Cable samples of Beznau NPP

In 2006, two subjects, stress corrosion cracking and the degradation of cable insulation were selected as the focus of the Stress Corrosion Cracking and Cable Ageing Project (SCAP). The project ran from 2006 to 2010, due to its relevance for plant ageing assessments and its implications on nuclear safety. In December 2010, the Committee on the Safety of Nuclear Installations (CSNI) agreed to support two SCAP follow-up activities, an experts meeting on a cable database and an experts meeting on the merging of the stress corrosion cracking and the Piping Failure Data Exchange (OPDE) projects [NEA/SEN/SIN(2010)2, item 33] to become the Component Operational Experience, Degradation and Ageing Programme (CODAP) [NEA/NE(2011)5].

The Cable Ageing Data and Knowledge (CADAK) Project was a follow-up acitivity to the cable ageing portion of the SCAP project. The CADAK Project aimed to establish the technical basis for assessing the qualified life of electrical cables in light of the uncertainties identified following the initial (early) qualification testing. The research investigated the adequacy of margins and its ability to address uncertainties. As a result of the first CADAK expert meeting, the following objectives with four main topics had been drafted:

Completion and maintenance

The executive summary of the final SCAP report, the corresponding IAEA report on cable ageing, as well as the NUREG/CR-7000 were to be transferred to various parts of the data and knowledge base.

For several member countries, cable data and information needed to be edited and added to the system (e.g. technical standards being applied in the qualification of cables and regularly used inspection methods). The SCAP Cable Working Group had created an encyclopaedia on cables useful for both novice and experienced nuclear power plant (NPP) regulators and operators which was used for the project.

Performance monitoring methods

For cable ageing, the crucial point is knowledge about the qualification procedure for harsh environments and the predictive capability of estimating the remaining qualified lifetime. The cable condition-monitoring techniques shared by SCAP participants became an up-to-date encyclopaedic source to monitor and predict the performance of every unique application of cables.

Ongoing research activities in different countries helped improve these methods. An extensive information exchange was beneficial in this technical area. Some national research activities could also be used for international benchmarking activities.

Commendable practices

Information-supporting ageing management programmes (AMPs) was of vital importance, given that ageing management was an essential and important aspect to be taken into consideration in connection with safe long-term operation (LTO). The use of the accumulated knowledge specifically in the area of equipment qualification (EQ) and condition monitoring formed the basis for commendable practice documents, e.g. CSNI technical opinion paper, generated as part of the CADAK Project. Such documents help regulators and operators to improve ageing management.

Extension of other technical items

The SCAP project yielded crucial knowledge in the area of cable ageing related to qualification procedures for harsh environments, as well as assessing cable degradation. The expertise could also be used to include other technical equipment in the data and knowledge base, such as cable penetration, pressure/level transmitters, etc. that have common elements in many countries.