环氧树脂固化放射性废树脂的配方初探北大核心CSCD

为了将中、低放射性废树脂固化成稳定的固化体,采用环氧树脂为基材,通过添加合适的固化剂、稀释剂、阻燃剂等进行固化配方试验研究。结果表明,配方为E-44环氧树脂∶651固化剂∶添加剂=1∶0.53∶0.05(38∶20∶2)、质量包容率50%时,其固化体性能最优,并满足国标GB 14569.2的要求,研究结果表明采用环氧树脂体系固化放射性废树脂是可行的。     

过氧化氢湿法氧化 IRN78阴离子交换树脂的初步研究

使用过氧化氢湿法氧化技术对核级IRN78阴离子交换树脂进行了氧化降解初步研究。 研究中用硫酸对阴离子交换树脂体系pH值进行了调节,比较了催化剂Fe²⁺、Cu²⁺、Fe²⁺/Cu²⁺混合催化剂对H₂O₂-阴离子交换树脂的催化效果。研究结果表明:使用混合催化剂Fe²⁺/Cu²⁺的摩尔数比为1∶2时湿法氧化IRN78阴离子交换树脂的催化效果优良,氧化降解率达到了99.7%,过氧化氢的利用率达到了 92.7%。实验结果表明过氧化氢湿法氧化技术对于 IRN78阴离子交换树脂有良好的氧化降解效果。     

Safety study of the coupling of a VHTR with a hydrogen production plant

The present paper deals with specific safety issues resulting from the coupling of a nuclear reactor (very high temperature reactor, VHTR) with a hydrogen production plant (HYPP). The first part is devoted to the safety approach consisting in taking into account the safety standards and rules dedicated to the nuclear facility as well as those dedicated to the process industry. This approach enabled two main families of events to be distinguished: the so-called internal events taking place in the coupling circuit (transients, breaks in pipes and in heat exchangers) and the external events able to threat the integrity of the various equipments (in particular the VHTR containment and emergency cooling system) that could result from accidents in the HYPP. By considering a hydrogen production by means of the iodine/sulfur (IS) process, the consequences of the both families of events aforementioned have been assessed in order to provide an order of magnitude of the effects of the incidents and accidents and also in order to propose safety provisions to mitigate these effects when it is necessary. The study of transients induced by a failure of a part of the HYPP has shown the possibility to keep the part of the HYPP unaffected by the transient under operation by means of an adapted regulation set. Moreover, the time to react in case of transfer of corrosive products in the VHTR containment has been assessed as well as the thermohydraulic loading that would experience the coupling pipes in case of very fast uncoupling of the facilities aiming at avoiding an excessive pressurization of the VHTR containment. Regarding the external events, by applying a method used in the process industries, the bounding representative scenarios have been identified on the basis of their consequences but also on the basis of their occurrence frequency. The consequences of the selected bounding scenarios, calculated taking into the source-term, the atmospheric dispersion and the pressure and toxic effects induced respectively by a hydrogen unconfined vapour cloud explosion (UVCE) and a sulfur dioxide release have been assessed. The resulting safety distance of about 100 m for the UVCE is fairly acceptable in terms of performance (head loss and thermal loss) of the coupling system. However, the longer safety distance (about 1.5 km) calculated for a SO₂ release implies to foresee a long distance to settle the control room of the site or to foresee provisions able to stop very fast the SO₂ leak.     

Safety assessment aspects of type B(U) packages containing wet intermediate level waste

Abstract

In Germany, the mechanical and thermal safety assessment of approved packages for the transport of RAM is carried out by BAM as the competent authority according to the International Atomic Energy Agency regulations. BAM was involved in several approval procedures with ductile cast iron containers containing wet intermediate level waste. These contents, which are not dried, only drained, consist of saturated ion exchange resin and a small amount of free water. Compared to the safety assessment of packages with dry content, attention must be paid to some more specific points. The physical and chemical compatibility of the content itself and of the content with materials of the package must be shown. From the mechanical resistance point of view, the package has to withstand the forces resulting from the freezing liquid. The most interesting point, however, is the pressure build-up inside the package due to vapourisation. This could be caused by radiolysis of the liquid and must be taken into account for the storage period. The paper deals primarily with the pressure build-up inside the package caused by the regulatory thermal test (30 min at 800°C) as part of the cumulative test scenario under accident conditions of transport. To determine the pressure, the temperature distribution in the content must be calculated for the whole period from the beginning of the thermal test until cooling down. In this case, calculating the temperature distribution requires, besides the consideration of conduction and heat radiation, consideration of evaporation and condensation including the associated processes of transport.     

