IR 05000259/1991011
| ML18033B723 | |
| Person / Time | |
|---|---|
| Site: | Browns Ferry  |
| Issue date: | 05/23/1991 |
| From: | Blake J, Chou R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| To: | |
| Shared Package | |
| ML18033B722 | List: |
| References | |
| 50-259-91-11, 50-260-91-11, 50-296-91-11, NUDOCS 9106060111 | |
| Download: ML18033B723 (18) | |
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UNITED STATES NUCLEAR REGULATORY COMMISSION
REGION II
ATLANTA,GEORGIA 30323 RePort NoseI 50-259/91-11, 50-260/91-11, and 50-296/91-11 Licensee:
Tennessee Valley Authority 6N 38A Lookout Place 1101 Market Street Chattanooga, TN 37402-2801 Docket NoseI '0-259, 50-260 and 50-296 E
Facility Name:
Browns Ferry 1, 2, and
License NoseI DPR-33, DPR-52, and DPR-68 Inspection Conducted:
!1arch 25-29 ahd April 15-19, 1991 ji Inspector:
Ric
.
u Dat Signed Approved by:
.
B ake, hie M
ials and Processes Section ineering Branch ivision of Reactor Safety ate cygne SUYiNARY Scope:
This routine, unannounced inspection was conducted in the areas of previous open items and expressed concerns in safety-related piping systems.
Results:
In the areas inspected, violations or deviations" were not identified.
All modifications for piping systems had been completed.
IE Bulletins 79-02 and 79-14 were closed.
There appears to be questions concerning the results of use of the licensee's Conan Computer Program.
The licensee also has a
weakness concerning single angle design and the use of unapproved desktop procedures.
An unresolved item was identified concerning the single angle design method differing from the TVA design criteria and use of unapproved desktop procedures by Bechtel.
(Paragraphs 3 and 5)
The unapproved form used by Bechtel civil design group for single angle design is attached as Attachment REPORT DETAILS Persons Contacted Licensee Employees
- J
- R
- M.
- J S.
- p
- L
- R.
- J E.
K.
- K
- L T.
- p
- J
- S
- A T.
G.
Allen, Site Procedures Manager Baird, Civil Engineer Batestan, Technical Support Manager Beasley, Site Quality Blake, Quality Assurance (QA)/Quality Engineering (QE) Manager Carier,, Site Licensing Manager Clardy, Quality Monitoring Supervisor Cutsinger, Lead Civil Engineer Davenport, Regulations and Licensing Frevord, Mechanical Engineer Supervisor Gromek, Civil Engineer Groom, Modifications Myers, Plant Manager Ritter, QA Evaluator Salas, Compliance and Licensing Manager Shaw, Engineering Support Supervi'sor - Technical Support Smith, Unit Operations Manager - Operations Sorrell, Maintenance Manager Thaxton, Jr.,
Pipe Support Technical Supervisor Turner, Site Quality Manager Other Organizations Bechtel North American Power Corporation S. Bernsen, Quality Engineer R.
Day, Project Engineer D. Dhar, Civil Engineer Supervisor J. Iqbal, Stress Analysis Supervisor W. Perry, Project Quality Engineer J. Ventura, Restart Director (Browns Ferry Nuclear Unit 2)
Other licensee employees contacted during this inspection included craftsmen, engineers, operators, mechanics, security force members, technicians, and administrative personnel.
NRC Resident Inspectors
- C. Patterson, Senior Resident Inspector W. Bearden, Resident Inspector E. Christnot, Resident Inspector
- G. Humphrey, Resident Inspector K. Ivey, Resident Inspector
- Attended exit interview on March 29, 1991
- Attended exit interview on April 19, 1991
- Attended exit interview on both dates 2.
Action on Previous Inspection Findings (92701, 92702)
a 0 b.
(Closed)
Violation 50-260/86-02-01, Inadequate Design Controls for Safety-Related Piping Systems This violation involved numerous pipe support design deficiencies for safety-related piping systems.
The licensee shut down all three units-in Browns Ferry Plant for reinspection and repair around 1985.
Since then, the licensee.developed
"Nuclear 'Performance Plan" in July 1986 to include the implement of IE Bulletins 79-02 and 79-14 program for piping systems.
