IR 05000289/2010006

IR 05000289-10-006; 4/12/2010 - 4/29/2010; Exelon Generation Company, LLC; Three Mile Island Station, Unit 1; Engineering Specialist Plant Modifications Inspection

ML101580446
Person / Time
Site:	Three Mile Island
Issue date:	06/07/2010
From:	Doerflein L Engineering Region 1 Branch 2
To:	Pacilio M Exelon Nuclear
References
IR-10-006
Download: ML101580446 (21)

Text

UNITED STATES NUCLEAR REGULATORY COMMISSION

REGION I

475 ALLENDALE ROAD KING OF PRUSSIA, PA 19406*1415 June i, 2010 Mr. Michael Pacilio Senior Vice President, Exelon Generation Company LLC President and Chief Nuclear Officer, Exelon Nuclear 4300 Winfield Rd.

Warrenville, IL 60555 SUBJECT:* THREE MILE ISLAND STATION, UNIT 1 - NRC EVALUATION OF CHANGES, TESTS, AND EXPERIMENTS AND PERMANENT MODIFICATIONS TEAM INSPECTION REPORT 05000289/2010006

Dear Mr. Pacilio:

On April 29, 2010, the U.S. Nuclear Regulatory Commission (NRC) completed an inspection at the Three Mile Island Station, Unit 1. The enclosed inspection report documents the inspection results, which were discussed on April 29, 2010, with Mr. Richard W. Libra, Plant Manager, and other members of your staff.

The inspection examined activities conducted under your license as they relate to safety and compliance with the Commission's rules and regulations and with the conditions of your license.

In conducting the inspection, the team reviewed selected procedures, calculations and records, observed activities, and interviewed station personnel.

Based on the results of this inspection, no findings of significance were identified.

In accordance with 10 CFR 2.390 of the NRC's "Rules of Practice," a copy of this letter, its enclosure, and your response (if any) will be available electronically for public inspection in the NRC Public Document Room or from the Publicly Available Records (PARS) component of the NRC's document system (ADAMS). ADAMS is accessible from the NRC Web site at http://www.nrc.gov/reading-rm/adams.html(the Public Electronic Reading Room).

Sincerely,

"-'1 C\

C)(~~ 7, lJ Lawrence T. Doerflein, Ch Engineering Branch 2 Division of Reactor Safety Docket Nos.: 50-289 License Nos.: DPR-50 Enclosure: Inspection Report No. 05000289/2010006 w/Attachment: Supplemental Information cc w/encl: Distribution via ListServ

June 7,2010 Mr. Michael Pacilio Senior Vice President, Exelon Generation Company LLC President and Chief Nuclear Officer, Exelon Nuclear 4300 Winfield Rd.

Warrenville, IL 60555 SUBJECT: THREE MILE ISLAND STATION, UNIT 1 - NRC EVALUATION OF CHANGES, TESTS, AND EXPERIMENTS AND PERMANENT MODIFICATIONS TEAM INSPECTION REPORT 05000289/2010006 Dear M

SUMMARY OF FINDINGS

IR 05000289/2010006; 4/12/2010 - 4/29/2010; Exelon Genration Company, LLC; Three Mile

Island Station, Unit 1; Engineering Specialist Plant Modifications Inspection.

This report covers a two week on-site inspection period of the evaluations of changes, tests, or experiments and permanent plant modifications. The inspection was conducted by three region based engineering inspectors and one inspector in training. No findings of significance were identified. The NRC's program for overseeing the safe operation of commercial nuclear power reactors is described in NUREG-1649, "Reactor Oversight Process," Revision 4, dated December 2006.

NRC-Identified and Self-Revealing Findings

No findings of significance were identified.

Licensee-Identified Violations

None.

ii

REPORT DETAILS

REACTOR SAFETY

Cornerstones: Initiating Events, Mitigating Systems, and Barrier Integrity

1R17 Evaluations of Changes. Tests. or Experiments and Permanent Plant Modifications

(IP71111.17)

.1 Evaluations of Changes. Tests. or Experiments (29 samples)

a. Inspection Scope

The team reviewed six safety evaluations to determine whether the changes to the facility or procedures, as described in the Updated Final Safety Analysis Report (UFSAR), had been reviewed and documented in accordance with 10 CFR 50.59 requirements. In addition, the team evaluated whether Exelon had been required to obtain NRC approval prior to implementing the change. The team interviewed plant .

staff and reviewed supporting information including calculations, analyses, design change documentation, procedures, the UFSAR, the Technical Specifications (TSs),and plant drawings to assess the adequacy of the safety evaluations. The team compared the safety evaluations and supporting documents to the guidance and methods provided in Nuclear Energy Institute (NEI) 96-07, "Guidelines for 10 CFR 50.59 Evaluations," as endorsed by NRC Regulatory Guide 1.187, "Guidance for Implementation of 10 CFR 50.59, Changes, Tests, and Experiments," to determine the adequacy of the safety evaluations.

