ML20206S428
| ML20206S428 | |
| Person / Time | |
|---|---|
| Site: | Vogtle  |
| Issue date: | 09/05/1986 |
| From: | Foster D GEORGIA POWER CO. |
| To: | Grace J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| References | |
| REF-PT21-86, REF-PT21-86-315-000 GN-1067, PT21-86-315, PT21-86-315-000, NUDOCS 8609220214 | |
| Download: ML20206S428 (13) | |
Text
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ot fi e x Waynest:oro, Georgia 30830
. Telrphona 404 554-99S1. Ext. 3360 404 724-8114. Ext. 3360 b0 bg g p t : 5 3 GeorgiaPower
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rrerrwr> mirantem September 5,1986 United States Nuclear Regulatory Commission Region II File: X78G03-M102 Suite 2900 Log:
GN-1067 101 Marietta Street, Northwest Atlanta, Georgia 30323
Reference:
Vogtle Electric Generating Plant-Units 1 and 2; 50-424, 50-425; Pipe Support tolerances and Installation Procedures; Letter GN-890 dated May 1, 1986; Letter GN-989 dated July 11, 1986 Attention: Mr. J. Nelson Grace In previous correspondence, Georgia Power Company described a potentially reportable condition whereby some pipe supports may have been installed to criteria which was subsequently modified or superseded such that present design requirements may not be met.
Except for an issue involving optional weld patterns, Georgia Power Company has completed its evaluation and has concluded that some aspects of this condition are reportable pursuant to 10 CFR 50.55(e) and 10 CFR 21.
A summary of our evaluation is attached.
Georgia Power Company expects to provide the USNRC with a report on the remaining portion of our evaluation by October 24, 1986.
This response contains no proprietary information and may be placed in the NRC Public Document Room.
Yours truly, 86092kO214 860905 ADOCK 050 4
gDR g
D. O. Foster REF/00F/tdm Attachment xc:
U. S. Nuclear Regulatory Commission Document Control Desk Washington, D. C.
20555 J. H. Miller R. A. Thomas L. T. Gucwa J. P. O'Reilly D. R. Altman C. W. Hayes G. F. Head P. R. Bemis G. A. McCarley R. E. Conway J. A. Bailey D. S. Read J. T. Beckham
- 0. Batum Sr. Resident (NRC)
R. H. Pinson G. Bockhold C. S. McCall (OPC)
P. D. Rice C. E. Belflower J. E. Joiner (TSLA)
- 8. M. Guthrie J. F. D'Amico D. Feig (GANE)
D. E. Dutton E. D. Groover NORMS 1 I e
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EVALUATION OF A POTENTIALLY REPORTABLE CONDITION PIPE SUPPORT TOLERANCE AND INSTALLATION PROCEDURES Initial Report:
On April 3,
1986, Mr.
R. E.
Folker, Vogtle Project Quality Assurance Engineer, informed Mr. W. H. Rankin of the USNRC Region II of a poten-tially reportable condition concerning pipe support tolerances and in-stallation procedures.
In subsequent correspondence, the NRC was advised that they would be informed of the results of the evaluation of this condition by September 5, 1986.
Background Information:
The design of the support system for safety-related piping is based on the piping stress analysis which is performed in accordance with ASME Code Section III, Subsections NB, NC, and ND.
The pipe supports are designed, fabricated, and installed in accordance with ASME Code Section III, Subsection NF and the AISC Code, which is applicable to the pipe support miscellaneous structural steel.
Pipe supports are individually designed and issued for fabrication and installation on engineering drawings which are identified by individual tag numbers.
The pipe supports are installed in accordance with these drawings by PullmanPowerProducts(PPP).
Construction specification X4AZ01, Division P-5, was prepared by Bechtel Power Corporation and provides engineering criteria applicable to the installation of the pipe supports.
This criteria is converted to con-struction guidelines by PPP in their field installation procedure IX-50.
Bechtel Power Corporation made changes in the construction specification that controlled the tolerances and installation procedures for pipe supports.
These changes were made between August 1985 and December 1985.