This program included the. walkdown reinspection, walkdown discrepancy evaluation, pipe stress reanalyses, pipe support evaluation, and field modifications.
The licensee has completed all modifications and calculations to comply the long term code requirements before restart.
The inspectors from Region II office and NRR have inspected-the above program several times during the last couple years and found the design to be generally acceptable.
, Therefore, this item is considered closed based on the completion of IE Bulletin 79-02 and 79-14 program.
(Closed)
Inspector Followup Item 50-260/89-16-13, Verification that Piping Supports on Portions of the Main Steam Line Are Analyzed for Water Filled Conditions.
Gal cul ati on No.
CD-Q2001-880969 CD-Q2001-880970 CD-Q2001-880971 CD-02001-880972 CD-Q2010-900250 CD-Q2071-880987 CD-Q2071-882301 CD-Q2073-880990
3
2
4
3
0
4
4 N1-201-1RA Nl-201-2RB N1-201-3R Nl-201-4R
"*H1-201-SRV Nl-271-4R N1-271-1R Nl-271-8R This item involved the fact that portions of the main steam system piping should be analyzed for water filled conditions, since Browns Ferry will achieve a safe shutdown condition, following an Appendix R
event (emergency shutdown with fire protection requirement),
with water flow through the main steam lines.
The.inspector discussed the matter with the licensee's engineers and reviewed the information provided.
Tennessee Valley Authority (TVA) reanalyzed or reevaluated eight stress calculations in the main steam lines to comply with the Appendix R requirements.
The new stress loads were sent to the pipe support design groups for evaluation.
The stress calculations which were reanalyzed or reevaluated fo'r Appendix R are listed below:
Rev.
No.
Associated I~lh A
d
- One standard calculation to qualify all 13 main steam safety relief valve discharge lines.
The calculation Nos.
CD-Q2001-880972 and CD-Q2010-900250 were randomly selected for review.
The first calculations is a similar
, model with and can represent calculation Nos.
CD-Q2001-880969,
-880970, and -880971.
The design conditions for the Appendix R event were:
temperature at 415.8'F and pressure at 250 psig.
For the piping qualification, two loading conditions were performed separately to include 1) dead weight (pipe, insulation, and water)
plus pressure and 2) thermal.
The inspector reviewed:
the input for.
coordinates, support directions, support locations, material properties, temperature, pressure, branch location, valve locations, and stress intensification factors; and the output for loads and directions against. stress isometrics and support detail drawings.
The majority of new piping stresses were lower than the original design bases when lines were filled with steam and at a higher temperatures of 548'F.
Some loads were slightly increased, but the applied loads were still within the allowables and the original piping design is acceptable.
Most of the new pipe support loads were lower than'the original design loads which included huge loads from design basis earthquake.
Even though some loads increased, all of them were still within the original design capacities.
After the stress reanalyses were completed, the new support loads were sent to the pipe support design group for evaluation.
The pipe support group reviewed the new loads comparing them to the design loads and sent them back to the stress analysis group with an impact review sheet,=
to state actions to be taken for the affected support calculations.
During the review, the supporting direction of snubber for support SSC-5 was found to have input off 31'.
The impact review sheet was incorrect in the remarks column since a support calculation which was listed to be revised, was not revised, due to the new loads still being below the design loads.
The licensee engineers evaluated the impact for the input being off 31'nd concluded there was no significant impact on safety.
The stress calculation will be revised to correct the input off 31'nd the impact review sheet.
The calculation No. CD-Q2010-900250 was reviewed for the input of support locations and load directions against the stress isometrics and support detail drawings.
No discrepancies were found.
Based on the above review, this Inspector Follow-up Item IFI is considered closed.
(Closed)
Unresolved Item 50-259, 260, 296/90-38-01, Conan Computer Program Evaluation and Correction This item concerned the fact that the maximum allowable loads were reduced for adjacent anchors with spacing violation, using the Conan Computer Program.
The output, or results, is different from the original assumption that the adjacent anchors will utilize their
maximum allowable loads and the calculations of the adjacent supports will not be required to be revised.
The inspector discussed this problem with the licensee's engineers and reviewed the information provided.
