Fukushima Nuclear Accident Research Articles

Research Progress of ODS FeCrAl Alloys-A Review of Composition Design.

After the Fukushima nuclear accident, the development of new accident-tolerant fuel cladding materials has become a research hotspot around the world. Due to its outstanding corrosion resistance, radiation resistance, and creep properties at elevated temperatures, the oxide dispersion strengthened (ODS) FeCrAl alloy, as one of the most promising candidate materials for accident-tolerant fuel cladding, has been extensively studied during the past decade. Recent research on chemical composition design as well as its effects on the microstructure and mechanical properties has been reviewed in this paper. In particular, the reasonable/optimized content of Cr is explained from the aspects of oxidation resistance, radiation resistance, and thermal stability. The essential role of the Al element in oxidation resistance, high-temperature stability, and workability was reviewed in detail. The roles of oxide-forming elements, i.e., Y (Y2O3), Ti, and Zr, and the solid solution strengthening element, i.e., W, were discussed. Additionally, their reasonable contents were summarized. Typical types of oxide, i.e., Y-Ti-O, Y-Al-O, and Y-Zr-O, and their formation mechanisms were also discussed in this paper. All aspects mentioned above provide an important reference for understanding the effects of composition design parameters on the properties of nuclear-level ODS FeCrAl alloy.

An optimisation method to improve modelling of wet deposition in atmospheric transport models: applied to FLEXPART v10.4

Abstract. Wet deposition plays a crucial role in the removal of aerosols from the atmosphere. Yet, large uncertainties remain in its implementation in atmospheric transport models, specifically in the parameterisation schemes that are often used. Recently, a new wet deposition scheme was introduced in FLEXPART. The input parameters for its wet deposition scheme can be altered by the user and may be case-specific. In this paper, a new method is presented to optimise the wet scavenging rates in atmospheric transport models such as FLEXPART. The optimisation scheme is tested in a case study of aerosol-attached 137Cs following the Fukushima Daiichi nuclear power plant accident. From this, improved values for the wet scavenging input parameters in FLEXPART are suggested.

Estimation of external dose for wild Japanese macaques captured in Fukushima prefecture: decomposition of electron spin resonance spectrum.

The signal intensities of CO2- radicals in teeth can be utilised as an individual indicator of the cumulative external dose for animals. To accurately determine the external dose, it is desirable to analyse the CO2- radical intensity and improve its detection limit. We recently reported a dose-response in the range of 0-200mGy and estimated the absorbed dose for seven wild Japanese macaques captured in/around the related areas to the Fukushima Daiichi Nuclear Power Plant accident. Herein, for further improvement of this method, we examined the electron spin resonance spectra of the teeth of these seven and an additional four macaques captured in Fukushima by applying two spectrum-decomposition algorithms.

Area Dose-Response and Radiation Origin of Childhood Thyroid Cancer in Fukushima Based on Thyroid Dose in UNSCEAR 2020/2021: High 131I Exposure Comparable to Chernobyl.

The FMU and the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) concluded that the high incidence of thyroid cancer after the Fukushima nuclear accident was not the result of radiation exposure, but rather might have been overdiagnosis based on the low thyroid dose estimated in the UNSCEAR 2020/2021 report. In this study, the origin of increased PTC in Fukushima was examined based on the thyroid dose estimated by UNSCEAR. The dose-response relationship of the incidence rate per person-years (PY) was analyzed for four areas in Fukushima prefecture via regression analysis. The linear response of the annual incidence rates to thyroid dose in the first six years showed that the dominant origin of childhood thyroid cancer was radiation exposure. Excess absolute risk (EAR) proportionally increased with thyroid dose, with an EAR/104 PY Gy of 143 (95%CI: 122, 165) in the second TUE (p < 0.001), which is approximately 50-100 times higher than the EAR/104 PY Gy ≒ 2.3 observed after the Chernobyl accident. This suggests an underestimation of the thyroid dose by UNSCEAR of approximately 1/50~1/100 compared with the thyroid dose for Chernobyl. The increased childhood thyroid cancer in Fukushima was found to arise from radioactive iodine exposure, which was comparable to that in Chernobyl.

