ML040500461

July 2003 Davis-Besse Reactor Vessel Head Damage, NRC Update, 11th Periodic Update

ML040500461
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Site:	Davis Besse
Issue date:	07/31/2003
From:	NRC/RGN-III
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July 2003 This is the eleventh periodic update on the NRC response to the reactor vessel head damage at the Davis-Besse Nuclear Power Station. The updates will be available at public meetings of the NRC Davis-Besse Oversight Panel which is coordinating the agencys activities related to the damage. Each update will include background information to assist the reader in understanding issues associated with the corrosion damage.

Ongoing Inspection of DB Ongoing and Planned NRC Inspections Safety Culture Programs The NRC has a series of inspections planned before any decision on whether or not the Davis-Besse plant may A NRC special inspection team is resume operations. These inspections include:

continuing its review of FirstEnergys efforts to evaluate and improve the safety ~ Ongoing - Management and Human Performance, culture at the Davis-Besse plant. This Phase III (Safety Culture) - This inspection focuses on review includes the utilitys program to FENOCs actions to improve management foster a safety conscious work effectiveness and human performance and its environment in which workers feel free to processes to survey and assess the safety culture raise safety issues without fear of among the staff at Davis-Besse - how the retaliation. management and workers will deal with safety concerns.

The inspection team, composed of NRC ~ Ongoing - Corrective Action Team Inspection - This specialists and outside consultants, inspection looks at the effectiveness of the corrective began its review in April. action program at Davis-Besse - how the utility finds, evaluates, and fixes problems.

Two public meetings are planned to ~ Ongoing - Safety System Design Reviews - The discuss safety culture, but no dates have utilitys Systems Health verification program and been set. One will review FirstEnergys earlier NRC inspections had found potential design plans for the long term improvement and questions that needed to be resolved. This evaluation the plants safety culture. In inspection will look at the effectiveness of the design the second meeting, the NRC inspection reviews.

team will present its preliminary findings, ~ Planned - Reactor Cooling System Test (Normal once the inspection is completed. Operating Pressure) - This inspection will monitor the plants test of the reactor vessel and associated The remaining inspection activities are (1) piping to assure there are no leaks in the system.

a continuing review of the external ~ Planned - Assessment of Backlog Issues - This assessment of safety culture performed inspection will evaluate the work Davis-Besse plans to by a FirstEnergy consultant; (2) defer until after the plant has resumed operations or observation of FirstEnergys internal to be performed during future outages. This review assessment of its staffs safety culture, will consider the appropriateness and safety impact of planned for mid-July; (3) review of the the proposed deferrals.

process for the plants internal ~ Planned - Restart Assessment Team - As the utility assessment of safety culture; (4) nears the point where it will seek NRC authorization observation of the activities of the plants for restart, this team inspection will thoroughly review Safety Conscious Work Environment the readiness of the plant and the plant staff to

NRC Update: Davis-Besse Reactor Vessel Head Damage July 2003 - Page 2 Review Team; and (5) review of FirstEnergys plan for long term assessment of plant staff safety culture.

In addition to the preliminary discussion of its finding at the planned public meeting, the inspection teams report will be available on the NRCs web site when it is issued.

Reactor Test Planned to Check for Possible Leakage FirstEnergy is planning a special seven-day test of the reactor cooling system to assure there are no leaks, particularly where tubes pass through the bottom of the reactor. The reactor will not be started up for the test; heat added through the operation of the reactor cooling pumps will be sufficient to reach normal operating pressure and approach normal operating temperature.

The NRC Oversight Panel is still discussing with FirstEnergy the testing methods that will be used to measure possible leakage during and following the test. When the test is conducted, the NRC will observe the activities throughout the seven-day period and evaluate the results of the test.

Ongoing Engineering Issues at Davis-Besse FirstEnergy is continuing its efforts to resolve a design issue with the high pressure injection pumps where under certain specific accident conditions, the pumps could be damaged. The pumps would provide cooling water to the reactor during a loss of coolant accident while the pressure in the reactor remained high. Other pumps would be available at lower reactor pressures.