The inspector reviewed Incident Investigation Report 11-8-91-012, dated January 4,
1991 and Conan, G-32 Violation Evaluation Program Users Manual Software ID No. 262260, dated October 1985.
The basic theory of the Conan Computer Program includes that:
I) the maximum allowable (tension)
of the concrete from the shear cone area is always 1'arger than the maximum allowable in the steel bar (bolt)
and can be reduced to the maximum allowable of the steel bar with a portion of shear cone overlapping into the shear cone of
.
adjacent supports; 2) the lower the applied loads is, the smaller the shear cone required; 3.) the anchor bolts from the adjacent supports will develop the maximum allowables and occupy the required shear cone area and the maximum allowable of the anchor bolts for the main support will be reduced.
The methodology of Conan Computer Program is as follows:
1)
Use the maximum allowables (Anchor)
from both the main and adjacent supports and generate the reduced anchor allowables for main support.
2)
Use the lowest computed anchor allowable to design baseplates.
3)
Check the reduced allowables against the applied loads for the main support.
4)
Check the reduced allowables (if found) against the
. applied loads for the adjacent supports.
5)
Use the results (anchor bolt loads)
from Baseplate II analysis as applied loads for the main support and maximum allowables for the adjacent supports as input into Conan Computer Program and check all the applied loads to.be less than the reduced allowables for the main support and the maximum allowables for the adjacent supports.
This process is also called "final verification analysis."
The licensee generated II-B-91-012 to address the problem and resolution.
The report concentrated on Bechtel generated pipe support calculations which had G-32 spacing violations.
A review of the Bechtel, Calculation Control Logs, showed 225 calculations ( 101 from Field Design Change Notices and an additional 124 from original design)
addressing
'Browns Ferry Nuclear Plant Unit 2 anchor bolt spacing violations.
The'icensee reviewed 117 readily available calculations and found 23 calculations, or 20 percent, to be lacking the final verification analysis.
All 23 were found to be acceptable after performing the final verification analysis.
The licensee concluded that the Conan Computer Program is acceptable method of resolving anchor bolt spacing violations.
(The licensee stated that information concerning the Conan Computer Program was sent to
Sequoyah and Watts Bar Nuclear Plants for their information).
Based on the licensee's evaluation for the Conan Computer Program Application, this unresolved item is considered closed.
,During the preliminary review of the theory presented in Conan User's Manual (Software ID No. 262260),
the inspector had the following concerns:
2)
The theory used in Section II.E; (concrete)
area distribution, was questioned because the method of dividing the overlapped a'reas and assigning the areas to respective anchors does not appear to address the effect of cumulative load on the overlapped area.
In the case of three anchors in close-proximity, the middle anchor can be located inside the overlap area of the two outside anchors.
In the example calculation No. CD-02303-885461 for Embedded Plate, MK-7, contained in the Conan User's Manual, the maximum allowable for anchor No.
4 (located in the center between anchor Nos.
3 and 5)
was not reduced even with 4" spacing to the left (Anchor No. 3)
and right (Anchor No. 5)
from the adjacent anchors.
Anchor Nos. 3, 4,
and 5 are 1" dia, with 20 3/4" embedded length.
There is no anchor to the left of Anchor No. 3.
The example showed a reduction of the, maximum allowable for Anchor No.
3 but no reduction for Anchor No. 4.
d.
(Closed)
IE Bulletins 79-02 and 79-14 for Unit 2 ( 1)
IFI 50-260/79-BU-02, Pipe Support Base Plate Designs Using Concret'e Expansion Anchor Bolts - IE Bulletin 79-02 (2)
IFI 50-260/79-BU-14, Seismic Analyses for As-Built Safety-Related Piping Systems
- IE Bulletin 79-14 IE Bulletin 79-02 vias issued, on March 8, 1979 with the subsequent=
issues of Revision
and supplement No.
1.
The bulletin concerns based plate flexibility and anchor installation deficiencies.
The bulletin required the licensee to take actions to review the minimum factors of safety, anchor bolt preload, interim operability criteria, base plate flexibility, low cycle dynamic loads, etc.'ailure" to account for these factors could affect the validity of the piping analyses performed on Seismic Category I Piping systems. to ensure operability following a seismic event.
