IR 05000390/2007006
| ML071100271 | |
| Person / Time | |
|---|---|
| Site: | Watts Bar  |
| Issue date: | 04/20/2007 |
| From: | Cain L NRC/RGN-II/DRS/EB1 |
| To: | Swafford P Tennessee Valley Authority |
| References | |
| IR-07-006 | |
| Download: ML071100271 (31) | |
Text
ril 20, 2007
SUBJECT:
WATTS BAR NUCLEAR PLANT- NRC COMPONENT DESIGN BASIS INSPECTION REPORT 05000390/2007006
Dear Mr. Swafford:
On March 9, 2007, the U. S. Nuclear Regulatory Commission (NRC) completed an inspection at your Watts Bar Nuclear Power Plant. The enclosed inspection report documents the inspection findings which were discussed on March 9 and April 18, 2007, with Mr. M. Lorek and other members of your staff.
The inspection examined activities conducted under your license as they relate to safety and compliance with the Commissions rules and regulations and with the conditions of your license.
The inspectors reviewed selected procedures and records, observed activities, and interviewed personnel.
Based on the results of this inspection, the inspectors identified one finding of very low safety significance (Green). This finding was determined to involve a violation of NRC requirements.
However, because of the very low safety significance and because it was entered into your corrective action program, the NRC is treating the finding as a non-cited violation consistent with Section VI.A.1 of the NRCs Enforcement Policy. If you deny this non-cited violation you should provide a response within 30 days of the date of this inspection report, with the basis for your denial, to the United States Nuclear Regulatory Commission, ATTN: Document Control Desk, Washington DC 20555-0001, with copies to the Regional Administrator, Region II; the Director, Office of Enforcement, U. S. Nuclear Regulatory Commission, Washington, DC 20555-0001; and the NRC Resident Inspector at the Watts Bar Nuclear Power Plant.
TVA 2 In accordance with 10 CFR 2.390 of the NRCs 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 NRCs 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,
/RA/
Loyd M. Cain, Acting Chief Engineering Branch 1 Division of Reactor Safety Docket Nos.: 50-390 License Nos.: NPF-90 and Construction Permit No. CPPR-92
Enclosure:
NRC Inspection Report 05000390/2007006 w/Attachment: Supplemental Information
REGION II==
Docket Nos.: 50-390 License Nos.: NPF-90 Report Nos.: 05000390/2007006 Licensee: Tennessee Valley Authority Facility: Watts Bar Nuclear Plant, Unit 1 Location: Spring City, TN 37381 Dates: February 12 - March 9, 2007 Inspectors: S. Rose, Senior Reactor Inspector (Lead)
R. Berryman, Senior Reactor Inspector W. Fowler, Reactor Inspector H. Campbell, Contractor J. Leivo, Contractor Approved by: Loyd M. Cain, Acting Chief, Engineering Branch 1 Division of Reactor Safety
SUMMARY OF FINDINGS
IR05000390/2007006; 2/12/2007 - 2/16/2007, 2/26/2007 - 3/9/2007; Watts Bar Nuclear Power
Plant; Component Design Bases Inspection.
This inspection was conducted by a team of three NRC inspectors and two NRC contractors.
One green finding, non-cited violation, was identified during this inspection. The significance of most findings is indicated by their color (Green, White, Yellow, Red) using IMC 0609,
Significance Determination Process (SDP). Findings for which the SDP does not apply may be Green or be assigned a severity level after NRC management review. The NRCs program for overseeing the safe operation of commercial nuclear power reactors is described in NUREG-1649, Reactor Oversight Process, Revision 3, dated July 2000.
NRC-Identified and Self-Revealing Findings
Cornerstone: Mitigating Systems
- Green.
