IR 05000390/2015007
| ML15070A535 | |
| Person / Time | |
|---|---|
| Site: | Watts Bar  |
| Issue date: | 03/11/2015 |
| From: | Bartley J NRC/RGN-II/DRS/EB1 |
| To: | James Shea Tennessee Valley Authority |
| References | |
| IR 2015007 | |
| Download: ML15070A535 (16) | |
Text
March 11, 2015
SUBJECT:
WATTS BAR NUCLEAR PLANT - U.S. NUCLEAR REGULATORY COMMISSION COMPONENT DESIGN BASES INSPECTION REPORT 05000390/2015007
Dear Mr. Shea:
On February 04, 2015, the U.S. Nuclear Regulatory Commission (NRC) completed an inspection at your Watts Bar Nuclear Plant. On March 4, 2015, the results of the inspection were discussed with Mr. Walsh and other members of your staff. Inspectors documented the results of this inspection in the enclosed inspection report.
This inspection was conducted to perform a focused review of selected systems whose design margins would be affected by Unit 2 startup. The inspection constituted a partial completion of Inspection Procedure 71111.21, Component Design Basis Inspection. As such, the scope of the Component Design Basis Inspection scheduled for 2016 will be reduced.
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, and interviewed personnel.
NRC inspectors documented two findings of very low safety significance (Green) in this report.
These findings involved violations of NRC requirements. The NRC is treating these violations as non-cited violations (NCVs) consistent with Section 2.3.2.a of the NRC Enforcement Policy.
If you contest the violations or significance of these NCVs, you should provide a response within 30 days of the date of this inspection report, with the basis for your denial, to the U.S. 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 Plant.
Additionally, if you disagree with a cross-cutting aspect assignment or a finding not associated with a regulatory requirement in this report, you should provide a response within 30 days of the date of this inspection report, with the basis for your disagreement, to the Regional Administrator, Region II, and the NRC Resident Inspector at the Watts Bar Nuclear Plant, Unit 1. In accordance with Title 10 of the Code of Federal Regulations (10CFR) 2.390, Public Inspections, Exemptions, Requests for Withholding, 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 NRC's Agencywide Document Access and Management 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/
Jonathan Bartley, Chief
Engineering Branch 1
Division of Reactor Safety
Docket Nos: 50-390 License Nos: NPF-90
Enclosure:
Inspection Report 05000390/2015007 w/ Attachment: Supplementary Information
REGION II==
Docket No.:
50-390
License No.:
Report No.:
Licensee:
Tennessee Valley Authority (TVA)
Facility:
Watts Bar Nuclear Plant, Unit 1
Location:
Spring City, TN 37381
Dates:
December 15, 2014 - February 4, 2015
Inspectors:
J. Eargle, Senior Reactor Inspector (Lead)
R. Bernhard, Senior Reactor Analyst
M. Yeminy, Contractor (Mechanical)
Approved by:
Jonathan Bartley, Chief Engineering Branch 1 Division of Reactor Safety
SUMMARY
IR 05000390/2015007; 12/15/2014 - 2/4/2015 Watts Bar, Unit 1; Component Design Bases
Inspection.
A team of two Nuclear Regulatory Commission (NRC) inspectors from Region II, and one NRC contract personnel conducted this inspection. Two Green non-cited violations (NCVs) were identified. The significance of inspection findings is indicated by their color (Green, White,
Yellow, Red) using the NRC Inspection Manual Chapter (IMC) 0609, Significance Determination Process, dated June 2, 2011. All violations of NRC requirements are dispositioned in accordance with the NRCs Enforcement Policy, dated January 28, 2013. The NRC's program for overseeing the safe operation of commercial nuclear power reactors is described in NUREG-1649, Reactor Oversight Process, Revision 5, dated February 201
NRC-Identified and Self-Revealing Findings
Cornerstone: Mitigating Systems
- Green.
The NRC identified a Green non-cited violation of 10 CFR Part 50, Appendix B,
Criterion III, Design Control, for the licensees failure to perform an adequate test to verify that anticipated water hammer forces would not exceed design limitations at high points in the essential raw cooling water piping associated with the upper containment coolers (UCC).
This issue was entered into the licensees corrective action program as problem evaluation report 981278 and an operability determination was performed that provided reasonable assurance of operability while corrective actions are being evaluated.