Monitoring of 137Cs, 239+240Pu, and 90Sr in the marine environment of South Korea and their impact on marine biota: 10 years after the Fukushima accident

This study conducted an analysis of the behavior of radionuclides and assessment their radioactive risk based on seawater and seabed sediment samples gathered from the East, South, and Yellow Seas of South Korea over the period from 2011 to 2020. The distribution for each radionuclides in seawater obtained from the East, South, and Yellow Seas were similar. However, the concentrations of 137Cs and 239+240Pu in sediments from the East Sea were observed to be higher compared to those from the South and Yellow Seas. This variation can be attributed to differences in the ocean inflow, water column properties, and seabed characteristics among the seas around South Korea. There were no statistically significant differences between the radioactive concentrations of seawater and seabed samples collected before and after the Fukushima accident, and no areas with unusually high radiation levels were detected. Using the distribution coefficient (Kds) and the concentration ratio (CR) calculated from the 2011-to-2020 data, we evaluated the radiological impact on fish. The ERICA tool was utilized to assess these data, and indicated a negligible radiological risk from radioactivity in the seawater, seabed sediments, and marine biota in the South Korean Ocean.

Association between the deaths indirectly caused by the Fukushima Daiichi nuclear power plant accident (disaster-related deaths) and pre-disaster long-term care certificate level: A retrospective observational analysis

The health of the vulnerable populations receiving the Long-Term Care (LTC) Insurance Programs was threatened by the direct and indirect effects of disasters. The 2011 Great East Japan Earthquake and Tsunami and the explosion at the Fukushima Daiichi nuclear power plant (FDNPP) forced 164,865 people's evacuation and caused many disaster-related deaths. We examined the relationship between these deaths and LTC certification. Data were collected from 520 people who were living in Minamisoma City during the earthquake and whose deaths were certified as disaster-related by the Minamisoma City Committee for Certification of Disaster-Related Deaths from September 2011 to February 2021; 467 (90.0%) responded to the LTC item on the survey form, of which 200 (38.5%) were not certified and 266 (51.3%) were certified for LTC. People with high levels of LTC certification needs during the acute phase of the earthquake were found to be more likely to die from circulatory and respiratory diseases. The mean time from disaster to death was shorter for those with higher levels of LTC; it was significantly shorter for those with long-term care level 3 and above. This study points out the importance of timely response with regard to disaster-related deaths and long-term care. Further studies are needed to examine how medical resources can be deployed in a timely manner.

Against an insufficient intervention for patients with alcoholism or PTSD: An activity report on a psychiatric clinic after the 2011 complex disaster in Fukushima, Japan

Despite numerous studies using questionnaires to assess mental health problems among disaster victims following a disaster, only a few have examined actual medical treatment situations. Surveys of residents in disaster-affected areas following the Great East Japan Earthquake and Fukushima nuclear power plant disaster also indicate deteriorated mental health among survivors; however, concrete evidence of increased individuals seeking treatment at psychiatric institutions is still scarce.Using medical records of a psychiatric clinic in an affected area during the chronic phase after a disaster, this study investigated the status of interventions for patients with alcoholism, post-traumatic stress disorder (PTSD), and others, including whether violence occurred during treatment.We found that 730 patients visited the clinic for a year, but a few with alcoholism received treatment. Patients who experienced traumatic stress during the disaster had a higher treatment discontinuation rate, though it is not correlated with their involvement in violence. However, a diagnosis of complex PTSD was correlated with involvement in violence during the treatment.The psychiatric clinic providing care during the chronic phase of the post-disaster period did not provide sufficient treatment for alcoholism, where therapeutic interpersonal interaction is emphasized, or for PTSD, where trauma-focused psychotherapy is the standard of care. It is difficult to ensure the availability of highly specialized resources and the establishment of comprehensive ties with the local people in affected areas, however, such a situation poses a challenge.