Evaluation study on properties of a macroporous silica-based CMPO extraction resin to be used forminor actinides separation from high level liquid waste

Basic properties of a silica-based octyl(phenyl)-N,N-diisobutylcarbamoyl-methylphosphine oxide (CMPO) extraction resin (CMPO/SiO2-P) was investigated.Adsorption behavior for some rare earth elements (RE) which are constituents of high level liquid waste (HLLW) and the long-term stability of the extraction resin in nitric acid solution were examined.The CMPO extraction resin was significantly stable in 3 mol·L?1 HNO3 solution at 50oC.Furthermore,the RE(III) were efficiently separated from non-adsorptive fission product (FP) elements such as Sr(II) in a column experiment using a highly nitric acid solution.The separation behaviors of the elements are considered to result from the difference in their adsorption and elution selectivity based on the complex formation with CMPO.There was no strong dependency of RE(III) separation efficiency on feed solution flow rate.Only from the perspectives of the acid-resistant behavior of CMPO extraction resin and the elution kinetics for the metal ions with the extraction resin,the CMPO extraction resin can be used in the modified MAREC process for HLLW partitioning.     

Safety design consideration for HTGR coupling with hydrogen production plant

Safety requirements and design considerations are examined for a nuclear hydrogen production system that consists of High Temperature Gas-cooled Reactor (HTGR) and a hydrogen production plant by thermochemical water splitting iodine–sulfur process (IS process). Requirements in order to construct hydrogen production plants under conventional chemical plant regulation are identified in order to take into account a fundamental difference in safety philosophy between the nuclear facility and chemical plant and meet requests from the potential users of nuclear heat. In addition, safety requirements for the collocation of the nuclear facility and hydrogen production plant utilizing IS process (IS plant) are investigated. Furthermore, design considerations to comply with the requirements are suggested and the technical feasibility of the design considerations is evaluated. The evaluation results for a reference plant showed that safe distance determined by the chemical plant regulation against combustible gas and hazardous chemical leakages comply with the plant layout design. Furthermore, the results demonstrated the feasibility of IS plant construction under non-nuclear regulation by showing that the tritium concentration in IS plant can be maintained below the regulation limit and reactor normal operation can be achieved during abnormal conditions in the IS plant. These results clarified that design considerations suggested for coupling the IS plant to HTGR are reasonably practicable. The proposed criteria can be used not only for coupling hydrogen production plants but also for other chemical plants such as steam reforming plants, etc.     

高放废液储罐氢气爆炸事故试验研究

高放废液在贮存过程中会产生氢气,若未能及时排出或被稀释,当混合气体中氢气的浓度达到爆炸临界点时,有可能发生爆炸,导致放射性物质释放。本文利用建立的高放废液储罐氢气爆炸事故试验装置,通过试验研究了氢气在储罐内的爆炸压力及壁面温度。测试结果表明,氢气浓度为30%,点火位置在储罐顶部中心附近时,约在点火后70 ms达到最大爆炸压力,最大爆炸超压值约为0.596 5 MPa,最高壁面温度约为110 ℃。     

Contact corrosion measurements on the pair UO2+x and carbon steel 1.0330 in brines and bentonite porewater with respect to direct waste disposal

Contact corrosion between carbon steel and UO₂ was studied in the MgCl₂ rich Q-brine, in bentonite porewater and in saturated NaCl solution by use of contact potential and contact current measurements. In all solutions the carbon steel dominates the contact potential, so that this potential is near to the rest potential of the carbon steel. Only in solutions without precipitation of iron corrosion products, the presence of metallic iron slightly reduces the UO₂ corrosion rate. If iron corrosion products precipitate, the relevant adsorption of the uranium species will be more effective than any direct cathodic corrosion protection.     

Dosimetric characteristic of VVR-M reactor with respect to tritium

Translated from Atomnaya Énergiya, Vol. 67, No. 2, pp. 111–113, August, 1989.     

Experience with piping in German NPPs with respect to ageing-related aspects

Thirteen nuclear power plants (NPPs) with pressurized water reactors (PWRs) and six plants with boiling water reactors (BWRs) are currently in operation in Germany. For almost 25 years, GRS has been systematically evaluating the operating experience of these plants. In this paper, the operating experience relating to piping damage in safety-relevant systems of German plants with light water reactors (LWRs) is evaluated with respect to ageing-related effects. The experience with actions taken against piping degradation is illustrated by examples. The results of the evaluation confirm the conservativeness of the safety concept chosen for the design of German NPPs with LWRs, as well as the effectiveness of ageing management.     