The team identified a violation of Technical Specification 5.7.1 associated with TVA's failure to develop a procedure that will provide tornado depressurization protection of the emergency diesel generator building. The finding involves a severe weather event (tornado) in which the Emergency Diesel Generator ventilation system would not be properly aligned to prevent inoperability of the Diesel Generators. Abnormal Operating Instruction - 8 (AOI-8) does not provide guidance on how to provide pressure equalization for mitigating atmospheric depressurization associated with tornadic conditions during weather where temperatures are below 68 degrees Fahrenheit.
This finding was more than minor because it is associated with the Mitigating Systems Cornerstone attribute of Procedure Quality. It impacted the cornerstone objective of ensuring the availability, reliability, and capability of systems that respond to initiating events. The team reviewed the finding for significance using the SDP Phase 1 worksheet for mitigating systems and determined the finding needed to be processed using the SDP Phase 3 due to the external event initiator (tornado).
The Regional Senior Reactor Analyst (SRA) performed an SDP Phase 3 for the finding. The risk of the finding was determined through a hand calculation using various estimates of the significant inputs. There was high uncertainty associated with most of the inputs. Because of this, conservative inputs were used, so the result was more of a bounding analysis than a calculation of the real risk. The dominant risk sequence involved: a tornado occurs onsite when the outside temperature is below 68 degrees, which results in a loss of offsite power; the plant staff fails to recognize and repair the loss of the ventilation system in time to prevent the loss of all the emergency diesels; the resulting loss of all Alternating Current (AC) power causes a Reactor Coolant Pump Seal Loss of Coolant Accident; and AC power is not recovered in time to prevent core damage. The result of the change in Core Damage Frequency calculation was
Green, primarily due to the low likelihood of the onsite tornado. Because of the amount of time available in the dominant sequence between the degradation in plant conditions and any potential release due to core damage, there would be time available to evacuate areas around the plant prior to any release. Because of this, there is not an increase in the significance of the finding due to Large Early Release Frequency. The finding is
- Green.
B. Licensee-identified Violations None
REPORT DETAILS
REACTOR SAFETY
Cornerstones: Mitigating Systems and Barrier Integrity
1R21 Component Design Bases Inspection
.1 Inspection Sample Selection Process
The team selected risk significant components and operator actions for review using information contained in the licensees Probabilistic Risk Assessment (PRA). In general, this included components and operator actions that had a risk achievement worth factor greater than two or Birnbaum value greater than 1 X10E-6. The components selected were located within the emergency raw water cooling (ERCW)system, coolant charging system (CCS), emergency diesel generator (EDG) ventilation, battery, and generator subsystems, and shutdown board (SBDB) ventilation. The sample selection included 19 components, five operator actions, and six operating experience items. Additionally, the team reviewed two modifications by performing activities identified in IP 71111.17, Permanent Plant Modifications, Section 02.02.a.
and IP 71111.02, Evaluations of Changes, Tests, or Experiments.
The team performed a margin assessment and detailed review of the selected risk-significant components to verify that the design bases have been correctly implemented and maintained. This design margin assessment considered original design issues, margin reductions due to modification, or margin reductions identified as a result of material condition issues. Equipment reliability issues were also considered in the selection of components for detailed review. These included items such as failed performance test results, significant corrective action, repeated maintenance, maintenance rule (a)1 status, Regulatory Issue Summary 05-020 (formerly Generic Letter 91-18) conditions, NRC resident inspector input of problem equipment, system health reports, industry operating experience and licensee problem equipment lists.
Consideration was also given to the uniqueness and complexity of the design, operating experience, and the available defense in depth margins. An overall summary of the reviews performed and the specific inspection findings identified are included in the following sections of the report.
.2 Results of Detailed Reviews
.2.1 Emergency Raw Cooling Water (ERCW) Pumps
a. Inspection Scope
The team reviewed the design basis documentation, including portions of the Updated Final Safety Analysis Report (UFSAR), Technical Specifications, System Description and station drawings to determine the design requirements for the ERCW pumps. The team reviewed ERCW system hydraulic and deep well shaft/column thermal expansion calculations, problem event reports (PERs) and industry operating experience notices.
