Wet granulation of mixed oxide powders de-nitrated by the microwave heating

A performance in a wet granulation of mixed oxide (MOX) powders prepared by the microwave heating de-nitration method was examined to fabricate MOX fuel pellets for fast breeder reactor at an extremely simplified process. An agitating granulator equipped with three blades and a chopper was used and its performance was evaluated. Characteristics and physical properties of the raw powder and the granules were measured together with observations by scanning electron microscopy before/after granulation. We could obtain the granules of 120–140 μm in diameter within a narrow range of water addition ratio 12.5–13.5 wt% combined with a flow-ability >73 and a product yield >90%. Specific surface area that corresponds to sintering performance was almost the same as that of raw powder. When the ratio was <9 wt%, no granule was observed, and flow-ability did not change from that of raw powder <30. It was estimated from an additional experiment that the reason was capillaries (or voids) in the raw powder. When the ratio was more than 14 wt%, the flow-ability saturated and the product yield decreased. This narrow range of water addition ratio and strong binding force were successfully understood based on the standard theory of granulation supposing the Pendular state and the Gorge method.     

MOX燃料堆芯热工特性及设计限值研究

使用MOX燃料的快堆核电站以其线功率高、燃耗高、堆芯出口温度高等特点,对堆芯热工设计提出了新的问题.本文在对MOX燃料热工性能分析的基础上,给出了主要的热工设计限值,并以电功率870 MW电站为参考,初步分析了其堆芯热工特性和设计裕量.结果表明对于MOX燃料,较高的堆芯热工参数合理可行,且具有足够的裕量.     

聚变-裂变混合堆设计研究

利用MCNP5和MONK9A程序对聚变驱动裂变混合堆进行了初步研究,在等离子体第1壁外侧依次包覆长方体形状的燃料组件和产氚组件,形成裂变堆芯包层和产氚区.对分别装载贫铀、天然铀、贫铀MOX和天然铀MOX等4种燃料的混合堆进行了研究分析,其中,后两种燃料在整个运行寿期内的功率放大倍数和氚增殖比满足设计要求.通过随燃耗变化的同位素含量分析,初步探讨了混合堆的铀-钚燃耗循环策略.     

混合氧化物燃料应用前景及核燃料循环战略

本文叙述了不同国家在不同核电发展条件下的核燃料循环战略初步考虑,并着重叙述了在快堆商业化进程推迟后所发展的混合氧化物(MOX)燃料的设计、制造技术及定量经济分析的基本情况,并建议我国近期应主要采用中间贮存并配以建造后处理中间试验工厂,为今后的商业后处理厂做好技术准备,同时还要跟踪 MOX 燃料技术。     

Sensitivity analysis of fuel pin failure performance under slow-ramp type transient overpower condition by using a fuel performance analysis code FEMAXI-FBR

The FEMAXI-FBR is a fuel performance analysis code and has been developed as one module of core disruptive evaluation system, the ASTERIA-FBR. The FEMAXI-FBR has reproduced the failure pin behavior during slow transient overpower. The axial location of pin failure affects the power and reactivity behavior during core disruptive accident, and failure model of which pin failure occurs at upper part of pin is used by reflecting the results of the CABRI-2 test. By using the FEMAXI-FBR, sensitivity analysis of uncertainty of design parameters such as irradiation conditions and fuel fabrication tolerances was performed to clarify the effect on axial location of pin failure during slow transient overpower. The sensitivity analysis showed that the uncertainty of design parameters does not affect the failure location. It suggests that the failure model with which locations of failure occur at upper part of pin can be adopted for core disruptive calculation by taking into consideration of design uncertainties.     

