ML20091G906
| ML20091G906 | |
| Person / Time | |
|---|---|
| Site: | Browns Ferry  |
| Issue date: | 12/12/1991 |
| From: | Zeringue O TENNESSEE VALLEY AUTHORITY |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 9112190141 | |
| Download: ML20091G906 (10) | |
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A tr$4 vu,e.e n u o e., om o w uca x,,m December 12, 1991 O J w Zemgx
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U.S. Nuclear Regulatory Commisalon ATTN: Document Control Desk Washington, D.C.
20555 Centlement In the Matter of
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Docket Hon. 50-259 Tennessee Valley Authority
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50-296 BROVNS PERRY NUCLEAR PLANT (BFN) - Std.LL BOP.E PIPING PROGRAM, TUBING, AND CONDUlf SUPPORT PLANS FOR UNITS 1 Af D 3 -- ADDITIONAL INFORMATION
References:
1.
TVA letter to NRC dated February 27, 1991 - Action Plan to Disposition Concerna Related to Units 1 and 3 Small Bore Piping 2.
TVA letter to NRC dated February 27, 1991 - Action Plan to Disposition Concern.) Related to Units 1 and 3 Tubing 3.
TVA letter to NRC dated May 6, 1991 - Action Plan to Disposition Concerns Related to Units 1 and 3 Conduit and Conduit Supports.
The purpose of this letter is to provid.e additional Information v'.ich t
clarifies TVA's plans for dispositioning concerna related to Units 1 and 3 Small Bore Piping, Tubing, and Conduit Support Programo. This additional information was requested by NRC during teleconferences held on October 21 and November 19 and 21, 1991. Thia letter augments the referenced TVA letters. to thin letter provides the requested information for the Small Bore and Tubing Programs. provides the requested information for the Conduit Support Program. Expeditious NRC review of this additional information and issuance of a supplemental Safety Evalua*.lon Report by December 31, 1991, are requented in order to support the design and nodifications required to be completed prior te restert of Unit 3.
9112190141 911212 PDR 40GCE 03000259 OOI P
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'U., Nuclear Regulatory Commission Deetmber 12, 1991 i
Enclosvre 3. summarizes the new commitmenta contained in this letter.
If you have any questione, please telephono J. E. McCarthy, Restart Licensing Manager, at (205) 729-2703.
Sincerely, klb%3" cu$
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D. J. Zeringue Enclouures cc (Enclosures):
I HRC Resident Inspector Browns Ferry Nuclear Plant
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Route 12, Box 637 Athens, Alabama 35611 Mr. Thierry. M. Ross,- Project Manager U.S. Nuclear Regulatory Commission
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One White Tlint, North 11555 Rockville pike Rockville, Maryland 20852 Mr. B..A. Wilson, Project Chief t
U.S. Nuclear Regulatory Commission
- i Region II-101 Marietta Street,- NW, Suite' 2900 Atlanta, Geor61a 30323 t
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ERCLOSURE 1 BFN Unit 3 Small Bore / Tubing programa Eukn2Vni _ Unit 2 milemon Rennt prons The Small Bore program resulted from the resolution of Significant Condition Report'(SCR) SCRBFNCEB85 0 and employee concerns which were identified for the entire plant. The Unit 2 and common small bore restart program consisted of l
approximately 715 ant' Mis problems covering 27,000 feet of piping and 4,500 supports. The Unit. and conmon small bore program developed the attributes for field walkdown originally by rigorously analyzing 31 problemn which consisted of approximately 1,500 feet of piping and 137 supports. The original 31 problems were selected based on vorst case loading conditiona, representative problems associated with employee concerna (EC), conditions adverse to quality (CAQ) and industry concerns. The selected problems contained two or more of the following itemst 1)
>200'T and/or >200 pai, 2) relief valve, 3) high elevation or heavy eccentric mass, 4) source movements,
- 5) schedule 160 pipe, 6) seismic non-seismic overlap, 7) diesel generstor building, and 8) standby gas creatment building. The 31 problems were distributed between the units with 20 being in Unit 2, 0 in Unit 3, eight'in Unit 1, and-three in Common.
Af ter _ the _small bore progron attributes were established, a walkdown procedure was vritten. The_walkdown procedure established a cet of minimum requirements.
Implementation _of the procedure was accomplished by training experienced pipe stress and support design engineers or engineering i
associates. The walkdovn team evaluated the small bore piping and supports for functionality and e.dherence to the design criteria. The field judgements and evaluations were based on conservative assumptions, which assured qualification to the design criteria for the accepted, repaired, or modified plant. configuration. During the course of the walkdowns, configurations in the field, that could not be accepted by engineering judgement were further
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evaluated. In order to perform these further evaluations, generally as-built data was obtained and rigorous analysis performed.