Further the team reviewed completed surveillances, work orders and preventative maintenance (PMs) for the past several years to assess overall pump operability. In addition, the team walked down portions of the ERCW system to verify that the installed configuration was consistent with design base information and visually inspected the material condition of the pumps, motors and associated piping.
b. Findings
No findings of significance were identified.
.2.2 ERCW Flow Control Valve to Residual Heat Removal (RHR) Pump Room Cooler
a. Inspection Scope
The team reviewed the valve specifications, and those portions of the ventilation system wiring diagrams and ERCW electrical logic diagrams which described the original and current design function of this flow control valve. It was learned that the valve controls had been electrically disconnected at the Motor Control Center due to potential Appendix R interactions. Discussions with licensee probabilistic safety assessment personnel focused on the impact of the valves potential failure on core damage frequency (CDF), primarily the concern for valve internal failure via dropped disc or blockage. This led to a review of monthly surveillances performed to ensure a flow path for adequate ERCW coolant to the RHR pump room coolers.
b. Findings
No findings of significance were identified.
.2.3 Centrifugal Charging Pumps (CCPs)
a. Inspection Scope
The CCPs have major Emergency Core Cooling System (ECCS) and charging/RCP-seal-injection functions, both which contribute significantly to the station CDF. The team reviewed the design basis documentation, including portions of the UFSAR, Technical Specifications, System Descriptions and station drawings to determine the design requirements for the CCPs. Completed surveillances, at both quarterly and 18 month frequencies, work orders and PMs for the past several years for the pumps were reviewed to assess overall pump condition and operability. Discussions with the system and design engineers provided further information on pump performance and requirements. Finally, calculations addressing net positive suction head and vortex concerns were reviewed.
b. Findings
No findings of significance were identified.
.2.4 Chemical Volume and Charging System (CVCS) Charging Header Flow/Pressurizer
Level Control Valve
a. Inspection Scope
The team reviewed design documentation as provided in the UFSAR and system descriptions, including valve specifications, P&IDs and electrical control diagrams.
Further, the team discussed operating history and maintenance with the CVCS system engineer. Finally, the team performed a review of the three most recent performances of the 18 Month Channel Calibration of Charging Header Flow Loop which addressed the control circuitry and operability of this valve.
b. Findings
No findings of significance were identified.
.2.5 Shutdown Board (SDBD) Air Handling Units (AHUs) Fans
a. Inspection Scope
The team reviewed the design requirements of the SDBD AHUs including portions of the UFSAR, Technical Specifications, flow diagrams, and electrical & control schematics.
Heat load calculations and associated AHU flow requirements were reviewed in addition to the flow balance tests and associated test deficiencies and resolutions. Discussions with the system and design engineers were performed. The team performed walkdowns of the fans and motors to assess the systems overall operability and condition.
b. Findings
No findings of significance were identified.
.2.6 SDBD Room Chiller Units
a. Inspection Scope
The team reviewed the design requirements of the SDBD room chillers including portions of the UFSAR, Technical Specifications, flow diagrams, and electrical & control schematics. Calculations evaluating heat loads during normal and accident conditions in the 480 V and 6.9 KV SDBD rooms were also reviewed.
Surveillances of the chiller pumps, associated instrumentation, and PERs addressing chiller trips were discussed with the system engineer. Walkdowns of the chillers, pumps and related piping was conducted to ensure conformance with design requirements and to assess the current condition of the system.
b. Findings
No findings of significance were identified.
.2.7 Emergency Diesel Generator (EDG) Building Ventilation Dampers
a. Inspection Scope
The team reviewed the UFSAR, system description, Abnormal Operating Instructions (AOI's), surveillance procedures, control logic, operator actions and calculations to verify the diesel building intake and Electrical Board Room (EBR) ventilation dampers can perform their safety functions of providing cooling to components in the diesel generator building. Automatic controls were compared with operator actions that may be required during certain conditions to determine their feasibility and the ability to detect inadequate ventilation conditions.
