Nuclear fission
INTRODUCTION 1.1Background
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- 1.2Starting considerations
1INTRODUCTION1.1BackgroundAn extended PSA (probabilistic safety assessment) applies to a site of one or several Nuclear Power Plant(s) (NPP(s)) and its environment. It intends to calculate the risk induced by the main sources of radioactivity (reactor core and spent fuel storages, other sources) on the site, taking into account all operating states for each main source and all possible relevant accident initiating events (both internal and external) affecting one NPP or the whole site [1]. A strategic reasoning regarding the topics on external hazards that can be examined within the ASAMPSA_E project has been applied to focus the activities where technical exchanges on identification of best practices will be the most useful. During the ASAMPSA_E End-Users workshop held in Uppsala [1], 10 important external hazards were identified as the minimum required to be addressed by the project. These hazards are the following: Earthquake, External Flooding, Extremes air temperatures, Snow pack, Lightning, Storm, Biological infestation, Aircraft crash, External fire and External explosion. Consequently, it has been decided to focus on those external hazards for developing guidance and that different reports would be prepared according to the hazards considered. This report proposes guidance on man-made hazards (mostly external fires and external explosions, occasionally release of toxic substances and related hazard) and aircraft crash. It includes:
1.2Starting considerationsAll sites are exposed to aviation accident hazards to some extent; plants near airports face a higher exposure rate to aviation hazards due to the higher aircraft traffic density, and the higher accident rates for aircraft taking off and landing. Civil aviation could pose a significant hazard and be worth to be considered. However, private aircraft have less potential to occur and to lead to severe consequences given their traffic density, their size, and their speed. Military aviation is a concern if the plant is situated near an operating military airbase or a training area. An explosion is defined as a rapid and abrupt energy release, which produces a pressure wave and/or shock wave. It can take the form of a deflagration (flame speeds are relatively low) or a detonation (extremely rapid and sharp compression occurring in a shock wave). The duration of the event is very short, differing from some others hazard durations, which may be much longer (hours). The intensity of the pressures acting on a targeted building can be several orders of magnitude greater than other hazards, but the explosive pressures decay extremely rapidly with distance from the source. External fire can be more or less frequent depending on the area where the nuclear plant is located (nature and combustible load of the surroundings). The impact on the plant will largely depend on the materials used for the confinement and the buildings. The sources for man-made hazards under consideration (external fire and external explosion) could be divided into stationary and mobile, as follows:
Each external hazard may result in a combination of various impact factors that have to be considered, because they may be great enough to affect the plant and to result in core damage and release of radioactive materials to the environment. For example, an aircraft crash may cause direct damage by the impact, or indirect via explosion, fire and vibration. Transportation or pipeline accidents in or near a nuclear power plant can result in the release of toxic chemicals, or burning/detonation of flammable or explosive materials, and may produce also missiles that can affect different parts of the plant. Additionally, vehicles with or without hazardous materials may collide with nuclear plant structures, resulting in damage to equipment. For a collision, the key parameter should be related to the impact; in the case of an aircraft colliding with a structure, the main parameters will be mass and velocity of the impacting object. If an explosion is induced after the direct impact, the key parameters should involve some combination of the amount of fuel and the other aircraft combustible loads (seats, cables, luggage…) and the mass of heavy engines that could damage a structure. In case of aircraft crash, we have to consider the effects on the plant of the projectiles; fire; explosion of fuel tanks and the other aircraft combustible loads. For many transportation related hazards, the actual danger is explosion or release of a dangerous material, and the key parameter should be the amount of material being carried or the maximum amount that could be released in an accident. For hazards such as pipeline accidents, the inventory of materials that could be released and the nature and pressure of the materials should be the appropriate parameters for characterization. In case of an explosion one has to consider the effects on the plant of the explosion pressure wave (deflagration, detonation); projectiles; smoke, gas and dust; associated flames and fires. For explosions, a safe distance (explosion would yield a pressure less than a critical one) can be calculated [2]. The fire analysis should take into account the side effects of external fires like impact on external grid, habitability of control room, induced internal fires, impact of smoke on equipment and human performance, impact of heat on equipment close to walls in adjacent compartments, etc. External hazards have a potential for affecting many different pieces of equipment simultaneously. The analysis needs to consider both externally induced failures as well as unrelated failures caused by internal plant faults. Some external hazards could compromise the containment and accident mitigation systems and/or their supporting systems, and/or can cause significant off-site damage and therefore the emergency response personnel may not be available and the communications, evacuation and sheltering may be affected. Consequently, the impact of external events on the results of a Level 2 and a Level 3 PSA may be more significant than on those of a Level 1 PSA. Another important issue is the treatment of human actions in case of external hazard occurrence, due to the fact that the stress levels and conditions in the plant may differ considerably from the ones after an internal initiating event. Modelling the external hazards in multi-unit context is also a challenging topic, so as the consideration of combination of hazards. Reasonable assumptions should be made on the probability of simultaneous occurrence of hazards. And there may be a need to consider combinations of more frequent / less extreme event, which may be not relevant as single event, but which might need to be considered for combined events. Directory: wp-content -> uploads -> 2016 2016 -> 2017 afoCo Landmark Scholarship Program 2016 -> Instructions for the Preparation of Camera-Ready Contributions to the Conference Proceedings 2016 -> Step student Scholarships for Year 10-13 2016 -> The united church of canada 2016 -> Idan raichel biography – May 2016 Brief Producer, keyboardist, Lyricist, composer and Performer Idan Raichel 2016 -> An introduction to centre’s interventions expanding access to justice 2016 -> Sanchar Shakti 2016 -> Unit analysis should help here. We want number of bananas 2016 -> The Autobiography of Elder Joseph Bates 2016 -> The Great Heat and the Rhode Island Deep Water Bay Scallop (Argopecten irradians) Fishery 1875-1905 Download 1 Mb. Share with your friends:
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