Actinide reformer concept

The partitioning and transmutation technology is effective to reduce the environmental impact from disposition of high-level radioactive wastes and improve the efficiency of geological disposal. However, Am and Cm and their daughter nuclides are difficult to handle in the fuel cycle because of their high decay heat and radioactivity. These nuclides also give the chemical instability which harms the soundness of fuel pellet properties.

We propose a new system concept “actinide reformer”, which reforms Am and Cm into Pu by neutron capture reactions and decay. Am and Cm are separated from the PUREX reprocessing process and converted to chloride molten-salt fuel. Using liquid-type fuel, above mentioned defects can be compensated. Actinide reformer is an accelerator-driven system which is composed of a 10 MW-class cyclotron, a tungsten target and a subcritical core. Spent molten-salt fuel is reprocessed as an on-line fuel exchange manner to extract fission products and recover Pu to send back to a power generation cycle. The decay heat and neutron emission from the fuel with recovered Pu are smaller than those of MOX fuel with 5% of minor actinide addition. It expects no significant engineering difficulties and cost increase for construction of MOX fuel based reprocessing/fabrication plant and power reactors.     

Investigation of decay modes of superheavy nuclei

A detailed investigation of different decay modes,namely alpha decay,beta decay,cluster decay,including heavy particle emission(Zc＞28),and sponta-neous fission,was carried out,leading to the identification of new cluster and beta-plus emitters in superheavy nuclei with 104≤Z≤126.For the first time,we identified around 20 beta-plus emitters in superheavy nuclei.Heavy-particle radioactivity was observed in superheavy elements of atomic number in the range 116≤Z≤126.292-293 Og were identified as 86Kr emitters,and 298122 and 300122 were identified as 94Zr emitters,whereas heavy-particle radioactivity from 91Y was also observed in 299123.Fur-thermore,the nuclei 300124 and 306126 exhibit 96Mo radioactivity.The reported regions of beta-plus and heavy-particle radioactivity for superheavy nuclei are stronger than those for alpha decay.The identified decay modes for superheavy nuclei are presented in a chart.This study is intended to serve as a reference for identifying possible decay modes in the superheavy region.     

OPERA: an on-line system of optical pumping in solids for unstable nuclei

An on-line system of optical pumping in solids for the study of unstable nuclei was developed. The system is operated in connection with mass separators on line. The mass-separated unstable isotopes are implanted into a host crystal set at the focal position of the separator and then spin-polarized with laser optical pumping in the crystal. The crystal can be cooled down to 20–100 K with a cold finger attached to a liquid He bath. The achieved nuclear polarization/alignment is detected by observing the asymmetry/anisotropy of the emitted beta-/gamma-radiation with scintillation/Ge counters. Nuclear magnetic resonances are observed by detecting the destruction and/or enhancement of the asymmetry/anisotropy distribution with an applied rf magnetic field. The system has been applied to the study of unstable Tm and Si isotopes. Apparatus and performance of the on-line system are described together with some of the results obtained.     

Upgrade of the TRIUMF on-line isotope separator, TISOL

The operational TISOL thick target, on-line isotope separator at the TRIUMF, 500 MeV proton cyclotron facility has been upgraded to be a production facility with an active experimental program. A new experimental area is now available and modifications are under design to handle remotely the expected radioactively “hot” targets. Two ion source systems are now available, a heated surface of normal design and a new ECR (electron cyclotron resonance) source resulting in ion beams from a wide range of elements. Details of the new upgraded facility will be presented along with its experimental program and plans for the future. The status of the previously proposed accelerated radioactive beams facility, ISAC, for which TISOL is a prototype front-end system, will also be mentioned.     

Calculation of Interaction Potential Between Spherical and Deformed Nuclei

Nuclear reactions and or-decay half-lives involving deformed nuclei are an important topic of research in nuclear physics. Recently, particular interest has been paid to the effects of nuclear deformation on the production and decay of superheavy nuclei. Because reasonable predictions of production cross section and or-decay half-life of superheavy nuclei require the knowledge of nuclear potential, the nuclear potential between the deformed interacting nuclei are essentially important in describing these reactions and decay processes.     