System walkdowns were performed to verify appropriate missile protection was in place, damper physical condition and linkages could operate as designed, effectiveness of identifying ineffective ventilating conditions and that debris accumulation in ductwork has not adversely affected ventilation flow paths.
b. Findings
Introduction.
The team identified a finding of very low safety significance involving a violation of Technical Specification 5.7.1 associated with TVA's failure to develop a procedure that will provide tornado depressurization protection of the emergency diesel generator building. AOI-8 does not provide guidance on how to provide pressure equalization for mitigating atmospheric depressurization associated with tornadic conditions during weather where temperatures are below 68 degrees Fahrenheit. The significance of this violation was determined using Phase III of the Significance Determination Process (SDP).
Description.
The diesel generator building (DGB) ventilation system at Watts Bar incorporates a once through cooling method where intake and exhaust dampers are interlocked with the ventilation fans. Upon fan startup both the intake and exhaust dampers receive their individual signals to open and building ventilation will occur by means of a once through cooling method. The only exception to this is if the diesel generator starts. This will then allow the intake damper to receive a signal to open, but if the exhaust room temperatures do not exceed the ventilation fan startup set point building ventilation will not occur, due to the exhaust damper being interlocked with the fan.
The UFSAR Section 9.4-33 states that both the DGB ventilation intake and exhaust dampers must be in the open position to mitigate atmospheric depressurization during a tornado. AOI-8 provides procedural guidance during a tornado watch and warning for an auxiliary operator to verify that both the intake and exhaust dampers are in the open position. If the dampers are observed to be in the closed position then the ventilation exhaust fans are to be started to provide the needed logic for the dampers to open.
Control switches for the exhaust fans are spring return to auto. In the event that exhaust room air temperature is either initially below the fan shutoff set point of 68 degrees Fahrenheit or in the event room temperatures fall below this during a tornado the ventilation fans will shutoff. Subsequently, both the intake and exhaust dampers will either fail to open or go closed, as the opening logic will no longer be satisfied. This will result in the inability to mitigate atmospheric depressurization of the DGB associated with a tornado. This represents a potential common-cause failure of all four emergency diesel generator ventilation systems and subsequent inoperability of the EDG.
Analysis.
TVA's failure to develop a procedure that will provide tornado depressurization protection of the DGB during temperatures below 68 degrees Fahrenheit is a performance deficiency associated with the Mitigating Systems Cornerstone. Traditional enforcement does not apply because an event did not occur that resulted in an actual safety consequence, the failure to have an adequate procedure did not impact the NRC's regulatory function, and was not the result of a willful violation of NRC requirements or TVA procedures. The finding is greater than minor because it is associated with the Mitigating Systems Cornerstone attribute Procedure Quality for AOIs. It impacts the cornerstones objective of ensuring the availability, reliability, and operability of the emergency diesel generators to perform their safety function during an initiating event, such as, a loss of offsite power. The finding involved the unavailability of a design feature described in the UFSAR that would ensure tornado depressurization mitigation during atmospheric temperatures below 68 degrees Fahrenheit.
The Regional SRA performed an SDP Phase 3 for the finding. The risk of the finding was determined through a hand calculation using various estimates of the significant inputs. There was high uncertainty associated with most of the inputs. Because of this, conservative inputs were used, so the result was more of a bounding analysis than a calculation of the real risk. The dominant risk sequence involved: a tornado occurs onsite when the outside temperature is below 68 degrees Fahrenheit, which results in a loss of offsite power; the plant staff fails to recognize and repair the loss of the ventilation system in time to prevent the loss of all the emergency diesels; the resulting loss of all Alternating Current (AC) causes a Reactor Coolant Pump Seal Loss of Coolant Accident; and AC power is not recovered in time to prevent core damage. The result of the change in Core Damage Frequency calculation was Green, primarily due to the low likelihood of the onsite tornado. Because of the amount of time available in the dominant sequence between the degradation in plant conditions and any potential release due to core damage, there would be time available to evacuate areas around the plant prior to any release. Because of this, there is not an increase in the significance of the finding due to Large Early Release Frequency. The finding is of very low safety significance (Green).