The pipe suprorts installed prior to the changes could potentially restrict pipe movement be. yond that calculated in the pipe stress analysis and could result in loads on pipe support structures in excess of the calculated design loads.
The six criteria in the construction specifica-tion which were revised or superseded and could affect the performance of installed pipe supports are:
1.
Embed Plate / Penetration Separation less than two inches 2.
Less than minimum required restraint gap in box frame pipe support configurations 3.
Non-engineered stop plate installed in axial restraint configuration 4.
Non-engineered filler plate installed in strap restraint configura-tion 5.
Non-engineered weld joint option with reduced load capacity 6.
Non-engineered shape / size substitution of structural steel
c a
Page~Two i-Engineering Evaluation:
Criteria 1 - Embed Plate Separation The original criteria in the construction specification for pipe support.
installation specification X4AZ01, Divisi.on P-5, did not include the configuration in Figure 1, which requires the reduction of the load capacity of an embed plate-if the embed plate is located less than two
.ind es (edge to edge) from a wall penetration.
The following cases could have existed under which an installed pipe support could be. located in the diminished load capacity portion of i
the embed plate (shaded area as shown on Figure 1).
1.
An embed plate is located closer than two inches to a wall penetra-tion as a result of a decision made by engineering during design f
or construction.
Subsequently,
- a. pipe support design required attachment to this embed plate.
+
2.
The pipe support installation is completed and subsequently a hole is core drilled less than two inches from an embed to which the i
l pipe support is attached.
}
3.
A pipe support design includes attachment to an embed in close i
proximity to a penetration, but the attachment location is totally outside the shaded area of Figure 1.
During installation, the attachment location shifts into the shaded area because of construc-l tion tolerance.
In case 1, the Civil / Structural (C/S) drawings show the close proximity of embed plate and penetration. C/S documents and pipe support documents (C/S drawing AX2D94V006 and Guidelines of Bechtel interoffice memorandum BB-21207, and Pipe Support design instruction memo Group 3, respectively) define the action which personnel take to qualify the embed plate for l
use and the pipe support design for attachment to the embed plate.
4 j.
In case 2, Georgia Power Company construction personnel will core drill the hole in accordance with Procedure GD-T-12.
Under this procedure, any core drilled hole which is closer than two inches from an embed plate is considered to be a nonconformance.
A Deviation Report (DR) i is initiated and an evaluation review is performed.
l.
The previous construction specification did not clearly address the l
conditions described in case 3.
Therefore, an evaluation was performed to demonstrate that any of the three penetration sleeve types shown on engineering drawing AX2D94V005 could be located directly adjacent to any of the embed types shown on engineering drawings AX2094V006 and i
AX2D94V017 without exceeding allowable load for embed plates. The evalua-J tion was performed in a manner consistent with the original design calcu-lation and assumed that the worst combination of design parameters existed j
simultaneously.
For example, the beneficial effects of possible penetra-1 tion sleeve collars were ignored.
(The existence of a collar would i
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.Page,Three 7
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i il reduce _ the interference of the penetration sleeve' = with thedsheir? cone \\ p s of the anchor bolt or stud.
It would also provide restraint ' foF the i shear cone of. the adjacent anchor bolt or stud since the shear cone t y, would have to also. shear or bend the collar -of the penetration sleeve.);
y 'n The sleeve was also assumed to _ be directly adjacent 1to the. embed Jat the location of the most critical bolt on the emped plate.
All othes 4 [ e O c
their imximun, or minimum hM
-[. l
- s parameters were assumed to be either at 4
g ff
'V required to develop the most critical configuration possible.
e t
With the conservative assumptions described above, a design calculat 3, h
[
(No. X2CQS.4) ~ was performed.
It indicates. that for bbth anchor bol,ts
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and studs the concrete capacity for both pullout and bursting still exceed the values utilized to create the existing: allowable load tables 4
for Vogtle embed plates, and there is no safety impact to thd plant.
~l( 7 s
3 Criteria 2 - Restraint Gap (Lateral Restraint / Box Frame Pipe Supports),
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i i
The original criteria in construction specification allowed a zero mi.nimum i e F 1
gap between the pipe outside diameter and each surface of a miscellaneous y
steel box-frame structure which serves as a one, or two, axis lateral-pipe restraint (Figure 2).
