ALARA Activities at Ohi NPP Ohi Nuclear Power Plant Kansai Electric Power Co., Inc.

Outline of Ohi NPP Unit 1 1,175MW Started March 1979 Unit 2 1,175MW Started December 1979 Unit 3 1,180MW Started December 1991 Unit 4 1,180MW Started February 1993 Osaka Kansai Wakasa ○Fukui Japan １

○World’s best reliability ・ Capacity factor: Over 92% (three-year-average) ・ Unplanned capacity factor loss: 0.2% and below (three-year-average) ・ Dose: 1.4 man ･ Sv (three-year-average) ・ Automatic Shutdown: 0.1 time (three-year-average) ・ Solid nuclear waste production: 1,000 drams and less (three-year-average) ・ Days without labor accidents: Continuing more than 1000 days ・ World’s best reliability ・ World-class economic efficiency ・ World-class nuclear power plant Three strategies for the vision Vision for 2010 Vision of Ohi NPP for the 21 century “The best nuclear power plant in the world” Actions to achieve the vision Established goals and strategies to achieve the vision In view of major changes in the management environment and present status of the company, the vision for 2010 was introduced to survive the 21 century. ２

Main Measures Taken at Ohi NPP to Reduce Dose Use of automatic positioner of R/V stud bolt tensioner Use of cavity decontamination equipment Use of tube-sheet inspection robot during S/G tube ECT Use of lead shielding of R/V head Decontamination of RCP internals Introduction of automatic equipment Reduction of dose equivalent in working environment Chemical cleaning of inside of primary coolant thermometer bypass piping/removal of piping Decontamination of primary coolant piping internal surface Decontamination of S/G channel head Streamlining work activities Permanent installation of S/G tube ECT cable Use of S/G tube ECT probe Use of S/G manway head handling tool Use of dose equivalent rate indicator Promotion of irradiation prediction training Implementation of joint patrol for radiation control Other measures Use of labels to draw attention to radiation and designation of waiting position Schedule adjustment 2000 S/G replacement Improved oxidization during reactor shutdown Start of Ohi-1 operation ３

Applied Primary Water Chemistry Program Programs Suppression of CP Generation Suppression of CP Transfer Removal of CP ･ Low Cobalt Material ・ TT690 SG Tubing ・ Improved Startup Chemistry during HFT ・ Improved pH Control ・ Ammonia Addition ・ Removal of CP during Shutdown (Improved Shutdown Chemistry) ・ Increase of Purification Flow Rate during Shutdown ・ Fine Mesh Filter (CVCS etc.) ４

Changes of dose per unit ５ Increase in dose due to repair work on Unit-3 reactor vessel head

Dose reduction activities at Ohi NPP Goal: Achieve the dose of 1.4 man-Sv/year/4 units (on a par with the achievement of Doel NPP, which is one of the best performers according to the WANO dose index) 1.Significant reduction in Belgium (reduced to about 1/3 in 10 years) 2.Ohi’s dose is nearly the same as Japan’s average, but has leveled off recently. Vision for 2010 Comparison of dose with major nations Current status: approx. 3.4 man-Sv/year (total dose from scheduled outage) ６

Dose from the 8th scheduled outage at Ohi Approx. 40% of inspection-related dose is from RCP inspection Approx. 90% of RCP-related dose is from assembling of backup internals, disassembling/inspection of internals and decontamination. ７

RCP （Ｒｅａｃｔｏｒ Ｃｏｏｌ ａｎｔ Pomp ） Internals

Comparison with other units in Japan The average dose related to RCP disassembling/inspection activities is 110 man ･ mSv/RCP. The doses from the same activities at Ohi 3 and 4 are approximately twice as much. ８ Committed to ｄｏｓｅ reduction in RCP inspection activities. Goal: Reduction to 100 man ･ mSv (lower than the average)

Establishment of system to review dose reduction measures ALARA working group consisting of all organizations related to RCP inspection Radiation Control Department of Kansai Manufacturers Maintenance Department of Kansai Inspection Contractors ALARA working group Opinions from various aspects Site-focused review ９ Plant management

Elicit exposure factors (by questionnaire survey) Questionnaires were sent to about 50 persons involved in inspection activities to identify factors from multiple aspects. 10

Elicit exposure factors 11 Major factors were identified using the cause and effect diagram. Workers: Skilled workers are required. Inspection method: The impeller still keeps high radiation dose even after decontamination; removing the impeller is time consuming; workers operate close to high dose parts. Tools: Handling of internals takes time. Environment: Shielding is inadequate. Workers: Skilled workers are required. Inspection method: The impeller still keeps high radiation dose even after decontamination; removing the impeller is time consuming; workers operate close to high dose parts. Tools: Handling of internals takes time. Environment: Shielding is inadequate.