The team also reviewed a sample of twenty three 10 CFR 50.59 screenings for which Exelon had concluded that no safety evaluation was required. These reviews were performed to assess whether Exelon's threshold for performing safety evaluations was consistent with 10 CFR 50.59. The sample included design changes, calculations, and procedure changes.

The team reviewed the safety evaluations that Exelon had performed and approved during the time period covered by this inspection (Le., since the last modifications inspection) not previously reviewed by NRC inspectors. The screenings and applicability determinations were selected based on the safety significance, risk significance, and complexity of the change to the facility.

In addition, the team compared Exelon's administrative procedures used to control the screening, preparation, review, and approval of safety evaluations to the guidance in NEI 96-07 to determine whether those procedures adequately implemented the requirements of 10 CFR 50.59. The reviewed safety evaluations and screenings are listed in the attachment.

b. Findings

No findings of significance were identified.

.2.1 Replacement of Caulking Material Inside Containment

a. Inspection Scope

The team reviewed a modification (Engineering Change Request (ECR) TM-07 -00453)that replaced caulk used as a moisture barrier between the containment floor and wall.

The modification removed all the old style caulk at the base of containment and replaced it with a new style caulking material. This change was performed because the new caulk was shown, via testing, to withstand design basis accident environmental conditions and the older caulk had not been tested to those worst case conditions. The team conducted the review to verify that the design bases, licensing bases, and performance capability of safety related structures, systems, and components (SSCs)were not degraded by the new caulking material.

The team discussed the modification and design basis with design and system engineers to assess the capability of the caulk to remain intact following a design basis accident (DBA). The team reviewed the manufacturer's recommended applications for the caulk to ensure that the calculated environmental conditions inside containment were enveloped by the manufacturer's guidelines. The team also reviewed the installation procedure to verify the caulk was installed in accordance with the manufacturer's requirements. Finally, the team verified that the new caulk would not change the assumptions used for the containment sump testing as discussed in the Exelon's Generic Letter (GL) 2004-02 response. The 10 CFR 50.59 screening determination associated with this modification was also reviewed as described in section 1R 17.1 of this report. The documents reviewed are listed in the attachment.

b. Findings

No findings of significance were identified .

.2.2 Nuclear River Water Outlet Isolation Valve Installation

a. Inspection Scope

The team reviewed a modification (ECR-TM-08-00251) that installed a new isolation valve in the nuclear river (NR) water system. Exelon implemented this modification in order to allow for maintenance on individual heat exchangers while maintaining adequate flow to other system loads allowing them to remain available for operation. In addition to the valve replacement, Exelon also replaced several sections of NR piping under the same work order. The team conducted the review to ensure that the design bases, licensing bases, and performance capability of the NR system had not been adversely affected by the modification.

The team reviewed the associated work order packages and conducted interviews with design and system engineers regarding the design, installation, and testing of the valve and piping to verify that the modification was adequate. The review included determining the safety classification of the new valve, piping and welding material. The team also reviewed the post maintenance testing of the welds and piping to verify it met the requirements of the American Society of Mechanical Engineers (ASME) code.

Additionally, the team verified that the hydraulic and seismic calculations had been revised to address the effects the new equipment had on the design of the system.

Finally, the team walked down the new valve and piping to assess the system configuration. The 10 CFR 50.59 screening determination associated with this modification was also reviewed as described in section 1R17.1 of this report. The documents reviewed are listed in the attachment.

b. Findings

No findings of significance were identified .

.2.3 Auxiliary Building Flood Analysis

a. Inspection Scope

The team reviewed a change to the flooding analysis (ECR-TM-06-00097) performed by Exelon to address a change in operating procedures associated with building spray (BS)pump operation. For certain design basis events, Exelon now operates the BS system so the analysis must assume a failure could occur in the system. This failure could result in flooding of certain safety related SSCs. Exelon's calculation revision and associated analysis determined that there was sufficient time for operators to respond to a failure such that no other equipment would be impacted. The team evaluated the change to confirm that the design bases, licensing bases, and performance capability of the .safety related SSCs would not be affected by the change.