Conditions, which did not meet the design criteria but met the operability criteria, vere acceptable for one cycle. Modifications or repairs vete made in accordance with the design criteria for items found to be deficient when compared to the operability criteria.
During the small bore program, the NRC req','ested that_TVA increase the rigorously analyzed population no that ten percent of the cupports vere specifically evaluated.
In response tc. their request and due to the program's need for further evaluations, 45 additional problems, which centained
.apprcximately 2,200 feet of piping and 200 nupports were as-built and analyzed r
-in the Unit 2 and common restart effort. The 45 problems were distributed between the units as three in Unit 1, 29 in Unit 2, one in Unit 3, and 12 in common. The additional 45 problems analyzed did not result in any additional attributes which required revision to the Unit 2 and common program procedure.
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j pasa 2 of 5 prior to the completion of the Unit 2 and common program, a confirmatory analysis was performed. This analysis included 12 additional problems which consisted of approximately 1,100 feet of piping and 109 aupports. The purposa of the confirmatory analysis was to demonstrate the adequacy of the judgements cade in the field. As-butit data was obtained and the analysis included the fixes made by the program (i.e., including modifications to supports, support
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additions, or support deletions as applicable for that problem). The results i
of this ana?ysis demonstrated that all-12 problems met the long term pipe stress and pipe support criteria. The confirmatory analysis did not result in any additional attributes or programmatic concernal thus confirming that valkdown instructions were consistent with the requirements-of the design 2
criteria for both pipe stress and pipe supports. The 12 problems vero distributed between the units as one in Unit 1, seven in Unit 2, two in Unit 3, and tv in common.
In retrospect, all of the evidence frcn the Unit 2 and common small bore restart program concluded that the attributes were properly identified in the original 31 problems and that the program has been properly implemented to assure that the small: bore piping and associated supports were qualified to the pipe and support design criteria.
Increasing the rigorous analysis sample size did not produce any additional generic _ attributes; therefore,_ increasing the= population had no effect on changing the. implementation of the program from the original developed attributes.
The tubing t rogram reen*>Jd from the resolution of SCRBFNEEB8535, SCRBFNEEB85%3, employee concerns and nonconforming conditions which were identified for the entire plant. The Unit 2 and common restart tubing program began as an as-constructed program consisting of 66 tubing installations and approximately 250 tubing supports. _Later the scope of the tubing program increased and then changed to an engineering attribute evaluation program similar to the small bore program. The generic tubing attributes were developed -from the as-built analysis of the original 66 tubing installations.
A valkdown procedure established inspection attributes to be used in the field and was implemented by using engineering judgement. Qualified engineers were trained and performed the walkdown and evaluations similar to those of the small bore program. No confirmatory analyals was performed. The Unit 2 and common restart program-included the as-built analysis of 20 tubing problems in Unit 3 and 23 tubing problems in Unit 1.
The scope of the-tubing program was approximately 200 problems consisting of 9,000 feet of tubing and 714 supports. Therefore, Units 1 and 3 installations were more than adaquately considered in the development of the' tubing at tributes.
. $jailAfitL.lktRen lh11LlEEL1!nitiL1_.a11L3 The primary systema, for all three units, used similar drawings for installation (Unit 2 is opposite hand of Unit 1 and Unit 3 is a_ slide along of Unit 2).
The small bore piping and tubing for all three unita vere field
-routed utilizing the same design criteria and construction methods. -The i
L seismic response spectra is the same for all unita and the operating modes are L
the same. The Unit 3 valkdowns to date have shown that the small bore and tubing supports are nimilar in that the supports consist of Unistrut framing l
members and light weight structural shapes (angles). The Unit 3 walkdowns to
-date are finding breakage-similar to Unit 2 breakage.
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-Page 3 of 5 llall_l flDILIUFua12 For the Unit 3 restart effort, the small bore and tubing programs have been i
combined into one program for efficiency. The Unit 3 scope is approximately as follows:
10.1A1 SEAL L Btt.c
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Problems 375 275 100 Footage (ft.)
19000 16000 3000 l
Supports 2500 2000 500 The Unit 3 small bore / tubing program is utilizing Unit 2 developed attributes und the same technical walkdown procedure. Walkdown personnel are experienced in piping and tubing stress analysis and support design. The as-built
-analysis data generated for Unit 2 and common restart effort is avwilable for.
use_by Unit 3 personnel and has-been used in training the Unit 3 personnel, e
The Unit 3 teams walk the plant down and make conservative judgements of the acceptability of the piping, tubing and their associated supports in the l
field.
Items, which are judged as possibly not being acceptable, are further evaluated which generally includes collection, and evaluation of_as-built data. The acceptability is based on the piping and-support design criteria.
No operability criteria is being used in the Unit 3 and Unit 1 small bore / tubing programs. Modifications and/or repairs are made to any item which is determined to be unacceptable.
