ML20195E954
| ML20195E954 | |
| Person / Time | |
|---|---|
| Site: | Comanche Peak  |
| Issue date: | 06/04/1986 |
| From: | Terao D Office of Nuclear Reactor Regulation |
| To: | Ballard R Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8606090306 | |
| Download: ML20195E954 (13) | |
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CH9/'t k'q UNITED STATES NUCLEAR REGULATORY COMMISSION
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WASHINGTON. D. C. 20555
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% tr Jun a M Docket Nos.: 50-445 and 50-446 MEf>00ANDUM FOR:
Ronald L. Ballard, Chief Engineering Branch Division of PWR Licensing-A THRU:
outam Bagchi, Section Leader
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Engineering Branch Division of PWR Licensing-A FROM:
David Terao, Mechanical Engineer Engineering Branch Division of PWR Licensing-A
SUBJECT:
AUDIT
SUMMARY
OF SPECIAL TECHNICAL ISS'JES On Ap*il 14-15, 1986, the NRC staff and its consultants conducted an audit at the offices of Stone & Webster Engineering Corporation (SWEC) in Cherry Hill, NJ. The audit was a continuation of the previous audit held on February 11-12, 1986 (see memorandum from D. Terao to L. Shao dated February 21, 1986). The purpose of this audit was to review the resolutions of the remaining special technical issues which were not addressed at the previnus audit. This activity is part of the implementation of the Comanche Peak CPRT Program Plan described in DSAP IX Attachment 2.
A list of the attendees at the audit is provided in Attachment I to this memorandum.
The audit included a review of 20 technical issues which have been evaluated by SWEC. The SWEC resolutions to these issues have been documented in a report entitled, " Report on Stone & Webster Engineering Corporation's Evaluation of Generic Technical Issues." Each technical issue resolution is presented in the report as a separate appendix. The staff was provided a preliminary copy of the appendices for the 20 issues reviewed during the audit and it is attached to this memorandum as Attachment 2.
The 20 special technical issues covered during this audit included the following topics:
1.
U-bolt Twisting (Appendix X) 2.
Strut / Snubber Angularity (Appendix CCI 3.
A36 and A307 Material (Appendix WI 4
Wall-to-Wall / Floor-to-Ceiling Restraints (Appendix C) 5.
Seismic Acceleration of Pipe Support Mass (Appendix T) 6.
Axial / Rotational Restraints (Appendix L) 7.
Component Qualification (Appendix DD) 8.
U-bolt Cinching (Appendix K) kh0bogK05000443 6 860604 A
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Ronald L. Ballard,
9.
Local Stress in Piping (Appendix B)
- 10. Local Stress in Pipe Support Members (Appendix U)
- 11. SSER 8 Peview (Appendix EE)
- 12. SSER 10 Review (Appendix FF)
- 13. SSER 11 Review (Appendix GG)
- 14. Anchor Bolts (Appendix BB) 15.
Safety Factors (Appendix V)
- 16. Gaps (Appen<iix M)
- 17. Richmond Inserts (Appendix A)
- 18. Welding (Appendix AA)
- 19. Valve Modeling/ Qualification (Appendix Y)
- 20. Pipe Support Generic Stiffness (Appendix E)
The detailed discussion of the issue resolution and implementation is provided in Appendix 1 of this memorandum.
The agenda of the audit is given in Attachment 3 to this memorandum.
A total of 80 staff-hours were involved with this audit.
O David Terao, Mechanical Engineer Engineering Branch
, Division of PWR Licensing-A
Attachment:
As stated cc:
V. Noonan T. Westerman C. Trammell A. Vietti-Cook G. Mizuno J. Fair D. Landers, TE5 R. Hookway, TES P. Chen, ETEC 4
DISTRIBUTION:
Central Files GBagchi PAEB Reading Files PAEB Plant File DTerao Office:
PAEBY PfEB' Surname:
D erao/tg GBagchi Date:
0 L /86 0
/86
h Appendix 1 Resolution of Special Technical Issues (April 14-15, 1985)
The following paragraphs summarize the issue resolution and their implementations as discussed during the April 14-15, 1986 audit at SWEC offices in Cherry Hill, New Jersey:
1.
