§ Mr. StunellTo ask the Secretary of State for Trade and Industry how many cracks have appeared in nuclear power stations in each of the last 20 years; and how many have been repaired. [65744]
§ Mr. BattleArrangements under nuclear site licences require the licensees to notify the Health and Safety Executive's Nuclear Safety Directorate (NSD) of the discovery of any cracks which might challenge their current safety case; some of these may have potential structural significance. Nuclear power stations, like all engineering structures, may also contain many structurally insignificant cracks, so the information is not available in the exact form requested.
Few of the many cracks identified over the years in nuclear power plants have been judged structurally significant and so necessitated repair. Examples of cracks that have necessitated repair are those found in Magnox coolant ducts during the 1980s, cracks in AGR steam headers and pipework and cracks in the boiler shells at Sizewell A power station. Details of these have been made publicly available via either the HSE's publication of the results of NSD's reviews of the licensees' Periodic Safety Reviews (PSRs) or in quarterly NSD reports over the years to local liaison committees.
Further operation of any plant in which a potentially significant crack has been detected is not permitted until the licensee has provided a written safety case that demonstrates it would be safe and NSD has agreed to it. If repairs are necessary to enable a satisfactory safety case 516W to be made, these must be made to the appropriate nuclear standard before NSD allows the operation of the plant to recommence.