AP1000核电厂事故下安全壳氢气浓度控制

在核电厂发生事故情况下,锆包壳与水或水蒸气发生化学反应产生大量氢气,可能在安全壳内引起氢气爆燃或爆炸,形成较大的压力载荷,对安全壳的完整性构成极大威胁。AP1000具有专设的安全壳氢气控制系统可限制安全壳内大气中的氢气浓度。     

AP1000核电厂氢气控制措施

福岛核事故之后,各国核电监管部门对于核电厂严重事故的预防和缓解措施都提出了更为严格的要求,确保在发生概率极低的严重事故的情况下,也能限制放射性物质向环境的释放。本文以AP1000针对严重事故的氢气控制措施为研究方向,介绍了严重事故情况下氢气的产生位置、反应机理、对安全壳的威胁、氢气点火器和非能动氢气复合器的布置。通过对上述设计和管理措施的介绍,结合其他研究成果,说明了AP1000核电厂对于严重事故情况下的氢气控制是有效的,能够满足国家核安全局的要求,可以确保安全壳的完整性。     

浅析秦山第二核电厂事故情况下安全壳消氢

在轻水堆核电厂严重事故进程中,锆合金包壳与水或水蒸汽产生大量的氢气,并通过反应堆冷却剂系统压力边界或压力容器破口释放到安全壳中。当氢气的浓度超过可燃浓度限值4%时,则可能发生燃烧,甚至爆炸。这将会引起安全壳超压和温度升高,从而对安全壳的完整性构成威胁,放射性裂变产物因此可能释放到环境中,造成严重后果。为了减小事故状态下氢气的威胁,目前国际上通常采用氢气复合器或氢气点火器等装置来降低氢气浓度。本文通过分析秦山二厂在事故状态下的氢气浓度变化,指出其在该领域的现状以及存在问题,并提出一些可行性建议,对核电厂的技术改造具有一定的借鉴意义。     

AP1000和M310安全壳冷却系统的对比与分析

随着核电发展对安全的要求越来越高,世界各国在新建核电项目上均以Ⅲ代核电技术为主,逐步取代原有的Ⅱ代和Ⅱ代+技术。AP1000作为Ⅲ代核电技术的代表,以非能动的特性显著提高了机组的安全性。通过对AP1000的非能动安全壳冷却系统(PCS)和M310的安全壳喷淋系统(EAS)进行比较分析,得出在安全壳冷却方面非能动系统较能动系统的优势。     

AP1000核电厂发电机冷却方式设计特点分析

本文比较详细地介绍了AP1000核电站发电机采用的冷却方式,包括冷却介质的选择,具体的冷却部位和内部通风流道的布置。此外,也介绍了AP1000核电站如何控制发电机冷却介质的参数以及氢气泄漏控制。     

核电厂严重事故下安全壳内消氢技术研究

福岛事故中氢气爆炸对全球核电厂安全提出了严峻挑战。因此,明确事故工况下的氢气来源,并及时采取合适的措施降低安全壳内氢气浓度对于核电厂安全至关重要。本文介绍了压水堆核电厂严重事故工况下氢气产生的机理,对目前采用的几种消氢装置如移动式氢复合器、点火器及非能动式氢复合器做了具体分析对比,阐明各自的运行特点,特别强调了非能动式氢气复合器的优点及运行注意事项,对核电厂的技术改造具有借鉴意义。     

方家山核电厂完全丧失热阱时的运行

针对方家山核电厂在RRA未接入时失去重要厂用水的事故,本文阐述了操作员在该事故下所应该进行的退防操作,并初步计算分析了用换料水箱通过安全壳喷淋系统管线、喷淋泵和喷淋热交换器构成冷却回路反冷设备冷却水系统的有效性。结果表明:对于方家山核电厂,即使在最恶劣的情况下只要操纵员能在8.6分钟内投入EAS热交换器以及安全壳喷淋泵的试验回路反冷设备冷却水并且同时采取在RRI回路减少负荷的措施,即可利用PTR水箱中的热惯性,延缓RRI失效的时间,给恢复热阱争取更多的时间,减轻事故后果。     

AP1000核电站钢制安全壳防锈蚀措施浅析

本文对AP1000核电站钢制安全壳寿期中的加工制造、存储、吊装及拼装等施工过程中可能导致锈蚀的原因进行了分析,并针对不同施工过程提出了一定的应对措施,如采用特定的防护材料及适当的防护等,从而达到控制工期及造价的目的。     

核电厂安全壳外小管道破裂事故的放射性后果分析

安全壳外含有一次冷却剂的小管道破损事故是同反应堆冷却剂系统相连接并贯穿安全壳的小管道(例如取样管)破裂引起的。为了满足该类事故后剂量验收准则,需分析相应的破口流量和源项以及发现破口的时间。本文以福清核电厂为例,分析计算了涉及安全壳外含一次冷却剂的核取样系统管道破口流量和源项,并验证是否符合剂量验收准则。     

