Nuclear mechanism for TRU burning oxide fueled core in Advanced Recycling Reactor

This paper presents an approximation approach to predict the core characteristics based on parametric survey and an analysis of nuclear mechanism in a conceptual nuclear design for enhanced transuranics (TRU) burning mixed oxide fueled and sodium cooled fast reactor which can be realized in the near future. The design study of Advanced Recycling Reactor was conducted in the context of the program for the industry in Global Nuclear Energy Partnership initiatives, including a core in the first plant for demonstration and cores with enhanced TRU burning capability for the future plants. Both concepts for the first plant; low core height and large volume fraction of structure are deployed, seeking small TRU conversion ratio (CR)^* and small void reactivity which are crucial in the design, but different approaches. In this paper, the TRU CR and the sodium void reactivity have been approximated with a single equation in these concepts, based on the theoretical formula related to the chain reaction in the reactor and the calculation results. Shortening the core height and increasing the structure volume fraction will enhance TRU enrichment through increased neutron leakage and capture, which will reduce a ratio of U-238 to sum of Pu-239 and Pu-241 so that TRU CR decreases from 0.78 to 0.57. A small ratio of sodium loss to plutonium fissile will be effective also in the reduction of positive reactivity effect by spectral hardening. On the other hand, when this ratio and geometrical buckling of flux reduce, negative contribution by the neutron leakage becomes small. Theses relations related to the positive void reactivity have been formularized by the approximation with few parameters within several percent respectively as well as the TRU CR, indicating that one of dominating parameters is the ratio of sodium loss to plutonium fissile in the void reactivity at large fast reactors. * = (1 − net loss of TRU/loss of heavy metal).     

钍基先进坎杜堆非能动慢化剂系统概念设计

以钍基先进重水堆（简称TACR）慢化剂系统作为研究对象,提出了一种满足非能动安全要求的概念设计。在此设计中,首次将慢化剂冷却系统和余热排出系统合二为一,并用热工水力分析程序CATHENA Mod3．5c／Revl分析了反应堆在正常工作时的稳态运行情况,为验证设计的可行性奠定了基础。     

混合评价核数据库系统HENDL3.0研发及其在先进核能系统设计中应用

FDS团队结合聚变堆、先进裂变堆、聚变驱动次临界堆、加速器驱动次临界堆等核能系统对应用核数据的需求,设计开发出混合评价核数据库HENDL。HENDL包括输运核数据库、嬗变与活化核数据库、辐照损伤核数据库等,并针对先进核能系统的物理特点,从能量自屏效应、热散射效应、温度多普勒效应等方面进行了精确的截面修正。HENDL已通过国际基准模型与实验的验证与确认,并在ADSCLEAR、FDS-SFB为代表的重大核工程与核能研究中得到了广泛应用。     

THETRIS: A micro-scale temperature and gas release model for TRISO fuel

The dominating mechanism in the passive safety of gas-cooled, graphite-moderated, high-temperature reactors (HTRs) is the Doppler feedback effect. These reactor designs are fueled with submillimeter-sized kernels formed into tristructural-isotropic (TRISO) particles that are imbedded in a graphite matrix. The best spatial and temporal representation of the feedback effect is obtained from an accurate approximation of the fuel temperature. Micro-scale models of TRISO particles are necessary in order to obtain accurate predictions during fast transients or when parameters internal to the TRISO are needed. Most accident scenarios in HTRs are characterized by large time constants and slow changes in the fuel and moderator temperature fields. In these situations, a meso-scale, or pebble- and compact-scale, solution provides a good approximation of the fuel temperature as the fission thermal energy transports out of the kernel and into the surrounding matrix with a much shorter time constant. Therefore, in most cases, the matrix can be assumed to be in quasi-static equilibrium with the kernels. These models, however, fail to provide accurate information on the state of the various components of the TRISO during the early stages of transients. Since the coated particles constitute one of the fundamental design barriers for the release of fission products, it becomes important to understand the transient behavior inside this containment system. An explicit TRISO fuel temperature model named THETRIS has been developed and incorporated into the CYNOD–THERMIX-KONVEK suite of coupled codes. The code includes gas-release models that provide a simple predictive capability of the internal pressure during transients. The new model yields similar results to those obtained with other micro-scale fuel models of TRISO particles, but with the added capability to analyze gas release, internal pressure buildup, and effects of a gap in the TRISO. Analysis of bounding benchmark transients yield good agreement with other codes in which the TRISO particles are modeled explicitly. In addition, a sensitivity study of the potential effects on the transient behavior of high-temperature reactors due to the presence of an inter-layer gap is included. Although the formation of a gap occurs under special conditions, its consequences on the dynamic behavior of the reactor can yield responses during fast transients that depart significantly from those in which no gap is present in the model. The new model was applied to an extreme (beyond design basis) scenario in order to observe the behavior of the fuel during a large prompt critical reactivity insertion. Although a large amount of fission energy was deposited rapidly into the fuel, the kernel temperature is shown to stay well below the melting point and the silicon carbide layer remained well below the temperature above which failure is expected to occur. The explicit treatment of the TRISO particle geometry leads to much lower estimations of power peaking during the transient and a greater degree of negative Doppler feedback.     

