Transuranium Nuclides Research Articles

Practicle example of the defence of a contamination incident

Abstract By routine examinations of a radiation worker, a contamination incident with transuranium nuclides was discovered. Immediate investigations showed a serious degree of the incident. First countermeasures were done to narrow the effects down and to avoid a spread of contamination. A complex decontamination followed for which the radiation protection infrastructure had to be built up.

Performance of an air sampler and a gamma-ray detector in a small unmanned aerial vehicle

The performance of an air sampler and a small gamma-ray spectrometer was tested in an unmanned aerial vehicle (UAV) able to carry payload with mass up to 0.5 kg. Operation of the sampler was investigated with the aid of radon progeny normally present in outdoor air. Detection limits for several transuranium nuclides in air are of the order of 0.3 Bq m−3 assuming 0.5 h sampling time and 1 h counting time in direct alpha spectrometry. Unshielded 137Cs and 60Co point sources at the ground level were used to test the CsI spectrometer. Detection limits are approximately 1 GBq or larger depending on the flying altitude.

Autonomous Control Strategies for Very High Temperature Reactor Based Systems for Hydrogen Production

This paper is focused on feasible autonomous control strategies for Generation IV very high temperature reactors (VHTRs)-based systems for hydrogen production. Various burnable poison distributions and fuel compositions are considered. In particular, utilization of transuranium nuclides (TRUs) in VHTRs is explored as the core self-stabilization approach. Both direct cycle and indirect cycle energy conversion approaches are discussed. It is assumed that small-scale VHTRs may be considered for international deployment as grid-appropriate variable-scale self-contained systems addressing emerging demands for hydrogen. A Monte Carlo-deterministic analysis methodology has been implemented for coupled design studies of VHTRs with TRUs using the ORNL SCALE 5.1 code system. The developed modeling approach provides an exact-geometry 3D representation of the VHTR core details properly capturing VHTR physics. The discussed studies are being performed within the scope of the U.S. DOE Nuclear Energy Research Initiative project on utilization of higher actinides (TRUs and partitioned minor actinides) as a fuel component for extended-life VHTR configurations.

東海再処理施設における排水中の超ウラン核種等に関する調査

We surveyed the concentration levels of Transuranium (TRU) nuclides in the effluent discharged from the Tokai Reprocessing Plant (TRP) from 1998 to 2003 for Light Water Reactor (LWR) Fuel Reprocessing. The survey was performed for upcoming the effluent monitoring in Fast Breeder Reactor (FBR) Fuel Reprocessing. It was confirmed that the TRU nuclides concentration discharged from the TRP was 1/150∼1/106 much lower than the concentration limits authorized in governmental notification. Then, we compared the normalized discharge amounts by the unit of generated energy from the TRP with those from the foreign reprocessing plants. As a result, the TRP has reduced the amounts of discharged nuclides, by the order of 1/100-1/107 compared with foreign ones. This survey provided the important and basic data in order to compare the effluent of TRU nuclides in FBR and the present nuclear fuel cycles.

Radiation surveillance using an unmanned aerial vehicle

Radiation surveillance equipment was mounted in a small unmanned aerial vehicle. The equipment consists of a commercial CsI detector for count rate measurement and a specially designed sampling unit for airborne radioactive particles. Field and flight tests were performed for the CsI detector in the area where 137Cs fallout from the Chernobyl accident is 23–45 kBq m −2. A 3-GBq 137Cs point source could be detected at the altitude of 50 m using a flight speed of 70 km h −1 and data acquisition interval of 1 s. Respective response for 192Ir point source is 1 GBq. During the flight, the detector reacts fast to ambient external dose rate rise of 0.1 μSv h −1, which gives for the activity concentration of 131I less than 1 kBq m −3. Operation of the sampler equipped with different type of filters was investigated using wind-tunnel experiments and field tests with the aid of radon progeny. Air flow rate through the sampler is 0.2–0.7 m 3 h −1 at a flight speed of 70 km h −1 depending on the filter type in question. The tests showed that the sampler is able to collect airborne radioactive particles. Minimum detectable concentration for transuranium nuclides, such as 239Pu, is of the order of 0.2 Bq m −3 or less when alpha spectrometry with no radiochemical sample processing is used for activity determination immediately after the flight. When a gamma-ray spectrometer is used, minimum detectable concentrations for several fission products such as 137Cs and 131I are of the order of 1 Bq m −3.