Assessment of the behavior of spent nuclear fuel in Ukraine

Abstract. Before June 2023 the Zaporizhzhya Nuclear Power Plant, which is the largest nuclear facility in Europe, had suffered a complete loss of external power seven times since the beginning of the Russian invasion. This forced it to rely on emergency diesel generators to guarantee the safety and security functions of the plant, such as reactor cooling. From that, it appears of meaningful importance to evaluate the performance of all its nuclear facilities, among which the building where the spent fuel storage pool (SFP) is located, to assess what consequences anomalous/abnormal or accident events may determine. Contrary to dry storage, the dry cask/packaging system is stored on open concrete pads within a protected area of the plant site; the wet storage requires a hydraulic environment such as the water pools where SF is safely stored. The hydraulic effluent and the physical containment barriers act as confinement and shielding, guaranteeing safety criteria are fulfilled. In this preliminary study, the attention is thus paid to the SFP; for this reason, a description of its behavior and filling status must be provided. Since 2001, spent nuclear fuel (SNF) from 6 VVER (water–water energy reactor)-1000 units has been stored in the dry storage facility at the Zaporizhzhya Nuclear Power Plant. This means that, despite radioactive decay, the total activity of such inventory may exceed 30 times that of the fourth damaged Chornobyl unit at the time of the accident, and this is due to long-lived actinides (2 × 1019 Bq), 137Cs (1 × 1019 Bq) and 90Sr (9 × 1018 Bq). Continued damage caused by a missile attack on the SFP (e.g., cyclic, dynamic, and thermal loadings) may increase the risk of loss of integrity, because, as it is widely known, concrete has low resistance under tension. In this assessment, an evaluation, therefore, the radiological risk is addressed. For such an evaluation, it is considered that an SFP in VVER-1000 is designed to store 687 fuel assemblies and 670 in VVER-440. When it is half full, which is the case for 15 Ukrainian units, it will store about 2200 t U, containing up to 1 × 1019 Bq of 137Cs, 7 × 1018 Bq of 90Sr and 1 × 1019 Bq of TUE. Moreover, if it is considered that the spent fuel pool represented the Achilles' heel of the nuclear power plant during the 2011 Fukushima accident, it appears quite obvious that there is a need to evaluate the threat associated with the SF storage condition in order to prevent the occurrence of a new severe accident or other challenging situations that the armed conflict has created and may create. The results of the analysis of the Zaporizhzhya Nuclear Power Plant behavior suggest firstly that the plant was/is subjected to high stresses its structures may not withstand for a long time. Secondly, damages may impact SFP instrumentation, which is used for monitoring, for example, radiation or hydrogen formation, leading to loss of control of the SFP facility. Further, it is shown that to prevent the global nuclear threat, nuclear safety and security systems must be maintained and upgraded with at least the introduction of new technical and environmental devices.

Origin and pathway of a subsurface maximum of 137Cs detected in the winter of 2012 after the Fukushima accident

This study investigates the dispersion behavior of 137Cs and evaluates its origin (atmospheric deposition or direct ocean release) from the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident using a Lagrangian particle tracking model. The ocean circulation fields based on the Modular Ocean Model Version 5 (MOM5) were adopted for the simulation. The MOM5 results represented the formation and migration of subtropical mode water (STMW) comparable with observations and reanalysis data. Particularly, anticyclonic eddies south of the Kuroshio extension promoted surface mixing over 300 m in the cooling season. The particle tracking simulation reproduced well the maximum subsurface activity between 142 and 146°E, where STMW is deep owing to anticyclonic eddies, compared to the activity found via measurements conducted around 149°E in the winter of 2012. It also demonstrated that the 137Cs of the tropical and subtropical regions (10–35°N, 142–146°E) in the winter of 2012 almost entirely originated from atmospheric deposition.

Impacts of environmental decontamination on the rebuilding of returnees' lives after the Fukushima accident.

Environmental decontamination after a nuclear disaster not only contributes to reducing the public's exposure to radiation, it also introduces waste disposal issues arising from the decontamination process. In addition to that issue, the optimisation of decontamination efforts necessitates the consideration of various environmental, economic, and societal factors. Stakeholders' perspectives are important for identifying the multifaceted aspects to be considered. We conducted a semi-structured interview survey in 2019 with ten residents in a rural community in Fukushima, Japan, which experienced a six-year-long evacuation due to the 2011 Fukushima Daiichi Nuclear Power Plant accident. The main survey questions addressed returnees' perceptions of the decontamination of farmlands and forests. The 'Steps for Coding and Theorization' procedure was used for qualitative analysis. The analysis illuminated the positive and negative impacts of the decontamination process on the rebuilding of the returnees' rural lives from various perspectives and identified elements to be considered for the optimisation of future remediation efforts. The removal of radioactive materials had a positive psychological impact on the returnees, fostering a sense of security that their crops were safe and instilling confidence that the high-quality environment of the region had been restored. These aspects were not included among the initial governmental objectives for decontamination, which were aimed solely at reducing radiation exposure. By contrast, the removal of fertile topsoil from farmland had a negative impact on the residents, making them hesitant to resume farming. Our findings suggest that emphasising procedural fairness in decision-making of decontamination options such as reflection of stakeholders' opinions led to residents perceiving their post-decontamination situation more positively. Our results provide valuable insights for optimising remediation strategies for the recovery process following a significant nuclear accident.

