4.0 Summary of Major DCISC Review Topics, 17th Annual Report - July 1, 2006 thru June 30, 2007
4.16 Steam Generator Performance
4.16.1 Overview and Previous Activities
Steam Generator (SG) tube reliability is important to operational safety, because the SG tubes are part of the Reactor Coolant System (RCS) boundary. The nuclear industry has experienced substantial problems with a variety of failure mechanisms, notably tube stress corrosion cracking. The DCISC reviews steam generator performance following each refueling outage.
The SGs are currently scheduled for replacement in the 2R14 (February – April 2008) and 1R15 (January – April 2009) refueling outages.
The long term plans for SGs have been reviewed in previous reporting periods. These were:
- Continued improvement in probe technology and repair criteria
- Chemical Cleaning - could mitigate the increasing trend of ODSCC. Performed in 1R12 and 2R12.
- Tube Plugging Limit Increase - Westinghouse analysis supports 15% per loop and overall. May need to revise analysis to allow one loop to exceed 15%.
- 1R12 Steam Generator Chemical Cleaning Preview
- Outage 1R12 Steam Generator Chemical Cleaning
- Outage 1R12 Steam Generator Tube Inspection
- Steam Generator Chemical Cleaning During 2R12
- Plans for New Steam Generators
During the previous reporting period, the DCISC reviewed the following SG items:
- Results of Steam Generator Inspection in 1R13
- 2R13 Steam Generator Inspection & Status of SG Replacements.
During previous periods, the DCPP steam generators appeared to be in adequate health and well within safety limits. PG&E’s monitoring plans appeared satisfactory. The replacement of Steam Generators for both units appear to be on schedule and DCPP is doing a good job in following the construction of them.
4.16.2 Current Period Activities
During the current reporting period, the DCISC reviewed the following SG item:
- Steam Generator Replacement Project (SGRP) Update
Steam Generator Replacement Project (SGRP) Update
Mr. Exner, Project Manager, presented an update on the new Steam Generators (SG) at the October 18 & 19, 2006 DCISC Public Meeting (Volume II, Exhibit B.3) and the June 13 & 14, 2007 Public Meeting (Volume II, Exhibit B.9).
An installation contract has been entered into with the SGT firm, and design change packages are now being developed, with 2 of the 20 design change packages now in final form, and the balance to be completed by the spring 2007. Development is beginning on approximately 150 work packages. Planning is also being undertaken in detail for 1R14, which will be the outage preceding the first installation of the replacement SGs. On-site staff is now being assembled, and currently there are about 40 persons working on the SGRP at DCPP. Activities are on schedule for the start of 2R14, scheduled for February 6, 2008.
All four SGs are completely assembled and ASME Section III hydrostatic tests are in progress. Manufacturing and QA program performance continues to be good. Plans for pre-service inspections are finalized. Shipment is scheduled for September 8-18, 2007 and arrival at DCPP is expected mid-October to mid-November, 2007.
DCPP has had full time eddy current analysis of the SG tubes performed by its own inspectors on duty at the tube manufacturer, Sandvik Steel of Sweden. Two full time PG&E resident inspectors are also on site at the ENSA facility. Plans for pre service inspections and shipping are now being finalized at ENSA, including full eddy current and welding examinations.
Design change packages (20 Unit 2 and common) will be completed and issued to PG&E by December 4, 2007. Task plans (26) are being developed and construction of Old Steam Generator Storage Facility (OSGSF) is in progress. Construction of outside lift system east of FHB will start this month. On site staff build-up is in progress and activities are on schedule for 2R14 schedule start in February, 2008. DCPP benchmarked the replacement of the SG at Comanche Peak plant to observe their activities.
The License Amendment Request (LAR) was submitted to the NRC in January 2007. They obtained the Costal Development Permits from California Costal Commission in March 2007 and have also obtained SLO County Building Permit for OSGSF. They have applied for SLO County Building Permits for temporary facilities.
Project Challenges are:
- Prompt submittal of LAR revision
- Obtaining NRC approval
- Integration of project and entire station into one team for World Class project performance
- Experience from Comanche Peak
- Working agreements and task plans
- Combining all 2R14 and 1R15 non-SG replacement scope and SG replacement scope into the most successful integrated outages possible
- Vertical slice and project integration activities
4.16.3 Conclusions and Recommendations
- Conclusions:
- PG&E has an effective Steam Generator (SG) health program. DCPP continues to perform the necessary Steam Generator inspections at each refueling outage to determine the condition of the tubes. Necessary corrective actions are taken prior to returning the SGs to operational service.
- PG&E will replace the four Steam Generators in each DCPP unit during two approximately 80 day outages (Unit 2 February 2008, 2R14 and Unit 1 February 2009, 1R15). PG&E appears to be managing the fabrication, quality, and installation of the SGs effectively and on schedule. The DCISC plans to follow the replacement program and to track potential safety changes and any increased or decreased trends in safety margins.
- Recommendations: None