ML20059N097
| ML20059N097 | |
| Person / Time | |
|---|---|
| Site: | Maine Yankee |
| Issue date: | 09/26/1990 |
| From: | Trottier E Office of Nuclear Reactor Regulation |
| To: | Frizzle C Maine Yankee |
| References | |
| IEB-88-011, IEB-88-11, NUDOCS 9010100095 | |
| Download: ML20059N097 (12) | |
Text
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September 26, 1990 i
Docket No. 50-309 Mr. C. D. Frizzle, President.
Maine Yankee Atomic Power Company
'83 Edison Drive Augusta, Maine 04336
Dear Mr. Frizzle:
SUBi)ECT: NRC BULLETIN NO. 88-11, PRESSURIZER SURGE LINE THERMAL STRATIFICATIOH; PLANT AUDIT On September 27-28 1989, the Mechanical Engineering Branch of NRR conducted an-audit at Maine Yankee Atomic Power Station.. The_ purpose of the audit was to I
review your surge line inspection results, corrective actions,-and use of.
information presented in the associated CE Owner's Group report (CEN 387-P).
As a result of this audit, including our review of additional information received subsequent to it, we conclude that Maine Yankee has implemented an acceptable inspection program in accordance with the guidance found in requested i
action item 1.a of the subject Bulletin. However, please note that we found that further justification is needed to include Maine Yankee in the bounding analysis performed by the CE Owner's Group (action item 1.b). Thus, the balance of the cetion items of this Bulletin that are applicable to Maine-Yankee (action items 1.b, 1.c and 1.d) remain open.
i Sincerely, Original signed by Ed Trottier, Project Manager Project Directorate 1-3 Division of Reactor Projects - I/II f
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Mr. Charles B. Brinkman Mr. G. D. Whittier, Manager Manager - Washington Nuclear Nuclear Engineering and Licensing i
Operations Maine Yankee Atomic Power Company i
Combustion Engineering, Inc.
83 Edison Drive 12300 Twinbrook Parkway, Suite 330 Augusta, Maine 04336 Rockville, Maryland 20852 Mr. Robert W. Blackmore John A. Ritsher, Esquire Plant Manager Ropes & Gray.
Maine Yankee Atomic Power Company 225 Franklin Street P.O. Box 408 Boston, Massachusetts 02110 Wiscasset, Maine 04578 State Planning Officer Executive Department 189 State Street Augusta, Maine 04330 Dr. E. T. Boulette Vice President - Operations Maine Yankee Atomic Power Company P. O. Box 408 Wiscasset, Maine 04578 Regional Administrator, Region I U.S. Nuclear Regulatory Commission 475 Allendale Road King of Prussia, Pennsylvania 19406 l
First Selectman of Wiscasset l
Municipal Building U.S. Route 1 Wiscasset, Maine 04578 Mr. Charles S. Marschall Resident Inspector Maine Yankee Atomic Power Station U.S. Nuclear Regulatory Commission P. O. Box E Wiscasset, Maine 04578 Mr. P. L. Anderson, Project Manager Yankee Atomic Electric Company 580 Main Street Bolton, Massachusetts 01740-1398
i E9 CLOSURE i
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Page 1 of 8 i
i Audit Trin Ranert
Purpose:
Audit of Maine Yankee on NRC Bulletin 88-11 Issues (Pressurizer Surge Line Thermal Stratification)
Location:
Maine Yankee Plant site, Wisensset, ME.
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Dates:
September 27, 1989 i
NRC Personnel:
Shou-Nien Hou (NRC)
Frank Vasiliadis (NRC Con'eultant / EAS)
Licensee Personnel:
Charles Eames Rob Crosby Howard Jones i
I 1.0 Backaround i
i In light of thermal stratification found in the Pressurizer Surge Line (PSL) of several PWR's, NRC issued Bulletin 88-11 on December 20, 1988.
Since thermal stratification causes changes in piping stresses, fatigue life and line deflec-tions from those predicted in the original design, all licensees were requested to conduct visual inspection of the PSL; to update stress and fatigue analysis for ensuring code compliance, and to aonitor thermal conditions and line deflections.
In addition, the striping phenomenon which may induce high cycle fetigue to the inner pipe wall, needs to be evaluated.
Combustion Engineering (CE), on behalf of the CE Owners Group' (CEOG) which includes the licensee of Maine Yankee, has i
submitted generic bounding evaluation report CEN 387-P, dated July, 1989, which consists of presentation material and explanatory text.
Additional input was also provided by the licensee during the meeting which clarified specific portions of the report.
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ENCLOSURE
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l 2.0 Audit scoom l
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The audit covered the following topics:
2.1 PSL inspection results and corrective actions.
I 2.2 NRC staff questions related to CEOG Report CEN 387-P.
2.3 Interrelationship between efforts of Maine Yankee and the CEOG, 2.4 Documentation _ review. including reports, drawings and calculation packages See enclosure 1 for audit agenda.
3.0 Hiahliohts of Audit 3.1 We fcand that the licensee had conducted a visual in-spection of the PSL on February 15, 1989 in accordance with Action la of Bulletin No. 88-11,.and found no evidence of permanent deformation or discernable dis-tross to either.the PSL or the 3 spring hangers with>the exception of crushed insulation.