Enforcement.
Technical Specification 5.7.1, "Procedures", requires in part that written procedures be established, implemented and maintained per Regulatory Guide (RG)1.33, Rev. 2, Quality Assurance Program Requirements. Appendix A of RG 1.33 states that procedures for combating emergencies and other significant events, such as tornados, shall be covered by written procedures. Contrary to the above, TVA did not develop procedures for mitigating tornado depressurization during temperatures below 68 degrees Fahrenheit. This finding was entered into Watts Bar's Corrective Action Program under PER 120005 and interim actions have been taken to ensure the ability to operate the ventilation exhaust fans at temperature below 68 degrees Fahrenheit until a permanent modification can be implemented. Because the finding is of very low safety significance (Green) and entered into the licensees corrective action program, this violation is being treated as a non-cited violation (NCV) consistent with section VI.A.1 of the NRC Enforcement Policy: NCV 05000390/2007006-01, Violation of Technical Specification 5.7.1 for TVAs failure to develop a procedure that will provide tornado depressurization protection of the DGB.
.2.8 Emergency Diesel Generator Building Generator and Electrical Panel Ventilation Fan
a. Inspection Scope
The team reviewed the UFSAR, system description, Heating Ventilation Air Conditioning (HVAC) duct flow balances and calculations to verify the generator and electrical panel ventilation fans are designed appropriately, such that, they are able to provide sufficient air-flow during elevated temperature conditions to prevent exceeding equipment design temperatures. Fan motor sizing and vane angle position design calculations were reviewed to verify they are adequate for the installed configuration. Also, control logic was reviewed to verify that adequate air supply would be provided for various ambient air temperatures.
System walkdowns were performed to identify any potential bypass flow paths, ductwork condition, debris accumulation and any additional heat loads, which were not taken into account in ventilation analyses.
b. Findings
No findings of significance were identified.
.2.9 CCP 1B-B Room Cooler Fan
a. Inspection Scope
The team reviewed the UFSAR, system description, heat load calculations, surveillance and maintenance procedures to verify the room cooler fan can provide adequate airflow to maintain room temperatures below design basis temperatures during accident conditions. Flow rates and temperatures used in the auxiliary building heat load nodal analysis were reviewed to identify any discrepancies with the installed configurations capabilities. Periodic maintenance and surveillances for the room cooler fan were reviewed to verify they are capable of identify degrading conditions.
Systems walkdowns were performed to identify any degrading airflow paths, dissimilar metal flanges, appropriate valve line-ups, and to verify monitored ERCW flow rates are above the design basis rate at which the fan can sustain the room temperature below the design limits during accident conditions.
b. Findings
No findings of significance were identified.
.2.10 ERCW Piping
a. Inspection Scope
The team reviewed the UFSAR, system description, modification packages, system layout drawings, chemistry procedures, wall-thickness monitoring procedures, and PERs to verify the ERCW system will be capable of performing its safety-related functions for providing cooling water to the diesel generators, CCP room coolers and performing the safety-related water supply for the Auxiliary Feedwater system (AFW). Microbiological Induced Corrosion (MIC) monitoring programs were reviewed to verify degradations are being identified and corrected. Licensee discussions were conducted to review the selection criteria of wall-thickness locations and the susceptibility of yard piping to both internal and external corrosion.
