Distribution Of Nuclides Research Articles

Estimating the effects of homogenized fuel temperature in group constant generation using Serpent 2

We extend the multi-physics capabilities of the Serpent 2 Monte Carlo code to coupled burnup calculations by implementing the Stochastic Implicit Euler depletion scheme with thermal feedback. We use these new multi-physics capabilities for the verification of the traditional way of generating group constants using an effective flat fuel temperature profile during the burnup calculation. We investigate the effects of this approximation on the generated nuclide compositions, group constants as well as the results on the simulation of the initial cycle of the EPR reactor using the ARES core simulator.The main findings state that while the use of an effective temperature model leads to significant differences in the radial nuclide distributions, the assembly wide homogenized group constants are reproduced fairly well and the effects on the simulation of the EPR initial cycle are modest, although interesting axial and radial power redistribution can be observed due to the slower speed of gadolinium burnout when effective fuel temperatures were used. The results indicate that better results for the full core calculations could be obtained by using a separate effective temperature for the burnable absorber rods in the burnup calculation and by considering the fuel temperature history effect in the group constant parametrization.

The potential for gamma-emitting radionuclides to contribute to an understanding of erosion processes in South Africa

Abstract. Several research projects undertaken by the authors and others over the last 14 years have used fallout and geogenic radionuclides for understanding erosion processes and sediment yield dynamics in South Africa over the last 100–200 years as European settlers colonised the interior plains and plateaux of the country and imported new livestock and farming techniques to the region. These projects have used two fallout radionuclides (210Pb and 137Cs) to date sediments accumulating in reservoirs, farm dams, wetlands, alluvial fans and floodouts and have used other fallout nuclides (7Be) and long-lived geogenic radionuclides (e.g. 40K, 235U) as part of a composite fingerprint exploring contemporary sediment sources and changes to sources through time. While successful in many parts of the world, applying these techniques in Southern Africa has posed a number of challenges often not encountered elsewhere. Here we explore some of the benefits and challenges in using gamma-emitting radionuclides, especially 137Cs, in these landscapes. Benefits include the potential for discriminating gully sidewall from topsoil sources, which has helped to identify contemporary gully systems as sediment conduits, rather than sources, and for providing a time-synchronous marker horizon in a range of sedimentary environments that has helped to develop robust chronologies. Challenges include the spatial variability in soil cover on steep rocky hillslopes, which is likely to challenge assumptions about the uniformity of initial fallout nuclide distribution, the paucity of stable (non-eroding) sites in order to estimate atmospheric fallout inventories, and the limited success of 210Pb dating in some rapidly accumulating high altitude catchments where sediments often comprise significant amounts of sand and gravel. Despite these challenges we present evidence suggesting that the use of gamma-emitting radionuclides can make a significant contribution to our understanding of erosion processes and sediment yield dynamics. Future research highlighted in the conclusion will try to address current challenges and outline new projects established to address them more fully.

Seeing is believing: Visualization of He distribution in zircon and implications for thermal history reconstruction on single crystals.

Zircon (U-Th)/He thermochronometry is an established radiometric dating technique used to place temporal constraints on a range of thermally sensitive geological events, such as crustal exhumation, volcanism, meteorite impact, and ore genesis. Isotopic, crystallographic, and/or mineralogical heterogeneities within analyzed grains can result in dispersed or anomalous (U-Th)/He ages. Understanding the effect of these grain-scale phenomena on the distribution of He in analyzed minerals should lead to improvements in data interpretation. We combine laser ablation microsampling and noble gas and trace element mass spectrometry to provide the first two-dimensional, grain-scale zircon He "maps" and quantify intragrain He distribution. These maps illustrate the complexity of intracrystalline He distribution in natural zircon and, combined with a correlated quantification of parent nuclide (U and Th) distribution, provide an opportunity to assess a number of crystal chemistry processes that can generate anomalous zircon (U-Th)/He ages. The technique provides new insights into fluid inclusions as potential traps of radiogenic He and confirms the effect of heterogeneity in parent-daughter isotope abundances and metamictization on (U-Th)/He systematics. Finally, we present a new inversion method where the He, U, and Th mapping data can be used to constrain the high- and low-temperature history of a single zircon crystal.