Preparation and evaluation of reduction measures 12 Important factors Proposed measures Proposed measures Specific measures Specific measures Evaluation of specific measures Including dose reduction and cost efficiency Evaluation of specific measures Including dose reduction and cost efficiency Detailed factors

Measure 1: Introduction of ultrasonic cleaning unit to decontamination tank Spray pipe Decontami nation tank Effluent discharge line Ultrasonic cleaning unit ＜ Currently ＞ Chemical cleaning (high-pressure cleaning) alone is inadequate to clean the inside of internals. Improved by 3.2 times Reduced by 32 mSv Expected reduction of 32 man ･ mSv ＜ Improvement ＞ The effectiveness of the ultrasound unit has already been proved with the cask with decontamination function. The cleaning unit is expected to enhance decontamination at the inner surface of the bottom of internals. 13

The walls of the inspection room consist of frames, lead sheets with 6-9 mm thickness and 1.6 mm steel sheets. The walls (shaded) are to be enhanced with the combination of lead and steel sheets. The enhanced shielding is comparable to the shielding effect of 20 mm lead sheet. The height is 2 m above the floor. Measure 2: Enhancement of shielding in greenhouse Expected reduction of 17 man ･ mSv RCP inspection room (greenhouse) 14

Lead shielding mats are used. They are removed when maintenance, measurement or PT inspection are conducted. The impeller shielding box, which enables maintenance, measurement and PT without removal, will be introduced mm steel sheets are used for shielding. 2.The shield part divided into two segments is equipped with a rotary shaft. The impeller can be revolved circumferentially. Also, it can be revolved axially with a gear box. 3.The shield has an inspection window, which allows maintenance, measurement or PT inspection without removing the impeller. Dose equivalent rate can be reduced to one seventh. Measure 3: Impeller shielding box Expected reduction of 15 man ･ mSv 15

Measure 4: Improvement of internals hoisting device Worker A Worker B Worker C Worker D High radiation Turn buckle Bracket Internals hoisting device Fixed with screw nuts ・ When handling internals with a crane, fine focusing is difficult. It takes time to fix the main flange and side bars. ・ When installing and removing the hoisting device, workers close to the radiation source receive higher dose. ・ All the activities can be performed on the main flange, which is expected to result in the reduction of dose. ・ Fewer workers ・ Shorter working hours Expected reduction of 9 man ･ mSv 16

Measure 5:Time reduction in removing the impeller Measure 6: Enhancement of training When removing the impeller from the rotor, a special tool is used to fix the impeller onto bolts. Adoption of electric tool instead of manual operation can save substantial time. Expected reduction of 3 man ･ mSv Training for less experienced workers has been enhanced by using audio and visual materials. Expected reduction of 4 man ･ mSv 17

Expected reduction Dose （ man ･ mSv ） The 8th scheduled outage at Ohi 4 After improvement (outage scheduled for 2008) Introduction of ultrasonic cleaning unit to decontamination tank Enhancement of shielding in inspection room Installation of impeller shielding box Improvement of Internals hoisting device Time saving in removing the impeller Enhancement of training ＜ Measures ＞＜ Expected reduction man ･ mSv ＞ ３２ １７ １５ ９ ３ ４ ８２ man ･ mSv 18

First step Second step Third step Dose reduction activities related RCP disassembling Reduction efforts for regular inspection activities not covered by the measures Reduction activities related to SG and R/V inspection Verification ＰＤＣＡ 19

Conclusion ・ Multi aspects of dose reduction possibilities were discussed through the participation of all the people involved in inspection activities including Kansai’s radiation control department, maintenance department, manufacturers and workers. Through discussions all the participants shared a common objective---the reduction of dose. The management and workers worked together to develop measures through trial and error processes. The efforts resulted in effective measures that met the needs of workers on site. ・ The validation of the measures will start in After the validation continuous improvement will be made through PDCA cycle. ・ The current program focuses on the inspection of RCP. We are continuously committed to dose reduction. Reduction efforts will be expanded to other inspection activities. 20

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