.

Development and validation of fully open-source R2S shutdown dose rate capabilities in OpenMC *

We present the first fully open-source capabilities for shutdown dose rate (SDR) calculations of fusion energy facilities based on the Rigorous 2-Step (R2S) methodology. These capabilities have been implemented in the OpenMC Monte Carlo particle transport code, building on its existing capabilities while also leveraging new features that have been added to the code to support SDR calculations, such as decay photon source generation. Each of the individual physics components in the R2S workflow—neutron transport, activation, decay photon source generation, and photon transport—have been verified through code-to-code comparisons with MCNP6.2 and FISPACT-II 4.0. These comparisons generally demonstrate excellent agreement between codes for each of the physics components. The full cell-based R2S workflow was validated by performing a simulation of the first experimental campaign from the Frascati Neutron Generator (FNG) ITER dose rate benchmark problem from the Shielding INtegral Benchmark Archive and Database (SINBAD). For short cooling times, the dose calculated by OpenMC agrees with the experimental measurements within the stated experimental uncertainties. For longer cooling times, an overprediction of the shutdown dose was observed relative to experiment, which is consistent with previous studies in the literature. Altogether, these features constitute a combination of capabilities in a single, open-source codebase to provide the fusion community with a readily-accessible option for SDR calculations and a platform for rapidly analyzing the performance of fusion technology.

Activity and Dose Rate Calculations for Joint European Torus Outer Long-Term Irradiation Station during Tritium and Second Deuterium Tritium Experiment Campaigns

The Joint European Torus (JET) is playing an important role in preparing for the operation of the future world’s largest tokomak, ITER. In this respect, the tritium campaign (C40) and second deuterium–tritium experiment (DTE2, C41) took place in the JET during the years 2021 and 2022. In this work, a corresponding irradiation scenario was utilized for the activation calculations of eight material foils located at the JET outer long-term irradiation station (OLTIS). Neutron-induced activities and dose rates at a 30 cm distance after shutdown at specified cooling intervals were calculated with the FISPACT-II code, employing the EAF-2010 nuclear and TENDL-2021 data libraries. The Monte Carlo MCNP6.2 particle transport code equipped with the FENDL-3.1d nuclear data library was used for the calculation of the neutron flux densities.

Voxel-wise dose rate calculation in clinical pencil beam scanning proton therapy

Objective. Clinical outcomes after proton therapy have shown some variability that is not fully understood. Different approaches have been suggested to explain the biological outcome, but none has yet provided a comprehensive and satisfactory rationale for observed toxicities. The relatively recent transition from passive scattering (PS) to pencil beam scanning (PBS) treatments has significantly increased the voxel-wise dose rate in proton therapy. In addition, the dose rate distribution is no longer uniform along the cross section of the target but rather highly heterogeneous, following the spot placement. We suggest investigating dose rate as potential contributor to a more complex proton RBE model. Approach. Due to the time structure of the PBS beam delivery the instantaneous dose rate is highly variable voxel by voxel. Several possible parameters to represent voxel-wise dose rate for a given clinical PBS treatment plan are detailed. These quantities were implemented in the scripting environment of our treatment planning system, and computations experimentally verified. Sample applications to treated patient plans are shown. Main results. Computed dose rates we experimentally confirmed. Dose rate maps vary depending on which method is used to represent them. Mainly, the underlying time and dose intervals chosen determine the topography of the resultant distributions. The maximum dose rates experienced by any target voxel in a given PBS treatment plan in our system range from ∼100 to ∼450 Gy(RBE)/min, a factor of 10–100 increase compared to PS. These dose rate distributions are very heterogeneous, with distinct hot spots. Significance. Voxel-wise dose rates for current clinical PBS treatment plans vary greatly from clinically established practice with PS. The exploration of different dose rate measures to evaluate potential correlations with observed clinical outcomes is suggested, potentially adding a missing component in the understanding of proton relative biological effectiveness (RBE).