The team reviewed the calculation and associated analysis to verify the assumptions used in the calculation were valid. Additionally, the team walked down portions of the system to assess the configuration of the system. The team reviewed surveillance procedures used to verify that the drainage paths and associated water detection alarms were being adequately maintained. Finally, the team interviewed design engineers to review the calculation assumptions, applicable operating procedures, and the calculation's methodology to determine if the analysis showed adequate time was available for operator action. The 10 CFR 50.59 screening determination associated with this modification was also reviewed as described in section 1R17.1 of this report.

The documents reviewed are listed in the attachment.

b. Findings

No findings of significance were identified.

.2.4 Decay Heat (DH) Removal System Valves (DH-V-6A and DH-V-6B) Motor Replacement

a. Inspection Scope

The team reviewed a modification (ECR-TM-07-00792) that replaced the motors and thermal overload heaters for valves DH-V-6A and 6B. Exelon implemented the modification following an analysis performed to evaluate the potential for thermal binding of the valves following changes associated with the reactor building (RB) sump modification performed in refueling outage 1R17. Since the analysis showed thermal binding conditions may exceed the capability of the motor operated valve (MOV)actuators, Exelon implemented the modification which installed larger motors with a higher starting torque, installed new thermal overload heaters, and changed the instantaneous setting on the DH-V-6A1B breakers to account for the higher inrush currents. The team conducted the review to verify that the design bases, licensing bases, and performance capability of valves DH-V-6A and B had not been adversely affected by the modification.

The team reviewed associated drawings, calculations, and maintenance procedures to ensure they had been properly updated to incorporate the changes to the DH-V-6A and 6B motors. In addition, post-modification testing was reviewed to verify proper operation of the MOVs. The team also discussed the modification and design basis with design engineers to assess the adequacy of the modification. The 10 CFR 50.59 screening determination associated with this modification was also reviewed as described in section 1R17.1 of this report. The documents reviewed are listed in the attachment.

b. Findings

No findings of significance were identified .

.2.5 Install New Air Handling Unit Starters and Components

a. Inspection Scope

The team reviewed a modification (ECR-TM-08-00607) that replaced the starters and associated components in the control circuits for each of the three RB recirculation air handling units (AH E-1A, -1B, -1C). Exelon implemented the modification because the existing parts were no longer supported by the vendor. The modification included replacing components in the motor control center (MCC) for each air handling unit, specifically the fast and slow speed starters, auxiliary contacts, and associated thermal overload relays and heaters. The team conducted the review to verify that the design bases and performance capability of the RB recirculation air handling units had not been adversely affected by the modification.

The team reviewed associated drawings and calculations to ensure they had been properly updated to incorporate the changes associated with the starters and related components of the RB recirculation air handling units. The team interviewed the responsible design and system engineers to understand the implementation of the modification and subsequent system performance. The team also reviewed condition reports (CRs) associated with the air handling units to verify that the modification had addressed identified deficiencies with the starters. The team reviewed the post modification test plan and results to ensure appropriate acceptance criteria had been established and met. The 10 CFR 50.59 screening determination associated with this modification was also reviewed as described in section 1R17.1 of this report. The documents reviewed are listed in the attachment.

b. Findings

No findings of significance were identified .

.2.6 Pressurizer Surge Nozzle and Decay Heat Drop Line Nozzle Weld Overlays

a. Inspection Scope

The team reviewed a modification (ECR-TM-07-00369) that applied a full structural weld overlay (SWOL) to the pressurizer surge nozzle to safe-end weld and a full SWOL to the decay heat drop line nozzle to safe-end weld. These welds were originally constructed using alloy 82/182 dissimilar metal weld material which industry experience has since shown to be susceptible to primary water stress corrosion cracking (PWSCC). Exelon implemented this modification to mitigate the effects of PWSCC. The team conducted the review to verify that the design bases, licensing bases, and performance capability of the pressurizer and decay heat removal system had not been adversely affected by the modification.

The team reviewed drawings and calculations to ensure they had been properly updated to incorporate the addition of the full SWOLs. The team also reviewed associated analyses to evaluate if the weld overlay would degrade the design basis of the pressurizer and to determine if the requirements of the ASME Boiler and Pressure Vessel Code were met. In addition, the team reviewed completed work orders and post modification testing to verify the acceptance criteria were met. The team also discussed the modification and design basis with design and system engineers to assess the adequacy of the modification. The 10 CFR 50.59 screening determination associated with this modification was also reviewed as described in section 1R 17.1 of this report.