Nuclear energy and waste management – pyroprocess for system symbiosis

The actinide management has become a key issue in nuclear energy. Recovering and fissioning transuranium elements reduce the long-term proliferation risks and the environmental burden. The better way of waste management will be made by system symbiosis: a combination of light-water reactor and fast reactor and/or accelerator-driven transmutation system should be sought. The new recycling technology should be able to achieve good economy with smaller plants, which can process fuels from different types of reactors on a common technical basis. Ease in handling the higher heat load of transuranium nuclides is also important. Pyroprocesses with the use of molten salts are regarded as the strong candidate for such recycling technology. In JAEA, the first laboratory for the high-temperature chemistry of Am and Cm has been established. The fundamental data will be combined with the computer code for predicting the molten-salts electrolytic processes.

Properties of cermet fuels for minor actinides transmutation in ADS

The sub-critical Accelerator Driven System (ADS) is now being considered as a potential means to burn long-lived transuranium nuclides. The preferred fuel for such a fast neutron reactor is uranium-free, highly enriched with plutonium and minor actinides. Requirements for ADS transmuter fuels are linked with the core design and safety parameters, the fuel properties and the ease of reprocessing. This study concerns the properties of metals as matrices, with the particular case of Mo. To improve the neutronic characteristics, enriched molybdenum (Mo-92) is required. To overcome the high enrichment cost, it is proposed to recover the matrix by pellet dissolution, and to recycle it for further use. Irradiation programmes are also planned to examine the in-reactor properties of the material. Based on the current status of the research, the results are promising, but irradiation results are still missing.

Determination of the plutonium content in samples from a 30-km zone around the Chernobyl nuclear power plant

A method of determining the content of α-emitting plutonium isotopes according to the characteristic Lx radiation line emitted from uranium in samples taken from the environment is proposed. Comparing the method decribed and the standard radiochemical determination of plutonium isotopes for soil samples taken from a 5-km zone around the Chernobyl nuclear power plant showed that the results are in good agreement with one another. The concentration of plutonium and americium in the zones with high contamination with transuranium nuclides is measured. It is established that the migration rate of americium is the same as that of plutonium. It is shown that about 90% of the α-emitting nuclides are located at depths of 5–10 cm.

FT-ICR: A non-destructive detection for on-line mass measurements at SHIPTRAP

The SHIPTRAP facility is set up behind the velocity filter SHIP at GSI. One of the main physics goals is the direct mass determination of trans-uranium nuclides by Penning trap mass spectrometry. In this contribution the applicability of the non-destructive Fourier Transform-Ion Cyclotron Resonance (FT-ICR) detection technique to mass spectrometry of short-lived nuclides is discussed.

Revised prompt neutron emission multiplicity distributions for 236,238Pu

The prompt neutron emission multiplicity distributions and average values ( P ν and 〈 ν 〉 , respectively) for nuclei which decay via spontaneous fission have been reevaluated. In the cases of 236Pu and 238Pu, inconsistencies were found in the recommended values for P ν and 〈 ν 〉 that were given in the most recent compilation of neutron emission multiplicity distributions from the fission of uranium and transuranium nuclides. In correcting for these inconsistencies, the values of 〈 ν 〉 for 236Pu and 238Pu have now been revised to 2.07 ± 0.13 and 2.19 ± 0.07 , respectively. The corresponding neutron emission probabilities for these two nuclei have also been revised in order to take into account the new recommended 〈 ν 〉 values.

Radiation consequences of seawater contamination during floating storage of reactor-compartment units from salvaged nuclear-powered submarines

The storage time before salvaging of decommissioned nuclear-powered submarines and the floating storage time of reactor units from salvaged submarines can total decades. During this time, radioactive contamination of seawater occurs as a result of the corrosion of the pressure hull in the region of the reactor system and rupturing of the pressure hull – as a result of corrosion of the components of the reactor system. A computational analysis shows that under standard storage conditions the specific activity of water is 105–106 times lower than the intervention level. In the case when the hull and the reactor system are destroyed even with remaining fuel, the specific activity of the sea water near the point of sinking also does not exceed the intervention level because of the slow emission of fission products and transuranium nuclides.

