The site licence for each station requires the CEGB to set up a senior committee to consider any proposal of major safety significance affecting the operating of the station. This committee is known as the Nu­clear Safety Committee (NSC). Even without the li­cence requirement, there would be a need for such a committee to provide authoritative advice to the station manager on major nuclear safety issues and to endorse, if appropriate, any actions he may take. Further, the committee assists in maintaining common standards between stations.

The NSC is chaired by the Director of the Nuclear Operations Support Group and has representatives from the health and safety department, the design department, the research department and two repre­sentatives from outside organisations, British Nuclear Fuels and UKAEA, who provide independent opin­ions. The station manager from the station in ques­tion or his representative is also a member of the committee. It is his attendance which identifies a particular meeting with a particular station, although at a single sitting several managers may be present and proposals from all those stations may be con­sidered. The technical secretary is provided by the Nuclear Operation Support Group and an agreed set of minutes is sent to the HSE within 14 days. The HSE are also supplied with the qualifications training and experience of the members of the NSC and the terms of reference.

The NSC is responsible for providing on behalf of the CEGB, the formal endorsement of any major nuclear safety submission associated with the operat­ing stations and the nuclear laboratories. The consent of the HSE is very rarely sought to any such proposal before the NSC have indicated their agreement.

The committee is free to consider any nuclear safety issue brought before it by the station manager, or any other member. There are, however, a few par­ticular proposals which under the conditions of the site licence must be endorsed by the NSC before the Nil will give their consent. These proposals include the content and any changes to the Operating Rules, and major modifications to plant.

Within the definitions of modifications to plant are changes to any of the safety arguments, and any major repair. These modifications to plant are covered by a procedure, approved by the Nil, which defines the degree of safety significance of any proposal re­quiring the attention of the NSC. Category 1 modi­fications which must be endorsed by the NSC and the HSE before implementation, are those involving a change in the principles upon which the safety case was based, or where an error in conception or implementation could materially affect the risk of a release of radioactive material to the environment. Category 2 modifications, although having safety sig­nificance, do not involve a change in principle and are not likely to have any major impact on the risk of a release of radioactive material. These need the endorsement of the NSC but the HSE only needs to be informed of the proposals; its explicit endorsement is not required. There is machinery for clearing urgent proposals out of committee.

The initial version of the Operating Rules required for fuel loading on the first reactor of a two-reactor station, is approved by the NSC prior to receiving HSE approval. Henceforth, any alteration or suspen­sion of the rules must be considered and endorsed by the committee before being put to the HSE, ex­cept in exceptional and urgent situations. In these exceptional circumstances, the agreement of the Di­rector of Health and Safety is sufficient to allow a change to the rules to be put to the HSE. In all cases, however, the agreement of the HSE to a proposal covering the operating rules is required before it can be implemented.

The nuclear safety committee considers and gives agreement for any experiments or non-routine tests on the reactor except when a station commissioning committee is in existence. The NSC may also be asked to consider any exceptional or unusual occurrence involving nuclear safety and to endorse, or otherwise, recommendations on future actions.

There are certain proposals which require the agree­ment only of those members of the NSC represent­ing the headquarters departments and divisions. These proposals, put forward by the station manager, in­clude changes to identified operating instructions, or to criticality certificates. Identified operating instruc­tions are detailed instructions which augment the in­formation in the Operating Rules. Criticality certifi­cates identify the manner and location of operations involving the handling and storage of enriched fuel.