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《科技视界》2016,(8)
压水堆核电厂正常运行时一回路压力为15.4MPa,组成一回路压力边界的主要设备为压水反应堆、蒸汽发生器、反应堆冷却剂泵、稳压器等部件组成,通过一回路压力边界内的设备运行将反应堆堆芯中核裂变反应产生的热量传送到蒸汽发生器,从而冷却堆芯,防止燃料元件烧毁,而蒸汽发生器供给汽轮发电机组(二回路)所必需的蒸汽。反应堆冷却剂系统组成的一回路压力边界内设备的正常运行对于保证反应堆稳定运行至关重要。正常运行时,反应堆冷却剂系统维持168吨温度为310℃、压力为15.4MPa的欠饱和水,这些冷却剂在主冷却剂泵的驱动下,循环流动,流经反应堆堆芯,带出裂变反应产生的热量,在蒸汽发生器中,将这些热量传递到二回路给水,产生蒸汽,驱动汽轮机发电。当一回路压力边界失效,将无法维持稳定的一回路压力,一回路压力下降,将使得温度为310℃的过冷水变为饱和水,从而产生大量的蒸汽,进入堆芯的冷却剂将变为汽液两相流或过热蒸汽,传热效果大大下降,同时产生大量的蒸汽,流经主冷却剂泵,将导致主冷却剂泵叶轮发生汽蚀,流量下降,进一步恶化的反应堆堆芯的冷却。堆芯核裂变或核燃料衰变产生的大量热量如果不能及时导出,将可能产生严重的后果甚至堆芯融化,从而造成重大的核安全事故。 相似文献
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钠冷快中子反应堆是第Ⅳ代先进核能系统的代表堆型,钠火安全是其重要安全设计之一。作为冷却剂的液态金属钠经堆芯活化后会产生强γ放射性,而且化学性质极为活泼,冷却剂的泄漏可能会造成强放射性钠火事故,因此,针对一回路冷却剂泄漏产生的放射性钠火事故监测对反应堆的安全设计具有重要意义。文章基于钠冷快堆正常运行工况下的一回路冷却剂活化水平,通过对放射性钠火产物放射性钠气溶胶的特性分析,开展对放射性钠火事故的辐射监测技术研究,从而实现对钠冷快堆放射性钠火事故的多样化监测,为反应堆的安全运行提供技术支持。 相似文献
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Beran GW 《Preventive veterinary medicine》2008,86(3-4):198-207
When early people made their appearance, zoonotic infectious diseases were already waiting, but epidemic diseases did not appear in human history until people began to live in large numbers under conditions of close contact, mainly during the last 10,000 years. Disease has decimated urban populations, conquered armies, and disrupted society. The focus here is on (1) the plague of Athens and the Black Death; (2) smallpox, influenza, and rabies; (3) avian influenza prion diseases, and foot & mouth disease; and (4) emerging and re-emerging diseases. All have veterinary public health associations. In Athens, Greece, in 430 BC, when the Spartans ravaged the countryside, hordes crowded into Athens so that orderly movements, space in which to live, and adequate supplies of food became impossible. Crowding of any population fosters disease transmission; chaos and disorder enhance it all the more. Out of northern Egypt came a terrible plague from across the Mediterranean Sea. The identity of the plague of Athens remains unsure, but the well-considered conclusion is Rift Valley Fever, a mosquito borne, viral zoonosis. The Black Death, also called the Plague, raged in Asia for centuries. In 1347, the Black Death was brought by a ship out of Asia to Sicily. The scenes of devastation were repeated throughout Europe, with 90% or more of the people dying in city after city. Influenza, too, has been a cause of periodic human epidemics, but the great pandemic of influenza occurred in the last months of World War I. In the years of highest occurrence, more than half the world's population became clinically infected. If veterinary public health had been born earlier, it could have led to elucidating the epidemiology of influenza and the plagues of Athens, Europe, and Asia. In turn, smallpox had also caused continual tragedy. In 1796, Edward Jenner began to harvest pustules of cowpox from children or infected cows and inject them into susceptible children. In 1980, the World Health Organization declared that smallpox had been eliminated from the world. Rabies, though, still strikes terror. A number of animal diseases, broadly termed emerging and re-emerging diseases, need surveillance because they have the potential to impact human health. From late in 2003 to 2007, the highly pathogenic H5N1 influenza virus in poultry infected at least 121 people and caused 62 deaths in four countries. The prion diseases, too, all have very high numbers in concentrated contacts. To control these diseases, veterinary public health is essential, with diagnosis, epidemiological surveillance, clinical manifestations, and prevention as primary measures. 相似文献
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Dekker A Dercksen D Snoep J van Wuyjckhuise L 《Tijdschrift voor diergeneeskunde》2007,132(18):695-701
On 26th of july 2007 a new case of bluetongue was notified in the Netherlands and on 2nd of august 2007 foot-and-mouth disease was diagnosed in Surrey, England, which raised the threat of having both infections simultaniously in one area. Bluetongue and foot-and-mouth disease have a different pathogenesis, but symptoms may resemble each other at a later stage of infection. The pathogenesis and possible clinical symptoms of both infections are discussed and illustrated with pictures. 相似文献
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在动物的异常行为中以刻板行为最为常见,而咽气癖又是马最常见的口部刻板行为之一。作者就咽气癖在生理方面和心智方面对马体产生的影响、行为基础、诱因的研究进展及常见的防治措施进行综述。 相似文献
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近几年,世界饲用添加剂市场增长较快,预计今后将进一步增长,据世界粮农组织(FAO)首领会议的倡议,到2015年,将使世界营养不良的人口削减一半,其间,肉制品将会以每年2%的速度增长,特别是加快猪肉和禽肉增长。这将促进世界添加剂,尤其是蛋氨酸和赖氨酸需求量的增加。 相似文献
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