U-Bolt Twisting (Appendix X)
Issue Resolution: SWEC will either eliminate or modify all U-bolt trapeze supports. Modifications will address stability, pipe torsional restraint, and cross-piece rotation. The modifications include using a frame / strut arrangement or replacing the U-bolt with strap _and adding lugs.
Implementation: Pro,iect Memorandum PM-041 provides guidance for the modification of U-bolt trapeze supports.
2.
Strut / Snubber Angularity (Appendix CC)
Issue Resolution: Strut and snubber swing angles for thermal, seismic, and fluid transient movements will be assessed to assure proper function and load rating of the hardware.
For Unit 1, the component angle construction tolerance is 5 degrees. Angles were resurveyed as a result of CPPP-5 walkdown, and were documented on SWEC as-built drawings when the angle exceeded 2 degrees.
For Unit 2, the component angle construction tolerance is 1 degree.
As-built angles exceeding 2 degrees are documented.
The effect of 5 degree kick load will be assessed by the pipe support engineer in the support design on a qualitative basis.
However, the effect of kick loads will not be assessed on a system basis. Because small snubbers are being replaced on large bore piping due to system stiffness concerns, the impact of kick loads overloading small snubbers will be significantly reduced.
Implementation: CPPP-7 Sections 4.2 and 4.2.6, CPPP-6 Attachment 9-10, and CPPP-9 Attachment 9-9 will be modified to explicitly address the impact of strut angularity on component function (load rating) and the effect of 5 degree kick load on support qualification.
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A36 and A307 Steel (Appendix W) lssue Resolution: The material used in U--bolt tests were SAD 6.
The threaded rod for Richmond inserts were SA-193 Grade B7 and 4 SA-36. Sqlts were A 490.
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w For SA-36 material in a preloaded condition (i.e. cinched U-bolts) m-material relaxation will be established by test. U-bolts used as 2-way restraints and Richmond insert,s' ara n6t preloitded.
SWEC has concluded that cinched U-bolts will not lose tension and
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restraints and Richmond inserts will be subject to a low number of i will not be subject to reversing stress fields. U-bolts as 2-way.
reversing stressyfields 'dus tb seismic and fluid transient load:
and, thus, fatigue is not a cqncern.
Implementation: Designallowablostressesare-determ[nedfromthe l
ASME Code and specified in CfFP-7 Section 2 2.. Cinched U-bolt methodology implemented by Pr'oject Meinorenfum PM-049 accounts, fe material relaxation, s
4 Wall-to-Wall / Floor-to-Ceiling Aestrddtsf(Appendix C)
Issue Pesolution: SWEC.determint>d that only 8 supports which span floor-to-ceiling and/or wall-ta-wall without slip-joints remain.
These 8 supports are all located in the service water tunnel and will be analyzed for differential building displacement due' to an operating basis earthquake.
The staff raised concerns regarding the use of NF-3231.1(a) allowables for shear'and the lack of evaluation for the safe shutdownearthquagirelativebuildingdisplacements. These concerns remain unresolved and will be addressed in a subsequent audit.
Implementation: CPPP-7 Attachment 4-19 will contain the design criteria for the design of All-to-wall / floor-to-ceiling restraints.
5.
Seismic A~c'celeration of Pipe Support Mass (Appendix T)
Issue Resolution: SWEC stated that seismic acceleration of pipe support mass (self-weight excitation) will be e/aluated for all
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pipe support frames. The load is-considered negligible on non-frame supports (i.e, struts, snubbers) and will not be evaluated.
The. load due to the seismic acceleration of pipe support mass will be combined with the piping seismic loads by SRSS. The analysis will utilize either equivalent static or dynamic methods.
Implementation: Design guidelines for the seismic acceleration of pipe support mass loads has been incorporated in Project Memorandum PM-045 and will be includeri in CPPP-7 (Revision 2) Attachment 4-21.