The utility is pursuing parallel paths to resolve this issue. It is continuing to test a possible modification to the pumps to prevent damage to the pump seals from debris which might be in the water being drawn from the containment building sump. The initial tests did not show that the modification would effectively correct the potential problem; FirstEnergy is preparing to test variations of the original modification to determine if they would be effective.

The second option being pursued is installation of unused pumps which FirstEnergy has acquired from a nuclear plant in Washington which was never completed. These pumps would require some modification before they can be installed at Davis-Besse. If this option is selected, the utility would need NRC authorization to use the existing pumps during the planned seven-day reactor cooling system test.

FirstEnergy is dealing with several other engineering and design issues which emerged during the companys extensive design and functional reviews of important plant safety systems.

Among the other issues being addressed by FirstEnergy:

1. Certain relays that are part of the system that starts safety equipment were replaced earlier in the outage, but the replacement relays do not have the correct voltage rating.

1. Deficiencies were found in the analysis of whether the plants electrical distribution system provided the necessary minimum voltage to safety equipment throughout the plant. The electrical distribution analyses are being updated.

1. FirstEnergy identified a problem with several air-operated valves requiring modifications and adjustments to valve actuators to make sure they will operate properly during certain accident conditions.

The NRC continues to evaluate these safety systems and the ongoing work by FirstEnergy to resolve the engineering and design issues.

NRC Update: Davis-Besse Reactor Vessel Head Damage July 2003 - Page 3 Four NRC inspection reports issued Five inspection reports were issued recently and posted to the NRCs web site at http://www.nrc.gov - select Davis-Besse from the key topics menu. The reports are on the news and correspondence page.

Radiation Protection report, (Report No. 50-346/03-08) issued May 30, documents the NRCs review of the Davis-Besse program for radiation protection for workers at the plant as well as for the general public. The inspection was an outgrowth of earlier inspections of worker radiation exposures and minor radioactive contamination that was found in offsite locations. The inspectors found that, overall, significant improvements to the radiation protection program have been made. The inspectors identified one minor violation related to the types of barriers plant personnel used to mark high radiation areas that existed during fuel loading activities.

Containment Sump Modification report, (Report No. 50-346/03-06) issued June 17, focused on the design and installation of new screens for the containment sump, which increased the surface area to avoid possible clogging of the screens during certain accident conditions. The inspectors concluded that the design and installation of the screens were satisfactory and identified one minor violation related to some errors in sump modification design calculations.

Program Effectiveness reports, (Report No. 50-346/02-11 and Report No. 50-346/03-09) issued July

7. The first report examined the effectiveness of the program review process for the plants key programs, while the second report covered the results of those program reviews. The inspections looked at included the corrective actions program, boric acid corrosion control program, the plants in-service inspection, the operating experience programs, including the adequacy of improvements and their implementation, and others. The inspectors concluded that, overall, the evaluation and improvement activities for these programs were effective. Further inspections of the Corrective Action Program, the Quality Audits and Self-Assessment of Programs, and the Boric Acid Corrosion Management Program are pending.

Resident Inspector report, (Report No. 50-346/03-13) issued June 16, documents inspections of routine plant activities during a seven-week period. Inspectors identified three minor violations. The first was related to installing relays into the safety features actuation system which were not electrically rated for this application; the second finding had to do with an inadvertent opening of valves in the borated water storage tank; and the third finding was related to poor implementation of work instructions for electrical work on reactor coolant system valves.

Pending NRC Inspection Reports Integrated Containment Leak Rate Test - This inspection monitored the testing by the plant staff of the reactor containment to assure that it meets the NRC requirements for "leak-tightness" of the containment. The results of the test, conducted April 8-9, are under review, and the report is pending.

Management and Human Performance, Phase II (Safety Culture) - This inspection focused on the work underway to survey and assess the safety culture among the staff at Davis-Besse - how the management and workers deal with safety concerns. The inspection results are under review, and a report is pending. Note: this inspection is different from the special team inspection evaluating safety culture described on page 1.