In 1987, TVA decided to combine -IE Bulletin 79-02 and 79-14 in one program to implement the stress reanalyzes, walkdown reinspection, engineering evaluation,
modification, and documentation.
For detail of TYA IE Bulletin 79-14/02 program, see IE Bulletin 79-14 below.
The NRC Region II Inspection Report Numbers 50-260/79-19, 79-23, 81-20, 81-33, 82-11, 83-22, 85-21, 85-26, 85-30, 85-.41, 86-19, 86-30, 87-07, 88-12, 88-19, 89-57, 90-09, 90-19, 90-26, 90-38 and NRR Inspection Report Numbers 89-15, 89-36, 89-44 for Unit 2 were performed to verify and review the IEB 79-02 procedures, inspection programs, analytical methods, modifications, and documentation for the concrete expansion anchor bolts.
IE Bulletin 79-14 was issued on July 2, 1979 with the subsequent issues of Revision 1 and two supplements.
The bulletin concerns that the as-built configuration of safety-related piping systems may not conform to the as-analyzed design.
This nonconformance could affect the validity of the analyses.
The bulletin required the licensees to verify that the seismic analysis applies to the actual configuration of safety-related piping systems.
The specific requirements include to identify inspection elements, inspect all safety-related systems, identify nonconfor-mances, and resolve then through the requalification in calculations or modifications in hardwares.
TVA committed to comply the bulletin in a response to NRC on August 31, 1979 (A27 790831 021).
TVA performed two walkdown inspections for IE Bulletin 79-14 between 1979 and 1987.
The results of the two walkdown inspections were not satisfied since numerous discrepancies were found after walkdown inspections by TVA gC and NRC inspectors.
In 1987, TYA initially proposed the use of a vertical slice/
horizontal slice concept to support restart of Browns Ferry Unit 2.
TVA developed and implemented IEB 79-14/02 program to combine IEBs 79-02 and 79-14 into one program.
Stone and Webster Engineering Corporation was hired to perform a third wal'kdown verification on piping systems for IE Bulletin 79-14.-
In March of 1989, TVA began a
100 percent IEB 79-14/02 program prior to restart, and recently completed the program, includeing all field modifications to meet the long term code requirements.
A TVA internal memorandum B2
'91 0129 004, dated January 29, 1991,
"Unit 2 -
IEB 79-14/02 Piping Program Final Report" was reviewed by the'nspector.
This report included the procedures, scope, walkdown inspection, design criteria, piping and support evaluations due to discrepancies, piping reanalyses, support modifications, base plate and anchorage evaluation, piping clearing evaluation, and Condition Adverse to guality Report (CARR)
and Employee Concerns (EC)
Evaluation.
The large bore portion contained 160 stress.
problems and 2936 supports, and the small bore portion contained
stress problems and 607 supports.
The large bores portion had 1531 modifications and 773 repairs and the small bore portion had
modifications and 283 repairs.
The implementation of these modifications and repairs prior to restart. provides assurance that the as-built condition is consistent with the as-analyzed design.
The NRC Region'I Inspection Report Numbers 50-260/79-23, 79-42, 80-05, 80-12, 81-20, 81-33, 82-11, 83-22, 85-21, 85-26, 85-30, 85-41, 85-51, 86-02, 86-19, 86-30, 87-07, 88-12, 88-19, 89-57, 90-09, 90-19, 90-26, 90-38 and NRR Inspection Report Numbers 89-15, 89-36, 89-44 for Unit 2 document inspections IEB 79-14 to verify and review the procedures, inspection programs, analytical methods, modifications, and documentation for the as-built safety-related piping systems.
TVA agreed to submit a final summary report to NRC for review in the near future.
Based on the licensee's completion of IEB 79-14/02 program and the inspection reports stated above, IE Bulletin 79-02 and 79-14 for Browns Ferry Unit 2 are considered closed.
3.
Manual Computation of Single angle Members
.
A concern, expressed to NRC, was that TVA has developed an unacceptable standard for manual computation of single angle members at the Browns Ferry site.
The concern indicated that the unbraced length requirement of the American Institute of Steel Construction (AISC) is missing from'he standard making all of the manual computations for single angle members using the standard erroneous.