No increase in translocated chromosomal aberrations, an indicator of ionizing radiation exposure, in childhood thyroid cancer in Fukushima Prefecture

To investigate the effects of radiation exposure due to the Fukushima nuclear power plant accident, following the disaster Fukushima Prefecture launched thyroid ultrasound examinations of residents who were generally younger than 18 years at the time of the earthquake. As the rate of pediatric thyroid cancer was higher than expected, we conducted biological dose assessment based on the frequency of translocated chromosome (Tr) aberrations using peripheral blood lymphocytes. Tr formation frequency was compared among the thyroid cancer (n = 38, median age 18 years, age range 12–26 years), thyroid-related disease (n = 30, median age 21 years, age range 15–28 years), and healthy controls (n = 31, median age 22 years, age range 20–23 years) groups. Tr aberration frequency was initially significantly higher in the thyroid cancer than in the other two groups; however, differences among the groups disappeared after adjusting for history of CT scan, as 92%, 67%, and 28% of those in the thyroid cancer, thyroid-related disease, and control groups, respectively, had undergone CT previously. Therefore, the significant difference in the initial number of Tr formations is presumably due to radiation exposure from CT. Accordingly, the effects of medical exposure on the chromosomes of children and adolescents should be noted.

Explaining the variation in 137Cs aggregated transfer factor for wild edible plants as a case study on Koshiabura (Eleutherococcus sciadophylloides) buds

The aggregated transfer factor (Tag) is commonly used to represent the actual transfer of radiocesium from soil to wild edible plants, but the values have shown substantial variation since the Fukushima nuclear accident. To elucidate the factors causing this variation, we investigated the effects of spatial scale and vertical 137Cs distribution in the soil on the variation of Tag-137Cs values for one of the most severely contaminated wild edible plants, Eleutherococcus sciadophylloides Franch. et Sav. (Koshiabura). The variation in Tag-137Cs values was not reduced by direct measurement of 137Cs deposition in soil samples from the Koshiabura habitat, as a substitute for using spatially averaged airborne survey data at the administrative district scale. The 137Cs activity concentration in Koshiabura buds showed a significant positive correlation with the 137Cs inventories only in the organic horizon of soil from the Koshiabura habitat. The ratio of 137Cs inventories in the organic horizon to the total 137Cs deposition in soil exhibited substantial variation, especially in broad-leaved deciduous forests that Koshiabura primarily inhabits. This variation may be the cause of the wide range of Tag-137Cs values observed in Koshiabura buds when calculated from the total 137Cs deposition in soil.

Does the Fukushima nuclear accident still matter? Analysis of its mediated effects on five dimensions of nuclear power acceptance by using the parallel multiple mediator model

Although 10 years have passed since the Fukushima nuclear accident, it continues to greatly impact global energy policy and the acceptance of nuclear power. This study aims to empirically analyze the Fukushima accident's effects on five dimensions of nuclear power acceptance and the interactions of these effects with various determinants of nuclear power acceptance. We analyze survey data from 1020 Korean respondents and find that they remain highly worried about the Fukushima accident 10 years later. The Fukushima accident has negative impacts on the general acceptance of nuclear power, acceptance of nuclear power's contributions to addressing climate change, acceptance of high-level radioactive waste disposal sites, and acceptance of extensions of old nuclear power plants. However, the accident has a positive impact on the acceptance of denuclearization policies. Our parallel multiple mediator model shows that the Fukushima accident has only an indirect effect on general acceptance; this effect is negative and significant. The accident has a positive direct and indirect effect on acceptance of denuclearization policies but negative direct and indirect effects on the acceptability of high-level nuclear waste disposal and extensions of old nuclear power plants. Finally, we find a positive direct effect and a negative indirect effect of the accident on acceptance of nuclear power's contributions to addressing climate change. The latter is greater than the former, meaning that acceptance of nuclear power in the context of addressing climate change fell in response to the accident. In short, the Fukushima accident has different direct and indirect effects across different dimensions of nuclear power acceptance.