Application of this minimum gap criterion.
7 may prevent free thermal movement of the piping as it aporoaches( the
_h design temperature.
t' y
During an as-built reconciliation walkdown, installed pipe supports j e were found with zero gap between the piping and the, lateral restraint
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structure.
The condition was reported to engineering.
An evaluation' a*
resulted in the development of modified minimum restraint gap criteria.
i These criteria ensure that the pipe is free to move in the unrestrafind j
4' axis under all operating conditions.
o installed, supports, whh h
l A retrofit inspection was initiated on all contain a lateral restraint structure and were installed during the time period when the zero minimum gap criteria existed in the construction p' '
,s specification X4AZ01, Division P-5.
During this retrofit insoection,'
)
192 installed supports were found which also deviated 'froml th'e' maximum
("
gap criteria of the construction specification.
DR's 'were issued ' to I
cover deviations from both minimum and maximum restraint < gap 'crituia,
./
thus expanding the scope of the' engineering evaluation'. After evalu nion (
i of the supports, it was determined that 86 tupports were acc'eptable and that 45 supports were required to have repair or rework.
Twenty-two i
of the 45 supports were located in safety-related systems. These support.;
l are listed in Table 1.
s An evaluation was performed of the pipe supports listed dn Table 1 (had
'n '
cluding associated piping) to determine the impact on 'plJnt.. safety.
,'t l
4 the condition gone uncorrected.
The evaluation was based on' the assump-tion that the gap condition noted in Table 1 co;1d have resulted in one of the following two piping failure modes:
P 3
f 1.
Minimum Restraint Ga*p Condition g
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Page Four 99 i'
o The pipe tries to move axially as the pipe -temperature approaches the design condition but binding of the pipe in 1
the restraint structure (see Figure 2) prevents axial movement.
The resultant reaction load on -the pipe support structure imposes stresses in the pipe support structural steel which exceeds the code allowable for the material and the pipe support y
separates from the building structure.
The pipe is unsupported at this location and fails because adjacent supports cannot carry the redistributed load (resulting from the pipe support
='
failure).
o The same initiating condition occurs as described above, how-v.
ever, the pipe support does not fail by separation from the building structure although it might bend if the yield strength is exceeded.
The pipe is restrained from moving axially and at some location the stresses in the pipe exceed the code allowable for the material and the pipe fails.
2.
Maximum Restraint Gap Condition o
The pipe is not restrained axially but, because the gap is excessive, the required lateral restraint is not applied.
This excessive freedom to move produces excessive stresses in the pipe at some location and the pipe fails.
o The same initiating condition occurs as described above, how-ever, the pipe is not overstressed but the excessive gap results in an unacceptable shock load on the pipe support structure which is imposed by the moving pipe during a seismic event.
The pipe support structure fails and the ultimate consequence is pipe failure.
The evaluation concluded that the failures of the twenty-two supports listed in Table 1 could have adversely affected plant safety.
For example:
o Pipe supports Vl-1204-124-H011 and V1-1204-127-H018 are located on lines 1-1204-124 - 10" and 1-1204-127 - 10" respectively.
These lines (project class 111) are located between the discharge of the SIS accumulator tank.; of loops 1 and 4 respectively, and the RCS cold legs of these two loops.
Failure of either of these supports represent a potential breach in the RCPB and/or degradation of the ECCS.
The line failure could also result in the loss of safety grade cold shutdown capability.
o Pipe supports V1-1204-020-H001 and H002 are located on line 1-1204-020 - 8" (project class 212).
This line is part of the RHRS hot leg injection crossover to RCS loop 1.
Failure of the piping could result in the loss of the long term ECCS.
o Pipe support V1-2403-035-H002 is located on line 1-2403-035 - 40" (project class 015) which is located at the exhaust to atmosphere of the diesel generator (equipment tag no.1-2403-G4-001).
Failure 1
b Page Five of the piping, when coupled with an additional single failure, could result in loss of onsite power.