Effects of grain size, mineralogy, and acid-extractable grain coatings on the distribution of the fallout radionuclides 7Be, 10Be, 137Cs, and 210Pb in river sediment

Grain-size dependencies in fallout radionuclide activity have been attributed to either increase in specific surface area in finer grain sizes or differing mineralogical abundances in different grain sizes. Here, we consider a third possibility, that the concentration and composition of grain coatings, where fallout radionuclides reside, controls their activity in fluvial sediment. We evaluated these three possible explanations in two experiments: (1) we examined the effect of sediment grain size, mineralogy, and composition of the acid-extractable materials on the distribution of 7Be, 10Be, 137Cs, and unsupported 210Pb in detrital sediment samples collected from rivers in China and the United States, and (2) we periodically monitored 7Be, 137Cs, and 210Pb retention in samples of known composition exposed to natural fallout in Ohio, USA for 294days.Acid-extractable materials (made up predominately of Fe, Mn, Al, and Ca from secondary minerals and grain coatings produced during pedogenesis) are positively related to the abundance of fallout radionuclides in our sediment samples. Grain-size dependency of fallout radionuclide concentrations was significant in detrital sediment samples, but not in samples exposed to fallout under controlled conditions. Mineralogy had a large effect on 7Be and 210Pb retention in samples exposed to fallout, suggesting that sieving sediments to a single grain size or using specific surface area-based correction terms may not completely control for preferential distribution of these nuclides.We conclude that time-dependent geochemical, pedogenic, and sedimentary processes together result in the observed differences in nuclide distribution between different grain sizes and substrate compositions. These findings likely explain variability of measured nuclide activities in river networks that exceeds the variability introduced by analytical techniques as well as spatial and temporal differences in erosion rates and processes. In short, we suggest that presence and amount of pedogenic grain coatings is more important than either specific surface area or surface charge in setting the distribution of fallout radionuclides.

Air concentration estimation of radionuclides discharged from Fukushima Daiichi Nuclear Power Station using NaI(Tl) detector pulse height distribution measured in Ibaraki Prefecture

ABSTRACTAir concentrations of 133Xe, 131I, 132I, 133I, 132Te, 134Cs, 136Cs, and 137Cs in the early stage of the Fukushima Daiichi Nuclear Power Station (FNPS1) accident were estimated for six locations in Ibaraki Prefecture from pulse height distributions measured with NaI(Tl) scintillation detectors continuously operated as a part of monitoring station systems. Air concentration of 133Xe in Ibaraki was estimated for the first time, which showed the maximum value of 150 kBq m−3 in the plume arrived at the southern part of Ibaraki around noon of 15 March 2011. The plume was found to consist mainly of noble gases without other nuclides at significant level and to correspond to the hydrogen explosion at Unit 3. Spatiotemporal distributions of 131I and other nuclides were discussed for the plumes detected during the periods of 15–16 and 20–21 March. Variations in radionuclide composition among the plumes and within each plume were also discussed.

Radioactive nuclides in phosphogypsum from the lowveld region of South Africa

We evaluated the suitability of phosphogypsum from the Lowveld region of South Africa (LSA), for the manufacturing of building materials, with reference to (1) the National Nuclear Regulator Act 47 of 1999 and (2) the radioactivity associated risks as quantified in terms of the external and internal hazard indices, the activity concentration index and the radium equivalent. The distribution of radioactive nuclides in the LSA phosphogypsum was also examined. Analyses of 19 samples of the phosphogypsum show that phosphogypsum contains lower activity concentrations of naturally occurring radioactive nuclides of uranium and thorium and their progeny than the 500 Bg/kg limit set for regulation in South Africa. The potassium-40 (40K) activity concentration was below the minimum detectable amount of 100 Bq/kg. The values obtained for external and internal hazard indices and the activity concentration index were: 2.12 0.59, 3.44 0.64 and 2.65 0.76 respectively. The calculated radium equivalent Raeq was 513 76Bq/kg. The final decision regarding phosphogypsum’s suitability for use as a building material should consider scenarios of use.

