Environmental Engineering Reference
In-Depth Information
As a result, today cable testing is often recommended in nuclear indus-
try standards and guidelines as a method for performing predictive mainte-
nance and managing the ageing of I&C equipment. For example, the IAEA
stipulates that 'aged I&C cables are expected to fully function to carry the
I&C signals to a control room for normal operation, Design Basis Event
(DBE) management and recovery.' Similarly, IEC standard 62465 ('Aging
of Electrical Cabling Systems') outlines requirements for in-situ testing tech-
niques to detect problems in cable conductors and cable insulation material.
IEEE standards for testing fi re travel and cables under fi re conditions are
similar to several of the IEC standards. There are also ANSI and ASTM
standards covering general cable testing as well as specifi c cable tests such
as partial discharge testing (AMS Corp., 2010).
Both the regulatory and industry pressure to manage cable ageing in light
water reactors has only intensifi ed as plants have been granted license renewal
to operate cables for an extended qualifi ed life as part of their efforts to extend
the initial design life of a nuclear power plant from 30-40 years to 60 years
(Hashemian, 2010). In some countries, plants have been able to replace some of
their critical cables as an ageing management strategy. For example, the Beznau
nuclear power plant in Switzerland has implemented a comprehensive cable
maintenance program and has thereby emerged as a leader in cable ageing
management in the worldwide nuclear power industry (AMS Corp., 2011).
Today, the nuclear power industry can obtain guidance for managing and
testing plant cables and wiring from an extensive collection of various cable
specifi cations and cable testing standards. This collection presents plant staff
with a variety of recommendations for testing, monitoring, and managing the
maintenance of plant cables (AMS Corp., 2010). However, because replac-
ing cables is expensive, radiation intensive, and typically impractical, utili-
ties operating nuclear power plants are not adopting wholesale replacement
of cables as a strategy. Rather, they are searching for ageing management
techniques that can identify cable problems and areas where maintenance
or replacement is needed (AMS Corp., 2011).
On a regulatory level, cable ageing has not been an afterthought, and the
U.S. NRC, DOE and others have sponsored ongoing research to improve
currently available techniques so as to enhance preventative mainte-
nance and proactive management of cable ageing. Others, such as the U.S.
Department of Defense (DOD), NASA, the National Institute of Standards
and Technology (NIST) and numerous international organizations have
also sponsored and performed research and development (R&D) on cable
condition monitoring and residual life estimation (AMS Corp., 2010).
As an example of increased regulatory concern over cable ageing, in
February 2007 the NRC issued NRC Generic Letter 2007-01; 'Inaccessible or
Underground Power Cable Failures that Disable Accident Mitigation Systems
or Cause Plant Transients.' This letter required responses from license hold-
ers to the issues of undetected ageing problems associated with underground
￿ ￿ ￿ ￿ ￿ ￿
Search WWH ::




Custom Search