**Author details**

118 Nuclear Power – Practical Aspects

**6. Maintaining the seismic qualification during operation** 

exists ensuring the adequacy of the design and procurement specifications.



During modifications, replacements and reconstructions, design and procurement can be executed by complying with the seismic safety requirements corresponding to the seismic and safety classification. These processes are part of the configuration management and subject to authority approval. There is a database for seismic and safety SSCs. A procedure

Adequate maintenance and status monitoring programs are in place in order to maintain the required status of elements classified from the point of view of seismic safety and requiring maintenance, e.g. the anchorage of piping and components, damping devices. Maintenance of the qualification for earthquake is also part of the ageing management programmes.

The proper housekeeping is not irrelevant from the point of view of seismic safety. The


According to the IAEA Safety Standard NS-G-2.10, the aim of the Periodic Safety Review (PSR) is "to determine by means of a comprehensive assessment of an existing nuclear power plant: the extent to which the plant conforms to current international safety standards and practices; the extent to which the licensing basis remains valid; the adequacy of the arrangements that are in place to maintain plant safety until the next PSR or the end of plant lifetime; and the safety improvements to be implemented to resolve the safety issues that have been identified." Regarding external hazards the objective of the review of hazard analysis is to determine the adequacy of protection of the nuclear power plant against internal and external hazards with account taken of the actual plant design, actual site characteristics, the actual condition of SSCs and their predicted state at the end of the period covered by the PSR, and current analytical

The period of the PSR is generally ten years. During ten years the knowledge and understanding of the site hazard may develop and a feedback from experiences of other plants may motivate review and upgrading programme. As it can be seen from the experiences of plenty of nuclear power plants, the seismic safety, just like the safety in

general, is not a static thing and it covers the whole life cycle of the facility.

**6.1. Modification design and procurement of equipment** 

**6.2. Operation and maintenance aspects** 

**6.3. Seismic housekeeping** 

**7. Periodic safety reviews** 

following actions have to be required:

requiring maintenance and review,

methods, safety standards and knowledge.

Tamás János Katona *Nuclear Power Plant Paks Ltd., Hungary* 

## **8. References**


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**Chapter 5** 

© 2012 Berg and Hauschild, licensee InTech. This is an open access chapter distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

© 2012 Berg and Hauschild, licensee InTech. This is a paper distributed under the terms of the Creative Commons

**Probabilistic Assessment of Nuclear Power Plant** 

In recent years new threats required safety assessment experts to reconsider the internal and external loads of nuclear installations, in particular nuclear power plants, focusing not only on internal hazards but also on the destructive power of external hazards such as aircraft crash, flooding including tsunamis, severe weather conditions and also explosions and blasts and their combination which can cause significant damage on the plant's operability, being potentially conducive to severe accidents. The cumulated effects of such external loads include the destruction of buildings and access ways, the debris build-up, the loss of electrical power supply as well as the loss of cooling capacity of the reactor core and the fuel

International experience has shown that internal hazards such as fire and external hazards can be safety significant contributors to the risk in case of nuclear power plant operation. This is due to the fact that such hazards have the potential to reduce simultaneously the level of redundancy by damaging redundant systems or their supporting systems or even to

This has been strongly underlined by the nuclear accidents at the Fukushima-Daiichi nuclear power plants in March 2011 resulting from a very strong earthquake and a

A challenging prerequisite for any effective protection against external hazards is to accurately assess them systematically regarding the adequacy of their existing protection

Therefore, comprehensive safety assessments have to be performed in advance with most actual site-specific data und current knowledge of new research results. Potential methods

equipment against hazards, in particular those built to earlier standards.

**Protection Against External Explosions** 

Heinz Peter Berg and Jan Hauschild

http://dx.doi.org/10.5772/51492

loose all redundancies at once.

consequential tsunami.

**1. Introduction** 

pools.

Additional information is available at the end of the chapter