System walkdowns were performed to verify "A" and "B" ERCW train valve line-ups were correct within the DGB for both the north and south diesels and that indications were consistent on both local controls and EBR breaker panels. Walkdowns were performed on the "A" and "B" ERCW discharge headers to verify the adequacy of float valve installations used to vent header air entrainment and that appropriate equipment was in place to ensure discharge header level was above procedural limits. The walkdowns were performed to ensure that the "B" AFW suction line does not contain air pockets which would prevent the AFW system from performing its design basis function. The ERCW intake structure was inspected for environmental impacts on the ERCW pumps and motors.
b. Findings
No findings of significance were identified.
.2.11 ECCS Discharge Relief Valves
a. Inspection Scope
The team reviewed the UFSAR, valve bench testing procedures, and applicable American Society of Mechanical Engineers (ASME) code requirements to verify that relief valve springs are sized according to specifications during maintenance activities.
Also, the team reviewed functional evaluations associated with inadvertent relief valve lifts and their impact on the safety injection systems ability to provide sufficient flow in the event they do not reseat.
The team observed licensee demonstrations of the relief valve bench testing stand and verified personnel follow procedural guidance on action related to valves that do not meet their acceptance criteria.
b. Findings
No findings of significance were identified.
.2.12 Current Limiting Bypass Breaker
a. Inspection Scope
The team reviewed the design and testing of the current limiting reactor bypass breaker control circuits to confirm that design basis functional requirements for the control logic were satisfied, and to assess the potential for single failure vulnerabilities and undetected failures. The team also visually inspected external portions of the 480 VAC switchgear for visible material condition and potential vulnerability to hazards or interactions; reviewed the corrective action history for the breakers; and reviewed the results of the most recent preventive maintenance activities for all of the 480 VAC current limiting reactor bypass breakers.
b. Findings
No findings of significance were identified.
.2.13 Generator for the Emergency Diesel Generating Unit
a. Inspection Scope
The team reviewed the EDG 1A-A loading analysis for a design basis event comprised of a loss of coolant accident, together with a loss of offsite power (LOOP). For selected loads (centrifugal charging pumps, ERCW pumps, component cooling system (CCS)pumps, and containment spray pumps), the team reviewed design input documents, including calculations that determined brake horsepower values, to confirm that worst-case operating modes under accident conditions had been assumed. In addition, the team reviewed recent health reports and corrective action history for the diesel generator, as well as pre-operational loading tests and periodic surveillance tests used in determining the transient loading capability of the EDG.
b. Findings
No findings of significance were identified.
.2.14 Relays Supporting Closure of EDG Output Breaker to 6.9 kV Buses
a. Inspection Scope
The team reviewed the design and testing of the EDG breaker control circuits to confirm that design basis functional requirements for the control logic were satisfied, and to assess the potential for single failure vulnerabilities and undetected failures. This included review of permissive circuits, setpoints, and devices for engine speed and output voltage, as well as associated margins established for instrument uncertainty. In addition, the team visually inspected external portions of the 6900 VAC switchgear for visible material condition and potential vulnerability to hazards or interactions; reviewed the corrective action history for the breakers and control devices; and reviewed the results of the most recent preventive maintenance activities for all of the EDG breakers, which included inspection, testing, and overhaul.
b. Findings
No findings of significance were identified.
.2.15 120 Vac Vital Inverters
a. Inspection Scope
The team reviewed the overall vital instrument bus configuration and inverter loading calculations, as well as the scope, design criteria, technical evaluation, selected electrical interfaces, and the 10 CFR 50.59 screening for design change notice (DCN)51370A, which had replaced the original equipment inverters. In addition, the team visually inspected external portions of the inverters for visible material condition and potential vulnerability to hazards or interactions; and reviewed the health reports and corrective action history for the inverters.
b. Findings
No findings of significance were identified.