Should offsite power become unavailable this condition could have an impact on' plant safety had it gone uncorrected.
Similar s'afety impacts were demonstrated for the other supports.
o The remaining 23 pipe supports are not located in safety-related systems and could not impact the safety of the plant had the condi-tiongoneundetected.l Criteria 3 - Stop Plate (Axial Restraint Pipe Supports)
The current construction specification allows the installer to add stop plates to a pipe support with prior engineering review.
The stop plates provide axial' restraints to the pipe in order to compensate for installa-tion tolerance build-up.
The original specification criteria did not include the engineering review requirement.
As a consequence, two possible conditions shown in Figure 3 may result when the installer adds stop plates.. The conditions could have been included in any of the axial restraint pipe supports which were installed while the original criteria existed in the construction specification.
A statistical sample -inspection list was prepared of all installed supports which include an axial restraint (approximate population 2100),
using the VAX-750 random number generator program, RANDU.
As a result, 108 pipe supports, which included an axial restraint were inspected and five were found with stop ' plates.
Statistically this sample inspection quantity meets the 95-95 criteria of the Project Reference Manual, Part C, Section 28.
The five supports found in the sample which contained stop plates in the as-installed configuration were evaluated.
In three of the five supports the stop plate configuration was included in the issued pipe support drawing and therefore is not considered an unverified addition to the design by PPP.
Analysis of the remaining two supports was per-formed because the stop plate was not included on the drawings (reference:
calculation no. X4CP-S0114).
The maximum stresses imposed on the stop plates in these two pipe support installations under all anticipated plant operating conditions did not exceed AISC Code allowables and the installed pipe supports are acceptable.
It is concluded with 95% confidence that 95% of the total population of pipe supports with axial restraints is acceptable and fall into one of the following categories:
o The installation 'does not contain stop plates.
o The installation conuins stop plates.
However, they were included in the issued design and are covered by an engineering calculation.
i
Page Six 4
o-The installation contains stop plates which were not on the issued pipe support drawing, but were added by PPP.
Although not shown on the pipe support drawing, the stop plate installation meets AISC Code allowables and is acceptable.
4 This condition has no impact on plant safety.
Criteria 4 - Filler Plate (Strap Restraint Pipe Supports)
The current construction specification allows the addition of a filler plate when installation tolerance. build-up results in a gap between a strap restraint and the support miscellaneous steel structure.
The original specification criteria allowed use of the configuration depicted in Figure 4 which could result in excessive bending stresses in the filler. plate and possible plate failure.
Plate failure would result in additional piping movement which could result in higher piping and support stresses.
Using the method previously described, a statistical sample of 108 pipe supports was selected from the total population of pipe supports which' include a strap restraint and which were installed while the original criteria existed in the construction specification (approximately 30,200).
This statistical sample is independent (although the sample size is the same) of the sample which represented axial restraint pipe supports.
Six installed pipe supports were found with filler plates.
These six supports were evaluated to determine whether any filler plates were added to the support design by PPP and, if so, whether the installed configuration was acceptable.
On one pipe, support the filler plate configuration was included in the issued pipe support drawing.
Therefore, it is not considered an unverified addition to the design by PPP.
Four pipe supports did not fall into the category defined in Figure 4 because the filler plate thickness exceeded 1/4 inch.
These installations were acceptable in accordance with pipe' support calculation X4CP-S0084.
Evaluation of the sixth pipe support indicated that PPP added an unspecified 1/4 inch thick filler plate, but the evaluation indicated that the stresses in the filler plate under all plant operating conditions were within AISC l
Code allowables and the installation was acceptable.
I It is concluded with at least 95% confidence that 95% of the total
)
population of pipe supports with strap restraints is acceptable and falls into one of the following categories:
o The installation does not contain a filler plate.
o The installation contains a filler plate which was included in the issued design and is covered by an engineering evaluation.
o The installation includes a filler plate which was added by PPP.
Although not shown on the pipe support drawing, the filler plate configuration satisfies project pipe support design criteria and AISC Code allowables.
___ -.. _ ~. _ _ _
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Page Seven 1
This condition has no impact on plant safety.