During a telephone conversation on April 15, 1991, with the concerned individual, the NRC learned that the
"TVA Standard" described in the concern was instead a
manual calculation guide presented on a Bechtel calculation sheet (the individual also questioned two other items during this conversation
- they are discussed in paragraph 4, below).
This inspection substantiated the, concern about the manual computation sheet used in design calculations.
A blank form, as shown in Attachment 1, for angle size 2"x2"xk" was obtained from the Bechtel Civil Design Group for Browns Ferry Plant Unit 2.
This form (other standard forms are used for various angle size) is used by the individual group and is apparently not contained in any procedures approved for use in calculations.
(An example of the use of this type of form is sheet 10, of calculation No. CD-(2003-885778,,
Rev.
0 for pipe support 2-4782650-614).
TVA General Design Criteria No. BFN-50-C-7100, Design of Civil Structures and BFN-50-C-7107, Design of Class I Seismic Pipe and Tubing Supports, require that the design method specified in AISC shall be used for all steel members used in Civil Structures and pipe supports.
Section 1.4.2. 12 of BFN-50-C-7107 gives permission to use References 1.5. 15a or 1.5.35 for a design of angle sections to meet the requirement of laterally unbraced length.
Reference 1.5. 15a is
"AISC Journal, 1st quarter 1984, Page 35."
Reference 1.5.35 is "Behavior and Design of. Angle Compression members, proceedings of the AISC Conference, June 1988."
The inspector questioned Bechtel's engineers about the source of the design method and formula used, and about meeting the unbraced length
'requirement of AISC.
Bechtel's engineers indicated that the AISC design method is too complicated for this type of calculation and the formula that they have used are conservative when compared to the AISC Design Method.
The source of the formula is Page 324, equation 10.20 of Basic Steel Design, second edition, by Bruce G. Johnston, Fung-Jen Lin, and T.
V. Galambos, published by Prentice-Hall, Inc.,
Englewood Cliffs, New Jersey.
Per Page 324 of this book for a spec'ial angle design, it states:
"If there is no lateral support, the allowable stress in bending about the strong axis will probably need to be reduced to provide safety against lateral-torsion buckling.
The AISCs (specification)
covers only specific cross sections.
In the present case a
conservative estimate of the critical moment that will cause lateral-torsion buckling is-provided by...equation 10.20."
The equation 10.20 is then converted to equation 10.21.
This equation is to serve the same purpose, as required by AISC, of reducing the allowable stresses used in designing or qualifying an angle member when an unbraced length or no lateral support in an angle member is encountered.
Proof of how conservative this= method is in comparison to the AISC design method was not available.
In addition, the standard forms used for the single angle designs are apparently not contained in any of the approved design procedures.
Pending the, licensee resolution.of this problem, this item is identified as Unresolved Item 50-259,260,296/91-11-01.
The Design Method, for Single Angle supports, Deviating from AISC Method for Resolution of this problem will involve comparative calculations to determine how conservative the method is when compared to AISC.
Also at issue is the subject of the use of unapproved desktop procedures deviate from design commitments.
See Paragraph 5 below for discussion on this problem.
4.
Additional Concerns Additional concerns were expressed to the inspector concerning methods used by TVA for Civil Structures and Piping System Designs at Browns Ferry Unit 2.
The concerns were that I) allowable loads on undercut anchors, in Table 3 of Civil Design Standard DS-C1.7. 1, are higher than ones published in the manufacturer's catalog; 2) interaction of shear and tension loads are not considered in the concrete capacity analysis described in pages
and 32 of Civil Design Standard DS-C1.7. 1.
'a
~
Allowable Loads for Undercut Anchors A concern was expressed concerning the fact that maximum allowable loads for undercut anchors in Table 3 of TYA Civil Design Standard DS-C1.7. 1 were less conservative than the allowable loads in the
"Maxi-Bolt" catalog.
The inspector found that the difference came from the fact that in the development of the Tables, TVA used a load factor of 1.6, and
"Maxi-Bolt" used a
load factor of 1.7.
The
inspector verified that the load factor of 1.6 is correct for use at Browns Ferry per procedur'e BFN-50-C-7100, Design of Civil Structures, Rev. l.
b.
Shear Load Consideration in Concrete Capacity Analysis A concern was expressed concerning the fact that the shear load is not considered with the tension load in evaluating the concrete capacity.