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- 6.
Axial / Rotational Restraints (Appendix L)
Issue Resolution:
For axial restraints, where pipe lugs are restrained by a rigid frame, the support will be modelled as a translational restraint. The support will be designed for a load on one-half of the lugs (not to exceed 2 lugs) applied at the most critical location.
For axial restraints of the trapeze-type utilizing riser clamps and pipe lugs, the support will be modelled as a translational restraint in the stress analysis when the stiffness of each structure is greater than Kmin in accordance.with CPPP-7 Section 3.10.8 or when the stiffness of each structure is less than Kmin but are similar. The riser clamp will be designed to the total load. The struts and snubbers will each be designed tv 75% of the total design load.
If the stiffnesses are not similar and both are not greater than Kmin, then the support will be modelled as an eccentric translational restraint.
For trapeze supports with U-bolts utilizing snubbers, SWEC plans to either eliminate the support, convert the snubbers to struts (with modifications to address stability, twisting, and moment restraint of pipe), or to replace with a single snubber and standard clamp.
For trapeze supports with U-bolts utilizing struts, SWEC plans to either eliminate the support or modify the support to address stability, twisting, and moment restraint of pipes.
For trapeze supports utilizing trunnions, SWEC will model the support as a translational and rotational restraint in the piping stress analysis. Any eccentricity and the stiffness of the support structure will be modelled. The strut design load for each leg will be obtained from the stress analysis. The snubber design load for each leg from the stress analysis will be increased 20 percent to account for differential lock up.
For single-sided trunnions with struts or snubbers, the support will be modelled as an eccentric translational restraint for the total load.
Implementation:
CPPP-7 Attachment 4-8 and Section 3.10.6.2 as amended by Project Memorandum PM-041 established the procedure for the qualification of axial, rotational, and trapeze restraints.
CPPP-7 Section 4-6 established the analysis procedure fo'r integral attachments.
. 7.
Component Oualification (Appendix DD)
Issue Resolution: Several items related to component qualification including frame gaps in the unrestrained direction, strut and snubber swing angles, snubber travel, and spring travel were raised in external source issues. SWEC's resolution of these issues is to specify the consideration of all applicable piping loads and load combinations in the design criteria and include checklists to ensure the pipe and support movements are properly checked.
Im lementation: The pipe support checklist in CPPP-6 Attachment and CPPP-9 Attachment 9-9 address spring travel and strut / snubber movement.
CPPP-7 Section 4.2 and 4.12 specifies that the predicted pipe displacements for all design conditions must be considered.
8.
U. bolt Cinching (Appendix K)
Issue Resolution: There are several issues related to U-bolt cinching including the stability of the U-bolt, local stresses induced in the pipe, forces and stresses in the U-bolt and crosspiece (including local stresses, various loads to be considered, preload, thermal expansion, pressure, and pipe reaction), relaxation characteristics of SA-36 material, and fatigue considerations of SA-36 U-bolt material.
SWEC's resolution to the U-bolt cinching issue includes the following commitments:
- assure structural stability of U-bolt by preload in the cold condition,
- perform material relaxation tests on SA-36 by TUGC0 to quantify material relaxation of U-bolts
- increase preload to account for relaxation and for a safety factor against collapse
- evaluate local pipe stresses for preload, thermal, pressure, and pipe reaction loads
- evaluate U-bolt and cross-piece using ASME Code Subsection NF allowables
- maintain U-bolt stresses within elastic limits 4
- evaluate local stresses in cross-piece member i
- use hardened washers under U-bolt nuts to prevent galling,
- eliminate fatigue concerns by maintaining U-bolt in the elastic range due to preload
4.
- assure adequate stiffness through preload in the U-bolt / cross piece assembly to prevent separation of pipe wall from the crosspiece.
The staff is currently reviewing the above items in detail ard will provide an evaluation in a detailed report.