General Description of Fission Observables: GEF Model Code

The GEF (“GEneral description of Fission observables”) model code is documented. It describes the observables for spontaneous fission, neutron-induced fission and, more generally, for fission of a compound nucleus from any other entrance channel, with given excitation energy and angular momentum. The GEF model is applicable for a wide range of isotopes from Z = 80 to Z = 112 and beyond, up to excitation energies of about 100 MeV. The results of the GEF model are compared with fission barriers, fission probabilities, fission-fragment mass- and nuclide distributions, isomeric ratios, total kinetic energies, and prompt-neutron and prompt-gamma yields and energy spectra from neutron-induced and spontaneous fission. Derived properties of delayed neutrons and decay heat are also considered.The GEF model is based on a general approach to nuclear fission that explains a great part of the complex appearance of fission observables on the basis of fundamental laws of physics and general properties of microscopic systems and mathematical objects. The topographic theorem is used to estimate the fission-barrier heights from theoretical macroscopic saddle-point and ground-state masses and experimental ground-state masses. Motivated by the theoretically predicted early localisation of nucleonic wave functions in a necked-in shape, the properties of the relevant fragment shells are extracted. These are used to determine the depths and the widths of the fission valleys corresponding to the different fission channels and to describe the fission-fragment distributions and deformations at scission by a statistical approach. A modified composite nuclear-level-density formula is proposed. It respects some features in the superfluid regime that are in accordance with new experimental findings and with theoretical expectations. These are a constant-temperature behaviour that is consistent with a considerably increased heat capacity and an increased pairing condensation energy that is consistent with the collective enhancement of the level density. The exchange of excitation energy and nucleons between the nascent fragments on the way from saddle to scission is estimated according to statistical mechanics. As a result, excitation energy and unpaired nucleons are predominantly transferred to the heavy fragment in the superfluid regime. This description reproduces some rather peculiar observed features of the prompt-neutron multiplicities and of the even-odd effect in fission-fragment Z distributions. For completeness, some conventional descriptions are used for calculating pre-equilibrium emission, fission probabilities and statistical emission of neutrons and gamma radiation from the excited fragments. Preference is given to simple models that can also be applied to exotic nuclei compared to more sophisticated models that need precise empirical input of nuclear properties, e.g. spectroscopic information.The approach reveals a high degree of regularity and provides a considerable insight into the physics of the fission process. Fission observables can be calculated with a precision that complies with the needs for applications in nuclear technology without specific adjustments to measured data of individual systems. The GEF executable runs out of the box with no need for entering any empirical data. This unique feature is of valuable importance, because the number of systems and energies of potential significance for fundamental and applied science will never be possible to be measured. The relevance of the approach for examining the consistency of experimental results and for evaluating nuclear data is demonstrated.

Application of melt and refining procedures in the CANDLE reactor concept

The application of melt and refining procedures has demonstrated great potential to solve the fuel integrity problem in the high-burnup condition of CANDLE reactors. However, if the melt and refining procedures are applied during operation, the reactor might lose all the nuclide distribution in the fuel pins and CANDLE burning becomes impossible to achieve. In this study, the application of melt and refining was simulated in two cases to overcome the cladding limitation at ⩾200dpa. It became clear that if the number of axial regions for the melt and refining procedure is chosen properly, CANDLE burning is possible to achieve even if each region is homogenized by the procedure. In addition, the fission products released by the melt and refining procedure increase the burnup performance of the CANDLE core remarkably. It is also possible to improve the engineering design by reducing the fuel volume fraction to a minimum at 48%.

Distribution of the 134Cs/137Cs ratio around the Fukushima Daiichi nuclear power plant using an unmanned helicopter radiation monitoring system

Large amounts of radioactive substances were released into the environment by the Fukushima Daiichi nuclear power plant (FDNPP) accident. Several research institutes have mapped the distribution of nuclides with long half-lives, such as 134Cs and 137Cs. Although the ratio of 134Cs and 137Cs has been believed to be equal without depending on the location of the contaminated area, several researchers report that it is different depending on places quite a little. We measured the energy spectrum of gamma rays in high resolution within an approximately 3-km radius of the FDNPP by using an unmanned helicopter equipped with a LaBr3(Ce) scintillation detector. Then, we analyzed the 134Cs/137Cs ratio in the area from these measured data in detail. The results show that the 134Cs/137Cs ratio is different between the plume trace extending north and the other plume traces. We have obtained valuable data for identification of which radioactive substances were released by individual reactor units.

Submicrometer Imaging by Laser Ablation-Inductively Coupled Plasma Mass Spectrometry via Signal and Image Deconvolution Approaches.