NRC Update: Davis-Besse Reactor Vessel Head Damage July 2003 - Page 4 Next Davis-Besse Oversight Panel Meetings - 2 p.m. and 7 p.m. - Tues., August 12 Oak Harbor High School Auditorium - 11661 West State Route 163, Oak Harbor Investigation continues into FirstEnergys handling of corrosion issue The NRCs investigation into whether Davis-Besse deliberately withheld or provided false or incomplete information to the NRC on the circumstances surrounding the reactor vessel head corrosion continues.

Although the details of the NRCs investigation cannot be discussed publically, the NRCs Oversight Panel maintains close and continuous communication with the NRCs Office of Investigations, which is conducting the investigation. The Oversight Panel will not make a recommendation for the plants restart until it is confident that the issues under investigation have been properly addressed.

Davis-Besse Restart Checklist The Oversight Panel has created a restart checklist categorizing 31 actions in seven major areas which FirstEnergy needs to complete before the NRC can consider making a decision on whether Davis-Besse may restart. The NRC oversight panel has determined that the utility has adequately completed thirteen of those actions. Two items were recently added to the checklist - one dealing with the high pressure injection pumps (item 2e) and a licensing issue on flow testing of certain pumps (item 6g). The completed items are shown in italics and have a check mark in front of the item.

1. Adequacy of Root Cause Determinations U 1.a Penetration Cracking and Reactor Pressure Vessel Corrosion U 1.b Organizational, Programmatic and Human Performance Issues

2. Adequacy of Safety Significant Structures, Systems, and Components 2.a Reactor Pressure Vessel Head Replacement 2.b Containment Vessel Restoration Following Reactor Pressure Vessel Head Replacement 2.c Structures, Systems, and Components Inside Containment 2.c.1 Emergency Core Cooling System and Containment Spray System Sump 2.d Extent-of-Condition of Boric Acid in Systems Outside Containment 2.e High Pressure Injection Pump Internal Clearance/Debris Resolution

3. Adequacy of Safety Significant Programs 3.a Corrective Action Program U 3.b Operating Experience Program 3.c Quality Audits and Self-Assessments of Programs 3.d Boric Acid Corrosion Management Program U 3.e Reactor Coolant System Unidentified Leakage Monitoring Program U 3.f In-Service Inspection Program U 3.g Modification Control Program 3.h Radiation Protection Program 3.i Process for Ensuring Completeness and Accuracy of Required Records and Submittals to the NRC

4. Adequacy of Organizational Effectiveness and Human Performance

NRC Update: Davis-Besse Reactor Vessel Head Damage July 2003 - Page 5 U 4.a Adequacy of Corrective Action Plan 4.b Effectiveness of Corrective Actions

5. Readiness for Restart 5.a Review of Licensees Restart Action Plan 5.b Systems Readiness for Restart 5.c Operations Readiness for Restart 5.d Test Program Development and Implementation

6. Licensing Issue Resolution U 6.a Verification that Relief Requests A8 and A12 regarding the Shell to Flange Weld (previously submitted by letter dated September 19, 2000) is not Impacted by the Midland RPV Head U 6.b American Socty of Mechanical Engineers (ASME) Code Relief Request for Failure to Maintain Original Radiographic Tests of the Midland Head to Flange Weld (Planned Relief Request A26)

U 6.c ASME Code Relief Request for Inability to Radiographically Test 100% of the Midland Reactor Pressure Vessel Head to Flange Weld (Planned Relief Request A27)

U 6.d Resubmit Relief Request A2 (previously submitted by letter dated September 19, 2000) for ASME Code for Inability to Perform 100% volumetric and surface examination of Head to Flange Weld U 6.e Reconciliation Letter that Demonstrates How the New Reactor Pressure Vessel Head Correlates With the ASME Code and QA Index for Section III and Section XI - Commitments U 6.f Verification Letter of Technical Specification Pressure/Temperature Curves for New Vessel Head - Commitment 6.g Request to relocate High Pressure Injection and Low Pressure Injection Subsystems Flow Balance Testing fromTechnical Specifications 4.5.2.h to Updated Safety Analysis Report Technical Requirements Manual

7. Confirmatory Action Letter Resolution 7.a Verification that Confirmatory Action Letter Items are Resolved, Including a Public Meeting to Discuss Readiness for Restart

Background:

What Happened at Davis-Besse In March 2002 plant workers discovered a cavity in the head or top of the reactor vessel while they were repairing control rod tubes which pass through the head.

