IR 05000259/1991012
| ML20138G104 | |
| Person / Time | |
|---|---|
| Site: | Browns Ferry  |
| Issue date: | 04/16/1991 |
| From: | Jape F, Whitener H NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| To: | |
| Shared Package | |
| ML20138G102 | List: |
| References | |
| 50-259-91-12, 50-260-91-12, 50-296-91-12, NUDOCS 9610180227 | |
| Download: ML20138G104 (8) | |
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/g# #810q'o UNITE) STATES
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NUCLEAR REGULATORY COMMISSION n
REGION il l,
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101 MARIETTA STREET, N.W.
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ATLANTA, GEORGI A 30323 s,...../
Report Nos..
50-259/91-12, 50-260/91-12, and 50-296/91-12 Licensee:
Tennessee Valley Authority 6N 3SA ' ookout Place
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1101 Market Street Chattanooga, TN 37402-2801 Docket Nos.:
50-259, 50-260 and 50-296 License Nos.:
and DPR-68 Facility Name:
Browns Ferry 1, 2. and 3 Inspection Conoucted:
Maren 15-20, 1991 i
Inspector:
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[&V H. L. Whitener ~
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' Date Signed Approved by:
//d#f F. Jape, Chief ~
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Test Programs Section Date Signed Engineering Branch Division of Reactor Safety SUMMARY Scope:
This routine, announced inspection was conoucted in the areas of witnes primary containment integra ted proceoures, test preparation, test performance and test results. leak rate
Results:
In the areas inspected, violations or deviations were not identified.
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The licensee had developed a thorough and detailed Containment Rate Test Integrated Leak requirements and cetailed pre-planning for test preparation Management involvement was evident in the development of procedures and a i
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expanded test organization which provided adequate support
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containment was demonstrated to be leak tignt.
The calculated leak rate for for tne test.
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the upper confidence limit (incluces probable error) was 0.258 weight percent per day.
This is approximately 17 percent of the allowable leakage limit of 1.5 weight percent per day.
Two concerns were identified curing this insoection: (1) the reactor building to torus vacuum breaker system air operated cutterfly valves opened on pressure rather than on vacuum and; r
9610180227 960416 PDR ADOCK 05000259 G
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(2) certain ventilation
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leakage problems during a local leak rate test. system air operated butterfly valves
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are discussed in paragraph 3 of this report.
Resolution of these concerns a
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REPORT DETAILS 1.
Persons Contacted Licensee Employees
- S. Austin, Mechanical Engineer, Compliance
- K. Clark, Supervisor, Corporate Maintenance L. Farmer, Engineer, Corporate Maintenance C. Miller, Engineer, Corporate Maintenance M. Morrison, Engineer, Compliance
- L. Myers, Plant Manager
- F. Nilsen, Engineer, Engineering Support
"J. Shaw, Supervisor, Engineering Support Other licensee employees contacted during this inspection included engineers, operators, and technicians.
NRC Resident Inspectors
- C. Patterson, Senior Resident Inspector W. Bearden, Resident Inspector E. Christnot, Resident Inspector K. Ivey, Resident Inspector i
" Attended exit interview
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2.
Containment Integrated Leak Rate Test (70313)
The inspector reviewed test documentation and witnessed test activit to determine that the Unit 2 primary containment (CILRT) was performed in accordance with test integrated leak rate Primary 10 CFR 50, Appendix J, Reactor Containment Leakage Testing For Water-Cooled Power Reactors; ANSI-45.4-1972, Leakage-Rate Testing of Containment Structures for Nuclear Reactors; Technical 2-SI-4.7. A.2.a-f, Primary ContainmentSpecification 4.7. A.2; test procedure Integrated Leak Rate Test; and, of Primary Containment Structures for Nuclear Power i
Selected sampling of the licensee's activities which were inspected included:
(1) review of the test procedure to verify that the procedure was properly approved and conforms with the regulatory requirements
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listed above; (2) observation of test performance to determine that tes prerequisites were completed, special equipment was installed, and
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appropriate data were recorded; and (3) preliminary evaluation of leak rate test results to verify that leak rate limits were met.
