快堆蒸汽发生器声学泄漏探测技术的研究──Ⅱ.利用经典滤波技术提取泄漏信号

根据在实验Ｎａ回路上得到的实验结果，在对泄漏信号和背景噪声特性研究的基础上，提出了用经典滤波技术处理数据的方法，并验证了这种方法对提高测量系统灵敏度的作用。最后，讨论了所构建的声学泄漏探测系统在我国即将建造的实验快堆电站上的实用化问题。     

The result of a wall failure in-pile experiment under the EAGLE project

The WF (wall failure) test of the EAGLE program, in which 2 kg of uranium dioxide fuel-pins were melted by nuclear heating, was successfully conducted in the IGR (Impulse Graphite Reactor) of NNC/Kazakhstan. In this test, a 3 mm-thick stainless steel (SS) wall structure was placed between fuel pins and a 10 mm-thick sodium-filled channel (sodium gap). During the transient, fuel pins were heated, which led to the formation of a fuel-steel mixture pool. Under the transient nuclear heating condition, the SS wall was strongly heated by the molten pool, leading to wall failure. The time needed for fuel penetration into the sodium-filled gap was very short (less than 1 s after the pool formation). The result suggests that molten core materials formed in hypothetical LMFBR core disruptive accidents have a certain potential to destroy SS-wall boundaries early in the accident phase, thereby providing fuel escape paths from the core region. The early establishment of such fuel escape paths is regarded as a favorable characteristic in eliminating the possibility of severe re-criticality events. A preliminary interpretation on the WF test results is presented in this paper.     

Formation of Volatile Radioiodine Compounds in Sodium Pool Burning

In sodium pool burning occurring in the case of an LMFBR accident, some radio-iodine in the sodium coolant may be transported into the gas phase and act in common with sodium oxide aerosol. If some iodine is converted to volatile compounds, the radioactivity may remain for many hours in the gas phase of the reactor containment. The present work was carried out in an attempt to throw more light on these circumstances.

Reactor-grade sodium with sodium iodide tagged with ¹³¹I in an amount of about 1 ppm was burned by heating in a closed vessel containing air. Most of the iodine released into the gas phase took the form of aerosol, but some amount remained in vaporous state. It was determined by Maypacks and radio-gaschromatography that the volatile radio-iodine compounds were of organic form. The proportion of organic iodide referred to total airborne iodine in the present experiments falls within the experimental data on what will be formed in a loss of coolant accident involving a light water reactor. It is concluded that volatile iodine formation would present similar aspects under accidental conditions affecting both LWR and FBR, though the mechanisms governing the two cases would be different.     

Application of Galerkin Finite Element Method to Subchannel Analysis

Most of the computer codes based upon subchannel analysis, which are important for thermal hydraulic analysis of the reactor core, use the finite difference method to solve the set of equations. In the present study, however, the Galerkin finite element method was tried, with the result that more accurate solutions and more efficient calculations were obtained than those by the finite difference method. The results of error evaluation obtained herein are useful for application of this method to actual subchannel analysis codes and to other general thermal hydraulic analysis codes. As an example, steady-state single-phase subchannel analysis was performed.     

Transmutation-incineration potential of transuraniums discharged from PWR-UO2 spent fuel in modified PROMETHEUS fusion reactor

This study presents the potential of the burning and/or transmutation (B/T) of transuraniums (TRUs), discharged from the pressured water reactor PWR-UO₂ spent fuel, in the modified PROMETHEUS-H fusion reactor. Two different design shapes (Models A and B) were considered. The transmutation zone (TZ), which contains the mixture of TRU nuclides (10%), was located in the modified blankets. The volume fraction of Pu in the mixture is raised from 0 to 40% stepped by 10% to determine its effect on the B/T. The fuel spheres were cladded with SiC (5%) and cooled with high-pressured helium gas (85%) for nuclear heat transfer. The calculations were performed for an operation period (OP) of up to 10 years by 75% plant factor (η) under a neutron wall load (P) of 4.7 MW/m². The results bring out that: (1) the Model B transmutes the TRUs more rapidly than the Model A; (2) the effective half-lives decrease about 20 and 40% with the increase of Pu fraction in the cases of Models A and B, respectively; (3) the M values are quite high with respect to the M value of the original PROMETHEUS fusion reactor; (4) the blankets can produce substantial electricity in situ.     

