Technical operating specifications (STEs)

The general operating rules (RGEs) contain the reactor's technical operating specifications (chapter III of the RGEs). Their role is

• to define the normal operating limits of the facility if it is to remain in conformity with the reactor design basis scenarios;
• depending on the state of the reactor in question, to define the safety functions necessary for the monitoring, protection and safeguard of barriers as well as implementation of incident and accident operating procedures;
• to specify the course of action to be followed if a normal operating limit is exceeded or if a required safety function is unavailable.

Permanent modifications to the STEs

EDF may be led to modify the STEs for various reasons: to take account of experience feedback, to improve safety, to improve reactor economic performance, or to take account of the consequences of changes made to the equipment. These changes in the STEs require prior authorisation by the ASN on the basis of safety justifications provided by EDF.

In 2005, the ASN reviewed a number of "amendment documents" modifying the STEs, which were approved or are the subject of additional justification requests. These include:

• an amendment document which concerns the 900 MWe series reactors and aims to modify certain requirements of the STEs to allow a rapid restoration of the national electricity transport grid in the even of a "generalised grid incident" (IRG);
• an STE amendment document concerning the 1300 MWe series reactors and which aims to meet the ASN's requests concerning risks during reactor outages

The ASN also reviewed the STE revision for the CPY and N4 plant series.

The ASN considers that EDF's document support policy, in particular through highlighting the proposed changes, facilitates analysis and review.

Temporary STE modifications

When a licensee considers that it is unable or does not wish, on safety grounds, to comply strictly with STEs during an operating phase or a maintenance operation, it must apply to the ASN for a waiver, on a case by case basis. The ASN then analyses this request and may accept it, if necessary provided that compensatory measures are taken.

The ASN keeps a close watch over the number of waivers granted. EDF is therefore required:

• periodically to re-examine the reasons for the waiver requests in order to identify those which would justify adaptation of the STEs;
• to identify "generic" waivers, in particular those linked to implementation of national modifications and periodic tests.
The number of waivers examined in 2005 was 148, or an average of about 2.5 per reactor, per year. The three most commonly evoked reasons for waiver requests in 2005 are linked to:
• the unavailability of reactor systems and electrical sources during modification work or owing to maintenance on the sources themselves;
• unavailability of equipment linked to the safety injection system, as a result of remedial maintenance work;
• maintenance on the nuclear auxiliaries building ventilation system.

Although most waiver requests are granted, the ASN's waiver approvals sometimes stipulate additional requirements owing to the inadequacy of the palliative measures proposed by the licensee.

Field inspection of normal operation

During site inspections, the ASN checks:

• compliance with the STEs and, as necessary, with the palliative measures associated with the waivers;
• the normal operating document quality such as operating instructions or certain alarm sheets;
• consistency between the normal operating documents and the STE;
• staff training in handling certain "sensitive" reactor transients, such as mid-loop operation (PTB RRA).