The inspector found that the combined effects of tension and shear on concrete anchors are included in Section 5.3.
This interaction check is required because application of shear stress to, the bolt or,stud (steel) will reduce the ultimate tensile capacity of the bolt.
Section 7.0 (pages
and 32) of DS-C1.7.1 covers the determination of the embedment of anchors, and the, shear cone area for determining the concrete pullout capacity.
No reduction in the tensile pullout capacity is made because the application of a shear load does not affect the capacity of the pullout cone.
American Concrete Institute (ACI) 349 requires checking interaction of shear and tension for anchor (steel)
but does not require shear loads to be included in the calculation of concrete tensile pullout capacity.
5.
Project Engineering Guide and Desktop Procedures During the inspection on the single angle design problem stated in Paragraph 3, the inspector learned that the forms used for single angle design by Bechtel deviated from the AISC design method and are apparently not contained in the approved procedures.
During further conversation
.
with TVA and Bechtel personnel, the inspector learned that Bechtel's engineers use controlled documents, such as Project Engineering Guide (PEG),
and uncontrolled documents, or desktop procedures, such as instructions, memos, forms, etc.
Neither PEGs nor Desktop Procedures (or files) used by individual groups are gA controlled documents.
The use of PEGs by Bechtel, was questioned during TVA audits on work performed by Bechtel, on desion of Civil Structures an4 Piping Systems for Unit 2, documented in Technical Review 89-05 (B22 '89 1102 002), dated November 2, 1989; and also in NRR Inspection Report No. 50-260/89-44, resulting in Unresolved Item EMG-034, Control of Desktop Procedures.
In a memorandum from Site guality Manager to the Manager of Site Licensing (R22 900205 817),
dated February 5, 1990, it was stated that the inclusion of technical requirements into desktop procedures without formal technical review and document control is unacceptable.
Bechtel letter No.
BFT 90/0352, dated February 5, 1990, to the Project Engineer of TVA stated that Project Engineering Guides, P-001 and P-002 are zo longer in use and are being removed from controlled distribution in accordance with Bechtel North American Power Corporation (BNAPC) procedures.
In a TYA response letter dated March 16, 1990, to the open item EMG-034, Control of Desktop Procedures, (from NRC Inspection Report No. 50-260/89-44), it is stated that the PEGs contained technical data and that the use of of the PEGs without formal technical review and document control is unacceptable.
It also stated that the PEGs are no longer in use and are being removed from distribution in accordance with the Bechtel procedure During the.inspection, the inspector questioned whether the single angle form, shown in Attachment 1, obtained from Bechtel civil design group, is a technical issue required to be approved by TVA before it is used, since the design method is different from the design method of AISC.
(Bechtel response was that this form or formula is "equivalent" to the AISC design method and can be used without TVA approval because the calculations contained on the sheet are gA documents which are signed by preparers and checkers).
The approval of a procedure, which deviates from Design Commitments, by the checking of the calculation results, appears to be a
dangerous practice, and as stated in Paragraph 3, is a part of Unresolved Item 50-259,260,296/91-11-01.
During this inspection,.
the inspector saw a
number of indications that copies of PEGs P-001 and P-002 are still readily available to people doing design work.
In fact, some of the people interviewed were under the impression that they were still being used.
This impression is particularly disturbing to NRC because the March 6, 1990 TVA response would give the impression that that is not the case.
Bechtel's actions regarding PEGs P-001 and P-002 should be addressed along with the answer to the question about the approval of the procedure discussed above.
6.
Exit Interview The inspection scope and results were summarized on March 29, and April 19, 1991, with those persons indicated in paragraph 1.
The inspector described the areas 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 TVA licensing manager was telephoned on April 30, 1991, about the new Unresolved Item 50-259,260,296/91-11-01.
(Closed) Violation 50-260/86-02-01 (Closed)
Inspector Followup Item 50-260/89-16-13 (Closed)
Unresolved Item 50-259, 260, 296/90-38-01, Conan Computer Program Evaluation and Correction (Closed)
IE Bulletins 79-02 and 79-14 (Open) Unresolved Item 50-259,260,296/91-11-,01, The Design Method for Single Angle Supports Deviating from AISC Method
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