Criteria 5 - Weld Joint Option The current construction specification allows substitution of certain optional weld patterns for the weld pattern shown on the pipe support i
drawing. However, the sectional properties of some optional weld patterns for structural angles and channels in the original specification criteria -
are lower (thus lower weld joint load capacity) than those properties of the specified pattern.
An example is shown in Figure 5.
The evalua-tion of this criteria is still proceeding.
Georgia 'ower Company expects
[
to report the results of this evaluation to the NRC oy October 24, 1986.
Criteria 6 - Structural Steel Shape / Size Substitution The current construction specification allows the installer to modify the shape / size of structural miscellaneous steel members defined on the pipe support drawing.
The original specification allowed the in-staller to make this substitution without notifying engineering as long as the table of allowable substitutions in the specification was followed.
This table allows the substitution of larger member sizes and, in some cases, stronger member shapes.
The specification was revised to require as-built documentation of any miscellaneous steel shape / size substitution
+
because some substitutions may have been made which may result in redis-tribution of loads within the structure and overloading of individual member (s) and/or connection (s).
t A statistical sample of 59 pipe supports was selected from the total population of approximately 32,000 pipe supports containing miscellaneous structural steel which were installed while the original criteria existed in the construction specification. This sample was inspected to determine whether a substitution for a specified steel member (either shape or size) was made by PPP and, if so, whether the as-installed configuration was evaluated for acceptability.
le supports in the 59 support sample contained a substituted structural steel member.
Analysis of each of these pipe support configurations indicated that the maximum stresses which would be imposed on the members and welds of the miscellaneous steel structure under all anticipated plant operating conditions would not exceed the AISC Code allowables.
l These pipe supports are acceptable as installed.
It is concluded with at least 95% confidence that 95% of the total popula-tion of pipe supports with miscellaneous structural steel is acceptable and fall into one of the following categories:
o The installation does not contain structural steel member substitu-tions.
o A substitution was made by PPP in accordance with specification X4AZ01, Division P-5, and the resultant installation meets AISC j
Code allowables.
)
Page Eight This condition has no impact on plant safety.
Evaluation of Breakdown of Quality Assurance Program:
The described conditions were the result of unclear representation of the pipe design criteria / tolerance in prior revisions of the construction specification X4AZ01, Division P-5.
This specification has since been revised according to project procedures to improve the clarity of the existing installation tolerance and/or criteria.
Furthermore, the potential impacts of these clarifications have been analyzed, and corrective actions, when necessary, have been initiated.
As a result, we concluded that this condition does not constitute a significant breakdown in Bechtel's Quality Assurance Program.
==
Conclusion:==
Based on the results of the engineering evaluation performed for Criteria 2 - Restraint Gap, Georgia Power Company has concluded that a reportable condition as defined by the reporting criteria of Parts 10 CFR 50.55(e) and Part 10 CFR 21 does e> 'st.
Also, Georgia Power Company intends to report to the NRC by Octo'
- 24, 1986, the results of the evaluation of Criteria 5 - Weld Joint Option:.
Corrective Action for Criteria 2 - Restraint Gap The lateral restraint structure of the installed pipe supports which have unacceptable restraint gaps will be reworked or repaired as required.
This action will be performed by construction in accordance with the disposition of the DR's and the requirements of the construction schedule.
This corrective action is also tracked by item no. 181721 in the program for completion of work (PCW).
1
e 0
TABLE 1 PIPE SUPPORTS REQUIRING REWORK / REPAIR OF RESTRAINT GAP CONDITION PIPE SUPPORT PROJ. PIPE GAP
__ TAG NO.
ISO NO.
CLASS DIA.
CONDITION MIN.
MAX.
