ML18033B007
| ML18033B007 | |
| Person / Time | |
|---|---|
| Site: | Browns Ferry  |
| Issue date: | 10/26/1989 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML18033B006 | List: |
| References | |
| NUDOCS 8911020180 | |
| Download: ML18033B007 (15) | |
Text
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t UNITEO STATES NUCLEAR REGULATORY COMMISSION WASHINGTON,O. C. Z0555 ENCLOSURE SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATING TO RELIEF FROM THE BOILER AND PRESSURE VESSEL CODE SECTION XI "RULES FOR INSERVICE INSPECTION OF NUCLEAR POWER PLANT COMPONENTS - DIVISION 1" TENNESSEE VALLEY AUTHORITY BROMNS FERRY PLANT, UNITS 1, 2
AND 3 DOCKET NOS. 50-259 260 296
1.0 INTRODUCTION
Section 50.55a, "Codes and Standards,"
of 10 CFR Part 50 requires, in part, that certain safety-related piping systems meet the requirements of Section XI of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code (hereafter "the Code" ).
The Tennessee Valley Authority (TVA or the licensee) submi tted to the NRC in a letter dated June 4, 1987 its revised first ten-year interval nondestructive examination Inservice Inspection (ISI) program including requests for relief for Browns Ferry, Units 1, 2, and 3.
The'rogram's requirements are specified in TVA's Surveillance Instruction (SI) 4.6.G.
The revision concerns changes to requests for relief ISI-4, ISI-5 and ISI-8.
The inservice inspection program description with requests for relief from inspection requirements were originally submitted by TVA in their letter of October 20, 1976.
After several supplemental letter inputs, ISI-8 (among others) was approved by an NRC Safety Evaluation Report (SER) dated August 30, 1983.
Requests for relief ISI-4 and ISI-5 were not granted.
The visual inspections of the surfaces of concern were to be inspected when the pumps or valves involved were disassembled for maintenance during the intervaI, and if this did not occur, TVA should then generate requests for relief for the specific components, or groups of components, which had not been inspected.
Regulation 10 CFR 50.55a(g)(6)(i) authorizes the Commission to grant relief from these requirements upon making the necessary findings and the Commission may impose alternative requirements.
This SE contains the NRC staff's findings with respect to relief requests ISI-4, ISI-5 and ISI-8 submitted as part of the licensee's inservice inspection program.
Any additional program changes such as revisions or additional requests for relief should be submitted to staff review and should not be implemented prior to review and approval by the staff.
89il020i80 89i02b PDR ADOCK 05000259 PDC
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- 2. 0 EVALUATION 2.1 Relief Re uest ISI-4 Relief request ISI-4 concerns postponing the visual examination of reactor recirculation pump internal pressure boundary surfaces, Table IWB-2500, Examination Category B-L-2.
Code Re uirement Category B-L PUMP CASINGS Areas Subject to Examinations.
The areas shall include the internal pressure boundary surfaces.
Extent and Fre uenc of Examinations One pump in each group of pumps performing similar functions in the system shall be examined during each inspection interval.
This examination may be performed on the same pump selected for the Category B-L-1 examinations.
The examination may be performed at or near the end of the inspection interval.,
Licensee's Basis for Re uestin Relief TVA supplemented this relief request with a letter dated August 29, 1988.
The original request stated that during maintenance, if required, visual examination of the recirculation pump internal pressure boundary surface is performed and documented under existing plant procedures.
In the absence of required maintenance, as is the case at Browns Ferry Unit 2 (BFN2) during the first ten-year interval, disassembly of a recirculation pump solely to perform a visual examination of internal surfaces is impractical.
This would represent unnecessary exposure of employees to high radiation and contamination areas.
Radiation dose rates of the pump exterior will average 10-20 rem/hour.
This could result in a cumulative dose of between 100 and 300 man-rem.
Disassembly of this pump could require transport of the motor outside of containment and possible consequent damage to pump components.
The supplemental letter of August 29, 1989 did not change this position, but provided additional input concerning cover and shaft cracking in Byron-Jackson recirculation pumps.
Included was General Electric Company's, SIL No. 459, "Byron-Jackson Recirculation Pump Shaft and Cover Cracking," dated December 15, 1987.
The SIL recommended scheduling of inspections of pumps with greater than 80,000 hours0 days <br />0 hours <br />0 weeks <br />0 months <br /> of pump operation to detect cracks and implement corrective actions before excessive crack growth occurs.
The BFN2 recirculation pumps at BFN2 have 57,399 hours0.00462 days <br />0.111 hours <br />6.597222e-4 weeks <br />1.518195e-4 months <br /> tied-to-line.
