CORDIS oferuje możliwość skorzystania z odnośników do publicznie dostępnych publikacji i rezultatów projektów realizowanych w ramach programów ramowych HORYZONT.
Odnośniki do rezultatów i publikacji związanych z poszczególnymi projektami 7PR, a także odnośniki do niektórych konkretnych kategorii wyników, takich jak zbiory danych i oprogramowanie, są dynamicznie pobierane z systemu OpenAIRE .
Rezultaty
The key objective of this study is to evaluate the impact of the implementation of Severe Accident Management (SAM) strategies on the radiological behaviour and to optimise the implementation such that any adverse radiological effects may be minimised. A second objective is to define a set of representative source terms for operating reactors, with provision made for the implementation of SAM measures. The framework for this study is based on a practical and systematic ''risked based'' methodology developed in a project (STU) in the earlier EC Fourth Framework Programme to assess the impact on radiological source terms from key issues of phenomenological uncertainty. This study is based on a broad spectrum of analysis involving reactor designs (represented by 11 reference plants) that are regarded as representative of the reactors operating in both current and prospective member states of the European Union.
The integrated severe accident analyses performed in this study has allowed an improved understanding of the complex interaction of fission product release/transport phenomena in realistic accident sequences, involving specific SAM measures. Overall, it was concluded that no significant adverse influence on the in-containment fission product behaviour, as a result of implementation of SAM measures, was seen in the case studies examined.
The optimisation analyses have focused on the use of existing plant capability and the potential for improvement in order to maximise its effectiveness (including the hardware and the operator procedures/guidance that are in place) in the mitigation of severe accident consequences. A number of potential plant applications across the contributing countries are envisaged from the results obtained, including: the refinement of the SAM procedures/guidance, revision of emergency operating procedures and providing the technical input for SAMG development. Many of the calculations also serve to provide an input to future plant studies and revision of plant specific PSAs. Some of the case studies are most pertinent in aiming to achieve an optimal framework in the prioritisation for the operation of SAM measures. Two such examples are:
- The optimisation of the filtered venting system and containment spray system in achieving a balance between the control of containment pressure and radiological release limits and
- The optimisation of the containment spray system and hydrogen control system in achieving their design requirement.
The effectiveness of the strategy optimisation is further measured by the impact on the environmental releases over the time period where early countermeasures would be implemented, which are seen to provide a more direct measure of the effectiveness of the strategy optimisation. For the volatile species, the predicted environmental release fractions are, as expected, less sensitive to the mitigation systems and very low release fractions are only seen where the containment remains essentially ''leak tight'' for an extended period (2 or more days). The potential for mitigation increases with the less volatile species, due to the scrubbing action of deep-water pools (in BWRs) and high efficiency filters (in some PWRs). Comprehensive source terms, derived from over 130 plant calculations based on 25 accident sequences, have been established for this study. A comparison of the predicted releases to the environment is made against threshold values chosen to represent a release to the environment at, or above, the allowable releases associated with the most onerous design basis faults. With the exception of the noble gases, it is seen that the environmental release fractions are, typically, below these threshold values and, in many cases, may be orders of magnitude lower than these thresholds.
Based on the results derived in this study, reasonably bounding values (together with a likely range) of the mass fractions defining the environmental releases are also proposed for accident sequences involving implementation of SAM measures. These values are, typically, applicable to the early phase of the accident (1 to 2 days) when early countermeasures would be considered and implemented. These values, should be regarded as preliminary, and may be revised or supplemented with information from further plant specific calculations which may include an extended accident duration.
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