.2.16 Degraded Voltage Protection
a. Inspection Scope
The team selectively reviewed the degraded voltage protection schematics, as well as the calculations that determined the basis for trip and reset setpoints, and associated instrument uncertainties. The team also reviewed the licensees load flow / voltage drop calculations to determine voltage at selected load terminals under design basis degraded voltage conditions. Selected loads included the containment hydrogen igniters, centrifugal charging pumps, ERCW pumps, component cooling pumps, and containment spray pumps. In addition, the team visually inspected external portions of the degraded voltage relays for visible material condition and potential vulnerability to hazards or interactions; and reviewed the testing and corrective action history for the degraded voltage relay circuits and devices.
b. Findings
No findings of significance were identified.
.2.17 Battery for the Emergency Diesel Generating Unit
a. Inspection Scope
The team reviewed the basis for the EDG battery load profile, battery sizing calculations, and voltage drop calculations for selected EDG devices. The team also reviewed the procedures and most recent results for battery surveillances as well as the most recent service and performance test results (the licensee recently replaced all of the cells) and the ground detection instrumentation and ground management procedures. The team reviewed the licensees history of Direct Current (DC) grounds for the past three years.
In addition, the team performed a visual inspection of the batteries, cells, and connections with respect to material condition, as-found configuration, and vulnerability to potential hazards.
b. Findings
No findings of significance were identified.
.2.18 Reactor Coolant Pump (RCP) Thermal Barrier Cooling Water Return Flow
a. Inspection Scope
Flow rates in the RCP thermal barrier cooling water supply and return lines are compared, so as to detect a mismatch in flow, which could be indicative of in-leakage to the CCS. The team reviewed the instrument uncertainty and basis for the setpoints and the instrument loops that are designed to alarm and close the thermal barrier cooling water supply and return isolation motor operated valves (MOVs) if a thermal barrier leak was detected. The team also reviewed the loop and schematic diagrams for the isolation MOVs to confirm that design basis functional requirements were satisfied, and that design basis single failure and independence criteria for redundant containment isolation would not be compromised. This included a review of the thermal overload (TOL) heater size and TOL bypass circuit testing for the associated MOVs, to confirm that premature trips would be precluded without unduly compromising motor protection.
The team also visually inspected the flow transmitter installations that were readily accessible, to assess the upstream / downstream process piping and instrument impulse line configuration (i.e. instrument material condition, line slope, and potential for differential heating). In addition, the team reviewed a sample of calibration / test procedures and results for these instrument loops, and assessed the corrective action history.
b. Findings
No findings of significance were identified.
.2.19 Motors and Control Circuits for ERCW, CCP, and Fans
a. Inspection Scope
For these loads, the team reviewed the adequacy of motor terminal voltage under degraded voltage conditions. The team also reviewed the design and testability of the breaker control circuits to confirm that functional requirements for the design basis control logic were satisfied, and to assess the potential for single failure vulnerabilities and undetected failures. In addition, the team reviewed calculations that established the basis for protective trip settings and tolerances, to confirm that premature trips would be precluded without unduly compromising motor and feeder protection.
In conjunction with an assessment of the licensees disposition of NRC IN 2002-12, Submerged Safety-Related Cable (listed in Section 1R21.4a of this report), for selected ERCW pump motor feeder cables, the team reviewed a sample of insulation resistance test results and manhole inspections associated with underground cable with potential for submergence. The underground cables connecting the EDGs to the associated 6900 VAC switchgear buses were also included in this sample.
b. Findings
No findings of significance were identified.
.3 Review of Low Margin Operator Actions
a. Inspection Scope
The team performed a margin assessment and detailed review of five risk significant and time critical operator actions. Where possible, margins were determined by the review of the assumed design basis and UFSAR response times and performance times documented by job performance measures (JPMs). For the selected components and operator actions, the team performed an assessment of the Emergency Operating Instructions (EOIs), AOIs, Alarm Response Instructions (ARIs), and other operations procedures to determine the adequacy of the procedures and availability of equipment required to complete the actions. Operator actions were observed on the plant simulator and during plant walkdowns.
