PLANS to equip Sizewell B, Britain鈥檚 first pressurised water reactor,
with a prototype computerised safety system still await safety clearance
six years after the Nuclear Installations Inspectorate (NII) first identified
problems with the system. The continuing delay in approving the safety system
could set back Nuclear Electric鈥檚 plans to load fuel into the Suffolk PWR
by 1993.
The prospect of delays came to light last week following the publication
of the report of the Hinkley C inquiry. The inspector made it clear in his
summary that important questions about the safety system planned for both
the Hinkley and Sizewell reactors remain unresolved.
The NII鈥檚 major concern is with the software used in the system, designed
by the American electronics giant Westinghouse. The inspectorate鈥檚 reservations
appear to be shared by computer specialists. Sources in the industry say
that the team at Nuclear Electric responsible for implementing the safety
software is under severe pressure. The sources say that the team is being
forced to keep costs of independent assessments of the system inside an
almost unworkable budget. Nuclear Electric agreed this week that 鈥榓 lot
of validation still needs to be done鈥�, but a spokesperson added 鈥榳e are
confident we are still on target鈥�.
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The novelty of the microprocessor-based hardware and the software involved
has persuaded Nuclear Electric, the state-owned generator, to agree to run
the system for 12 months before it loads any nuclear fuel. Yet the NII and
Nuclear Electric disagree sharply on whether the system is safe enough to
go ahead.
The control software, known as a safety-critical system, is thought
to consist of several hundred microprocessors. Such a large, interdependent
system is hard to test against international standards and to verify.
The NII鈥檚 concerns come as the government commences a high-profile programme
called 鈥楽afe IT鈥� to examine the safety of computer-controlled systems. This
programme, led by the Department of Trade and Industry, aims to coordinate
standards for all industrial sectors. These standards will describe best
practice for designing safety critical software. The programme involves
representatives from industry, and most government departments.
Despite the fact that this crucial safety issue remains unresolved,
the British government last week approved in principle a plan to build a
PWR, to be called Hinkley C, on the Somerset coast.
Opponents of the Hinkley C plan condemned the decision. But the government
has accepted a number of recommendations made by the inspector as a result
of concerns raised during the 182-day inquiry into the project. Whitehall
has agreed to publish more accurate figures on the amount of plutonium produced
by civil nuclear stations following pressure from CND.