AP1000设备冷却水系统缓蚀剂和pH控制剂的应用研究

本文通过对当前核电厂设备冷却水系统常用的几种缓蚀剂以及pH控制剂的比较分析,结合AP1000闭式冷却水系统(CCS)材料和运行要求,选择了适合AP1000 CCS的缓蚀剂和pH控制剂,为CCS的缓蚀剂和pH控制剂的选择和使用提供指导。     

商会自治的基石——商会自治规范研究

在现代法律秩序中,商会自治规范是制定法的基础和必要的补充,甚至在某些方面替代了制定法;商会自治规范主要包括商会组织规范、行为规范、惩罚规范以及争端解决规范等;其效力仅及于其内部成员;商会自治规范和制定法之间存在冲突,但也存在整合的基础。     

癸氧喹酯干混悬剂含量测定的改进

采用高效液相色谱法测定癸氧喹酯干混悬剂的含量,在2-250μg/mL范围内,峰面积的常用对数与进样量浓度的常用对数呈良好的线性关系,R^2=1(n=5),平均回收率为99.24%~99.51%,RSD在0.05%~0.28%。此方法分析时间短,样品前处理简便、定量结果准确,重现性好,结果满意,为其质量控制提供了依据。     

猪毛色遗传的研究进展

本文概述了猪的毛色类型、猪的毛色遗传模式,着重综述了猪毛色基因分子基础的研究进展,指出存在问题并就未来发展方向做了思考。     

Comparison of 2 methods of centesis of the bursa of the biceps brachii tendon of horses

REASONS FOR PERFORMING STUDY: Centesis of the bicipital bursa using an 8.9 cm long spinal needle has been reported but the alternative of employing a 3.8 cm long hypodermic needle requires validation. OBJECTIVE: To compare the efficacy of 2 different methods of centesis of the bicipital bursa and to evaluate the usefulness of ultrasonographic imaging to determine the location of solution administered when centesis of the bursa is attempted. METHODS: For Trial 1, 6 clinicians, who had no previous experience of centesis of the bicipital bursa, attempted to inject a solution composed of an aqueous radiopaque contrast medium and physiological saline solution (PSS) into the bicipital bursae of 2/12 horses using the previously described distal approach to inject one bursa and a proximal approach to inject the contralateral bursa. The bicipital tendon and bursa were examined ultrasonographically before and after injection; and both shoulders were examined radiographically to identify the location of the medium. In Trial 2, another 6 clinicians, also with no previous experience of centesis, repeated Trial 1, using 6 horses, but the radiopaque contrast medium was mixed with air instead of PSS. RESULTS: Accuracy of centesis using the proximal approach was 39% and that of the distal approach 28%. Ultrasonographic examination of the shoulder allowed the location of solution and air to be accurately predicted in all 12 shoulders examined. CONCLUSIONS: Clinicians who have had no previous experience performing centesis of the bicipital bursa are unlikely to be successful in centesis using either approach. Radiographic examination after injecting a radiopaque contrast medium may be necessary to assess the success of centesis especially if bursal fluid is not obtained during centesis. Injecting air along with the radiopaque contrast medium provides more accurate ultrasonographic confirmation of centesis and better radiographic definition than does injection without air.     

不同样本商品蜂蜜中硒含量的测定

用硝酸和高氯酸消化蜂蜜,使硒游离出来,在微酸性环境下,硒和2,3-二氨基萘(DAN)生成有较强荧光的物质,用环己烷萃取,在激发波长378nm,荧光波长518nm处测定其荧光强度。蜂蜜中硒含量范围:0.10～0.82μg/g。表明:蜂蜜应视为天然富硒营养品。     

乳酸杆菌益生作用机制的研究进展

乳酸杆菌作为益生菌广泛用于人和动物。本文综述了乳酸杆菌改善宿主健康的机制。乳酸杆菌可通过产生抗菌物质如乳酸、过氧化氢、细菌素,或者通过竞争营养或肠道黏附位点来抑制致病菌;通过诱导黏附素的分泌或阻止细胞凋亡而增强肠道的屏障功能,从而保护肠道。文章重点讨论了乳酸杆菌表面成分（表面蛋白、脂磷壁酸和肽聚糖）与肠道受体（Ｃ型凝集素受体、Ｔｏｌｌ样受体和 Ｎｏｄ样受体）,阐述了他们结合后启动免疫调节信号,调控肠道免疫功能以发挥改善健康作用的机制。     

Effects of size of ingestively masticated fragments of plant tissues on kinetics of digestion of NDF