Assessment of radiation environmental risks for fish fauna of the cooling pools of a number of operating nuclear power plants

Relevance. The need to assess radiation risks for the main types of fish in pools that are under the constant influence of the nuclear power plants. Aim. To assess the radiation environmental risks for the ichthyofauna of cooling pools of the operating nuclear power plants, to analyze the sources and features of formation of the radiation risks at different stages of their operation. Objects: monitoring studies of radiation environmental risks for reference fish species in cooling reservoirs of the Leningrad, Beloyarsk and Novovoronezh NPP. Methods. Calculation of the exposure dose rate and quantitative assessment of the risk of exposure to technogenic radionuclides of the ichthyofauna of the cooling pools of the Beloyarskaya, Leningradskaya and Novovoronezhskaya NPPs were carried out using the international computer complex of the updated version of ERICA Tool 2.0. Results. The paper demonstrates that the radiation ecological risks for the ichthyofauna in the cooling pools of the operating nuclear power plants are caused by the combined effect of radioisotopes of the different origin. The features of the formation of the radiation risks for each pool are specific and depend on the current radiation situation. The cooling pool of the Beloyarskaya NPP is characterized by a pronounced dependence of the radiation load on the types of operating power units. The ichthyofauna experienced the greatest radiation risks during the operation of the first two power units with thermal reactors AMB-100 and AMB-200. The decommissioning of the first power units and the construction of the units with the fast neutron reactors (BN-600 and BN-800) led to a significant reduction in the radiation load on the ichthyofauna of the cooling pool. At present, the radiation risks are caused mainly by the influence of 90Sr, which is almost not discharged from the Beloyarskaya NPP into the cooling pools, but has a predominantly global origin. Therefore, the formation of the risks is more associated with atmospheric fallout of 90Sr, and not with the operation of the nuclear power plant. The radiation risks for the ichthyofauna of the Leningradskaya NPP cooling pool are caused by the combined effect of 137Cs as a result of the radiation accident at the Chernobylskaya NPP and radionuclides with induced activity (14C; 60Co; 3H 54Mn and 65Zn), the origin of which may be associated with the operation of the nuclear reactors of the NPP. The level of radiation risk for the fish fauna of the Novovoronezhskaya NPP cooling pool for 2009–2019 increased 2.2 times due to an increase in the content of 60Co in many components of the pool. As a result, 81.7% of the radiation risks in demersal fish species were formed by the influence of 60Co. It cannot be ruled out that the increase in the 60Co content in the cooling pool of the Novovoronezhskaya NPP is a consequence of radioactive contamination of the groundwater as a result of the 1985 accident. The ecological risks for the fish fauna in all cooling pools are two to three orders of magnitude lower than the maximum allowable hazard coefficient. Thus, the normal operation of the nuclear power plants does not create unacceptable radiation risks that pose a real environmental threat to the fish fauna of the cooling pools.

Efficiency of variance-reduction techniques using TRIPOLI-4®: Application to equivalent dose rate calculations in a spent-fuel cask

This paper presents the comparison of different variance-reduction methods implemented in the Monte Carlo code TRIPOLI-4® in the case of a deep penetration problem. In this complex radiation transport situation, where the shielding is very thick to ensure protection, variance-reduction methods are necessary to obtain results with a good accuracy in a reasonable calculation time. The configuration investigated in this work is a spent-fuel transport cask. The various variance-reduction methods used here consist either of Importance Sampling with the Exponential Transform method, or of sophisticated population-control methods. These methods are detailed, then the results are presented and compared and the efficiency of these methods is investigated. While all methods implemented in TRIPOLI-4® are efficient versus analog simulations, the pre-calculation of importance maps with deterministic methods enables a faster convergence of the Monte Carlo simulations, especially when combined with the Exponential Transform.

A weight window approach for dose rate calculations in Lead-cooled Fast Reactors with OpenMC

This paper presents the application of a variance reduction technique for radiation shielding calculations in Lead-cooled Fast Reactors (LFRs) using the OpenMC Monte Carlo code. The study focuses on assessing the computational efficiency of the Method of Automatic Generation of Importances by Calculation (MAGIC). This technique is employed to generate weight windows for Monte Carlo simulations, aiming at enhancing the efficiency of dose rate estimations for LFRs. Through a detailed study of a LFR mock-up model, the performance differences between a MAGIC-accelerated and a non-accelerated simulation are investigated in terms of both accuracy and computational cost. The results demonstrate the benefits of the variance reduction method, showing its effectiveness in spreading particles throughout the model while improving the accuracy of Monte Carlo estimates far from the core. In addition, this work demonstrates the performances of the MAGIC method in eigenvalue calculations. This work shows an interesting optimisation of Monte Carlo simulations for LFRs and can be considered as a first milestone for newcleo’s radiation shielding studies.