In this work, pre- and postacquisition procedures for enhancing the lateral resolution of laser ablation-inductively coupled plasma mass spectrometry (LA-ICPMS) in two- and three-dimensional (2D, 3D) nuclide distribution mapping beyond the laser beam waist are described. 2D images were constructed by projecting a rectangular grid of discrete LA positions, arranged at interspacings smaller than the dimensions of the laser beam waist, onto the sample surface, thus oversampling the region of interest and producing a 2D image convolved in the spatial domain. The pulse response peaks of a low-dispersion LA cell were isolated via signal deconvolution of the transient mass analyzer response. A 3D stack of 2D images was deconvolved by an iterative Richardson-Lucy algorithm with Total Variance regularization, enabling submicrometer image fidelity, demonstrated in the analysis of trace level features in corroded glass. A point spread function (PSF) could be derived from topography maps of single pulse craters from atomic force microscopy. This experimental PSF allows the approach to take into account the laser beam shape, beam aberrations, and the laser-solid interaction, which in turn enhances the spatial resolution of the reconstructed volume.

Rutile U–Pb age depth profiling: A continuous record of lithospheric thermal evolution

Understanding of the thermal and geophysical evolution of the lower continental crust is limited by the resolution of conventional thermochronology. Intracrystalline daughter nuclide distribution profiles preserve a rich and underutilized record of thermal history. Using Laser Ablation Inductively Coupled Plasma Mass Spectrometry, we outline here a method to simultaneously acquire 206Pb/238U age and trace element profiles from U-bearing accessory phases. Inversion of 206Pb/238U age depth profiles yields thermal history information from an extended temperature range compared to inversion of age versus grain size relationships. Thermally-activated volume diffusion of Pb and Zr in rutile is sensitive to the thermal evolution of the mid- to lower-lithosphere. We document the ability of Laser Ablation depth-profiling to simultaneously resolve 206Pb/238U age and Zr diffusion profiles in the outer ∼35 μm of lower-crustal rutile euhedra from the Ivrea Zone, Southern Alps, with <1.2 μm depth resolution. Inversion of the age profiles reveals a continuous cooling history characterized by initially rapid cooling from >600°C at ∼180 Ma followed by a period of slower cooling from ∼525°C to ∼450°C. Combined with the topology of Zr diffusion profiles, these data indicate that the Ivrea Zone underwent a brief thermal pulse in the early Jurassic, plausibly associated with hyperextension of the Adriatic margin. Inversion of near-surface 206Pb/238U age distributions can be employed to resolve otherwise inaccessible thermal history information from the lower lithosphere.

The long-term denudation rate of granitic regolith in Qinhuangdao, North China determined from the in situ depth profile of the cosmogenic nuclides 26Al and 10Be

This study quantifies the surface denudation rate of granitic regolith via the application of the in situ cosmogenic 26Al and 10Be depth profile in China. The concentration ranges of 26Al and 10Be in the quartz along the ~3-m granitic regolith profile in Qinhuangdao are (4.9–23.1) × 105 and (2.3–36.6) × 104 atoms/g, respectively. With the exception of the surface sample, both 26Al and 10Be concentrations decrease exponentially with sample depth. The Chi-square best-fitting results revealed a total denudation rate of ~9 m/Ma averaged over a 103–105 a timescale, which is lower than the values observed in global granitic outcrops. Compared with global datasets, the flat terrain due to the lack of tectonic activities is most likely the dominant factor that controls the local denudation process. The surface sample offsets from the theoretical cosmogenic nuclide distribution implies that the denudation rate from river basin sediment could be overestimated because of the bioturbation in the surficial soil layer.

Optimization study of Ultra-long Cycle Fast Reactor core concept

An optimization of an Ultra-long Cycle Fast Reactor (UCFR) design with a power rating of 1000MW (electric), UCFR-1000, has been performed. Firstly, geometric optimization has been performed in the aspects of core size and core shape in terms of thermal–hydraulic (TH) feedback. Secondly, fuel composition optimization has been performed by adopting pressurized water reactor (PWR) spent fuel (SF) as a blanket material as well as natural uranium (NU). Thirdly, thorium has been loaded in the inner core for the optimization of radial power distribution. Lastly, a small-size UCFR with a power rate of 100MWe has been developed with optimization of maximum neutron flux and fast neutron fluence limit for a short term deployable nuclear reactor.The equivalent diameter and the height of the optimized UCFR-1000 core are 5.9 and 2.4m, respectively, while the equivalent diameter and the height of the optimized UCFR-100 core are 4.3 and 1.0m, respectively. The size of the optimized UCFR-1000 has been enlarged in the radial direction and shortened in the axial direction from those of the initial UCFR design (Tak et al., 2013a) and this modification makes the burning speed of active core movement slower. It has been confirmed for both designs that a full-power operation of 60years without refueling is feasible with respect to isotopics and criticality by a breed-and-burn strategy. The core performance characteristics of both designs have been evaluated in terms of axial/radial power shapes, neutron flux and nuclide distributions, breeding ratio, reactivity feedback coefficients, control rod worth, etc. By the design optimization study in this paper, the reductions of maximum neutron flux, fast neutron fluence, and axial/radial power peaking have been achieved, which are favorable for the safety of the UCFR.