The documents reviewed are listed in the attachment.

b. Findings

No findings of significance were identified.

.2.7 Pressurizer Surge Line Restraint Modification

a. Inspection Scope

The team reviewed a modification (ECR-TM-07-00453) that changed the dimension of the pressurizer surge line restraint. Exelon implemented this modification in conjunction with the pressurizer surge nozzle weld overlay modification. The modification involving the SWOL was performed to add weld material to the pressurizer surge line nozzle.

This required the inner diameter of the surge line restraint to be increased. The team conducted the review to verify that the design bases and performance capability of the restraint had not been adversely affected by the modification.

The team reviewed drawings and calculations to ensure they were properly updated with the new dimensions of the restraint. The team reviewed the associated analysis to verify the structural integrity of the modified restraint was maintained. In addition, the team reviewed completed work orders to verify the appropriateness of the testing acceptance criteria and evaluated test results against the criteria. The team also discussed the modification and design bases with design engineers to assess the adequacy of the modification. The 10 CFR 50.59 screening determination associated with this modification was also reviewed as described in section 1R17.1 of this report.

The documents reviewed are listed in the attachment.

b. Findings

No findings of significance were identified .

.2. B Main Steam Atmospheric Dump Valve Replacements

a. Inspection Scope

The team reviewed a modification (ECR-TM-OB-00145) that replaced the 'A' and 'B' main steam atmospheric dump valves (ADVs) and actuators. The new actuator design also required a modification to the instrument air system. The ADVs were replaced to improve reliability associated with seat tightness. In addition to evaluating valve capabilities and design characteristics, the modification evaluated and made changes to the instrument air system piping and pneumatic controllers. The ADVs are credited to mitigate several DBAs and are automatically operated by the integrated control system that can be remotely or locally operated for decay heat removal. The team conducted the review to ensure that the design bases, licensing bases, and performance capability of the ADVs had not been adversely affected by the modification.

In addition to reviewing the engineering analyses and supporting information within the modification package, the team reviewed calculations to verify that the two-hour backup instrument air system capacity requirements and time to reach cold shutdown were not adversely impacted by the modification. The team verified that Exelon evaluated the automatic operation of the ADVs as controlled by the integrated control system. The team verified that the post-modification test results were acceptable and that surveillance procedures, operating procedures, and the vendor manual were appropriately revised. The team also verified that operating personnel were appropriately trained on local operation of the replacement ADVs. Finally, the team walked down the 'A' and 'B' ADVs to identify abnormal conditions and reviewed operating procedures posted for local operation and discussed the.modification and design basis with design engineers to assess the adequacy of the modification. The 10 CFR 50.59 screening determination associated with this modification was also reviewed as described in section 1R17.1 of this report. The documents reviewed are listed in the attachment.

b. Findings

No findings of significance were identified .

.2.9 Station Blackout (SBO) Battery Replacement

a. Inspection Scope

The team reviewed a modification (ECR-TM-08-00055) that replaced all cells that make up the 125Vdc SBO battery. The SBO battery was replaced to ensure continued battery reliability. The SBO battery is a necessary support system of the SBO diesel generator.

The modification was performed using redesigned cells that offered improved battery performance because the original battery cells were no longer available. The team conducted the review to ensure that the design bases, licensing bases, and performance capability of the SBO diesel and its associated battery had not been adversely affected by the modification.

The team verified that Exelon appropriately evaluated all changes and characteristics of the new battery including cell internals and external connections to the battery jar.

Additionally, the team reviewed the engineering analyses and supporting information within the modification package and battery capability calculations to verify that the SBO battery and SBO battery charger were appropriately sized to respond to a SBO event.

The team verified that Exelon incorporated all vendor recommendations related to battery installation, maintenance, and testing into work orders and procedures. The team reviewed pre-installation, post-installation, and recent surveillance test results to verify that battery performance was consistent with vendor specifications and design assumptions. The team also walked down the SBO battery to identify abnormal conditions and determine if the installation was consistent with vendor recommendations.

Finally, the team discussed the modification and design basis with design engineers to assess the adequacy of the modification. The 10 CFR 50.59 screening determination associated with this modification was also reviewed as described in section 1R 17.1 of this report. The documents reviewed are listed in the attachment.

b. Findings

No findings of significance were identified .