The licensees failure to perform an adequate test to verify that anticipated water hammer forces would not exceed design limitations at high points in the essential raw cooling water piping associated with the UCCs was determined to be a performance deficiency. The team determined that the performance deficiency was more than minor because it affected the cornerstone objective of ensuring the availability, reliability, and capability of systems that respond to initiating events to prevent undesirable consequences. The team determined the finding to be of very low safety significance (Green) because the finding was a deficiency affecting the design or qualification of a mitigating structure, system, or component (SSC), and the SSC maintained its operability. The team determined that no cross-cutting aspect was applicable because the finding was not indicative of current licensee performance. (Section 1R21.2.b.1)
- Green.
The NRC identified a Green non-cited violation of 10 CFR Part 50, Appendix B,
Criterion XVI, Corrective Action, for the licensees failure to promptly identify a condition adverse to quality. Specifically, following post cleaning tests of the A and C component cooling system (CCS) heat exchangers (HX), a negative fouling factor was recorded to meet the fouling factor acceptance criteria without being entered into the licensees CAP to determine if the data was credible and representative of the HX performance. The violation was entered into the licensees corrective action program as problem evaluation report 969404 and an operability determination was performed that provided reasonable assurance of operability while corrective actions are being evaluated.
The licensees failure to promptly identify the negative fouling factor as a condition adverse to quality was a performance deficiency. The team determined that the performance deficiency was more than minor, because if left uncorrected, it had the potential to lead to a more significant safety concern. Specifically, if the licensee fails to evaluate abnormal fouling factor test results then the potential exists for parameter uncertainties to go undetected and potentially result in test results that are not representative of adequate HX performance. The team determined the finding to be of very low safety significance (Green)because the finding was not a design deficiency, did not represent a loss of system and/or function, and did not represent the loss of any trains of Technical Specification or Non-Technical Specification equipment. The finding has a cross cutting aspect in the Conservative Bias component of the Human Performance area as defined in NRC IMC 0310, because the licensee failed to use decision-making practices that emphasize prudent choices over those that are simply allowable. Specifically, the licensee failed to recognize that a negative fouling factor while less than the test acceptance criteria, did not represent an expected test result [H.14]. (Section 1R21.2.b.2)
REPORT DETAILS
REACTOR SAFETY
Cornerstones: Initiating Events, Mitigating Systems, Barrier Integrity
1R21 Component Design Bases Inspection
.1 Inspection Objective
To gain reasonable assurance that risk significant structures, systems, and components can adequately perform their design basis function. This includes reasonable assurance that the risk significant component can fulfill their design basis function during or after licensees activities (e.g., maintenance, surveillance) which can affect components availability, reliability and capability. Additionally, this includes that reasonable assurance that risk significant issues resulting from the generic communications have been adequately addressed.
.2 Component Reviews
a. Inspection Scope
Components
- Component Cooling System Pumps
- Component Cooling System Heat Exchangers
- Essential Raw Cooling Water Pumps
For the 3 components listed above, the team performed the following reviews:
- Reviewed system pressure drop calculations to verify that design flow rates will be met for safety related users of essential raw cooling water (ERCW) and component cooling system (CCS), and to assure that design and licensing bases had been appropriately translated into these documents.
- Reviewed the heat removal capacity of the CCS heat exchangers to validate their capability to remove the required heat load for various modes of operations.
- Reviewed plant procedures to confirm that proper operator actions are assumed in design calculations and analyses.
- Reviewed design drawings to validate that design calculations and analysis used the proper system configurations.
- Reviewed computer programs used for analysis of safety related components to validate that their use resulted in conservative output.
- Reviewed test procedures and recent test results against the system descriptions and the safety analyses to verify that acceptance criteria for tested parameters were supported by calculations or other engineering documents, and that individual tests and analyses served to validate component operation under the most challenging plant conditions. This included pre-operational fluid transient testing of the ERCW system piping associated with the upper containment coolers.
- Reviewed system modifications, vendor documentation as well as preventive and corrective maintenance history and corrective action program documents to verify that the performance capabilities of the affected components were not negatively impacted, and that potential degradations were monitored or prevented.