The tubes, which pass through the reactor vessel head, are called control rod drive mechanism nozzles. Cracks were detected in 5 of the 69 nozzles. In three of those nozzles, the cracks were all the way through the nozzle, allowing leakage of reactor cooling water, which contains boric acid.

Corrosion, caused by the boric acid, damaged the vessel head next to Nozzle No. 3, creating an irregular cavity about 4 inches by 5 inches and approximately 6 inches deep. The cavity penetrated the carbon steel portion of the vessel head, leaving

NRC Update: Davis-Besse Reactor Vessel Head Damage July 2003 - Page 6 only the stainless steel lining. The liner thickness varies somewhat with a minimum design thickness of 1/8 inch. Subsequent examination by Framatome, FirstEnergys contractor, found evidence of a series of cracks in the liner, none of which was entirely through the liner wall.

Earlier indications of the problem: Through-Wall Cracking of Nozzles in France and at the Oconee Nuclear Power Station in South Carolina In the early 1990's control rod drive mechanism nozzle cracking was discovered at a nuclear plant in France.

These cracks penetrated the nozzle wall along the length of the nozzle (referred to as 'axial' cracking).

In 1997 the NRC issued Generic Letter 97-01 to gather information on the inspection activities for possible cracking in the control rod drive mechanism nozzles in plants in the United States. Subsequently, through-wall circumferential cracks -- around the nozzle wall -- were discovered in two control rod drive mechanism nozzles at the Oconee Nuclear Power Station, Unit 3, in 2001. While axial cracking had been found at several other plants and repaired, circumferential cracking had not been seen before. Circumferential cracking is more significant because it could lead to complete separation of the nozzle and a resulting loss-of-coolant accident.

After the Oconee discovery, the NRC issued Bulletin 2001-01, requiring all pressurized water reactor (PWR) operators to report to the NRC on structural integrity of the nozzles, including the extent of any nozzle cracking and leakage and their plans to ensure that future inspections would guarantee structural integrity of the reactor vessel boundary. The NRC's Bulletin instructed nuclear power plants with similar operating history to Oconee Unit 3, including Davis-Besse, to inspect their reactor vessel head penetrations by December 31, 2001, or to provide a basis for concluding that there were no cracked and leaking nozzles.

FirstEnergy Nuclear Operating Company requested an extension of the inspection deadline until its refueling outage beginning March 30, 2002, and provided the technical basis for its request. The NRC did not allow the plant to operate until March 30, but agreed to permit operation until February 16, provided that compensatory measures were taken to minimize possible crack growth during the time of operation. The NRC was unaware that nozzle leakage or corrosion had occurred at Davis-Besse when it agreed to the February 16 date.

Boric Acid Corrosion Control Procedure The water that circulates through a pressurized water reactor to cool the nuclear fuel contains a low concentration of boric acid. This borated water can potentially leak through flanges, pump and valve seals, and other parts of the reactor cooling system and cause corrosion.

The NRC has taken steps to make sure that PWR operators are aware of and pay attention to the corrosion boric acid can cause in certain environments:

• In 1986-89, the NRC issued a series of documents, called generic communications, informing PWR licensees that boric acid can corrode and damage steel reactor components.

• The NRCs Generic Letter 88-05 requested PWR operators to implement a program to ensure that boric acid corrosion does not lead to degradation of the reactor cooling system components. All nuclear power plants with PWRs, including Davis-Besse, reported to NRC that the Boric Acid Control Procedures had been established and would be implemented.

Barriers Built into Nuclear Plants to Protect Public Health and Safety The design of every nuclear power plant includes a system of three barriers which separate the highly radioactive reactor fuel from the public and the environment. The Davis-Besse reactor head damage represented a significant reduction in the safety margin of one of these barriers, the reactor coolant system.