Pertinent aspects of the test are discussed in the following paragraphs.
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General Observations a.
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The inspector witnessed and/or reviewed portions of the test preparation, containment pressurization, temperature stabilization, and data processing during March 15-20, 1991.
The following items were inspected:
t (1)
The test was conducted in accordance with an approved procedure maintained at the test control center.
l changes to the procedure were properly documented, Test discrepanc
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(2) Selected test prerequisites were reviewed and found to be
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completed.
(3)
Selected plant systems, required to maintain test control, were l
reviewed and found to be operational.
(4) Special test instrumentation was reviewed and found to be installed.
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Data required for the performance of the containment leak rate calculations were recorded at 10-minute intervals.
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Events encountered during the test were described in the test event log.
(7)
Pressurized gas sources were reviewed for proper isolation and through containment isolations valves. venting to preclude (8)
draining.Certain system alignments were reviewed to verify venting No violations were identified in the above areas.
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Procedure Review, Unit 2 (70307)
Review of 2-SI-4.7.A.2.a-f showed that adequate test controls, instructions and acceptance criteria are specified.
Acceptance criteris for both the short duration (8 hour9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br />) and the 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> te are included.
instructions are included as attachments to the procedure systems in service and the add on leakages are specified in the Also, procedure.
The inspecter concluded that the procedure was acceptable.
Other instructions or procedures reviewed for the
included:
leak rate test d
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Technical Instruction 2-TI-173, Primary Containment Inspection Revision 1.
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Technical Instruction
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Setup, Revision 0.
2-TI-179, CILRT Data Acquisition System
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Containment Temperature Survey
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Test Performance (1) Method The containment integrated leak rate analysis program of TVA has the capability of analyzing the data in accordance with the t
requirements of BN-TOP-1 for a short duration test or in Containment System Leakage Testing Requirements for a 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> test.
For the Unit 2 test, the data met the BN-TOP-1 criteria.
Consequently, the BN-TOP-1 analysis for a short duration test. licensee used the The mass point analysis method was simultaneously calculated.
(2) Description Containment pressurization was initiated at 2305 hours0.0267 days <br />0.64 hours <br />0.00381 weeks <br />8.770525e-4 months <br /> on March 17, 1991, subsequent to final containment inspection.
following sequence of events was taken from the test log:
The Date Time Condition 3/17 2305 Air compressors started.
2315 Inboard reactor building to Torus Vacuum breaker valves opened at 1.5 psig.
The outboard check valves held the pressure.
3/18 0511 0537 One air compressor shutdown.
Pressurization terminated at 50.46 psig.
0555 Compressors isolated from 0715 containment and vented.
Leak checking in accordance with TI-173 initiated.
No significant leakage was identified.
0751 Stabilization period started.
3/19 1201 Stabilization period i
terminated.
Temperature criteria me _ _.
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1211 First data point for the
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Type A test.
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2011 Eight hour Type A test (
terminated.
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2151 Verification test started 0151 after one hour stabili:ation.
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Four hour verification test terminated.
0530 Began depressurization of containment.
(3) Test Results - Unit 2 i
(a) Type A Test Technical specification allowable leakage (La) for Browns Ferry Unit 2 is 2.0 weight percent per day.
Therefore, the integrated leak rate test leakage limit of 0.75 La as (
required by Appendix J is 1.5 percent per day.
The following are the results of the eight hour leak rate I
measurement and the leak rate compensated for error (95
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percent Upper Confidence Limit) for both the Mass Point
(MP) analysis according to ANSI /ANS 56.8 and total time (TT) analysis according to BN-TOP-1:
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Measured Leak Rate Upper Confidence Limit MP 0.234 wt.% per day 0.238 wt.% per day
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TT 0.234 wt.% per day 0.258 wt.% per day The inspector's calculated values agreed closely with licensee calculations.
