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     

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.     

冷却剂丧失条件下钠冷快堆棒束传热的三维蒙特卡罗模拟方法

采用蒙特卡罗方法分析钠冷快堆在假想冷却剂丧失条件下燃料棒束的钠两相流传热问题。以分子运动理论的基本定律为基础，开发出替代宏观经验模型来分析反应堆棒束中的钠蒸发率和冷凝率的微观模型，且采用三维蒙特卡罗方法模拟分子的运动轨迹，分子间的碰撞率以及分子与棒束、分子与棒束组件盒壁的碰撞率。对包壳干涸区的再浸润现象用动力膜模型描述，并计算了通过液膜的液体速度分布和平均液膜速度，对于从冷凝液膜蒸发的钠分子则被重新记为蒙特卡罗计算的源项。用微观和宏观模型相结合的方法数字模拟了德国卡斯鲁尔研究中心的堆外钠沸腾实验。     

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.     

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.     

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。     

贮液容器爆炸事故中的载荷模型及能量释放分析

对贮液容器内部低速炸药爆炸载荷模型的选取及其能量释放的分析进行了研究。以液态金属快中子增殖反应堆的假想堆芯破损事故为例 ,评价了国外采用的各种低速炸药爆炸载荷计算模型及事故中总释放能量的估计方法 ,提出用能量释放总量来反推载荷模型初始条件的“5 %截断准则”。     

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.     

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.     

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.