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压水堆冷却剂系统中存在各种气体,它们来自随初次充水或补水带入的空气,气体添加物,水本身和化学添加物的辐照分解产物,水中气体杂质的中子辐照产物,以及因燃料元件包壳破裂或其表面沾污有燃料而进入系统的裂变气体。这些气体主要溶解在作为冷却剂的水中,也有一部分气体逸入稳压器的蒸汽空间和附着在系统的结构材料上。象氧这样的气体还要进一步与结构材料形成氧化腐蚀产物。如无适当的除气措施,这些气体在系统中积聚量过大,可能影响泵和仪表的正常工作;引起反应性变化;破坏传热效果和增加装置的放射性。
Various types of gas exist in pressurized water reactor coolant systems from air entrained with initial charge or recharge, gaseous additives, irradiated decomposition products of water itself and chemical additives, neutron irradiation products of gaseous impurities in water , As well as fission gas entering the system due to ruptured fuel cladding or contaminated fuel on its surface. These gases are mainly dissolved in the water as a coolant, and some of the gas escapes into the vapor space of the regulator and adheres to the structural materials of the system. Such gases as oxygen also further form oxidative corrosion products with the structural material. Without proper outgassing, these gases accumulate too much in the system and may affect the proper operation of the pump and meter; cause reactive changes; disrupt the heat transfer and increase the radioactivity of the unit.