钠冷快增殖堆池式钠火事故分析计算

针对钠冷快堆严重事故下可能发生的池式钠火事故 ,描述了钠火现象 ,采用池式钠火程序SOFIREⅡ的“一腔室”模型 ,并在该模型基础上 ,更客观地模拟池式钠火过程 ,编制程序POOLFIRE。SOFIREⅡ认为池式钠火过程一开始就生成Na2 O和Na2 O2 的混合物 ,生成量也不确定。POOLFIRE认为早期生成Na2 O ,大约 30分钟后向Na2 O2 转变 ,最后计算得出池式钠火引起的安全壳内温度及压力响应 ,并与SOFIREⅡ结果进行了比较     

A Method for Determination of Plutonium in Blood by Anion Exchange

The anion exchange behavior of Pu(IV) and Pu(VI) were studied in solutions of both nitric acid and of ethanol-nitric acid mixture, and a method of determining plutonium content in blood was developed. About 10 ml of blood were wet-incinerated with concentrated nitric acid and evaporated to dryness. The residue was dissolved in 8 ml of 8 N nitric acid, and 12 ml of ethanol was added. The solution was passed through a resin column of Dowex 2, X8 (9 mm diam., 3.0cm long). After washing the column with ethanol-nitric acid mixed solution, plutonium was eluted with 10 ml of 1N nitric acid containing sulfur dioxide. The eluate was transferred to a cell for electrodeposition, which was carried out with 500 mA/cm² for 3 hr using a stainless steel disk as cathode.

The plutonium yield from the ion exchange was 85~91%, and the electrodeposition quantitative. The blank activity from the reagents, resin and disk was 10^?14Ci. With this method a 10-hr count with silicone semiconductor spectrometer, will permit determination of 5 × 10^?14 10^?13Ci of plutonium in 10 ml of blood.     

Optimization of Refueling Scheme of Sodium-Cooled Fast Reactor Core Using Heuristic Enumeration Method

Abstract

Basic considerations are discussed in the area of LMFBR refueling optimization. The procedure of search for the optimum refueling scheme is based on a systematic enumeration algorithm embodying the heuristic rule “Elimination of Hopeless End States (EHES)”. The optimization procedure thus developed reveals the global characteristics of the refueling scheme, on the basis of a macroscopic regression model which describes the burnup-dependent core performance.

Sample numerical results are obtained on problems of optimizing the refueling scheme for the 4-zone zone-loaded and 2-zone scatter-loaded cores of a typical sodium cooled mixed-oxide fueled fast power reactor. Case studies are conducted on the effect of change in the elimination factor adopted in applying the EHES, in the upper or lower boundaries of constraints, in the performance criterion, and in various parameters governing the mode of reactor operation such as the duration of one cycle period. The study has revealed several notable characteristics particular to LMFBR core refueling, such as the common trait of optimized refueling schemes for 2-region cores of repeated identical refueling patterns, and incompatibility between radial power flattening and sustained useful life for the core.     

Sodium Mist Behavior in Cover Gas Space of LMFBR Out-Pile Experiment

Sodium mist behavior in argon cover gas space over sodium pool was investigated experimentally using of a test vessel having cover gas volume of ～100l. Mass concentration and gravitational settling flux of the mist (i.e. sodium aerosol) were determined between pool temperature range of 290～520°C. Apparatuses used for the concentration determination were a He-Ne laser mist concentration meter (LCM) and mist traps, which were developed specifically for the present experiment. The mist gravitational settling flux φ was determined by using of collection plates, which were exposed to the mist entrained cover gas over sodium pool.

The experimental results revealed that the concentration C was very high from 0.15 to 20g/m³. It increased with pool temperature. The mist particle radii, which were determined from the gravitational settling flux φ and decay curve of the concentration, were from 1.5 to 13 μm in the range of the present experiment. The vapor evaporation rate φe from the pool surface, which were also determined from the experimental φ data, were found to increase with saturated vapor pressure P_s at pool surface. This rate did not depend so strongly on experimental geometries and cover gas flow convection pattern over sodium pool. Evaluations of transient C changing and steady state C fluctuation indicated that the mist formation was occurred near the pool surface.     

Sodium Fire Code SFIRE1C for Pool Fire Characteristics

Sodium pool fire code, SOFIRE II, written for the constant value of stoichiometric combustion ratio and heat of reaction is used to compute the buildup of pressure and temperature in a containment. In the SOFIRE II model, for the formation of a mixture of Na₂O and Na₂O₂ in the sodium pool, the input stoichiometric combustion ratio and heat of formation values need to be varied to corresponding values admissible for the mixture. In the present work, the SOFIRE II one-cell model is revised and the present version SFIRE1C (Sodium FIRE 1 Cell model) accounts for the formation of Na₂O in an early stage of the fire and shifts to the formation of Na₂O₂ at a later stage. Thus SFIRE1C computes in a more realistic manner the reaction products which are formed in the pool. The model for sodium oxide aerosol release is also modified in this version, by incorporating a more appropriate aerosol release rate equation. The calculated values using the SFIRE1C one-cell model are compared with sodium pool fire experimental results.