Distribution of radioactive nuclides of boring core samples extracted from concrete structures of reactor buildings in the Fukushima Daiichi Nuclear Power Plant

Since the start of the severe accidents at the Fukushima Daiichi Nuclear Power Plant in March 2011, concrete surfaces within the reactor buildings (RBs) have been exposed to radioactive contaminants. Released radionuclides still remain too high to permit entry into some areas of the RBs to allow the damage to be assessed and to allow carrying out the restoration of lost safety functions, decommissioning activities, etc. In order to clarify the situation of this contamination in the RBs of Units 1, 2 and 3, samples of contaminants were collected and subjected to analyses to determine the surface radionuclide concentrations and to characterize the radionuclide distributions in the samples. Especially, decontamination tests on the boring core sample of Unit 2 were conducted to quantitatively determine the effectiveness of several basic decontamination techniques. As a result of the tests, the level of radioactivity of this sample was reduced with the removal of ∼97% of the contamination present near the sample surface, and it was confirmed for the boring core sample that the contamination mainly had the characteristics of fixed contamination of the surface.

Reconstruction of finer voxel grid transmission images in Tomographic Gamma Scanning

Tomographic Gamma Scanning (TGS) is a technique used to assay the nuclide distribution and radioactivity in nuclear waste drums. Limited to few transmission measurements, the drum is divided into large voxels and thus leads to the inhomogeneity of the voxels and negatively affects the results. A new algorithm is presented to reconstruct finer voxel grid transmission images with the same number of measurements. The small voxel size decreases the effect of the inhomogeneity and makes the result more accurate. The algorithm employs total variation minimization and precisely describes the attenuation process. The influences of the different scan modes are discussed with Monte Carlo simulations. Experiments are performed to verify the effectiveness of our method.

The Influence of Changes in Iron Cross Section in the Thermal Region between CENDL-3.1 and ENDF/B-VII.0

The cross section of iron has an important impact on thermal neutron flux distribution in a reactor pressure vessel. The thermal neutrons affect RPV activation, thus influencing the composition of RPV and the distribution of nuclides originated. Moreover this cross section influences the calculated prediction of pin power density in the boundary row of fuel pins. The relevance of this quantity is in fact that fuel conditions are a very important criterion reflected in limits and conditions of reactor operation, which must not be violated.

Investigation of radionuclides in the Yenisey River floodplain systems: Relation of the topsoil radionuclide contamination to landscape features

Landscape–radiometric survey and soil sampling performed in the islands of Beriozovy and Balchug (20km downstream the Krasnoyarsk Mining and Chemical Combine), and in the Mikhin Island (180km downstream) showed that the distribution of technogenic radionuclides depends upon the history of contamination and landscape features of the floodplain. Contamination densities of 137Cs appeared to be significantly higher than could be expected from global fallout (1.75–2.5kBq/m2): in 2000 the maximum value for 137Cs in the Beriozovy Island equaled 663kBq/m2, in the Balchug site — 577kBq/m2 and in the Mikhin Island — 518kBq/m2). 137Cs contamination density was practically independent of the remoteness from the KMCC that proved its considerable migration in the water-soluble or fine particulate forms. Vertical distributions of man-made nuclides in soil cores depended upon the different half-life of the studied radionuclides, the soil profile relative altitude, its structure and texture. The two main burial depths of 137Cs activity depended upon the intensity of sedimentation and varied from 5cm to 20–25cm. In 2000 maximum contamination by 60Co and 152,154Eu isotopes was associated with the top layer and decreased exponentially with depth.Obtained data is believed to be important for ecological monitoring of the flood plains subjected to radionuclide contamination.