Implementation: Project Memoraadum PM-049 conts;ns the cinched U-bolt evaluation methodology which addresses stability, loadings, pipe stress, U-bolt stresses, crosspiece stresses, support stiffness, mechanical and' material relaxation. TUGC0 will perform relaxation tests of SA-36 steel to quantify material relaxation, TUGC0 will certify U-bolt preload.
TUGC0 will install hardened washers. These TUGC0 commitme,ts are considered to be confirmatory items and will be reviewed by the staff when completed.
9.
Local Pipe Stress (Appendix B)
Issue Resolution: Local pipe stress caused by integral attachments
,, (rectangular lugs and trunnions) and bearing loads were addressed by SWEC in this issue.
The local pipe stress induced by rectangular lugs will be evaluated using the PILUG computer program.
The program is based on WRC Bulletin 107 and will use the ASME Code Case N-318-1.
The local pipe stress induced by pipe trunnions will be evaluated using the PITRUST computer program which is based on WRC Bulletin 107 or the PITRIFE computer program which is based ou finite element analysis. ASME Code Case N-392 will be used.
Bearing loads will be evaluated using either Roark formulas (using stress allowables from ASME Cada Case N-318-1) or finite element plastic analysis.
Implementation:
Evaluation methods for irtegral attachments are incorporated in CPPP-7 Section 3.6.3 itnd 4.6.
Evaluation methods for bearing loads will be incorporated in CPPP-7.
- 10. Local Stress in Pipe Sup) ort Members (Appendix U)
Issue Resolution: SWEC 1as developed pro:edures to evaluate local stresses in tube steel members.
The procedures include the following design considerations:
(1) tube-to-tube connections both stepped and size-on-size 6
(2) welded brackets to tube steel joints
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(3) nuts bearing on tube walls I
- (4) washer plate design (5) rear brackets on cap plates welded to the end of tube steel (6) web crippling of tube steel under pipe line contact (7) web crippling of flange bending of I-shapes (8) short structural members Implementation:
Project Memorandum PM-042 addresses items 1 through 7 above and provides a procedure for the evaluation of local stresses in pipe support members.
Project Memorandum PM-042 will be incorporated into CPPP-7 (Revision 2) Attachment 4-13.
The procedure for the evaluation of short members will be included in CPPP-7 (Revision 2) Attachment 4-13.
- 11. SSER 8 Review (Appendix EE)
Issue Resolution:
In the SWEC review of the CPSES SSER 8, SWEC identified a design related item concerning confirmation by TUGC0 of the concrete design strength in safety-related areas by the test program. The concrete strength is related to the capacity of Richmond inserts and anchor bolts in which they are embedded. SWEC determined that Richmond insert allowables and concrete expansion anchor bolt allowables are based on a concrete design strength of 4000 psi.
Implementation: Project Memorandum PM-022 provides the Richmond insert allowables. Concrete expansion type anchor bolts allowables are provided in Project Memorandum PM-020. TUGC0 must confirm that the concrete design strength is appropriate.
- 12. SSER 10 Review (Appendix FF)
Issue Resolution: SWEC's review of the SSER 10 identified four issues that affect piping design.
(1) Uncontrolled plug welds (2) Main Steam Cold Pull (Loop 1)
(3)
Inspection of Skewed Fillet Welds on Stanchions (4)
Isolation of Seismic Piping from Nonseismic Piping Uncontrolled plug welds is being addressed by the CPRT Issue-Specific Action Plan V.D.
Unit 1MainSteamLoop1coldpullisbeingaddressedbyCPRTISAPiV.E.
Skewed fillet welds on stanchions is being addressed by CPRT ISAP V.A.