压水堆燃耗数据库的制作与验证

基于评价数据库ENDF/B-Ⅷ.0和EAF-2010研制了一套适用于CINDER90程序的压水堆用燃耗数据库,该数据库包含中子反应截面、衰变数据和裂变产额数据3部分。中子反应截面的加工分为两步,首先采用Inverted Stack算法和CRECTJ6程序将EAF 2010库的截面分支比融入ENDF/B Ⅷ0库全套中子评价数据,然后用NJOY2016程序处理成63群截面。衰变数据和裂变产额数据分别由MF8/MT457和MF8/MT454数据加工得到,裂变产额数据共包含36个裂变核的60组产额数据。以SFCOMPO 20中Takahama 3压水堆燃料组件为基准题,对研制的燃耗数据库进行了验证。结果表明,本文制作的燃耗数据库的方法是正确的,对于某些核素,如242Amm,制作的数据库比自带库的计算结果更接近实验值。     

Nuclear energy strategy in the environment of utility business deregulation

Nuclear power has contributed to the reduction and stabilization of electricity rate in Japan. However, its economic competitiveness has been eroding since mid 80's. Deregulation is hitting nuclear power just at the time its competitiveness is declining, and it poses a threat to drive short-sighted market orientation and precludes long term focus on achieving a balance between “environmental agenda” and “competitiveness in market”. Lowering the electricity rate is one of the important agenda to improve the nation's industrial competitiveness in the global market. However, it will be very difficult to win the competition of gas and oil prices with other developed countries in Europe and North America due to a handicap of long transportation distance. Only nuclear power and natural energy have no relation to such a handicap of economic distance from resources. Without securing economic superiority of those energy sources, Japan will not be able to clear the handicap of energy costs. The Japanese utilities are trying hard to regain the competitive edge of nuclear power. We have established short-term strategies for both existing and new LWRs as well as a long-term strategy for technological development. With these strategies we will be able to regain the competitiveness of nuclear power.     

Status report of the SARA IGISOL used in the study of the U(α 40 MeV, ƒ) reaction

A new ion guide isotope separator on-line (IGISOL), operating with the SARA facility, has been constructed. Using the ²³⁸U(α 40 MeV, ƒ) reaction to produce very neutron-rich radioisotopes, all mass chains from A = 96 to 122 have been scanned by conventional methods of nuclear spectroscopy. Provided the stopping volume is separated from the primary beam, it has been proved that the yield is nearly proportional to the He pressure. In addition to the usual advantages (quasi-independence from physical and chemical properties of elements), this makes IGISOL a powerful technique for high energy recoil products. During the experiments the boundary of known neutron-rich nuclei was reached such as ¹¹⁷Rh(440 ms) and several unknown activities were detected in the range A = 113–118.     

On-line monitoring of instrument channel performance in nuclear power plant using PEANO

On-Line monitoring evaluates instrument channel performance by assessing its consistency with other plant indications. Industry and EPRI experience at several plants has shown this overall approach to be very effective in identifying instrument channels that are exhibiting degrading or inconsistent performance characteristics “On-Line Monitoring of Instrument Channel Performance by EPRI (2000)”.

On-Line monitoring of instrument channels provides information about the condition of the monitored channels through accurate, more frequent monitoring of each channel's performance over time. This type of performance monitoring is a methodology that offers an alternate approach to traditional time-directed calibration. On-line monitoring of these channels can provide an assessment of instrument performance and provide a basis for determining when adjustments are necessary. Elimination or reduction of unnecessary field calibrations can reduce associated labor costs, reduce personnel radiation exposure and reduce the potential for miss-calibration.

PEANO “A Neuro-Fuzzy Model Applied to Full Range Signal Validation of PWR Nuclear Power Plant Data by Fantoni (2000)” is a system for on-line calibration monitoring developed in the years 1995–2000 at the Institutt for energiteknikk (IFE), Norway, which makes use of Artificial Intelligence techniques for its purpose. The system has been tested successfully in Europe in off-line tests with EDF (France), Tecnatom (Spain) and ENEA (Italy). PEANO is currently installed and used for on-line monitoring at the HBWR reactor in Halden. This paper describes the results of performance tests on PEANO with real data from a US PWR plant, in the framework of a co-operation among IFE, EPRI and Edan Engineering, to evaluate the potentials of PEANO for future installations in US nuclear plants.     