Ingestively masticated fragments were collected and sized via sieving. Different sizes of esophageal masticate and ruminal digesta fragments, and ground fragments of larger masticated pieces were incubated in vitro, and undigested NDF remaining at intervals of up to 168 h of incubation was determined. The ruminal age-dependent time delay (tau) for onset of digestion of NDF was positively correlated (P < 0.004) with the mean sieve aperture estimated to retain 50% of the fragments between successive sieve apertures (MRA). Degradation rate of potentially degradable NDF (PDF) and level of indigestible NDF were not related (P > 0.10) to MRA of masticated and ground fragments. Estimates of tau were positively related to MRA, with slopes of bermudagrass < corn silage < ruminal fragments of corn silage. It was concluded that fragment size-, and consequently, ruminal age-dependent onset of PDF degradation of a mixture of different fragment sizes results in an age-dependent rate of degradation of the more rapidly degrading of two subentities of PDF. Models are proposed that assume a tau before onset of simultaneous degradation of PDF from two pools characterized as having gamma-modeled age-dependency and age-constant rates. The ruminal age-dependent pool seems to be associated with the faster-degrading pool, and its rate parameter increases with range in MRA in the population of fragments. Conceptually, the ruminal age-dependent rate parameter for PDF degradation seems to represent a composite of several effects: 1) effects of the size-dependent tau; 2) range in MRA of the population of ingestively masticated fragments; and 3) subentities of PDF that degrade via more rapid age-dependent rates compared with subentities of PDF that degrade via age-constant rates. The estimated fractional rates of ruminative comminution of ingestively masticated fragments (0.060 to 0.075/h) were of a magnitude similar to the mean fractional rates of PDF digestion (0.030 to 0.085/h), which implies that ruminative comminution may be first-limiting to fractional rate of PDF digestion. The in vivo roles of ingestive and ruminative mastication of fragments on PDF degradation must be considered in any kinetic system for estimating PDF digestion in the rumen. These results and others in the literature suggest that the rate of surface area exposure rather than intrinsic chemical attributes of PDF may be first-limiting to degradation rate of PDF in vivo.     

Mechanism of Action of Probiotic Function of Lactobacilli

乳酸杆菌作为益生菌广泛用于人和动物.本文综述了乳酸杆菌改善宿主健康的机制.乳酸杆菌可通过产生抗菌物质如乳酸、过氧化氢、细菌素,或者通过竞争营养或肠道黏附位点来抑制致病菌;通过诱导黏附素的分泌或阻止细胞凋亡而增强肠道的屏障功能,从而保护肠道.文章重点讨论了乳酸杆菌表面成分(表面蛋白、脂磷壁酸和肽聚糖)与肠道受体(C型凝集素受体、Toll样受体和Nod样受体),阐述了他们结合后启动免疫调节信号,调控肠道免疫功能以发挥改善健康作用的机制.     

Evaluation of serum concentrations of biomarkers of skeletal metabolism and results of radiography as indicators of severity of osteochondrosis in foals

OBJECTIVE: To determine whether serum concentrations of biomarkers of skeletal metabolism can, in conjunction with radiographic evaluation, indicate severity of osteochondrosis in developing horses. ANIMALS: 43 Dutch Warmblood foals with varying severity of osteochondrosis. PROCEDURE: 24 foals were monitored for 5 months and 19 foals were monitored for 11 months. Monthly radiographs of femoropatellar-femorotibial and tibio-tarsal joints were graded for osteochondral abnormalities. Serial blood samples were assayed for 8 cartilage and bone biomarkers. At the end of the monitoring period, foals were examined for macroscopic osteochondrosis lesions. RESULTS: Temporal relationships were evident between certain serum biomarkers and osteochondrosis severity in foals during their first year. Biomarkers of collagen degradation (collagenase-generated neoepitopes of type-II collagen fragments, type-I and -II collagen fragments [COL2-3/4C(short)], and cross-linked telopeptide fragments of type-I collagen) and bone mineralization (osteocalcin) were positive indicators of osteochondrosis severity at 5 months of age. In foals with lesions at 11 months of age, osteochondrosis severity correlated negatively with COL2-3/4C(short) and osteocalcin and positively with C-propeptide of type-II procollagen (CPII), a collagen synthesis marker. Radiographic grading of osteochondrosis lesions significantly correlated with macroscopic osteochondrosis severity score at both ages and was strongest when combined with osteocalcin at 5 months and CPII at 11 months. CONCLUSIONS AND CLINICAL RELEVANCE: The ability of serum biomarkers to indicate osteochondrosis severity appears to depend on stage of disease and is strengthened with radiography. In older foals with more permanent lesions, osteochondrosis severity is significantly related to biomarker concentrations of decreased bone formation and increased cartilage synthesis.