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Isolation Of seismic piping from non-seismic piping will be addressed by SWEC. SWEC will review piping systems in their analysis scope that are l
routed from seismic buildings to non-seismic buildings. However, the staff raised a question regarding the Class 5 piping not in the SWEC scope which are routed from seismic buildings to nonseismic buildings (e.g. feedwater). TUGC0 will address this unresolved issue later.
l Implementation:
j (1) Uncontrolled Plug Welds - No SWEC action required (2) Main Steam Cold Pull - No SWEC action required I
(3) Skewed Fillet Welds on Stanchion - No SWEC action required I
(4)
Isolation of Seismic Piping from Nonseismic Piping CPPP-7
' -10 provides the design procedure for interface anchors
- 13. SSER 11 Review (Appendix GG) j Issue Resolution: SWEC's review of SSER 11 identified six pipe support-j related issues and one piping-related issue.
Pipe support issues included:
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(1) excessive snubber spherical bearing clearance (2) load pin locking device missing 3
(3) pipe clamp halves not parallel 4
l (4) snubber adapter plate bolts not fully engaged j
(5) Hilti bolts installed with less than minimum embedment (6) absence of locking devices for threaded fasteners l
The piping issue concerned the radial shrinkage of girth butt welds in thin-walled j
stainless steel pipe being not adequately considered in the analysis.
For the pipe support issues, no SWEC actions was required. The as-built QA l
verification issues in SSER 11 will be addressed by TUGCO/CPRT.
i Excessive girth butt weld shrinkage wili be evaluated by SWEC.
Implementation:
CPPP-7 Section 3 will be revised to provide design
- criteria for evaluating excessive girth weld shrinkage.
- 14. Anchor Bolts (Appendix BB)
Issue Resolution: Embedded plate design and attachment spacing is TUGCO's responsibility. SWEC will transmit embedment plate loads-to TUGCO. Similarly, through bolt loads will be transmitted to TUGC0 for evaluation. Anchor bolts including spacing and embedment will be evaluated by SWEC. -A guideline for consideration of as-built anchor bolt location tolerances in baseplate analysi's will be incorporated in SWEC' design criteria.
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l Implementation:
Project Memorandum PM-004 identifies embedded plate i
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. design and attachment spacing as TUGC0 responsibility..CPPP-6 Section 7.5.7 and CPPP-9 Section 7.5.4 control the transmittal of pipe support reaction loads on embedded plates to TUGCO. CPPP-6 Section 7.5.7 and CPPP-9 Section 7.5.4 control the transmittal of the pipe support through bolt loads to TUGCO. Project Memorandum PM-020 provides the SWEC procedure for the design of anchor bolts.
A project guideline for the consideration of anchor bolt location tolerances in baseplate analysis will be incorporated into CPPP-7.
- 15. Safety Factor (Appendix V)
Issue Resolution:
SWEC has evaluated each known generic technical issue and its resolution has beer, incorporated into CPPP-7 design criteria. Thus, the issue of safety factors will be moot because the design evaluation will include the effects of these generic technical issues.
Small potential load variation's may result from tolerances and standard industry practices for which design margins established in codes and standards are intended to cover.
Implementation: The special technical issue resolutions are provided in CPPP-7.
- 16. Bolt Hole Gaps (Appendix M)
Issue Resolution: Certain bolt hole sizes for base plates and Richmond insert supports exceeded that allowed by NF-4721 Table NF-4721(a)-1 for bearing connections. However, in a subsequent revision to the ASME Code (1983) NF-4721 including Summer 1985 addenda, bolt holes for concrete expansion anchors were permitted to be increased by 1/16 inch. Thus, the bolt hole sizes at CPSES meet the later ASME Code revision. The 1985 Summer Addenda (NF-4721(a) will be adopted by CPSES.
Implementation: Section 4.5.1 and Attachment 4-4 of CPPP-7 will incorporate the CPSES anchor bolt sizes as acceptable for bearing connection design. ASME NF-4721(a) 1985 Summer Addenda will be added to the CPSES Code of Record in CPPP-7 Section 2.2 and in the FSAR.