Source-term characterisation and solid speciation of plutonium at the Semipalatinsk NTS, Kazakhstan

New data on the concentrations of key fission/activation products and transuranium nuclides in samples of soil and water from the Semipalatinsk Nuclear Test Site are presented and interpreted. Sampling was carried out at Ground Zero, Lake Balapan, the Tel’kem craters and reference locations within the test site boundary well removed from localised sources. Radionuclide ratios have been used to characterise the source term(s) at each of these sites. The geochemical partitioning of plutonium has also been examined and it is shown that the bulk of the plutonium contamination at most of the sites examined is in a highly refractory, non-labile form.

Determination of the optimal plutonium fraction in transuranium discharged from pressured water reactor (PWR) spent fuel for a flat fission power generation in the force-free helical reactor (FFHR) along the transmutation period

Transmutation of transuranium (TRU) discharged from PWR spent fuel and the possibility of a flat fission power (FFP) generation along the transmutation process have been investigated in the force-free helical reactor (FFHR), which is a demo relevant helical-type D-T fusion reactor, for an operation period (OP) of up to 10 years by 75% plant factor (η) under a neutron wall load (P) of 1.5 MW/m 2. For this purpose, the TRUs discharged from four different pressured water reactor (PWR) spent fuels have been selected as fuel, which include minor actinides (MAs) and plutonium isotopes, and in each spent fuel, the MA has been mixed with the plutonium by using various fractions. The MA–Pu mixture has been spherically prepared, and cladded with SiC to prevent the TRU nuclides from contacting coolant and the fission products from contaminating coolant. The mixture has been located in transmutation zone (TZ) of the FFHR to incinerate and/or transmute the TRU nuclides effectively, and helium has been used for the nuclear heat transfer in the TZ. The calculations have brought out that the fission power generation profiles are quasi-linear for the mixtures with small Pu fractions, in the range of 0–30%, along the transmutation period. The optimal Pu fraction in the mixture for the FFP generation has been determined individually for each mixture by applying interpolation method to the fission rate (R F) values obtained for the relevant mixture with various the Pu fractions along the transmutation period. In consequence of the calculations, the optimal Pu fractions are obtained as 18.94, 19.90, 18.10 and 11.85% for the fuel types A, B, C and D, respectively. In the mixture types A, B, C and D with their optimal Pu fractions, the R Fs are quasi-constant and about 0.84, 0.73, 0.94 and 0.79, respectively. At the end of operation period (EOP), the averages of effective half-lives of 237Np, 239Pu, 241Pu, 241Am and 243Am can decrease to 9.8, 9.4, 9.9 and 9.6 years in the mixture types A, B, C and D, respectively. The average net transmutation fractions (TFs) for the whole TRUs and MAs are about 31 and 52%, respectively.

Actinide analysis of a depleted uranium penetrator from a 1999 target site in southern Serbia

Following the detection of 236U in depleted uranium (DU) ammunition used during the Balkans conflict in the 1990s, concern has been expressed about the possibility that other nuclides from the nuclear fuel cycle and, in particular, transuranium nuclides, might be present in this type of ammunition. In this paper, we report the results of uranium and plutonium analyses carried out on a depleted uranium penetrator recovered from a target site in southern Serbia. Our data show the depleted nature of the uranium and confirm the presence of trace amounts of plutonium in the penetrator. The activity concentration of 239+240Pu, at 45.4±0.7 Bq kg –1, is the highest reported to date for any penetrator recovered from the Balkans. This concentration, however, is comparable to that expected to be present naturally in uranium ores and, from a radiological perspective, would only give rise to a very small increase in dose to exposed persons compared to that from the DU itself.

R&D activities based on fast reactor cycle technologies for transmutation of TRU and LLFP by JNC

Research and development(R&D) activities on partitioning and transmutation of trans-uranium nuclides (TRU) and LLFP and future R&D program in JNC were summarized. Feasibility design studies have been conducting to investigate the characteristics of a fast reactor core with TRU and LLFP transmutation. It was reconfirmed that the fast reactor has a strong potential for transmuting TRU and LLFP, effectively. R&D for establishing partitioning process of TRU apart from the high-level radioactive wastes have been carried out. By several counter-current runs of the TRUEX process using highly active raffinates, a process flow sheet capable of selective partitioning of actinides and fission products was newly developed. JNC has settled a new R&D program concerning partitioning and transmutation of long-lived radioactive waste based on recommendation of check & review for OMEGA program performed by the Ad Hoc Committee under the Atomic Energy Commission of Japan (AEC). The R&D program is composed of the design studies and development of element technologies (fabrication, irradiation) in the “Feasibility Studies” on commercialized fast reactor system and the basic studies with experiments (nuclear data, reactor physics, fuel property, etc.) to establish database and analytical tools for the TRU- and LLFP- containing fuel and core design.