REACTOR COOLANT SYSTEM (1201)
V1-1201-036-H018 1K4-1201-036-01 111 12 X
X V1-1201-042-H002 1K4-1201-042-02 111 12 X
X SAFETY INJECTION SYSTEM (1204)
V1-1204-020-H001 1K4-1204-023-03 212 8
X X
V1-1204020-H002 1K4-1204020-02 212 8
X V1-1204-021-H009 & 16 1Kb1204-021-03 111 6
X V1-1204042-H015 & 22 1K4-1204042-01 111 6
X V1-1204-043-H011 1K4-1204-039-02 111 6
X V1-120404 4H007 & 09 1K4 120404 401 111 6
X V1-1204044-H010 1K4-1204-044-01 111 6
X X
V1-1204-045-H024 1K4 1204045-01 111 6
X X
V1-1204-045-H025 1K4-1204-045-01 111 6
X V1-1204-124H011 1K4-1204-12401 111 10 X
V1-1204-127-H018 1K4-1204-045-01 111 10 X
X RESIDUAL HEAT REMOVAL SYSTEM (1205)
V1-1205-003-H005 1K3-1205-003-01 212 14 X
V1-1205-003-H042 1K3-1205-003-02 212 12 X
V1-1205-004-H020 1K7-1205-004-01 212 14 X
V1-1205-040-H004 1K3-1204038-01 212 12 X
CONDENSATE SYSTEM (1305)
V1-1305-060-H001 1K5-1305-058-01 212 16 X
SEISMIC CAT.1 FIRE PROTECTION WATER SYSTEN (2403)
V1-2403-035-H002 1K5-2403-035-01 015 40 X
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Figure 1 EMBED PLATE / WALL PENETRATION PROXIMITY EMBED PLATE e**
WALL PENETRATION TV O 1 A X
- 4 "-
IF X OlMIN$10N <2" PLATE LOAD CAPACITY IN SHADED ARE A 15 DIMINISHED. ATTACMMENT OF MISCELLANEDUS STEEL IN THIS AREA MUST BE LIMITED Figure 2 ZERO RESTRAINT GAP 0" CLEAR ANCE EACM SIDE POS$1BLE A*
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/
kmme 9
p
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1 le e e p
9 es es 9
9
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WITM 0" CLEARANCE ON EACM SIDE (CUMULATIVE 0" CLEARANCE POS$1B LEITHE PIPE M AY NOT BE FREE TO MOVE ARIALLY
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Q Figues 3 STOP PLATES 9
as--== AMIAL MOVEMENT Tl
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$ NIM PLATE l
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T N
RESTRAINING LUG RESTRAINING STEEL MEMBE R -
ON CORNER RADIUS LUG CONTACTS STEEL MEMBER CONDITION A i
AX4AL MOVEME NT l
f7 11/4" MAX. SHIM PLATE STOP PLATE
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O a-i y
9 RESTRAINING LUG N/4 WIN.
,e RESTRAINING STE EL MEMBE R g
LUG CONTACTS STOP PLATE CONDITION 3 04 UN. SUPPORTED PLATE EDGE l
lW BOTH CONDITIONS THE AXIAL PIPE MOVEMENT CAUSES THE LUG TO CONTACT I
THE RESTRAINING MISCELLANEOUS STEEL STRUCTURE. BUT CONTACT MAY BE INADEDUATE FOR PROPERLY APPLYING RESTRAINT.
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Figure 4 FILLER PLATE OPERATING LOAD 241 FAY RESTRAINT STRAP PIPE p
l 1/4" FlLLER PLATE A
L
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OPE R ATING LOAD TRANSMITTED THROUGH STRAPINTO FILLER PLATE. PLATE DESIGN 5HOWN RESULTS IN HIGH BENDING LOAD IN PLATE WHICH MAY DVERSTRESS MATERIAL.
Figure 5 WELD PATTERN OPTION K
M////////MA n
a WE LD PATTE RN WELO PATTERN SPECWlED ON PIPE OPfl0N ALLOWED BY SUPPORT DRAWING WECIFICATION THE SECT 10NAL PROPERTIES OF THE OPfl0NAL WELO PATTERN (ON RIGHTI ARE LOWER THAN THE PATTERN SPECIFIED ON DRAWING (ON LEFTI.#USE OF OPfl0N AL PATTERN RESULTS IN INSTALLED WELD WITH LOWER LOAD CAPACITY THAN INTENDED BY DESIGN.
-