Hypothetical integration of a fast reactor to the fuel cycle in Slovakia

The inspiration for dealing with the topic of fuel cycle back-end was attendance at a European project called RED-IMPACT – Impact of Partitioning Transmutation and Waste Reduction Technologies. This paper includes an image how to re-use energetic potential of stored spent fuel and at the same time how to effectively reduce spent fuel and radioactive waste volumes aimed for deep repositories. The first part is based on the analysis of Pu and minor actinides (MA) content in actual VVER-440 spent fuel stored in Slovakia. The next parts present the hypothetical possibilities of reprocessing and Pu re-use in a fast reactor under Slovak conditions. For the hypothetical transmutation of heavy nuclides (Pu and MA) contained in Slovak spent fuel a SUPERPHENIX (SPX) fast reactor with increased power was chosen because a fast nuclear reactor cooled by sodium belongs to the group of Generation IV reactor systems. This article deals with the analysis of power production and fuel cycle indicators. The indicators of the SPX calculation model were compared with the results of the VVER-440 spent fuel with the initial fuel enrichment of 4.25% U-235 + 3.35% Gd₂O₃. The created SPX model in the spectral computer code HELIOS 1.10 consists of a fissile (fuel) and a fertile part (blanket). All kinds of calculations were performed by the computer code HELIOS 1.10. This study also exposes the HELIOS modelling and simulating borders.     

MOX燃料在轻水堆核电站中的应用

目前MOX燃料已成为一种可用于轻水堆核电站成熟的核燃料。简要介绍了国外该领域的发展状况以及MOX燃料对反应堆性能的主要影响和应对措施。探讨了MOX燃料在国内压水堆核电站中的应用问题。     

不完全燃烧焚烧灰的微波处理初步研究北大核心CSCD

由于工艺、设备、投料等变化,焚烧灰存在不完全燃烧现象,因而不满足后续处理要求,存在安全隐患。通过使用微波灰化炉对不完全燃烧焚烧灰以及较完全燃烧焚烧灰进行加热,对加热前后焚烧灰进行减重量、减重率及组分等一系列测试,研究微波加热对焚烧灰处理的可行性以及作用原理,并初步探索微波处理的工艺条件。结果表明,微波加热处理焚烧灰具有可行性,可达到与传统马弗炉同样的效果。微波处理焚烧灰的性能与加热功率、加热时间和处理量有关。加热功率和加热时间决定了微波处理焚烧灰的效率,而处理量决定了微波处理焚烧灰的能力。     

Optimized analysis of ionospheric amplitude modulated heating parameters for excitation of very/extremely low frequency radiations

It is now well known that amplitude modulated (AM) high frequency (HF) radio wave transmissions into the ionosphere can be used to generate very/extremely low frequency (VLF/ ELF) radio waves using the so-called ‘electrojet antenna’. Duty cycle and heating frequency are analyzed and discussed with the lower-ionosphere modulated heating model, so as to improve the radiation efficiency of VLF/ELF waves in AM ionospheric heating experiments. Based on numerical simulation, the ranges of parametric selectivity in optimal duty cycle and heating frequency ( fHF) are derived. The International Reference Ionosphere 2015 (IRI-2015) model and two-parameter model are used to predict background electron density profiles, and optimized ranges of duty cycle for different density profiles are analyzed and compared. The influences of wave polarizations on optimal duty cycle are also discussed. It is shown that intensity of the VLF/ELF equivalent radiation source (M) firstly rises and then falls with the increase of duty cycle. When using the IRI model, M peaks at a duty cycle of 50%, optimally ranging from 40% −70%. For the two-parameter model case, an optimal duty cycle is 40% and the optimized ranges vary from 30%−60%. Heating with an X-mode polarization is more efficient than with the O-mode case in VLF/ELF wave generation. Nevertheless, an optimal duty cycle is almost independent of HF wave polarizations. To obtain better VLF/ELF generation, optional fHF may be 0.8−0.9 times of foE for the O-mode heating and 0.75−0.85 times for the X-mode polarization case. Finally, the variations of these two parameters in different latitudes are discussed.     

The prospect of mox fuel based PbBi cooled small nuclear power reactors

Safety performance of MOX fuel based PbBi cooled small fast power reactors has been analyzed and discussed. Though the thermal conductivity of MOX fuel is not large relative to that of nitride or metal fuel, but by proper combination of relatively small power density and relatively large natural circulation it can compensate fuel temperature decrease with coolant temperature increase smartly during unprotected loss of flow accident. Under such condition, accident analysis discussed in this paper show that under unprotected total loss of flow (ULOF) accident the reactor can survive inherently using combination of reactivity feedback. For unprotected rod run out transient over power (UTOP) accident the MOX reactor can overcome external reactivity by smaller power increase compared to that of nitride fueled reactors case. In this case doppler feedback plays much more important role compared to radial expansion component. So the MOX fueled small power reactors discussed here can survive both UTOP and ULOF accident with still enough temperature margin.     

