ML031260496

May 2003 Davis-Besse Reactor Vessel Head Damage, NRC Update, Ninth Periodic Update

ML031260496
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Site:	Davis Besse
Issue date:	05/01/2003
From:	NRC/RGN-III
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May 2003 This is the ninth 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.

FIRST ENERGY SUBMITS Ongoing and Planned NRC Inspections SAFETY CULTURE REPORT The NRC has a series of inspections planned before FirstEnergy has submitted the report of a review any decision on whether or not the Davis-Besse plant of the Davis-Besse safety culture performed in may resume operations. These inspections include:

February by its consultant, Performance, Safety, and Health Associates, Inc. The review n Management and Human Performance, Phase team was headed by Dr. Sonja Haber. III (Safety Culture) - This inspection focuses on FENOCs actions to improve management The report concluded that FirstEnergy has effectiveness and human performance and its taken a number of steps to improve the safety processes to survey and assess the safety culture of plant management and staff, but that culture among the staff at Davis-Besse - how the resulting performance is not at a consistent the management and workers will deal with level. safety concerns.

n Corrective Action Team Inspection - This Areas identified in the report as needing inspection looks at the effectiveness of the continuing effort and attention include: corrective action program at Davis-Besse - how the utility finds, evaluates, and fixes problems.

 Although safety is a recognized value in n Reactor Vessel Test (Normal Operating the organization, it is inconsistently Pressure) - This inspection will monitor the accepted and understood across all plants test of the reactor vessel and associated levels of personnel. Problems still exist piping to assure there are not leaks in the in the transmission and implementation system.

of the safety message. n Safety System Design Reviews - The utilitys Systems Health verification program and earlier

 Accountability and ownership for safety NRC inspections had found potential design are not yet universally accepted in the questions that needed to be resolved. This organization. Although some individuals inspection will look at the effectiveness of the readily accept responsibility and take design reviews.

ownership of problems, others are still n Boric Acid Corrosion Management Program -

reluctant to do so. This inspection will focus on the utilitys program for controlling boric acid leakage and its

 Safety is not yet consistently integrated possible effects.

into all activities in the organization. n Reactor Coolant System Integrated Leakage Processes and programs are in various Program - This inspection will evaluate the stages of transition, which often reduces utilitys program for detecting and responding to their effectiveness. small amounts of leakage from the reactor cooling system for comprehensiveness and

 An integrated and cohesive effectiveness.

organizational safety leadership process

NRC Update: Davis-Besse Reactor Vessel Head Damage May 2003 - Page 2 does not yet exist. The values and attitudes of the workforce are generally NRC Inspections - Contd positive, but the many differences found between work groups, and between  Assessment of Backlog Issues - This management and staff indicate that inspection will evaluate the work Davis-personnel are not yet aligned with a Besse plans to defer until after the plant has common set of values. Managements resumed operations or to be performed safety goals have not been consistently during future outages. This review will communicated to nor understood by station consider the appropriateness and safety personnel. impact of the proposed deferrals.

 Restart Assessment Team - As the utility

 Safety is not learning driven in the nears the point where it will seek NRC organization. Efforts to improve future authorization for restart, this team inspection performance by learning from the Stations will thoroughly review the readiness of the past performance, from others plant and the plant staff to resume plant performance, and from the day-to-day operations safely and in compliance with implementation of the organizations NRC requirements. The inspection findings programs and processes, are not will be considered by the NRC Oversight systematic or recognized to be of high Panel in making its recommendation to the value for the organization.

The safety culture evaluation and recommendations will be reviewed during the ongoing NRC management and human performance inspection.

This inspection is focused on the approach used by FirstEnergy and its consultants to gather and evaluate data and develop conclusions regarding safety culture and a safety conscious work environment at Davis-Besse. The inspection is also reviewing the utilitys plans for future monitoring of safety culture and the implementation of its employee concerns program.

The NRCs Oversight Panel will consider the FirstEnergy consultants report and the results of the NRC management and human performance inspection, combined with the results of other completed and ongoing inspections, to evaluate the effectiveness of the utilitys corrective actions. Management and human performance -- i.e. the safety culture -- has been identified as a key contributor to the corrosion damage to the reactor vessel head. NRC regulations require utilities to take effective corrective action when problems occur

- thus FirstEnergy must correct the safety culture problems which contributed to the vessel head damage and take steps to prevent a recurrence of those problems.