As was done for the. Unit 2 and common program, the Unit 1 and 3 small bore / tubing program vill perform rigorous analysis which will consist of ten percent of the piping / tubing and ten percent of the supports. The i
confirmatory analysis is contained in the teu percent.
The Unitf2 and common restart tubing program performed analysis on approximately 20 problems physically located in Unit 3.
These problems encompassed tubing throughout the Unit 3 reactor building (including _ ins.e containment) and the diesel generator building.- No additional analysis will be performed on the Unit 3 tubing or supports unless the need to do so is
' identified during the program implementation.
The Unit I tubing scope is currently undefined. However, the Unit 2 and common restart program analyzed 11_ problems in the Unit I reactor building and diesel generator building and 12 probitma in the Unit 1 control bay areas.
Depending on the total Unit 1 tubing scope,.if the Unit-2 and common analysis l
provide-an adequate sample, no further tubing analysis vill be performed unless required for the program implementation.
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Unit;_ Land 3 Pyrngm Detaila 11n the development of attributes for the Unit 2 and common small bore and
' tubing program, a list of 27 attributes was made. The_ Unit 2 and common small bore and tubing rigorous analysis sample identified that 12 of the attributes were applicable as deficiencies at BFN. The smn11 bore and tubing programs evaluated the other 15 attributes by having experienced and trained engineers performing the walkdown. The Unit 3 checklist of walkdown procedure BC-012-
"Ensincering Attribute Walkdown Instructions for Seismic Class I Small Bore P' ring, Tubing, and Associated Supports" contains an attribute which requires an evaluation to identify any other condition abith to Judged to be detrimeneal to the qualification of the piph gf tuking or rupport. Training la pit vlied to walkdown personnel to assure that the syec a, sa functional and will meet the design criteria.
Erla11shv. hip _Le WeldingJJnrAt The BFN veld program report identified a Unit 3 small bore support with a deficient veld. The deficiency was veld born through of the Unistrut attached to the base plate. This type of condition vould have been identified
_during the Unit 3 small bore / tubing walkdevn and evaluated as part of the evaluation of any condition deemed to be detrimental to the qualification of the system. Additionally, the veld program repart identified a Unit 1 small bore support with a daficient veld. The deficieacy was a one sided veld used to attach Unistrut to structural steel.
This type of condition vould have been identified during the small bore / tubing walkdown and eva7uated as part of the evaluation of any condition deemed to be detrimental to the tus11fication of the syster.. Welds are evaluated by the walkdown team from a craftsmanship aspect and from a functional perspective. During.the walkdown, the team decides if the veld is acceptable, or requires further evaluation, or if repair is needed. Those requiring further evaluation vill have as-Suilt data C
' collected. prior to performing the teructural analysia. This procedure satisfies the intent of the velding project report. The Unit 3 mmall bore / tubing program walkdovn procedure BC-012 states that as-build data vill be obtained by uri"; Unit 3 valkdown procer/tre BC-005 "Walkdown Instruction for Piping and Pipt ouppcrts."
Unit 3 Small Bore /Tubina p aaraJl_11.31];Jg
' As of November B, 1991, c prerde v:1y 20 percent of the program-is complete.
Ninety problems have been field
- aluated consisting of approximately 4,000 feet of p! ping and 305 supports.
PJfty-six of the problema require some further evaluation for pipe strens concerne. Of_the 505 supports evaluated:
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(a) 24 supports have be'n evaluated as acceptable without any repair or modification being required.
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-(b) 52 supports require modifications (i.e., adding brace, changing the
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-support _ direction, adding a U-bolt, delecing a support).
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- (c)-303 supports required generic repairs (i.e., torquing of U-bolts nuts, l
torquing of clamp bolts, replacing of existing clamp 1vith Unistrut or l
B-line brand clamp). Some of these support s had other non-generic repairs
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l (d) 75 supporta require. repairs consistJng of adding of washers for oversized L
holes, replacing missing hardware, pipe to suppert attachment, and l
replacing defectiv ' ardware.
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-(e) During the review of tnese 90 problems, an addition of 24 new supports were identified as being required to qualify the pfping installations.
To date the' Unit 3Levaluation has found that the percentage of repairs, modifications and-new support additions is comparable to Unit 2.
Canilmalan 1The use of the Unit 2 and common small bore and tubing programs' attributes for the evaluation of Units 1 and 3 is justifiabic based on the following conclusions:
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The primary systems, for all three units,- used similar drasings for installation. The small bore piping and tubing were field routed-utilizing 1the same design criteria and construction methods. The' seismic-response spectra;is'the same for all units and-the operating modes are the same.
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The increased nize of the Unit 2 and common rigorous)y analyzed population for small bor. did not result in any additional atti-ibutes or changes to the Unit 2 an, commun restart program from what was developed in the original 31-problem sample, 3.