By adding a
lOX factor for other hours where the pump would be at or near operating temperature, and an additional 18-month operating cycle, total hours would be approximately 76,000 at the end
of this next operating cycle.
The BFN2 recirculation pumps would still remain below the levels stated for recommended inspection after the next operating cycle.
- However, because of the cracking incidences in the pump covers and shafts at other sites, TVA will develop a plan of action after startup of BFN2 considering the vendor and other utility findings on this problem.
Subsequent to the August 29, 1988 TVA letter, there was a
pump shaft failure with less than three years service, demonstrating that the 80,000 hour0 days <br />0 hours <br />0 weeks <br />0 months <br /> operating time limit before performing inspections was not appropriate unless other measures were taken to monitor for the presence of cracks.
Alternative Ins ection None planned before BFN2 startup.
As long as the flows, pressure and temper-atures are as specified in the Byron-Jackson recirculation pump manual, no disassembly for routine maintenance is recommended.
Staff Evaluation Because of thermal fatigue cracking in pump covers and pump shafts found to date in Byron-Jackson pumps, the staff does not consider it prudent to grant relief without alternative requirements.
The data in the August 29, 1988 letter indicates that cracks in the covers or the shafts caus'ed by thermal fatigue could be present in these pumps at BFN2 now.
TVA has not provided any data or engineering analysis to demonstrate that the probability of the presence of cracks is low, or if cracks are present, that they will not grow to a size of engineering concern before the next outage.
TVA should take precautionary steps for each
- pump, such as, monitoring for shaft vibration caused by mechanical fatigue-driven crack growth of thermal fatigue initiated
- cracks, and monitoring of component cooling water (CCW) effluent for contamina-tion by reactor coolant which might be caused by cover crack growth to the extent of providing a leak path between the tw'o systems.
Monitoring for these events wi 11 provide early warning necessary for corrective actions and should minimize damage or contamination of the external CCW system and equipment in the event of a crack growing to significant size.
The staff believes it prudent to perform the required inspection, even with monitoring, during the cycle 6 refueling outage.
Based on the staff's review of the licensee's request for relief ISI-4, the staff concludes that technical concerns about the presence of cracks in the cover and shafts of Byron-Jackson recirculation pumps have to be addressed.
Monitoring for crack growth would allow for shutdown before the cracks could grow to a size of concern for the pumps themselves, or other systems.
Accordingly, the NRC imposes the following alternative requirements for granting of relief from visual inspections of the interior of pressure boundary components of the Byron-Jackson recirculation pumps as requested in ISI-4.
A.
Insta'll monitoring instrumentation on each pump for pump shaft vibration caused by mechanical fatigue-driven crack growth with appropriate control room instrumentation.
B.
Install monitoring instrumentation for contamination of component cooling water (CCW) by reactor coolant water caused by crack growth in the pump covers to the extent that a leak path develops between the two systems with appropriate control room instrumentation.
C.
Conduct the required Code inspections during the Cycle 6 outage.
Based upon TVA performing the above NRC imposed alternative requirements, the staff concludes that TVA's request for relief ISI-4 from specific requirements of the Code is acceptable.
2.2 Relief Re uest ISI-5 Relief request ISI-5 concerns postponing the visual examination of the internal surfaces of valves exceeding 4 inch nominal diameter pipe size required by Tab'le IWB-2500, Examination Category B-M-2.
Code Re uirement Category B-M VALVE BODIES Areas Subject to Examinations.
The areas shall include the internal pressure boundary surfaces, on valves exceeding 4 inch nominal pipe size.
Extent and Fre uenc of Examinations One valve in each group of valves of the same constructional design (e.g.,
globe, gate, or check valve manufacturing method and manufacturer that performs similar, functions in the system) shall be examined during each inspection interval.
This examination may be performed on the same valve selected for the category B-M-1 examination.
The examination may be performed at or near the end of the inspection interval.
Licensee's Basis for Re uestin Relief TVA in letters dated April 14, 1982 and June 4, 1987 stated that those valves which had not been opened for maintenance during the inspection interval would require the fuel to be removed and the reactor vessel drained, or would need to be leak rate tested after reassembly, and in some cases, would additionally require other extensive operations, such as breaking of seal welds and reweld-ing, or placing both RHR loops out of service, simultaneously.
These operations could cause extensive radiation exposure to workers and generate large amounts of radioactive waste.
Alternative Ins ection If no valves from a particular group have been disassembled as the end of the interval approaches, the valves comprising that group shall be visually examined for leakage when the system pressure tests (IWA-5000) are conducted in accordance with the requirements for Category B-P.