SHIPTRAP—a capture and storage facility for heavy radionuclides at GSI

SHIPTRAP will be an ion-trap facility for heavy radionuclides delivered from SHIP. Ion traps are a perfect instrument for precision measurements since the ions can be cooled to an extremely small phase space and can be stored for a very long time. In addition one can achieve very high purity by removing contaminant ions. SHIPTRAP will extend the possibilities of measurements in traps to transuranium nuclides and provide cooled and isobarically pure ion bunches.

Chemical analysis of transuranium nuclides in the uranium solution of the JCO criticality accident

Atom numbers of 239Np and 239Pu, which had been produced by the neutron capture reaction of 238U in the uranium solution of the JCO criticality accident at Tokai-mura, Japan, were determined precisely by a radiochemical method. It was found that the measured atom ratio of 239Np/239Pu at termination of the criticality depends sensitively on the history of the neutron capture reaction during the accident (about 20-hours continuance). The history was evaluated by comparing the measured value and those calculated by a burnup calculation code. The percentage of the number of the neutron capture reaction at the initial stage of the criticality during 25 min against the total events was determined to be 24±6%.

A Physics Case for SHIPTRAP: Measuring the Masses of Transuranium Elements

SHIPTRAP will allow direct measurement of masses of transuranium nuclides. The method of choice is a Penning trap spectrometer coupled to the SHIP (Separator for Heavy Ion Products) facility at GSI, Darmstadt. In this paper the impact of the SHIPTRAP facility, with its capability of systematic mass measurements with high precision, is explored. Rather few masses of nuclides above uranium are presently known experimentally. In the region of nuclides above Z = 100 no ground state masses were measured directly. SHIPTRAP will play an important role in systematically mapping out this area. Possible candidates for direct mass measurements, even with small or very small production cross sections, are presented.

WASTE TREATMENT AT THE RADIOCHEMICAL ENGINEERING DEVELOPMENT CENTER

ABSTRACT At the Radiochemical Engineering Development Center (REDC), irradiated targets are processed for the recovery of valuable radioisotopes, principally transuranium nuclides. A system was recently installed for treating the various liquid alkaline waste streams for removal of excess radioactive contaminants at REDC. Radionuclides that are removed will be stored as solids, and thus the future discharge of radionuclides to liquid-low level waste tank storage will be greatly reduced. The treatment system is of modular design and is installed in a hot cell at REDC, where preliminary testing is in progress. The module incorporates the following: (1) a resorcinol-formaldehyde resin column for cesium removal, (2) a cross-flow filtration unit for removal of rare earths and actinides as hydroxide, and (3) a waste solidification unit. Process flowsheets for operation of the module, key features of the module design, and its computer-assisted control system are presented. Good operability of the cross-flow filter system is mandatory to the successful treatment of REDC wastes. Results of tests to date on the operation of the filter in its slurry collection mode and its slurry washing mode are presented. These tests include the effects of entrained organic solvent in the waste stream to the filter.

Radiolytic decomposition and corrosion of a heavy-water blanket for accelerator driven transmutation Modeling and experimental tests

The concept of a chemical-engineering complex and its operation stability is described for a radioactive-waste separation and transmutation plant. In the framework of the plant, this chemical complex runs in a closed cycle with a nuclear transmutation reactor driven by a 1 GeV–100 mA class accelerator. Heavy water provides circulation of materials to be transmuted in the reactor blanket and transports the irradiated suspension to and from the chemical-engineering complex for reprocessing and further disposal of transmutation products. Modeling and experimental tests of radiolytic decomposition and corrosion were made in order to evaluate the operation stability of the desired separation and transmutation cycle. Preliminary calculations were made for some methods to suppress gas evolution from water (deuterium) solutions with thorium and transuranium nuclides or from suspensions of their oxides at a pressure of 10 MPa, a temperature of 285°C and radiation doses up to 5×10 7 Gy. The results were checked experimentally. Also the change in size of the suspended particles during irradiation was measured. Additionally, corrosion rates of zirconium alloy tubes were estimated from experiments under the same conditions.