- Walkdowns were conducted (where plant conditions permitted), to verify that the installed components and their design configurations would support their design and licensing bases functions under the most challenging plant conditions and had been maintained in a condition at least as adequate as assumed in design documents.
b. Findings
b.1 Failure To Perform An Adequate Water Hammer Test
Introduction:
The NRC identified a Green non-cited violation (NCV) of 10 CFR Part 50, Appendix B, Criterion III, Design Control, for the licensees failure to perform an adequate test to verify that anticipated water hammer forces would not exceed design limitations at high points in the essential raw cooling water (ERCW) piping associated with the upper containment coolers (UCCs).
Description:
In 1988, prior to initial operation of Watts Bar Unit 1, calculation B26880719066, WBN Fluid Transient Event Identification For Essential Raw Cooling Water System (67), was completed to identify fluid transients which could cause significant loads on piping, components, and associated supports. One of the transients identified was that during a LOOP the ERCW pumps would trip and column separation was possible at high points in the ERCW piping associated with the UCCs. The water columns may subsequently rejoin when the ERCW pumps are restarted and develop severe water hammer impact forces.
To resolve the issue, the licensee chose to test and measure the pressure in the piping to confirm that it was below design pressure. The calculation recommended a test plan of tripping both ERCW pumps simultaneously and restart them after 25 seconds.
Additionally, it recommended that pressure readings be taken in various locations including the top piping elevation upstream of the check valve. In 1995, the licensee performed a test to verify that the pressures due to the transient did not exceed the design pressure of 160 psi. The test did not involve stopping the pumps, but instead the licensee closed a 4 gate valve to the A train UCCs, waited 20 seconds, and had an individual rapidly open the valve. Additionally, the test did not locate a pressure transmitter at the top of the pipe, but instead located it approximately 75 feet lower. This test resulted in measurement of 107 psi which satisfied the acceptance criteria of <160 psi.
The inspectors determined that the use of a gate valve was not adequate to simulate the stopping and starting of the ERCW pumps. Additionally the inspectors determined that the test was not adequate to simulate the timing of the system, because the EDG acceptance criteria is 10 seconds, and the ERCW pumps will not sequence on until 20 seconds later. This would allow an additional 10 seconds of column separation over what the test specified. The inspectors concluded that the test did not verify that a water hammer due to column separation would not exceed design pressures and result in damage to the system. This issue was entered into the licensees corrective action program (CAP) as problem evaluation report (PER) 981278 and an operability determination was performed that provided reasonable assurance of operability while corrective actions are being evaluated.
Analysis:
The licensees failure to perform an adequate test to verify that anticipated water hammer forces would not exceed design limitations at high points in the ERCW piping associated with the UCCs was determined to be a performance deficiency. The team determined that the performance deficiency was more than minor because it was associated with the Design Control attribute of the Mitigating Systems Cornerstone and affected the cornerstone objective of ensuring the availability, reliability, and capability of systems that respond to initiating events to prevent undesirable consequences.
Specifically, the licensee did not appropriately verify the adequacy of the system design with respect to water hammer, which could challenge the ERCW system integrity. The team used IMC 0609, Att. 4, Initial Characterization of Findings, issued June 19, 2012, for Mitigating Systems, and IMC 0609, App. A, The Significance Determination Process (SDP) for Findings At-Power, issued June 19, 2012, and determined the finding to be of very low safety significance (Green) because the finding was a deficiency affecting the design or qualification of a mitigating SSC, and the SSC maintained its operability. The team determined that no cross-cutting aspect was applicable because the finding was not indicative of current licensee performance.
Enforcement:
Title 10 CFR Part 50, Appendix B, Criterion III, Design Control, required, in part, that design control measures shall provide for verifying or checking the adequacy of design, such as by the performance of design reviews, by the use of alternate or simplified calculational methods, or by the performance of a suitable testing program.
Contrary to the above, since June 24, 1995, the licensee failed to appropriately verify or check the adequacy of design of the ERCW system. Specifically, the licensee failed to perform an adequate test to verify that anticipated water hammer forces would not exceed design limitations at high points in the ERCW piping associated with the UCCs.
