HYDROGEN EXPLOSIONS - AN EXAMPLE OF HAZARD AVOIDANCE AND CONTROL

摘要

Many nuclear chemical plants have to deal with hydrogen gas generation caused by reactions such as radiolysis of water. Because of the continuing major construction and decommissioning activities on the Sellafield site, guidance has been developed to build in safety as early as possible to ensure the safety of new plant and to continuously review existing plant. The guidance adopts the approach that prevention is better than complicated design. Therefore a hierarchy has been adopted that: ⅰ) the design should be such that hazards are avoided ⅱ) the design should use passive features ⅲ) any failure or fault should produce no significant deviation ⅳ) the plant should be brought to a safe state by continuously available safety measures ⅴ) administrative safety measures are an option only when there is no reasonable alternative ⅵ) finally mitigation is taken into account The aim is to develop a design as close to the top of this list as possible, and to tailor assessment methods appropriate to the stage of design development. The application of these principles has been developed for the review of existing plant. The guidance is supported by data and methods that may be required in making an assessment in detail (e.g. radiolysis generation rates, ventilation calculations, etc), and references further sources of information.