Controls on seawater 231Pa, 230Th and 232Th concentrations along the flow paths of deep waters in the Southwest Atlantic

Measurements of dissolved 230Th, 231Pa and 232Th were made for twelve full-depth profiles along a Southwest Atlantic section during GEOTRACES cruise GA02S. Sampling captures all the main Atlantic deep water masses along their meridional flow paths and allows insight into the control on Th and Pa in a setting where waters are flowing in opposing directions, with direct relevance to understanding the use of 231Pa/230Th as an ocean-circulation proxy. Water-column 230Th increases linearly with depth, in line with expected reversible scavenging models. 231Pa increases from the surface to ∼1200–1500 m, but is invariant or decreases with greater depth, deviating from the behavior expected for reversible scavenging. Dissolved 231Pa/230Th ratios display a mid-water-column maximum at ∼1000–2000 m which is broadly coincident with Upper Circumpolar Deep Water. Below 2000 m, nuclide distributions and ratios exhibit no dependence on water mass, nor any indication of progressive change within a water mass, challenging the use of 231Pa/230Th as a past circulation tracer in the South Atlantic. Calculation of horizontal transport of 230Th and 231Pa by ocean circulation indicates a net southward export out of the Atlantic of 19% of the 231Pa and 3% of the 230Th produced in that ocean. This removal is all from the North Atlantic while, in the South Atlantic, removal to sediment equals production. Simple one-dimensional modeling can simulate 230Th profiles but not the mid-water-column maximum observed in 231Pa profiles, suggesting an additional source of 231Pa (perhaps lateral transport from the margin) or removal at depth due to bottom scavenging. Near seafloor minima in concentrations indicates bottom scavenging of 230Th and 231Pa, which is enhanced in the presence of nepheloid layers, particularly for 231Pa. This additional scavenging fractionates 230Th and 231Pa and, in the presence of nepheloid layers, may lead to an increase in sedimentary 231Pa/230Th ratios. 232Th concentrations were paired with 230Th-derived residence times in the upper 250 m of the water column to test the application of Th as a tracer of dust deposition. Maxima in 232Th indicate high dust input from the African and possibly South American continents.

Transmutation of minor actinides in the pressurized water reactors

We study the effects of adding MA nuclides to the PWR core and the MA nuclide transmutation rate in the PWRs. Our calculation results show that even 1% homogeneous addition of MA nuclides to the nuclear fuel can reduce keff of the PWRs drastically. The uniform distribution of MA nuclides in the uranium dioxide fuel can also affect the lifetime of a fuel loading. Calculation results also indicate that the uniform distribution of MA nuclides in the uranium dioxide fuel results in a reactivity mismatch and control difficulties in the PWRs. The spatial self-shielding effects of the heterogeneous distributions of MA nuclides in the PWR core can avoid the initial reactivity to drop significantly, and the reactivity mismatch and control difficulties in the PWRs can be also overcome.During 300-day-exposure of MA nuclides in the PWRs 14.8% Pu-238 and 7.7% Pu-239 of the initial MA nuclides are created, this explains at least 22.5% MA nuclides transmute to plutonium isotopes during 300-day-exposure in PWRs by various nuclear processes. We may incinerate plutonium-239 and plutonium-238 isotopes in the subsequent MOX fuel loading of the PWRs. Alternatively, we may also use Pu-238 created in the transmutation of MA nuclides in the PWRs to fabricate the nuclear batteries. Pu-238 mainly transmuted from neptunium-237 in PWRs, neptunium-237 constitutes 56.2% of the total minor actinides in the depleted nuclear fuel of PWRs. The majority of commercial reactors in operation in the world are PWRs, if we get the neptunium-237 transmuted in the PWRs during their power generating, the inventory of high level long-lived radioactive minor actinides in the world will be greatly reduced.Our study show MA nuclides actually can act as the burnable poisons in the PWRs. MA nuclide transmutation materials may be used to partially substitute for the burnable poisons in the PWRs, or reduce the concentration of the boric acid in the coolant of the PWRs and increase the negative temperature coefficient of the PWRs. This is a distinct advantage to transmute MA nuclides in the PWRs. The transmutation characteristics of MA nuclides in PWRs and high flux thermal reactors are also compared in this research.

Radiocesium Distribution in the Tissues of Japanese Black Beef Heifers Fed Fallout-Contaminated Roughage Due to the Fukushima Daiichi Nuclear Power Station Accident

This study examined the accumulation and tissue distribution of radioactive cesium nuclides in Japanese Black beef heifers raised on roughage contaminated with radioactive fallout due to the accident at the Fukushima Daiichi Nuclear Power Station on March 2011. Radiocesium feeding increased both (134)Cs and (137)Cs levels in all tissues tested. The kidney had the highest level and subcutaneous adipose had the lowest of radioactive cesium in the tissues. Different radioactive cesium levels were not found among parts of the muscles. These results indicate that radiocesium accumulated highly in the kidney and homogenously in the skeletal muscles in the heifers.