This violation is being treated as an NCV consistent with section 2.3.2 of the NRC Enforcement Policy. The violation was entered into the licensees CAP as PER 981278 and an operability determination was performed that provided reasonable assurance of operability while corrective actions are being evaluated. This violation is identified as NCV 05000390/2015007-01, Failure To Perform An Adequate Water Hammer Test.
b.2 Failure To Identify A Condition Adverse To Quality For Negative Fouling Factors
Introduction:
The NRC identified a Green NCV of 10 CFR Part 50, Appendix B, Criterion XVI, Corrective Action, for the licensees failure to promptly identify a condition adverse to quality. Specifically, following post cleaning tests of the A and C CCS heat exchangers HX, a negative fouling factor was recorded to meet the fouling factor acceptance criteria and it was not entered into the licensees CAP to determine if the data was credible and representative of the HX performance.
Description:
The CCS provided safety-related functions of removing heat from the residual heat removal HXs and other potentially or normally radioactive fluids. This is accomplished through the use of a closed loop system in which the CCS removes heat from various component coolers and transfers it to the CCS HXs where the heat is rejected to the ERCW. Technical Instruction (TI) 1-TI-79.701 Component Cooling Heat Exchanger A Performance Test, Revision 0, and 1-TI-79.703 Component Cooling Heat Exchanger C Performance Test, Revision 0, verifies the heat removal capacity of the A and C CCS HXs respectively. These TIs were part of the licensees Generic Letter 89-13 HX Test Program. These TIs are performed at least every other refueling cycle and include steps to test the heat exchangers prior to cleaning the HXs, and again following the completion of the cleaning of the HXs. The acceptance criterion for both the pre and post cleaning tests was a fouling factor that does not exceed
.002 4347 HR-FT²-F/BTU.
The team noted that a negative fouling factor of -.0010200 HR-FT²-F/BTU was calculated and recorded after performing the TI on March 23, 2005. The TI was conducted following the cleaning of the A CCS HX. Additionally the team noted while performing the TI following the cleaning of the C CCS HX on October 12, 2012, a negative fouling factor of -.0025060 was calculated and recorded to meet the acceptance criteria of the test. The team questioned the validity of the test results that indicate negative fouling factor because the HXs had been in service for approximately 20 years, and a negative value would likely indicate an overestimation of the heat removal capacity of the HXs. The team also reviewed the CAP history and determined that the licensee did not identify either test result as a condition adverse to quality and did not enter the issues into their CAP.
Subsequent to the teams questions, the licensee entered the issue in their CAP as PER 969404, and determined that the operability of the CCS HXs were not in question due to the recent cleanings and past pre-cleaning test results being acceptable. The licensee contacted Zachary Nuclear Engineering, Inc., who provides the software used to perform the test, about the interpretation of the test results. Zachary Nuclear Engineering, Inc.,
responded by letter dated January 15, 2015. The letter stated, in part, that From our experience, clients that encounter negative fouling resistances from thermal performance testing should review the analytical model, measured data, test execution and assumptions, and contributions to parameter uncertainties. Each of these factors contributes to the calculated fouling resistance and the level of uncertainty in these factors can be reflected in the fouling resistance. In the event of calculated negative fouling resistances, the thermal performance test is not automatically invalid; however, the test should be reviewed to ensure that the data is credible and representative of the heat exchanger performance. Based on the information above, the team determined that the two tests that resulted in negative fouling factors represented conditions adverse to quality and should have been identified and entered into the licensees CAP.
Analysis:
The licensees failure to promptly identify a condition adverse to quality was a performance deficiency. Specifically, following post cleaning tests of the A and C CCS HX, a negative fouling factor was recorded and was not entered into the licensees CAP to determine if the data was credible and representative of the HX performance. The team determined that the performance deficiency was more than minor, because if left uncorrected, it had the potential to lead to a more significant safety concern.
Specifically, if the licensee fails to evaluate abnormal fouling factor test results then the potential exists for parameter uncertainties to go undetected and potentially result in test results that are not representative of adequate HX performance. The team used IMC 0609, Att. 4, Initial Characterization of Findings, issued June 19, 2012, for Mitigating Systems, and IMC 0609, App. A, The Significance Determination Process (SDP) for Findings At-Power, issued June 19, 2012, and determined the finding to be of very low safety significance (Green) because the finding was not a design deficiency, did not represent a loss of system and/or function, and did not represent the loss of any trains of Technical Specification or Non-Technical Specification equipment. The finding has a cross cutting aspect in the Conservative Bias component of the Human Performance area as defined in NRC IMC 0310, because the licensee failed to use decision-making practices that emphasize prudent choices over those that are simply allowable.