.2.10 Prevention of Spurious Operation of Reactor Building Sump Isolation Valves

a. Inspection Scope

The team reviewed a modification (ECR-TM-08-00786) that made control circuit changes to the decay heat removal pump reactor building sump isolation valves, DH-V-6A and DH-V-6B. Spurious operation of the DH-V-6A and 6B due to electrical cable damage was determined by Exelon to be a credible scenario during certain fire scenarios. For fire areas outside the main control room, the circuit modification eliminated the possibility of a fire induced hot short that would spuriously operate DH-V-6A or 6B. In addition to wiring changes, the modification included new disable/enable switches located on the main control room panels. As a result of the modification, valve operation would require operation of both the associated new switch and the normal control switch in order to open each valve. The team conducted the review to ensure that the design bases, licensing bases, and performance capability of the decay heat removal system had not been adversely affected by the modification.

The team verified that Exelon reviewed all aspects of the circuit changes and failure modes to ensure reliable control room operation of DH-V-6A and 6B for non-fire scenarios was maintained. The team also verified that the circuit changes eliminated the possibility of a hot short outside the main control room from spuriously opening the valves. The team reviewed voltage drop calculations and post-modification test results to ensure the circuits operated as designed. The team reviewed operator training records and operating procedures to ensure the operators were appropriately trained and procedures were revised to incorporate the operation of the new switch when the decay heat valves were required to be repositioned. The team observed the new disable/enable switches on the main control board and verified the labeling and human factor considerations were adequate. The team also discussed the modification with design engineers to assess the adequacy of the modification. The 10 CFR 50.59 screening determination associated with this modification was also reviewed as described in section 1R17.1 of this report. The documents reviewed are listed in the attachment.

b. Findings

No findings of significance were identified.

2.11 Main Inverter Replacements

a. Inspection Scope

The team reviewed a modification (ECR-TM-08-00281) that replaced three electrical inverters to address obsolete parts issues and nuisance transfers from the preferred 480Vac power supply to the 125Vdc battery backup. Exelon purchased the new inverters such that they would be qualified to the original specifications and maintain the same footprint for plant installation. The inverters are designed to provide a reliable and redundant source of essential power to several vital 120Vac distribution panels. The team conducted the review to ensure that the design bases, licensing bases, and performance capability of the ac power system had not been adversely affected by the modification.

The team reviewed the operating characteristics of the new and old inverters to ensure the quality of the new inverters was equal or better. The team noted that Exelon had identified that the minimum dc input voltage for the new inverters was slightly less. The team verified that Exelon appropriately evaluated the discrepancy via an engineering equivalency review. The team also reviewed the work orders that installed and tested the new inverters and ensured that all inverter test results were within specification and all installation issues had been appropriately evaluated and dispositioned. Additionally, the tea~ verified that Exelon had revised its 120Vac breaker coordination study and evaluated the potential for the new inverter electrical characteristics impact on the 120Vac power system. The team verified that operators were appropriately trained on the new inverters and the operating procedures were properly updated. The team also discussed the modification and design basis with design engineers to assess the adequacy of the modification. Finally, the team walked down the inverters to identify abnormal conditions. The 10 CFR 50.59 screening determination associated with this modification was also reviewed as described in section 1R 17.1 of this report. The documents reviewed are listed in the attachment.

b. Findings

No findings of significance were identified.

OTHER ACTIVITIES

40A2 Identification and Resolution of Problems (IP 71152)

a. Inspection Scope

The team reviewed a sample of CRs associated with 10 CFR 50.59 and plant modification issues to determine whether Exelon was appropriately identifying, characterizing, and correcting problems associated with these areas, and whether the planned or completed corrective actions were appropriate. In addition, the team reviewed CRs written on issues identified during the inspection to verify adequate problem identification and incorporation of the problem into the corrective action system.

The eRs reviewed are listed in the attachment.

b. Findings

No findings of significance were identified.

40A6 Meetings, including Exit The team presented the inspection results to Mr. Richard Libra, Plant Manager, and other members of Exelon's staff at an exit meeting on April 29, 2010. The team returned the proprietary information reviewed during the inspection to the licensee and verified that this report does not contain proprietary information.

ATTACHMENT

SUPPLEMENTAL INFORMATION

KEY POINTS OF CONTACT

Exelon Personnel

R. Libra Plant Manager

B. Carsky Engineering Director

P. Bennett Design Engineering Manager

w. McSorley Mechanical Design Engineer

R. Ezzo Manager, Electrical and I&C Design Engineering

LIST OF ITEMS

OPENED, CLOSED AND DISCUSSED

None.