- 17. Richmond Inserts (Appendix A)
Issue Resolution: Several concerns related to Richmond inserts were raised in external source issues. The concerns included:
- a factor of safety of 2 instead of the vendor recommended factor of safety of 3 was used
- the effect of axial torsion in tube steel / Richmond insert supports may not have been properly considered
- the modelling of the end connections of the tube steel / Richmond insert support and bolt angularity was questioned j
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. - bending of the Richmond insert bolt and the interactio.n equation should be addressed
- due to 1/8 inch oversize holes, the distribution of the shear load on the inserts should be evaluated
- the close spacing should reduce the insert allowables
- fatigue of the Richmond insert bolts and potential overstress of the insert / bolt due to large frame thermal expansion The resolutions developed by SWEC were as follows:
- A factor of safety of 3 against actual insert tests will be used.
- Finite element results for axial torsion in tube steel show that the concrete resistive force is located at the tangency point of the tube steel corner.
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- An " outrigger" design has been developed for single ' tubes loaded in torsion.
- A modelling procedure has been developed that considers the tube steel / Richmond insert connection as fixed but does take into account the bolt stiffness.
- An interaction equation that accounts for bolt bending has been derived.
- The resolution of the sharing of shear loads is addressed with 4
gaps.
- SWEC will use actual insert spacing and reduce the allowable loads accordingly.
- The elastic response of the insert and the number of seismic cycles indicate that the insert fatigue is not a concern. The insert / bolts in large frames subject to thermal expansion will be evaluated on a case-by-case basis.
Implementation:
Project Memorandum PM-022 addresses Richmond insert and threaded rod qualification.
- 18. Welding (Appendix AA)
Issue Resolution:
For undersized fillet welds, minimum weld size will be checked until ASME Code Case N-413 is approved for use.
For subsurface cracking in welds with deep penetration and/or small
. included angles, SWEC reviewed TUGC0 weld procedures and concluded they are adequate to preclude this situation.
For fillet welds on trunnions which exceed AWS prequalified weld requirements, all CPSES welds are qualified and inspected in accordance with ASME and credit will not be taken for portions of welds on included angles which exceed 135.
For eccentricities of three-sided welds, the center of gravity of member will be considered in the design of unsymmetrical welds.
For linear vs. plate and shell weld design for baseplates, SWEC determined that ASME Section III NF-1230 allows qualification of baseplate welds to linear design requirements.
For attachment of baseplates to building structures using both bolts and welds,. welds will be designed for the entire shear load on the face of the plate.
For crosspiece cover plate welds, shear flow will be considered.
For permissible increases in allowable weld stresses in the emergency and faulted conditions, a one-third increase will be used.
Implementation: CPPP-7 will contain the design criteria for the above issue resolutions.
- 19. Valve Modellina/ Qualification (Appendix Y)
Issue Resolution: SWEC has discussed the double ported SRV flow distribution concern (55/45) with Crosby Valve and agrees with Crosby's position that the flow distribution is 50/50. SWEC has evaluated the leading conditions on the Main Steam Line due to multiple SRV actuation and concurs with CYGNA that the design is governed by the simultan'eaus opening of the 5 SRV's for support design. SWEC has evaluated the Fischer Valve Support concern raised by CYGNA and concurs with the requirement for interface control of supported valve operators.
Implementation: CPPP-7 Section 4.5.6 defines the applicable analytical method for the design and analysis of open discharge SRV piping systems.
A 50/50 flow distribution between discharging branches will be used.
Any imbalance of load due to the flow path will be addressed in the final as-built analysis.
SWEC will incorporate pertinent SRV combinations into System Information Documents (SID) in order to control the loading combinations evaluated in the MS pipe stress packages.
CPPP-6 Section 7.4.3 defines the items which need evaluation by others.
.. t Valves with supports will have both valve accelerations and support loads transmitted to the appropriate group (TUGCO) for evalua' tion.
20.
Pipe Support Generic Stiffness (Appendix E)
Issue Resolution:
SWEC developed a new set of generic stiffness values for pipe sunports to be used in the piping stress analysis.
These stiffnesses more accurately reflect the actual stiffnesses of the pipe support designs found in CPSES.
Implementation: CPPP-7 Section 3.10.8 provide the guidelines for stiffness representations of pipe supports.
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