An on-line method to monitor bwr core stability based on an autocorrelation method

An on-line monitoring method is introduced for BWR core stability. The method utilizes only autocorrelation values for two delay time intervals. Its simplicity makes it suitable for an on-line monitor. Accuracy of the core decay ratio calculated by the method improves as the core condition approaches instability. The error in the decay ratio for regional limit cycle oscillations is 0.2% when calculated from local signals in the most unstable region, and 4% when calculated from core averaged signals.     

线性子链法在排放源项计算中的应用

根据线性子链法原理和流出物排放源项计算模型的特点,本文建立了全面自动搜索核素链的方法,覆盖了所有核素涉及到的核素链,推导出了排放源项模型的解析表达式,将复杂的衰变链分解为数条线性链,对每一条核素链分别进行解析计算得到每个核素的核素浓度。将这一方法用于核电厂排放源项的活度计算,并将本方法求解结果与PWR-GALE的ORIGEN求解模块的结果比较,以及将最终排放源项的计算结果与国内某核电厂排放源项比较,对比表明,大部分核素浓度计算结果与ORIGEN一致,短寿命核素浓度的计算中由于ORIGEN采用长期平衡近似以及衰变链简化处理后所得结果偏于保守;本方法计算排放源项所得结果与国内某核电厂排放源项结果非常符合。本方法应用了全面自动搜索的线性子链法,自动搜索添加衰变链,并使用解析法依次对每条衰变链的每个核素进行计算,使得计算结果更加全面,结果更准确。     

Evaluation of Shutdown Gamma-ray Dose Rates around the Duct Penetration by Three-Dimensional Monte Carlo Decay Gamma-ray Transport Calculation with Variance Reduction Method

For the evaluation of gamma-ray dose rates around the duct penetrations after shutdown of nuclear fusion reactor, the calculation method is proposed with an application of the Monte Carlo neutron and decay gamma-ray transport calculation. For the radioisotope production rates during operation, the Monte Carlo calculation is conducted by the modification of the nuclear data library replacing a prompt gamma-ray spectrum with a decay gamma-ray spectrum. By multiplying each correction factor, which is ratio of the actual activation level after shutdown to the production rate during operation, with each decay gamma-ray flux due to each radioisotope, the decay gamma-ray dose rate is evaluated. In order to improve the statistical error, a variance reduction method is proposed by the application of the weight window importance technique and the specification of the decay gamma-ray generation location. We identify the cell producing the decay gamma-ray which can contribute the decay gamma-ray flux in evaluation locations, and forcibly terminate the gamma-ray transport calculation in the cells except for the identified cells. In order to validate the effectiveness of the method, shielding calculation for actual ITER (International Thermonuclear Experimental Reactor) configuration is performed, and small statistical errors below criteria are obtained. The effectiveness of the proposed method for ITER design analysis is demonstrated.     

Burnup Calculation Sensitivity and Uncertainty Analysis Method of Fission Yield and Decay Half-life

The calculation model of sensitivity coefficient for decay half-life and fission product yield in burnup calculation was derived based on generalized perturbation theory, which considered the interaction between nuclear concentration and neutron flux. A code was developed to calculate sensitivity and uncertainty of effective neutron multiplication factors and nuclide concentration caused by nuclear data. Covariance matrix of fission yield for a simplified burnup library was generated based on standard deviation data of independent fission yield in evaluated nuclear data library to improve the accuracy of uncertainty quantification. Uncertainties induced by decay half-life and fission yield on infinite neutron multiplication factors and nuclide concentration for TMI-1 pin-cell in the UAM burnup benchmark were quantified based on ENDF/B-Ⅶ.1. The numerical results show that the uncertainty of infinite neutron multiplication factors induced by decay half-lives and fission yields is low, while the uncertainty of concentration of some fission product nuclide is high.     

The separation techniques for secondary beams

In-flight separation of unretarded nuclear reaction products has made considerable progress in recent years. Electromagnetic separators for exotic species produced by nuclear fission, heavy ion fusion, target spallation, or projectile fragmentation have been developed to separate isotopes over the whole periodic table of elements with energies up to the GeV/u range.