Staff Evaluation The NRC staff has reviewed the licensee's request for relief, ISI-5, from the visual inspection of internal pressure boundary surfaces of valves exceeding 4-inch diameter nominal pipe size.
Requiring the valves to be disassembled only for this inspection would place an unnecessary burden on the licensee without a compensating increase in the level of safety or quality.
The disassembly required to perform the inspection involves radiation exposures which are not warranted given the low incidence of problems revealed during such examinations.
Thus, the licensee's proposed alternative, to perform a
visual examination for leakage during system pressure tests (Class 1 system pressure tests) is authorized pursuant to 10 CFR 50.55a(a)(3)(ii).
This granting of relief does not apply to other regulatory requirements, such as, NRC Bulletin 89-02, "Stress Corrosion Cracking of High-Hardness Type 410 Stainless Steel Internal Preloaded Bolting in Anchor Oarling Model S350W Swing Check Valves or Yalves of Similar Oesign."
2.3 Relief Re uest ISI-8 Relief request ISI-8 concerns relief from the inservice inspection volumetric examination requirements for certain Class I and Class 2 piping welds of the ASNE Code,Section XI, 1974 Edition, Summer 1975 Addenda because of physical obstructions or because the geometry of the components joined by the welds prevents the performance of all of the required scans for meaningful ultrasonic inspections.
TVA had originally submitted ISI-8 and supplemental changes in several letters, with the most important of these letters being dated Novem-ber '16, 1981 and April 14, 1982.
Request for relief ISI-8 was granted by NRC letter dated August 30, 1983.
TYA revised the listing of welds in ISI-8 with the deletion of specific welds and the addition of other welds in its Revision I submitted by TVA letter dated June 6, 1987.
Additional changes in the listing of welds were made by Revi-sion 2 submitted by TVA letter dated September 28, 1988.
The September 28, 1988 submittal also addressed the changes in the lists of welds for which relief had been requested between the original submittals, Revision I, and Revision 2 of Request for Relief ISI-8.
This safety evaluation considers only those welds listed in Revision 2, and the relief granted for welds listed in the safety evaluation enclosed in our letter of August 30, 1983 as superseded by the relief granted by this safety evaluation.
Those welds listed in the original version of ISI-8 for which relief was granted by our letter of August 30, 1983 and which are not listed in TVA's letter of
September 28, 1988 are to,be inspected to Code requirements unless the welds have been removed.
Specifically, the September 28, 1988 TVA submittal requested relief from performing 100K of the required volumetric examination of the following pressure retaining welds:
ittdld Idt I
d C
~II" I
I TCCW-2-1 (8")
TCCW-2>>5 (8")
DCS-2-3 (12")
DCS-2-12 (12")
TCS<<2-406 (12" )
TCS-2-421 (12N)
RCRD-2-49 (4")
RCRDS-2-2 (6")
KFW-2-26 (24")
KFW-2-28 (20")
N4A-SE (12")
N48-SE (12")
N4D-SE (12")
N4E-SE (12")
C-F C2. 1 C-F C2. 1 8-J 84.5 8-J 84.5 8-F 84.5 8-F
- 84. 5 8-J 84,5 8-J 84.5 8-J 84.5 8-J 84.5 8-F 81.6 8-F
- 81. 6 8-F Bl.6 8-F 81.6 85 90 65 90 80 50 75 75 70 90 60 40 Penetration, Weld-0-Let Penetration, Pipe Attach.
Valve Geo.. Penetration Valve Geo., Penetration Valve Geo.,
Welded Brace Valve Geo., Instru. Line Valve Geo.,
Inner Radius Tee 8 Reducer Geo.
Pipe Attach.
Pipe Attach.
Safe-End Configuration Welded Pads Configuration, Sensor Line Attach.
Configuration, Sensor Line Attach.
II Id Id ttdt tt C
d C t. It
~tl tt I
THPCI-2-72 (10" )
GMS-2-2 (26")
GMS<<2-2-LS (26")
B<<F 81.6 8-J 84.5 8-J 84.5 8-J 84.5 70 80 50 Safe-End Configuration Valve Geo.,
Brace Valve Geo.. Penetration Penetration
GMS-2-10<<LS (26" )
KMS-2-25-LSl 9 6:00 (26")
KMS-2-54-LS (26")
DRMC-2-1A (6")
DRMC-2-2 (6")
DRWC-2-3 (6")
GR-2-3-LS2 9 12:00 (28")
GR-2-8 (28")
GR-2-34 (28")
GR-2-56 (28")
GR-2-63A (4")
KR-2-51-LS (28")
DRHR-2-3 (24")
8-J 84.5 8-J 84.5 8-J 84.5 8-J 84.5 8-J 84.5 8-J 84.5 8-J 84.5 8-J 84.5 8-J 84.5 8-J 84.5 8-J 84.5 8-J 84.5 8-J 84.5 33 67 40 60 90 50 Penetration Covered by I-beam Non-Removabl e Insul ati on Reducer and Valve Geos.