How to reduce the impact of contaminated seafood on public health with the discharge of Fukushima nuclear wastewater

As wastewater from the Fukushima nuclear disaster continues to drain into the sea, the supply system for healthy seafood is being seriously challenged. To protect public health, it is necessary to restructure the seafood supply mode. The seafood supply mode is divided into the original mode, land farming mode, and strengthen monitoring mode. To derive the applicable scope of the various modes of the seafood supply chain and to provide recommendations for the safety and sustainability of seafood supply chains for governments and enterprises, three differential game models are constructed in this study. Then, the equilibrium results obtained by the models are compared and analyzed. Based on the findings, the health impact of seafood pollution is relatively small, and the government tends to choose the original supply mode. As the health impact of seafood grows, governments tend to prefer land-based farming. The social benefit to the government is directly proportional to the monitoring cost of seafood. To protect public health, enterprises tend to choose the mode of strengthen monitoring if the proportion of unqualified seafood is low. In addition, if sea products show a high degree of adaptation to the land environment, they tend to choose land farming.

Concurrent datasets on land cover and river monitoring in Fukushima decontaminated catchment during 2013–2018

After the Fukushima nuclear accident, the Japanese government implemented extensive decontamination work in 137Cs contaminated catchments for residents’ health and local revitalization. Whether dramatic land use changes in the upstream decontaminated regions affected river suspended sediment (SS) and particulate 137Cs discharge downstream remain unknown because of the poor quantification on land cover changes and long-term river SS dynamics. We here introduce a 6-year concurrent database of the Niida River Basin, a decontaminated catchment, including the first available vector decontamination maps, satellite images in decontaminated regions with a spatial resolution of 10 m, and long-term river monitoring datasets spanning decontamination (2013–2016) and subsequent natural restoration stages (2017–2018). These datasets allow us, for the first time, to directly link the transport dynamics of river SS (particulate 137Cs) to land use changes caused by humans in real-time, which provide fundamental data for better understanding the river response of sediment to land use change. Moreover, the data obtained by interdisciplinary methods offer a template for land use change impact assessment in other river basins.

Restoring areas after a radioactive fallout: A multidisciplinary study on decontamination

Land remediation is an important part of restoration measures after a radioactive fallout containing long-lived fission products such as 137Cs. In this multidisciplinary study, we focused on three main issues related to remediation of contaminated urban areas. First, we assessed how much decontamination contributes to reducing resident radiation exposure and how much this reduction depends on the timing of implemented measures. Second, we calculated direct and indirect costs of decontamination in an industrialized country such as Sweden. Finally, in a survey study, we considered reactions of Swedish citizens to being given the hypothetical option of moving to a site decontaminated after radioactive fallout and how this predicted response might influence the design of contingency plans.The main findings are that clean-up operations must be done within the first few years after a fallout to contribute significantly to reducing residual dose. If conducted within 1–2 years, large-scale decontamination can, on average, avert 20–200 manSv per km2 residential area and unit ground deposition of 137Cs (1 MBq). The estimated direct costs (in 2020 purchasing power) would amount to 100 million Euro per km2 decontaminated residential area (comparable to Japanese estimates after the Fukushima accident), generating 39,000 m3 of radioactive waste on average, mainly in the form of 137Cs-contaminated topsoil. In our survey study of 2291 Swedish respondents about their willingness to return to decontaminated homes, women, families with resident children, and high-income earners exhibited more skepticism about returning, even if authorities were to deem it safe. The demographic pattern in attitudes was similar to that found among evacuees in the Fukushima prefecture after 2011.We conclude that predefined ranges of measured 137Cs ground deposition can be used as guidance for rescue leaders in the early post-accident phase in long-term planning for affected areas. This planning should include timing and intensity of decontamination measures, duration of evacuation, and risk communication to citizens. Because some citizens expressed both high risk perception and risk aversion, however, timely and dialogic communication is unlikely to limit a shift after the incident to an older and more male-dominated population composition. There is a risk that those who can afford to do so will move away, whereas people whose wealth is locked in property (houses or businesses) will feel stuck. Perceptions of unfairness may fray the social fabric and complicate resettlement, which in some cases may mean inefficient outlay of decontamination costs. We believe that the issue of monetary compensation to affected residents requires priority in future work.