超临界水氧化处理核电站废阴离子交换树脂研究

在间歇式超临界水氧化(SCWO)设备中,对粉碎处理后的阴离子交换树脂水悬浮液在超临界条件下进行了氧化降解处理。实验研究了反应温度、反应压力、反应时间、过氧系数对COD去除率的影响,同时考察了催化剂种类、反应压力和反应温度对氨氮去除率的影响。通过正交试验,得到主要因素对处理效果影响的显著程度排序为:反应温度>反应压力>反应时间>过氧系数。结果表明:在反应温度540 ℃、反应压力26 MPa、反应时间8 min、过氧系数3的条件下,COD去除率为99.65%。针对阴离子树脂中NH₃-N含量高难以去除的问题,选用不同的催化剂CuSO₄、MnO₂、CeO₂添加到反应体系中,结果表明对NH₃-N的氧化效果顺序为CuSO₄>CeO₂>MnO₂,对NH₃-N的最高降解率达到96.53%。     

Experimental strategy of fuel performance testing with respect to PCI

Basic metallurgical investigations have revealed that stress corrosion cracking of Zircaloy tubes requires critical stress and iodine concentration for a minimum of time. Based on this observation KWU has structured its experimental strategy on the RSST approach. This means the evaluation of a defect-free power Range below a PCI defect threshold and a defect-free LHGR Step (naturally beyond the threshold), a limited Speed of power increase if both limits are exceeded, and a minimum Time for any mechanism to become effective.KWU has initiated a large ramp test program at HFR, Petten, the results of which are backed by the participation in international ramp test programs at Studsvik. The first target was the determination of the failure threshold as a function of burnup for the different fuel rod designs. Then, the allowable safe speed for passing the defect threshold was investigated. The defect-free range was confirmed by power reactor experiments on a broad statistical basis with rods of original length. In forthcoming experiments in Petten the verification of safe steps shall be a point of main priority. The permissible time above the thresholds may be controlled purely by the crack nucleation. In the Studsvik Demo Ramp II Program this is a point of special consideration.Detailed PIE results show that these performance limits can well be interpreted by observable phenomena like grain growth, fission product redistribution, fission gas release etc.     

中低放固体放射性废物处置中的α废物在线检测及位置判定方法初探

根据在核废料回取分类、压缩减容的处置工艺及部分专用设备开发等方面的研究和初步实践,提出了利用现代测试技术和自动控制原理对a型废物进行在线探测、位置判定、目标成像、定性分析、比活度粗测的方法。     

Air exposure and sample storage time influence on hydrogen release from tungsten

In investigations of hydrogen retention in first wall components the influence of the conditions of the implanted target storage prior to analysis and the storage time is often neglected. Therefore we have performed a dedicated set of experiments. The release of hydrogen from samples exposed to ambient air after irradiation was compared to samples kept in vacuum. For air exposed samples significant amounts of HDO and D₂O are detected during TDS. Additional experiments have shown that heavy water is formed by recombination of releasing D and H atoms with O on the W surface. This water formation can alter hydrogen retention results significantly, in particular - for low retention cases. In addition to the influence of ambient air exposure also the influence of storage time in vacuum was investigated. After implantation at 300 K the samples were stored in vacuum for up to 1 week during which the retained amount decreased significantly. The subsequently measured TDS spectra showed that D was lost from both the high and low energy peaks during storage at ambient temperature of ∼300 K. An attempt to simulate this release from both peaks during room temperature storage by TMAP 7 calculations showed that this effect cannot be explained by conventional diffusion/trapping models.     

碱矿渣水泥固化核废物研究现状

着重从碱矿渣的结构特征、碱矿渣水泥水化产物及碱矿渣水泥固化体的性能等方面论述了碱矿渣水泥固化核废物的研究现状,并初步分析了固化机理,展望了其应用前景。     

废树脂微波处理工艺研究

废树脂微波处理工艺主要利用微波的穿透能力强和体加热的特点,首先将废树脂中的水分除去,然后将废树脂中的有机组分去除,从而达到有机废物无机化的目的。与原始废树脂相比,微波干燥、灰化处理后,得到的灰分减容和减重比均极大。利用该技术处理得到的产物,可以方便的进行后续处理。通过研究,确定了废树脂微波桶内干燥及废树脂微波灰化工艺参数。