Valve Geo., Weld-0-Let Valve Geo.,
Vent, Pipe 8
Instrument Line Support Lug Cross to Tee 5 Tee Geo.
Cross to Tee 5 Tee Geo.
Configuration, Meld Attach.
Seal Welded Blind Flange Rigid Restraint Valve Geo., Penetration DRHR-2-3-LS (24")
8-J 84.5 33 Penetration DRHR-2<<5 (24")
8-J 84.5 80 Valve Geo.,
Support Attach.
DRHR-2-12 (24N) 8-J 84.5 TRHR-2-110 (18")
C-F C2.1 TRHR 262 (20")
C-F C2. 1 90 80 Valve Geo., Penetration Non-Removable Support Hanger Mounting Bracket 8
Catwalk Support
" TRHR-2-462 (6")
C-F C2.1
'0 Welded Support Abbreviations:
Geo.
= Geometry, Attach.
= Attachment, Instru.
= Instrument
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e
Code Re uirements Category B-F, Item B1.6 Nozzle to Safe End Welds Volumetric and surface examinations shall be performed dur ing each inspection interval and shall cover the circumference of 100> of the welds.
Category B-J, Item B4.5 Circumferential and Longitudinal Pipe Welds Volumetric weld examinations shall be performed during each inspection interval and shall cover all of the area of 25% of the circumferential joints including the adjoining I foot sections of longitudinal joints and 25% of the branch connection joints.
Category C-F; Pressure-Retaining Welds in Piping,
- Pumps, and Valves in Systems which Circulate Reactor Coolant The examination shall cover 100K of the weld.
The number of examinations to be performed within intervals and periods are to be in accordance with IWC-2411.
Licensee's Basis for Re uestin Relief In some cases it will be impractical to inspect all'welds in accordance with paragraph T-532 of At ticle 5,Section V, of the ASNE Code, i.e.,
nonremovable hanger interferences or valve and pump casing geometries adjoining the welds prevent performing meaningful ultrasonic examinations of the welds.
Alternative Ins ection In addition to the visual examination performed during system leakage and hydrostatic tests, a "best effort" ultrasonic examination will be performed.
- Also, a surface examination will be performed on accessible areas of the welds.
Staff Evaluation Because of the geometric configuration of the fittings, or the presence of immovable obstructions near the welds, it is considered impossible to obtain meaningful examination, results on lOOX of the inspections required to be performed by the Code.
No more than a small percentage of welds are involved in any one system.
For the majority of these welds, more than half of the ultrasonic examinations may be performed.
As proposed by the licensee, a best-effort ultrasonic examination and surface examination on the accessible areas of the welds is practical for the Category B-F, B-J, and C-F welds.
The ultrasonic examination should cover the estimated weld volume percentages given in the request for relief.
(The proposed surface examination is required by the Code for the Category B-F welds, but not for the other two categories.)
Visual examinations would also be performed during system leakage and hydrostatic tests.
The reduction of ultrasonic examinations allowed by granting this relief request is a small fraction of the examinations
- ~
f'
required,. and the performance of the remaining required examinations should detect deteriorations occurring in the systems for which these examinations are being performed.
Based on the staff review of the licensee's requests for relief ISI-8 the staff concludes that TVA's relief, request from specific requirements of Section XI of the ASME Code are acceptable, provided that the licensee incorporates the alternative inspections/requirements in its appropriate Surveillance Instruction.
2.4 Conclusion The staff has determined.that relief may be granted for ISI-4, ISI-5 and ISI-8 pursuant to 10 CFR 50.55a(g)(6)(i) and (a)(3)(ii) based on (I) our finding that certain requirements of Section XI of the Code are impractical, and (2) requir-ing compliance with the code would result in hardship or unusual difficulties without a compensating increase in the level of quality and safety, Based on the alternative requirements imposed, this relief, is authorized by law and will not endanger life or property, or the common defense and security, and is otherwise in the public interest considering the burden that could result if the requirements were imposed on the facility.
For ISI-4, the relief is contingent on the, licensee performing the NRC alternative requirements des-cribed in Section 2.1 above.
For ISI-5, this relief does not apply to other regulatory requirement as NRC Bulletin 89-02.
For ISI-B, the relief is contingent on the licensee incorporating the NRC alternative inspections/
requirements, described in Section 2.3 above, in its appropriate Surveillance Instruction.
Principal Contributor:
D. E. Smith Dated:
October 26, 1989