Development of reference material for quality control of uranium analysis in marine sediments

Environmental radioactivity monitoring is strengthening due to public concerns over radioactive contamination since the Fukushima nuclear power plant accident. Therefore, various research laboratories, institutes, and universities have been conducting environmental radioactivity surveys around nuclear power plants (NPPs). However, the reliability of the results continues to trigger controversy in society. This study was conducted to develop reference material (RM) for the quality control of 238U and 234U analyses in marine sediments. The RM was prepared according to ISO Guides 31, 34, and 35. A homogeneity test of the marine sediment RM was implemented by analyzing two batch samples from ten bottles using multiple acid digestion and alkali fusion, respectively. We found that the 238U and 234U reference values of the RM were 43.0 ± 1.7 Bq kg−1(k=1) and 41.5 ± 1.9 Bq kg−1(k=1), respectively. This marine sediment RM will be useful for the quality control of analytical methods for similar samples and proficiency tests.

CrN–NbN nanolayered coatings for enhanced accident tolerant fuels in BWR

The accident tolerant fuel (ATF) concept has emerged in the years after the 2011 Fukushima accident as part of a renewed effort in research for light water reactors. The primary focus is to further improve safety measures under and beyond design basis accident conditions, and to improve fuel cladding performance in normal operation. The application of a coating on zirconium claddings can achieve both these aims without extensive changes to the reactor design. Metallic chromium coatings have been profusely studied as solution for pressurized water reactors, but the search for an effective ATF coating able to withstand the environment inside boiling water reactors (BWRs) is still ongoing. In this work, two different versions of a novel nitride coating composition were studied. Zirconium claddings coated with 8 µm thick layers of superlattice CrN–NbN and a nanolayered CrN–NbN were tested in autoclave under BWR operating conditions for 60 days. Scanning electron microscopy, transmission electron microscopy, energy dispersive x-ray spectroscopy, electron back-scattered diffraction, x-ray diffraction, and atom probe tomography were employed to characterize as-deposited and autoclaved samples of these two materials. During exposure, both coating versions formed a stable, dense and passivating oxide scale (200–300 nm thick) on the surface, demonstrating improved oxidation protection under operating conditions. Some differences in the oxide growth mechanism were observed between the superlattice and the nanolayered CrN–NbN coatings, which allowed to glimpse at the effect of the layer thickness on the oxidation protection provided by these coatings. The nano-structured morphology of both coatings remained unaffected by the autoclave test, but a 35 nm thick Zr-Cr-N phase was found at the coating-substrate interface of the superlattice CrN–NbN coated cladding.

Constructing and using an experimental space for resolving crisis: A case study of a chemical leak following an industrial accident

AbstractThis article argues that space plays an active role in shaping collective responses to crisis situations. While it is well known that the physical features of a place affect the way industrial accidents can be managed by response and rescue teams, this article will examine another important aspect of space: its role in helping to resolve crises. We present a case study involving a French complex where a chemical cloud, emitting an odor reminiscent of household natural gas, was accidentally released. Based on interviews with key participants, as well as a variety of documents, we will explain how the physical and material features of the accident site can be used to transform a situation of great uncertainty and chaos into a well‐designed and controlled experiment, thereby aiding in crisis resolution. This article contributes to crisis literature by shedding new light on the role of space in crisis resolution using the concepts of boundaries, movement, and distance, and by contrasting the case with the Fukushima Daiichi accident. By conceptualizing space not only as a reservoir of information and evidence, but also as a tangible foundation, it becomes feasible to utilize it as a valuable resource for managing and resolving future crises.

Internal organ dose rate conversion coefficients of Japanese macaques to 134Cs,137Cs and 131I†.

The purpose of this study was to estimate the internal dose of radiation in Japanese macaques (aka Nihonzaru or snow monkey) due to the Fukushima nuclear power plant accident. Images of a male Japanese macaque weighing ~10kg were acquired using a multi-slice computed tomography (CT) scan with a 64-row segment detector. The CT images were used to create voxel phantoms of the bones, bone marrow, brain, eyes, heart, lungs, stomach, liver, spleen, pancreas, kidneys, intestines, bladder, testes, thyroid and miscellaneous tissue. The Particle and Heavy Ion Transport System (PHITS) Monte Carlo code was used to calculate the internal exposure rate conversion factors for 134Cs, 137Cs and 131I isotopes for the created voxel phantoms with a statistical precision higher than 1%. The PHITS-calculated energy deposits were compared with those for rhesus monkeys. The results showed that the fractions of energy deposits for β-radiation in different organs were almost identical between the two species. For γ-radiation, there was excellent agreement in the self-absorption rate with the approximate curve of the Japanese macaque, with an average deviation of 2%. The maximum deviation of 12% was for the kidney, which has two organs, so the error with the approximate curve is slightly larger due to the energy loss created between organs.