The reactor coolant system, however, remained intact, as well as the other two barriers, the fuel and the containment.

NRC Update: Davis-Besse Reactor Vessel Head Damage July 2003 - Page 7

1. Fuel Pellets and Rods The first barrier is the fuel itself. The fuel consists of strong, temperature-resistant ceramic pellets made of uranium-oxide. The pellets are about the size of a little finger-tip. They retain almost all of the highly radioactive products of the fission process within their structure.

The pellets are stacked in a rod made of a zirconium alloy. At Davis-Besse, each fuel rod is about 13 feet long. The rods are assembled into bundles, with each assembly containing 208 rods. The reactor core contains 177 fuel assemblies. Any fission products which escape from the pellets are captured inside the cladding of the rod, which is designed to be leak-tight.

Small pin hole leaks do occasionally occur, however, and the operating license requires leakage monitoring and contains limits on the maximum allowable leakage of radioactive materials from the fuel rods.

2. Reactor Coolant System The second barrier is the reactor coolant system pressure boundary. The reactor core is contained inside the reactor pressure vessel, which is a large steel container. Thick steel pipes supply cooling water to the reactor and carry away the heated water after it passes through the reactor core. The pressure vessel, the connected piping, and other connected components make up the reactor coolant system pressure boundary.

At Davis-Besse, the reactor coolant system contains about 60,000 gallons of cooling water, circulated by four large pumps at a rate of about 360,000 gallons per minute.

This system is designed to be leak-tight at operating conditions which include a water temperature of 605E F and a water pressure of 2,150 pounds per square inch. The operating license contains limits on the maximum allowable amount of leakage from the system, and it specifies requirements for monitoring any leakage. If a leak is identified as being through any solid wall of the system (reactor vessel, cooling pipes or other components) continued operation of the plant is prohibited, no matter how small the leak rate.

3. Containment Building The third barrier is the containment building. This is a large cylindrical building which contains the entire reactor coolant system. None of the piping that contains the high-temperature and high-pressure reactor coolant water extends outside the containment building. The containment is a 1 1/2 inch thick steel cylinder, rounded at the top and bottom, which is designed to be leak-tight. This steel structure is surrounded by a reinforced concrete shield building, which is the round building visible from the outside of the plant. Its walls are 2 to 3 feet thick.

NRCs Response to Vessel Head Damage The NRC responded to the vessel head degradation with a series of actions, some specific to Davis-Besse and others aimed at other PWR plants. The agency began a review of its regulatory activities as well.

Davis-Besse On March 12, 2002, the NRC initiated an Augmented Inspection Team to examine conditions that led to the head degradation and on March 13, 2002, the NRC issued a Confirmatory Action Letter to Davis-Besse documenting a number of actions the plant needed to implement for the unit to be allowed to restart. On April

NRC Update: Davis-Besse Reactor Vessel Head Damage July 2003 - Page 8 29, 2002, the NRC established an Oversight Panel under the Agencys Manual Chapter 0350, to coordinate and oversee NRC activities necessary to address repairs and performance deficiencies at the plant in order to guarantee that it can operate safely. The plant will not restart until the NRC is satisfied that plant operators have met all necessary safety requirements.

Generic On March 18, 2002, the NRC issued Bulletin 2002-01, instructing PWR licensees to report on the condition of their head, past incidents of boric acid leakage and the basis for concluding that their boric acid inspection programs were effective. All plants sent their responses and indicated that no evidence of extensive corrosion of reactor vessel heads was found at these plants. On August 9, 2002, the NRC issued Bulletin 2002-02 advising PWR operators that more stringent inspection techniques may be necessary to detect head penetration nozzle cracks. Visual examination of reactor vessel heads and nozzles may need to be supplemented with other inspection techniques, such as the use of ultrasound, electric currents and liquid dyes. In October, the agency also requested PWR licensees to provide additional information on their boric acid inspection program with greater detail than initially covered in the responses to Bulletin 2002-01.