Recently, the possibility to produce exotic nuclear beams with energies far above the Coulomb barrier by projectile fragmentation opened a new field of secondary beam physics, the direct use of isotopically separated beams of unstable nuclei for nuclear reactions. Characteristic examples of in-flight separation will be discussed with emphasis on the new generation of projectile fragment separators, including the future application of cooled and stored secondary beams for the application in nuclear physics.     

Nuclear Data Sheets for A = 198

The 2002 version of Nuclear Data Sheets for A = 198 (2002Zh04) has been updated and revised on the basis of the experimental results from various decay and reaction studies before June 2008. The experimental data for all known nuclei of A = 198 (Ir,Pt,Au,Hg, Tl,Pb,Bi,Po,At,Rn) have been reevaluated. The experimental methods, references, Jπ arguments, and necessary comments are given in the text. The theoretical internal conversion coefficient (ICC) (and its associated uncertainty) for γ-rays have been interpolated from theoretical values based on the “Frozen Orbital” approximation (2002Ba85) using the BRICC(v2.2) computer program. Summary band-structure drawings and level schemes from both radioactive decay and reaction studies are presented. Also of special interest are the new levels of ¹⁹⁸Ir, ¹⁹⁸Tl nuclei and identification of new superdeformed bands in ¹⁹⁸Pb and ¹⁹⁸Po.     

在线穆斯堡尔谱测量装置

穆斯堡尔效应自从被发现以来,已经成为研究超精细相互作用的不可缺少的工具,具有十分广泛的应用.然而其应用又受限制于一些长半衰期母核的核素.随着放射性核束技术的发展,基于加速器与在线同位素分离(Isotope Separator On-Line,ISOL)技术的短寿命放射性核束在线穆斯堡尔测量技术也得以发展起来,扩展了穆斯堡尔谱学的应用范围.目前国际上许多加速器(如RIKEN、CERN等)的在线同位素分离装置上都已经建立了在线穆斯堡尔实验装置,并在离子注入、半导体领域取得了成功的应用.本文介绍了在中国原子能科学研究院HI-13串列加速器上尝试建立的用于在线穆斯堡尔谱测量的装置以及初步测量结果.     

Nuclear Data Sheets for A = 72

Experimental data on ground- and excited-state properties for all known nuclei with mass number A = 72 have been compiled and evaluated. States populated in radioactive decay, as well as in nuclear reactions, have been considered. For these nuclei, level and decay schemes, as well as tables of nuclear properties, are given. This work supersedes the 1994 evaluation by W.-T. Chow and M.M. King (1994Ch45).     

The MARS nuclear reactor plant: A inherently safe, small/medium size multipurpose nuclear plant

The crucial aspects of nuclear safety: the need of a safe shutdown and of a reliable decay heat removal system have been the starting points in the development of a medium size, inherently safe, multipurpose “new” nuclear reactor: the MARS nuclear reactor.     

Nuclear data sheets for A = 209

Detailed level schemes, decay schemes, and the experimental reaction and decay data on which they are based, are presented for all nuclei mass number A = 209. The experimental data are evaluated; inconsistencies and discrepancies are noted, and adopted values for level and gamma-ray energies, gamma intensities, as well as other nuclear properties are given.     

基于抽样方法的燃耗计算核素积存量不确定度分析

基于抽样基本原理研究了应用于燃耗计算的不确定度分析方法,并开发了燃耗计算不确定度分析程序。基于评价核数据库ENDF/B-Ⅷ.0的裂变产额标准差和衰变常量标准差计算得到了衰变常量协方差矩阵和带相关性的裂变产额协方差矩阵,并结合SCALE6.2程序包的56群反应截面协方差数据库,对Takahama-3压水堆组件基准题中SF95-4样品进行不确定度分析。计算了反应截面、衰变常量和裂变产额不确定度引起的核素积存量的不确定度。计算结果表明,反应截面的不确定度是锕系核素积存量不确定度的主要来源,裂变产额和衰变常量的不确定度对部分裂变产物的积存量会引入较大的不确定度。但考虑裂变产额相关性后,裂变产额引起的不确定度显著降低。