关于PWR及CANDU堆先进燃料管理策略的研究

阐述开展先进燃料管理策略研究的必要性与紧迫性。对我国秦山核电厂的燃料管理策略的改进进行了初步探讨,包括提高富集度延长循环长度、增大平均卸料燃耗、应用先进可靠毒物和低泄漏优化换料、改进燃料组件设计和适当提高功率等,并对可能取得的重大经济效益进行了讨论。提出研究ＰＷＲ的乏燃料在ＣＮＡＤＵ堆中应用及形成ＰＷＲ／ＣＡＮＤＵ联合燃料循环的可行性,以提高燃耗深度,增加能量输出,降低发电成本。     

轻水堆严重事故及可能的缓解措施

现有概率安全评价指出，常规轻水堆的堆芯熔化频率及安全壳失效，放射性大量释放的频率都是是很低的。但这些风险对于下一代先进轻水堆说是不能忽力听，近年来西方对下一代先进轻水堆的安全目标作了更高的要求，即在严重事故的条件下，仍然能保证安全壳的完整性，而无需采取应急措施，这就要求对严重事故现象可有足够的认识，以便对严重事故设置相应的缓解措施，本文简述了严重事故的物理现象，机理及可能的缓解策略，综述了这方面的     

法国先进核燃料组件在中国应用前景浅析

介绍了法国先进燃料组件（ＡＦＡ）系列核燃料的特点及其在中国的应用现状，阐述了广东核电集团有限公司核电发展战略和第三代先进燃料组件（ＡＦＡ－３Ｇ）在中国的应用前景，并从物理，热工水力和燃料组件的机械完整性等方面作了初步论证，对当前开展的有关工作进行了讨论。     

Oxidation of Parachloronitrobenzene in Dilute Aqueous Solution by O3 + UV and H2O2 + UV : A Comparative Study

This laboratory study was designed to investigate the degradation of 4-chloronitrobenzene ([CNB] = 2.4 × 10^?6 mol L^?1; pH = 7.5) by H₂O₂/UV and by O₃/UV oxidation processes which involve the generation of very reactive and oxidizing hydroxyl free radicals. The effects of the oxidant doses (H₂O₂ or aqueous O₃), liquid flow rate (or the contact time), and bicarbonate ions acting as OH· radical scavengers on the CNB removal rates were studied. For a constant oxidant dose, the results show that the O₃/UV system appears to be more efficient than the H₂O₂/UV system to remove CNB because of the greatest rate of OH· generation by ozone photodecomposition compared to H₂O₂ photolysis. However, for a given amount of oxidant decomposed, the H₂O₂/UV oxidant system was found to be more efficient than O₃/UV. Moreover, high levels of bicarbonate ions in solution (4 × 10^?3 mol L^?1) significantly decrease the efficiency of CNB removal by H₂O₂/UV and by O₃/UV oxidation processes.     

VALIDATION OF PREDICTIVE AXIS CONTROL STRUCTURE WITHIN A VIRTUAL OPEN ARCHITECTURE MACHINE TOOL

This paper first presents the elaboration of a virtual machine tool within an open architecture framework, including CAM (Computer Aided Manufacturing) modules such as trajectory generation and visualization facilities. The proposed advanced controller is then introduced within this simulator. Based on predictive strategies, it appears as an excellent control alternative coupled to a simple design procedure and implementation facilities. Moreover, the resulting controller, structured under the polynomial RST form, considered as a generic formalism for any SISO (Single Input Single Output) numerical controller, fulfills the requirements towards an open architecture framework. Validation tests are achieved within this virtual environment and compared to those obtained on a real machining center under its current control structure.