(b) Supplemental Test - Unit 2 Appendix J requires that a supplemental test be performed
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of the CILRT instrumentation to measure a chan l
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method as described in Appendix C of ANSI N45.4 - 1972.test A known leak rate (Lo) is imposed on the containment and the measured composite leak rate (Lc) must equal, within 10.25 La, the sum of the measured leak rate (Lam) plus the known leak rate (Lo).
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The acceptance criteria is expressed as:
Lo + Lam - 0.25 La < Lc < Lo + Lam + 0.25 La
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A four hour verification test was performed.
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The following day): measured values were obtained (Units are in wt. percent per II MP LAM 0.234 0.234 Lo 1.67 1.67 Lc 2.26 2.27 0.25 La 0.5 0.5 Substitution of these values into the acceptance criteria shows that the inequality equation was satisfied as follows:
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l TT 1.404 < 2.26 < 2.404 Mp 1.404 < 2.27 < 2.404
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The inspector concluded that the verifi.ation test confirmed the instrument system capability to measure the containment leak rate.
(d) Type A Test Status The Unit 2 Type A test was classified as a failed test.(CIRLT) performed in February 1983 Since this was the first failed Type A test the NRC allowed Unit 2 to remain on a
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l 401 10 month CIRLT schedule.
i The decision to keep Unit 2 shutdown indefinitely was made while the unit was in an outage in 1985 for which no Type A test was scheduled.
inspector concluded that due to the extended outage and The numerous modifications, the Type A test just performed would be treated as a preoperational test and no "as found" s.
leak rate penalty applied.
rate must be determined for future Type A tests.However, the
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The plant remains on a 401 10 month test schedule.
3.
Concerns Relating to Leak Rate Testing (61720)
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Reactor Building to Torus Vacuum Breaker a.
the reactor building atmosphere with the torus outer 20 inch check valve and an inner (closest to contain inch air operated butterfly valve.
allow air flow from the building to the torus in the event of aThe ch
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The air operated butterfly valve opens on differential pressure between reactor building and torus.
This-design provides double isolation barriers against containment leak if the containment
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torus from negative pressure.is at pressure and vacuum relief to protect the
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During the CILRT the opposite to its intended function. inner valve appeared to operate in a manner The butterfly valves in the two
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systems, 64-20 and 64-21, opened at 1.5 psig when pressurizing the containment and closed at 0.6 psig when depressurizing containment.
The inspector informed licensee management at the exit interview that
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the Resident Inspectors will follow this matter.
a b.
Ventilation System i
Just prior to the CILRT a local leak rate test was performed which involved leak testing five ventilation system air operated butterfly valves simultaneously.
Significant leakage was identified.
In attempting to identify and repair the leaking valves, the licensee cycled. certain valves with the result that leakage increased dramatically.
The licensee determined that the inner valves far penetrations 26 and 231 were leak ti between the inner and outer valves, ght and elected to open vents the inner valves during the CILRT. thereby taking credit for only The repaired and locally tested before startup. leaking valves will be Since ventilation system valves have a leakage problem history, the inspector asked licensee management what corrective action will be taken to improve the leakage performance of these valves.
Management indicated that the valve performance will be pursued and resolved.
The options available are being evaluated.
Included in these options is possible replacement of these valves with valves of improved design and leakage characteristics or rebuilding the current valves to improve design.
This matter. will be reviewed during future leak rate inspections.
4.
Exit Interview The inspection scope and results were summarized on March those persons indicated in paragraph 1.
20, 1991, with inspected and discussed in detail the inspection results listed below Proprietary information is not contained in this report.
Dissenting comments were not received from the licensee.
- The inspector stated that a leak tight containment was demonstrated by the CILRT.
- The inspector discussed two identified concerns as follows:
(a) vacuum breaker system valves opening on a pressure rather than a vacuum signal.
(b) ventilation system valve leakage problems.
The licensee has agreed to investigate and resolve these concerns.
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