The following operator actions were observed on the licensees operator training simulator:
- Operation of the containment hydrogen igniters: E-1, Loss of Reactor or Secondary Coolant
- Actions to reestablish CCS flow to RCP thermal barriers after phase-B containment isolation signal: ARI-125-B, Containment Hi-Hi Pressure Spray Actuate
- Loss of ERCW: AOI-13 Loss of Essential Raw Cooling Water
- Operation of TDAFW pump and establishing flow after station blackout: ECA 0.0, Loss of Shutdown Power, AOI-40, Station Blackout, and SOI-3.02, Auxiliary Feedwater System Additionally, the inspectors walked down, table-topped and investigated the following operational scenarios:
- Manual actions to install spool pieces to supply CCS from ERCW during flooding event: MI-17.021, Installation of Spool Pieces Between ERCW System and Component Cooling System
- Local Operation of TDAFW Pump without electric instrumentation: SOI-3.02, Auxiliary Feedwater System
b. Findings
No findings of significance were identified.
.4 Review of Industry Operating Experience
a. Inspection Scope
The team reviewed selected operating experience issues that had occurred at domestic and foreign nuclear facilities for applicability at the Watts Bar Nuclear Plant.
The team performed an independent applicability review, issues that were identified as applicable to the Watts Bar Nuclear Power Plant were selected for a detailed review.
The issues that received a detailed review by the team included:
- NRC Event Notification 42844 "Improper Valve Springs in Pressure Relief Valves"
- NRC Information Notice (IN) 94-45, Potential Common Mode Failure Mechanisms for Large Vertical Pumps
- NRC IN 2002-12, Submerged Safety-Related Cable.
- NRC IN 2006-07, Recent Operating Experience of Service Water Systems due to External Conditions
- NRC Generic Letter 89-13, Service Water Problems Affecting Safety Related Equipment
b. Findings
No findings of significance were identified.
.5 Review of Permanent Plant Modifications
a. Inspection Scope
The team reviewed two modifications related to the selected risk significant components in detail to verify that the design bases, licensing bases, and performance capability of the components have not been degraded through modifications. The adequacy of design and post modification testing of these modifications was reviewed by performing activities identified in IP 71111.17, Permanent Plant Modifications, Section 02.02.a. Additionally, the team reviewed the modifications in accordance IP 71111.02, Evaluations of Changes, Tests, or Experiments, to verify the licensee had appropriately evaluated them for 10 CFR 50.59 applicability. The following modifications were reviewed:
& "B"
- DCN-52179, Shutdown Board Room A and B Air Handling Unit A-A Motor Replacement and Circuit Protective Devices Settings Changes, Rev. A
b. Findings
No findings of significance were identified.
OTHER ACTIVITIES
4AO6 Meetings, Including Exit
Exit Meeting Summary
On March 9, 2007, the team presented the inspection results to Mr. M. Lorek, Plant Manager, and other members of the licensee staff. The team returned all proprietary information examined to the licensee. No proprietary information is documented in the report.
On April 18, 2007, a telephone exit was conducted to present the results of the SDP Phase 3 for the DGB ventilation finding (Section 1R21.2.7) to Mr. M. Lorek and other members of the licensee staff.
SUPPLEMENTAL INFORMATION
KEY POINTS OF CONTACT
Licensee
- M. Lorek, Plant Manager
- W. Justice, General Manager TVAN Engineering
- T. Carter, Manager, Engineering Design
- B. Thomas, Site Licensing
- J. Smith, Site Licensing and Incident Response Manager
- C. Borrelli, PSA Specialist
NRC
- J. Bartley, Senior Resident Inspector, Watts Bar Nuclear Plant
- C. Ogle, RII, Engineering Branch 1, Chief
ITEMS OPENED, CLOSED, AND DISCUSSED
Open/Closed
- 05000390/2007006-01 NCV Violation of Technical Specification 5.7.1 for TVAs failure to develop a procedure that will provide tornado depressurization protection of the DGB. (Section 1R21.2.7)