Specifically, the licensee failed to recognize that a negative fouling factor while less than the test acceptance criteria, did not represent an expected test result [H.14].
Enforcement:
Title 10 CFR Part 50, Appendix B, Criterion XVI, Corrective Action, required, in part, that measures shall be established to assure that conditions adverse to quality, such as failures, malfunctions, deficiencies, deviations, defective material and equipment, and nonconformances are promptly identified and corrected. Contrary to the above, since October 15, 2012, conditions adverse to quality were not promptly identified. Specifically, the licensee failed to identify that negative fouling factors calculated from the CCS HX performance testing was a condition adverse to quality and enter it into their CAP. This violation is being treated as an NCV consistent with section 2.3.2 of the Enforcement Policy. The violation was entered into the licensees CAP as PER 969404 and an operability determination was performed that provided reasonable assurance of operability while corrective actions are being evaluated. This violation is identified as NCV 05000390/2015007-02, Failure To Identify A Condition Adverse To Quality For Negative Fouling Factors.
b.3 (Opened) Break In Non-Seismic ERCW Discharge Piping
Introduction:
The team identified an unresolved item (URI) related to the licensees failure to consider the effects of an open break in the non-seismic portion of the ERCW discharge flow path to the cooling tower basin in the calculation used to determine the net positive suction head (NPSH) available to the AFW pumps. This URI is to determine if the performance deficiency is More-than-Minor.
Description:
The non-seismic normal discharge flow path of the ERCW system is to the cooling tower basin. The team noted that ERCW system description document WBN-SDD-N3-67-4002, Essential Raw Cooling Water System, System 67, Revision 0028, stated, in part, that nonsafety-related ERCW system components shall be designed such that their failures do not jeopardize safety-related components. The team also noted that calculation EPMJKJ011191, WBN AFW System - Pump Net Positive Suction Head (NPSH) Available Calculation, Revision 010, was used to determine the available NPSH for the AFW pumps.
Upon review of this calculation, the team determined that the licensee failed to model the ERCW system considering an open break in the non-seismic portion of the discharge flow path to the cooling tower basin. A break of this type could result in a lower backpressure on the ERCW system, which could result in a reduction of available NPSH to the AFW during accident conditions. Subsequent to the inspectors questioning, the licensee entered the issue into their CAP as PER 979323. The licensee is performing an evaluation to determine the magnitude of the loss of available NPSH. This issue will remain open pending the teams review of the licensees evaluation in order to determine if the performance deficiency is More-than-Minor. (URI 05000390/2015007-03, Break In Non-Seismic ERCW Discharge Piping)
4OA6 Meetings, Including Exit
On March 4, 2015, the team presented the inspection results to Mr. Walsh and other members of the licensees staff. The inspectors verified that no proprietary information was retained by the inspectors or documented in this report.
ATTACHMENT:
SUPPLEMENTARY INFORMATION
KEY POINTS OF CONTACT
Licensee personnel
Kevin Walsh, VP Watts Bar Nuclear Plant
- J. ODell, Compliance Manager
- G. Scott, Compliance Engineer
NRC personnel
- B. Monk, Senior Resident Inspector, Division of Reactor Projects, Watts Bar Resident Office
- J. Nadel, Senior Resident Inspector, Division of Reactor Projects, Watts Bar Resident Office
- J. Hamman, Resident Inspector, Division of Reactor Projects, Watts Bar Resident Office
- J. Dion, Project Manager, Office of Nuclear Reactor Regulation, Watts Bar Special Projects
Branch
LIST OF ITEMS OPENED, CLOSED, DISCUSSED, AND UPDATED
Opened and Closed
Opened
Failure To Perform An Adequate Water Hammer Test [Section 1R21.2.b.1]
Failure To Identify A Condition Adverse To Quality For Negative Fouling Factors [Section 1R21.2.b.2]
Break In Non-Seismic ERCW Discharge Piping
[Section 1R21.2.b.3]