While the management and human performance inspection is focused on the steps being taken by the utility and its consultants to assess and improve safety culture, all NRC inspections provide additional measures of the plants safety culture and the utilitys efforts to improve the culture. The NRC staff and FirstEnergy will meet to discuss engineering and design issues:

Ongoing Engineering Issues at Davis- 1 p.m. CDT - Wednesday, May 7 Besse NRC Region III Office 801 Warrenville Rd.,Lisle IL FirstEnergy is dealing with several engineering and design issues which emerged during the companys extensive The meeting is open to the public. To listen design and functional reviews of important plant safety by telephone call (800) 857-9602 and use systems. pass code Davis-Besse and Cheryl Hausman at the prompt. The meeting will

 The emergency diesel generator room ventilation also be available for public viewing by video system may not have sufficient cooling capability conference at the NRC Headquarters, when outside temperatures are high. Room T-2B5, One White Flint North, 11555 Rockville Pike, Rockville, Maryland.

NRC Update: Davis-Besse Reactor Vessel Head Damage May 2003 - Page 3

 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.

 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.

 A design issue with the high pressure injection pumps was identified by FENOC where under certain specific accident conditions, the pumps could be damaged. The utility is reviewing options to correct the problem, including possible replacement of the pumps.

 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.

Reactor Test Planned to Check for Possible Leakage FirstEnergy is planning a special seven-day test of the reactor and 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 approach normal operating temperature and pressure.

Because of a design issue with the high pressure injection pumps, part of the emergency core cooling system, FirstEnergy is considering several options, including modification or a request for a one-time amendment of its NRC license to permit the test to be performed before the high pressure pumps are modified or replaced. The pumps are normally required to be fully operable when the reactor is taken to normal operating temperatures and pressures.

Such an amendment request requires a review and approval by the NRC staff.

Update: Preliminary Red Safety Significance Earlier this year the NRC staff issued its preliminary finding that performance deficiencies at the Davis-Besse Nuclear Power Plant which led to the cracking of the control rod drive tubes and the resulting corrosion damage to the reactor vessel head were of high safety significance. Under its safety significance determination process, NRC officials classify inspection findings at nuclear power plants as being one of four colors which delineate increasing levels of safety significance, beginning with "green" and progressing to "white," "yellow" or "red." A red category indicates high safety significance.

On April 24, 2003, FirstEnergy responded that it did not contest the preliminary red finding and provided some recommended minor changes to the NRCs evaluation. The NRC staff is now completing its final determination of the safety significance.

Under the agencys Reactor Oversight Process, a red finding would result in strong actions by the NRC to improve plant performance, including development of a performance improvement plan by the utility and follow-up NRC inspections. In the case of Davis-Besse, however, the NRC implemented its procedure for plants in extended shutdown with performance problems and established a special NRC Oversight Panel to coordinate the agencys response to the performance problems which led to the reactor vessel head damage.

Next Davis-Besse Oversight Panel Meetings - 2 p.m. and 7 p.m. - Tuesday, June 3 Camp Perry - Highway 2 west of Port Clinton OH

NRC Update: Davis-Besse Reactor Vessel Head Damage May 2003 - Page 4 Resolved Restart Checklist Items The Oversight Panel has created a restart checklist categorizing 29 actions in seven major areas 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 seven of those actions:

1. a The technical part of the root cause evaluation of the corrosion damage to the reactor vessel head.

6.a-f Licensing issues related to the installation and operability of the new reactor vessel head.

NRC Inspection Reports to be Issued in Mid-May n Radiation Protection - This inspection examined 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 inspection findings were discussed in a public meeting April 15, and an inspection report will be issued in mid-May.

n Containment Sump Modification - This inspection, completed April 11, reviewed 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 inspection results are under review, and a report will be issued in mid-May.

n 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 inspection teams report will be issued in mid-May.

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 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

NRC Update: Davis-Besse Reactor Vessel Head Damage May 2003 - Page 5 In the early 1990s 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 NRCs 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

NRC Update: Davis-Besse Reactor Vessel Head Damage May 2003 - Page 6 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.

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

NRC Update: Davis-Besse Reactor Vessel Head Damage May 2003 - Page 7 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 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 May 2003 - Page 8

• 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.