Impica utation of the Unit-2 and common attributes on Unit 3 have resulted in a-ct.acrvative-program.. The percentage.of repairs, modifications and-new support additions-to.date is comparable to Unit 2.
The Unit 3 ulkdowns have abovn that-the small bore and tubJng supports are similar nt veen-the units consisting of Unistrut framing members and light weight uctural shapes'(angles).
Th: Unit 1 and 3-small bore / tubing program vill perform rigorous unalysis sh th will censist-of ten percent of the piping / tubing and ten percent of the supports. This vill confirm that the application of the attributes
.ed on the Unit 2 and common provideo a conservative program for 'Unita 1 and 3.
.Throu6h '1s program it will be demonstrated that the Unit'I and 3 small-bore and tubing meet the design criteria.
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ENCLOSURE 3 Summary of Conairments 1.
The Unit I and 3 Small Bore and Tubing Program will perform analysis which will consist of ten percent of the piping / tubing and ten perient of_the
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l ENCLOSURE 2 BFN Unit 3 Conduit programo RALIKL9 Mud The Unit 2 and common restart effort for the conduit system qualification utilized Design Criteria DC-50-C-723 an a basis for acceptance.
(This criteria was later consolidated into DC-50-C-7104 as the current criteria).
For the Unit 2 and common restart effort, the rc.d hung conduit installation comprised approximately 70 percent of the total population. When the wc!kdovn teams evaluated the rod hung conduit systems, each system was identified as an outlier.
In order to qualify the rod hung systems, Unit 2 and common initially performed rigorous computer analysis of these systems. This approach was considered inefficient and extremely costly considering the large number of problems that would require analysis.
In order to assure seismic qualification of the rod hung conduit systems, Unit 2 and common utilized the seismic experience data base information by having EQE Inc. perform the review of these systems in all three units. The EQE review was able to show that the BFN rod hung conduit systems were bounded by the seismic experience data base.
During the NRC review of the Unit 2 and common conduit program, the NRC did not accept the use of the aeismic experience data base information as a method for resolving the qualification of the rod hung systems.
In order to resolve the NRC crviewers concerns, TVA agreed to rigorously analyze five rod hung systems at bounding cases for the seismic experience data base information.
Bounding case problens were selected. These problems included the maximum parameters that were accepted bi the use of the seismic experience data base (i.e., long epans, large axial spans, mixed rod length, heavily loaded trapeze hangers, mix support conditionn such as braced and unbraced trapezes). This analysis validated the use of seismic experience data base information for BFN. The NRC overviewed the five problems and concentrated their review on two of these problems (DN 40-10 and DN 40-212). Tie review of these problems are discussed in NRC inspection reports 50-260/88-38, 50-260/89-29 and 50-260/89-42.
Unic 1 and 3 ProgLan j u m ny The Unit 3/ Unit 1 programs will utilite the Unit 2 and common results for the evaluation of the rod hung conduit systems.
The Unit 2 systems were bounded by the seismic experience data.
During the Unit 2 restart program, EQE reviewed conduit installations in Unit I and Unit 3.
No conditions were identified for the rnd hung conduit systems in any unit that would not be bounded by the seismic experience date base information. TVA's interim stegram for the seismic qualification of the remaining Units 1 and 3 conduit I
and conduit supports will consist of engineering evaluations of these commodities with a focus on the attributes which resulted in modifications in the Unit 2 and common program.
These walkdownn will include the Units 1 and 3 areas of the Reactor Building which were not included in the Unit 2 and commor restart effort.
Dlacrepancies will be evcluated against the criteria and the enveloping (wornt) cases used in the Unit 2 and common restart program. The resolution of identified discrcpancies will be implemented prior to the restart of Units 1 and 3 respectively.
Based on the Unit 2 and common experience, BFN expects no hardware deficier les to be identified on the rod hung systems.
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page 2 of 2 TVA's final program for the seismic qualification of the remaining Unita 1 and 3 conduit and conduit supporta vill be in accordance with the Unit 2 post-rentart commitments. TVA vill evaluate and upgrade, as needed, the Unita 1 and 3 aluminum and steel conduit and supports against the USI A-46 program guidelines Canth 12193M The use of the Unit 2 and common rod hung conduit information for Unit 1 or Unit 3 is justifiable based on the following conclusions:
1.
The conduit systema and supports for all unita were field routed and supported to the same specification.
2.
The conduit unterial type is the same for all units.
Conduit was and is procured for all three units to the same procurement specification.
3.
The-rod hung condu.it systems are supported approximately to the same spans (4 feet to 7 feet). Conduits have the same maximum fill ratio and have similar support types (trapeze, braced trapeze) in all units.,
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The response stectra in identical for all reactor buildinga.
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