Feasibility Study on the Analysis of MOX Particle Behavior

A plenty of plutonium is dealt in Plutonium Fuel Fabrication Facility and the facility is required to confine plutonium within a limited space such as glove box (GB) because plutonium is a-emitter and causes an internal exposure. The MOX particles entrainment occurs and some of them are transiting to the outlet of GB without deposition to floor and wall. The entraining rate and the transiting rate are reported as Airborne Release Fraction (ARF) and Respirable Fraction (RF) in the literatures. However, no activities of model development and analytical approach have been found for ARF and RF. Thus, a feasibility study is done in this paper on the behavior of MOX particles in GB such as entraining and transiting. A modeling code has been developed by improving AQUA-SF code and the RF values for abnormal occurrences, such as free-fall spill, outflow and fire, have been analyzed and compared with those reported. This paper also shows the analytical results of the improved code together with the simulated experimental results. It is found that the calculated values are almost corresponded to those reported and that the improved code can estimate MOX particle behavior in GB well.     

Incipient Boiling Pressure Pulse of Sodium under Forced Convection by Direct Heating

An account is given of experiments on incipient boiling pressure pulses imparted by liquid sodium, performed in a forced convection loop. The sodium is heated by direct current applied to the liquid metal itself in a vertical tube of 14.9 mm inner diameter through which the medium pumped. The experiments were carried out with the following ranges:

Input power: 6–12kW,Pressure at condenser: 0.6–1.0 kg/cm², Inlet temperature: 780^°–850^°C, Flow rate: 1.0–3. 5 l/min

Typical pressure pulses registered during incipient boiling presented the form of damped oscillation. The initial pressure pulses were dependent on the location of boiling inception along the test section, the incipient boiling pattern and the degree of superheat. The initial pressure pulses observed were in the range of 0–3. 5 kg/cm². The pressure pulses increased with the degree of superheat, which ranged 0^°–150°C.

The magnitudes of pressure pulses exceeded the saturation vapor pressure corresponding to the temperature of superheated liquid. Consideration of a simplified model indicated that, during incipient boiling, the pressure in the vapor phase oscillates while approaching asymptotically the saturation pressure.     

生活污水微波二级消毒及机理的研究

电磁场与生物系统的相互作用能导致不同生物层次上形态、结构、功能等方面的变化.采用连续电磁波对生活污水进行二次消毒,细胞内有一定偶极矩的微观分子和介电特性生物分子聚集体在外加电磁场的作用下产生介电损耗,并将吸收的微波能量转化为无规则运动的热能,使温度升高,产生热效应;在外加电磁场的影响下,膜电位的改变使细胞膜构象发生变化,影响K 、Na 通道的开启.同时使电压依赖性的钙离子通道开启,膜外浓度较大的Ca2 顺电位梯度进入细胞内,导致细胞消亡,产生非热效应.细胞的跨膜电压变化越大,引起的细胞死亡率就越高.结果表明,微波对生活污水具有较好的消毒效果.该方法具有高效、廉价、操作简单、便于实现自动化、不需添加任何物质和不产生任何二次污染等优点.     

Visual study of ex-pin phenomena for SFR with metal fuel under initial phase of severe accidents by using simulants

In the present Korean sodium-cooled fast reactor (SFR) program, early dispersion of the molten metal fuel within a subchannel is suggested as an inherent safety strategy in the initiating phase of a hypothetical core disruptive accident (HCDA). This safety strategy provides a negative reactivity driven by the melt dispersion; therefore, it could reduce the possibility of occurrence of a severe recriticality event. In the initiating phase, the melt could be injected into the subchannel horizontally by the internal pressure of the fuel pin. Complex phenomena occur during intermixing of the melt with the coolant after the horizontal injection of the melt. It is rather difficult to understand the several combined mechanisms that occur that are related to the dispersion and fragmentation of the melt. Thus, it seems worthwhile to study the horizontal injection of melt at lower temperatures, which could help to observe the dispersion phenomenon and understand the fragmentation mechanism. In this work, for a parametric study, tests were performed under structural conditions, coolant void conditions, and boiling conditions. As a result, in some cases, the injected molten materials were stuck around the injection hole. On the other hand, the molten materials were dispersed upward sufficiently well under the boiling condition when R123 was used as the coolant. The built-up vapor pressure was found to be one of the driving forces for the upward dispersion of the molten materials.     