On February 11, 2003, the NRC an order to all Pressurized Water Reactor operators establishing interim inspection requirements for reactor pressure vessel heads. The Order requires specific inspections of the reactor pressure vessel head and associated penetration nozzles depending on the licensee's susceptibility to primary water stress corrosion cracking.

NRC Davis-Besse Oversight Panel An NRC Davis-Besse Oversight Panel was created to make sure that all corrective actions, required to ensure that Davis-Besse can operate safely, are taken before the plant is permitted to restart and that Davis-Besse maintains high safety and security standards if it resumes operations. Should the plant restart, the Oversight Panel will evaluate if Davis-Besses performance warrants reduction of the NRCs heightened oversight and, if so, recommend to NRC management that the plant return to a regular inspection schedule. The panel was established under the agencys Manual Chapter 0350.

The panel brings together NRC management personnel and staff from the Region III office in Lisle, Illinois, the NRC Headquarters office in Rockville, Maryland and the NRC Resident Inspector Office at the Davis-Besse site. The eight-member panels chair and co-chair are John Grobe, a senior manager from Region III and William Ruland, a senior manager from NRC headquarters.

As part of determining if plant corrective actions are adequate to support restart, the Oversight Panel will evaluate FirstEnergy's return to service plan, which is divided into seven areas of performance that the utility calls "building blocks." A series of NRC inspections are being performed to verify the company is taking proper actions in each of the seven areas. These reviews will include the work by the FirstEnergy staff and, in addition, the NRC staff will perform independent inspections in each of the "building block" areas.

Issues to be resolved in order for Davis-Besse to restart The NRC Oversight Panel will only consider recommending that Davis-Besse resume operations when the plant has demonstrated its readiness to operate safely. Key elements will include:

• Davis-Besse management and personnel properly understand the technical, organizational, programmatic and human performance problems that led to the extensive degradation of the plants reactor vessel head.

NRC Update: Davis-Besse Reactor Vessel Head Damage July 2003 - Page 9

• Davis-Besse enhances programs for operating the plant safely, detecting and correcting problems, controlling boric acid corrosion, and is fostering a more safety-conscious environment among plant managers and workers.

• Davis-Besse improves the performance standards of its managers and workers, including their ownership of the quality of work products and the safety focus of decision-making.

• The replacement of the vessel head is technically sound and all reactor components are inspected, repaired as necessary, and demonstrated to be ready for safe operation.

• Plant safety systems inside and outside containment are inspected, repaired as necessary, and have been confirmed to be ready to resume safe operation of the plant.

• Plant operators demonstrate appropriate safety focus and readiness to restart the plant.

• Any organizational or human performance issues resulting from the ongoing investigation conducted by the NRCs Office of Investigations are addressed.

• All licensing issues that have arisen as a result of the reactor head replacement have been resolved.

• Resolution of radiation protection issues associated with the radiation exposure to workers during steam generator work and the particle contamination found in offsite locations.

• Modification of the strainer system for the containment sump, which would be the source of cooling water for recirculation in the event of a loss-of-coolant accident.

What Happens If the Plant is Allowed to Restart If the facility is permitted to restart, the NRC Oversight Panel will continue to monitor plant activities and operations until panel members are confident that the root cause(s) of the problem have not recurred. Should FirstEnergy achieve that performance level, the NRC Oversight Panel would recommend to NRC management that responsibility for the plant oversight be transferred back to the Region III line organization for monitoring under the Reactor Oversight Process. The panel would then cease to exist. Should FirstEnergy not demonstrate sustained improved performance, the panel will recommend appropriate regulatory actions.

Public Participation in the Process The NRCs experience is that members of the public, including public officials and citizens, often raise questions or provide insights that are important to consider. If you have questions or want to provide information or a point of view, please contact us. For feedback on this newsletter, contact Viktoria Mitlyng 630/829-9662 or Jan Strasma 630/829-9663 (toll free 800/522-3025 - ext -9662 or -9663). E-mail: opa3@nrc.gov. Extensive information about the Davis-Besse reactor vessel head damage and the ensuing activities is available on the NRC web site: http://www.nrc.gov - select Davis-Besse under the list of key topics.