Calibrations and characteristic tests of electrical and instrumentation equipment such as process monitoring instruments are conducted to confirm their soundness. Corrections are made for drifts in instrumentation caused by changes over time, as necessary.

iii)Evaluations and reflection on operating experiences in other plants

Issues which should be solved to ensure the safety and the reliability of the plant are clarified, based on comprehensive surveys and evaluations of operational information not only on the plant of concern, but also on other plants, domestic and overseas. Necessary actions are taken and measures are implemented to resolve the issues during the plant shutdown for periodical inspections.

2. Periodical Inspections and Periodical Utility Inspections

The present inspection system was established in October 2003, as part of the system modifications initiated by the Japanese government

Voluntary inspections which had been practiced by electric utilities on their own initiatives were changed to periodical utility inspections required by law. Electric utilities operating NPPs are obliged to verify that the plant designs are in conformity with the technical standards defined by the METI. In addition, systems of utilities to execute the inspection are periodically examined by the JNES, and subsequently by government examiners who evaluate the results comprehensively.

Furthermore, maintenance activities by electric utilities are considered as part of the activities to assure the quality (or nuclear safety) of plants, and the government or the JNES evaluate the performance and the system of maintenance activities as part of quality assurance activities. Quality assurance requirements are also specified in the plant safety preservation rules set up by the utilities and approved by the government. Subsequently, the government verifies the adherence of utilities to the requirements as part of its inspections.

Periodical inspections are executed on the safety­important systems and functions. 'Hie government or JNES verifies the results of periodical inspections of utilities by witnessing the actual inspections or

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Inspections and Assessments by the Government

Periodical Inspections (by NISA/JNES)

Periodical Assessments of Safety ManagementQNES)

Safety Preservation Inspections (NISA)

Safety Preservation Activities by Utility Based on Safety Preservation Rules

Application of Quality Assurance Rules OEAC4111-2003)

Safety Preservation Inspections: Inspections by the Government to verify adherence to safety preservation rules of utilities

Periodical Inspections: Inspections by the Government to verify the compatibility of safety-important systems to applicable technical standards Periodical Assessment of Safety Management; Assessment by the Government to verify systems of utility to execute periodical utility inspections (Periodical Utility Inspections): (Inspections by the utility to verify the compatibility of plant systems to applicable technical standards)

[Source] Material distributed at the "20th study committee on proper inspection systems” (Sept.7, 2006)

Figure 5.2.2 Framework of plant in-service inspection system

by checking the inspection records. The time between periodical inspections of plant systems and periodical utility inspections is limited in the Electricity Utilities Industry Law and Ordinances and Rules of the Law, so as not to exceed 13 months.

(1)Planning and timing of the periodical inspections and the periodical utility inspections

Timing of the periodical inspections and the periodical utility inspections of a plant is decided by the utility when laying down a service plan and is based on consideration of the following factors:

1. )to execute the inspections within the period defined in the Electric Utilities Industry Law;

2. )to ensure electricity production based on the service plan;

3. to keep plant power generation rates and grid demands in balance; and

4. to manage burnup of fuel.

Duration of the inspections is decided considering time needed for the following activities, in addition to a certain time period for the standard activities in the plant shutdown, refueling and startup operations:

1. execution of the periodical inspections and the

periodical utility inspections;

2. special checks or large-scale modifications of the plant, if any, based on a long-term maintenance scheme; and

3. feedback on problems or operational experiences in domestic and overseas plants.

(2) Items and schedules of the periodical inspection and periodical utility inspection

Items of the periodical inspections are defined in Section 90, Item 2 of the Electric Utilities Industry Law. The government, represented by inspectors from the NISA (Nuclear and Industrial Safety Agency) or the JNES, witness inspection activities and check inspection records made by the utility.

The important electric structures, defined as items to be inspected in the periodical inspections, are the reactor vessel, reactor coolant system equipment, fuel assemblies, radiation control system, waste disposal system equipment, containment vessel, emergency standby generating unit, and the steam turbine and its appurtenances. The main items of periodical inspections by the government are shown in Table 5.2.1.

Equipment which should be verified as to its compatibility to the technical standards in the

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periodical utility inspections of a plant is defined as follows in the Ordinances and Rules of the Electricity Utilities Industry Law, Section 94: reactor vessel; reactor coolant system equipment; instrumentation and control system equipment, fuel; radiation control system; reactor containment system; exhaust stack; auxiliary boilers; emergency standby generating unit; steam turbine; and appurtenances of steam turbine

Details of inspected items are shown in JEAC4209-2003 “Maintenance Management Rules of Nuclear Power Plants” published by the Japan Electric Association, and summarized in Figure 5.2.3.

During a periodical inspection period the inspections defined in the Electricity Utilities Industry Law are carried out, as well as refueling operations, government checks based on the Industrial Safety and Health Law, and modifications of plant systems to improve the overall reliability and maintainability. A typical schedule of periodical inspections of a PWR NPP is shown in Figure5.2.4.

Although the periodical inspections and the periodical utilities inspections are important to ensure the plant safety, long times needed for the

inspections cause degradations in plant availabilities and affect stabilization of electricity service. The utilities have struggled to shorten the durations of the inspections, based on analyses and evaluation of performance of equipment in the past, improvement of techniques and personnel skills, improvement and development of tools for checks and inspections, and improvement of plant systems. Standard durations of the inspections range between 40 to 60 days at present. When special check activities or large scale modifications of plant systems are executed, more time is needed for the activities. Other efforts have been made to reduce durations of periodical inspections, such as the pre-purchasing of materials, the seeming of personnel, and managing of detailed schedules of sub-activities to keep the planned inspection schedules. Moreover, since many of the activities for the periodical inspections and the periodical utility inspections have to be done in areas with radioactivity, utilities have also struggled to improve the conditions for inspections by reducing radioactivity levels, to conduct check and inspection work automatically, to use remotely operated equipment, and so on.

All Facilities of the Power Generating Plant |

Service Buildings, etc. Maintenance Management Rules!

■ [Technical Standards for Nuclear Power Plants |

-Facilities, fences and so on, functions of which are ensured by routine checks -Facilities, fire extinguisliing systems and so on, which are required to be checked under other legislations or regulations

-Vessels

-Piping

-Pumps

-Valves

-Support structures

Periodical Inspections"!—

Safety-important systems defined in the Electricity Utilities Industry Law

-AM systems

-Reactor water level gauge (PWR) -Dew-point hygrometer (BWR) -Other equipment necessary for power generation plant management

Technical Standards of

S'— the Thermal and Nuclear Power Engineering Society

Technical Standards for Electric Equipment

-Associated equipment of steam turbines (PWR)

-Auxiliary boilers

-Steam turbines

-Emergency standby power generation devices

-Turbine-generators -Main transformers

[Source] Material distributed at the “11th Study committee on proper inspection systems” (Nov.14,2003)

Figure 5.2.3 Scope of applicable systems of the maintenance management rules (JEAC4209-2003)

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