Continuous Boiling Phenomena of Sodium under Forced Convection by Direct Heating

The results of an experimental study on the continuous boiling behavior of sodium with upward forced convection loop are reported. The sodium was passed through a vertical tube of 14.9 mm I.D., where it was heated by d.c. power (~4V,~5,000 A) directly applied through the flowing sodium. The experiments were carried out in the following range of conditions:

Input power:6–12kW Pressure at the condenser: 0.9–1.1 kg/cm² Flow rate: 1.0–3.0 l/min Inlet temperature: 750°–830°C.

Under certain conditions, steady boiling occurred, but boiling generally had a tendency to become unstable, and flow patterns representing violently pulsating boiling were observed. These latter flow patterns were either of single bubble ejection type with expulsion and subsequent re-filling of sections of the tube mainly by liquid sodium falling back from above, or else of slug type with periodical expulsions, without fall-back of liquid. For these patterns of pulsating boiling, the frequencies of oscillation ranged from 0.5 to 1.0 Hz. The film thickness remaining on the channel wall was also measured.     

Incipient Boiling Phenomena of Sodium under Forced Convection by Direct Heating

The results of an experimental study on incipient sodium boiling with upward forced convection loop are reported. Forced convection sodium in a vertical tube of 14.9mm I.D. was directly heated by direct current (–4V, –5,000A). The experiments were carried out under the following conditions:

Input power: 6–12kW, Pressure at the condenser: 0.9–1.1 atm

Flow rate: 1.0–3.0l/min, Inlet temperature: 7,500°–830°C

The incipient boiling phenomena observed were either violent single bubble ejection or else slow vapor formation depending on the conditions.

It was indicated from observations of the position of boiling inception that the boiling did not always occur at the position of maximum temperature.     

核燃料循环成本与核电的竞争力

国际市场核燃料价格变幻莫测,对我国核电的成本和发展产生影响,本文提出了控制整个核燃料循环成本的设想,以提升中国核电的竞争力,促进核燃料产业和核电产业的共同发展。     

Behavior of Irradiated ATR/MOX Fuel under Reactivity Initiated Accident Conditions

Pulse irradiation experiments with irradiated ATR/MOX fuel rods of 20MWd/kgHM were conducted at the NSRR in Japan Atomic Energy Research Institute to study the transient behavior of MOX fuel rod under reactivity initiated accident conditions. Four pulse irradiation experiments were performed with peak fuel enthalpy ranging from 335 J/g to 586 J/g, resulted in no failure of fuel rods. Relatively large radial deformation of the fuel rods due to pellet-cladding mechanical interaction occurred in the experiments with peak fuel enthalpy above 500 J/g. Significant fission gas release up to 20% was measured by rod puncture measurement. The generation of fine radial cracks in pellet periphery, micro-cracks and boundary separation over the entire region of pellet were observed. These microstructure changes might contribute to the swelling of fuel pellets during the pulse irradiation. This could cause the large radial deformation of fuel rod and high fission gas release when the pulse irradiation conducted at relatively high peak fuel enthalpy. In addition, fine grain structures around the plutonium spot and cauliflower structure in cavity of the plutonium spot were observed in the outer region of the fuel pellet.     

双频加热的LECR3离子源设计及初步的调试

研制成功了一台新的ECR（Electron Cyclotron Resonance）离子源LECR3（Lanzhou ECR No.3）。该离子源能为原子核物理与表面物理研究提供高电荷态离子束流，LECR3的设计主要基于IMP（Institute of Modern Physics）的14.5GHz ECR离子源（Lanzhou ECR No.2），但采用了双频加热、波导直接馈入微波功率及铝制等离子体弧腔等新技术和新方法。另外，LECR3的弧腔容积比LECR2的大，增加可注入的微波功率，可有效地增加引出的高电荷态离子束流的强度。虽然增大了弧腔的内么，但仍然保持径向六极磁铁在弧腔内壁上产生最大磁场强度与LECR2的同样大小。