Directly under the PSL in the vicinity of hanger SL-SH-L 11, there are two 1" diameter, non-nuclear safety, field j
supported lines.
Line I.D.
System Site Drawina 1-SA-62-151 Auxiliary Steam 1" SCH 80 FP-33E 1-ASC-48-121 Service Air 1" SCH 80-FP-33E The visual inspection recorded indentations in the insulation of the PSL.
The observed gap between the troughs of the lines' insulation dents is 0.45" (0.25"-
of clearance between the PSL and the uninsulated 1",
Service Air line and 0.45" between the surge line and the insulated auxiliary steam line).
This indicates that at some point during Maine Yankee's operation, the PSL had displaced an additional 0.45" downward from the hot standby position where the visual inspection was.
conducted.
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Page 3 of 8 An additional interference was observed between the PSL-and a 10" (10-RC-28-302) SCH 40 Reactor Coolant line (Maine Yankee drawing #FP-13A, 5, C & D).
A 1" deep by 6" vide indentation existed on a horizontal portion of the PSL's insulation which appears to have' been crushed by the vertical 10" line.
Since the 4" calcium silicate insulation which exist on the PSL, can be crushed with minimum force, it is.un-likely that the 1" and the 10" pipes had restrained much of.the movement of the 12" Surge Line.
Deficiency report DR-842-89 (DR) was initiated to tria insulation at both interference locations.
Since.the calcium silicate insulation cannot transmit any:appre-ciable loads, it can be concluded that this insulation interference will not substantially restrict the free thermal movement of the PSL.
The staff agrees with this reasoning and feels that the disposition of the DR to tria the insulation and to avoid further interference is acceptable. (DR did not needed to be completed prior to restart).
However, the staff feels that further investigation is required to j
assess the impact of anticipated larger piping movements I
during a seismic event, due to likely insufficient clearances with the adjacent 1" and the 10" lines.
The l
impact of possible interaction of pipes during seismic event should be assessed.
j In the generic analysis of the CEOG report, it was assumed that all spring hangers have at least two inches of free travel from the cold position setting.
The staff questioned the validity and justification of this assumption since restraint oftfree t!,armal growth asso-ciated with the stratification condition will impose additional stresses.in the PSL and higher loads on the support.
The licensee reported that, based on the 1982 l
In-Service-Inspection (ISI) of the PSL, the remaining available free travel from the cold position setting in.
2 of the 3 PSL supports was more than 2".
For the third support, SL-SH-11, the remaining available free travel from the cold position setting was 1.94".
The effects of stopping the spring hanger travel 0.06" early was calculated in the CEN-387-P report and the highest stressed point, which is the elbow of the hot leg, increased from 5.74Sa to 6.65Sa or 16%.
ENCLOSURE Page 4 of 8-In addition, CE calculated the load on support SL-SH-11
-when travel limitations of 0.06" were imposed on the support for AT= 3 2 00F, and reported a load of 20830 lbs, which is far in excess of the allowable spring load of 5200 lbs.
The licensee's position is that tk:e CE generic bounding evaluation is conservative regarding the PSL displace-ments values when the stratification effects are in-cluded.
The most recent visual inspection of the PSL conducted in response to action item la of the NRC Bulletin 88-11 recorded a hot setting condition of 4375 lbs.
which corresponds to a spring displacement of 2-1/2".
Since the maximum available spring displacement for this type of spring is 3-1/2". th*n the remaining-travel from the observed hot se+1ing position.is 1.0".
Furthermore the two 1" lines df.rectly under the PSL in the vicinity of SL-SH-11 indicate that the PSL does not displace more than 0.45" and t%at there is.still 0.55" of free travel available on thw spring can before it bottoms out.
The staff requested support location drawings for the 1" lines.
The licensee indicated that since those pipes are Non Nuclear Safety field run, no support location drawings are available.
The staff's concern la that since these lines are very flexible when comp 6 red to the PSL, they will displace with minimal force without significantly damaging the calcium silicate insulation, and bottoming out of the spring-can may occur during heatup.
Furthermore,-the vertical seismic ac7emen*a at the SL-SH-11 location may exceed the 0.55" rc.,enle j
travel, in which case bottoming out of the sptsag may 1
also occur during a seismic event.
The staff tiguests
'that displacement values due to thermal stratift:ation and seistic affects be provided at the.three supporus and the two horizontal elbow locations, to property assess this condition.
1 3.2 The staff reviewed CEOG report'CEN 387-P as it p0 tains specifically to Maine Yankee operations and raised a number of questions.
The generic analysis assumed a maximum temperatura differential between the Pressuriser and the Hot Leg of A T* 3 200F.
Tech Spec. Table 3.4.1 " Limits of Operation for the Reactor Coolant System" specifies that the maximum temperature difference between the operating-loops and the Pressuriser is 3400F.
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ENCLOSURE 4
1 Page 5 of 8 Review of the maximum temperature and pressure curves for heat-up and cooldown indicates that this maximum temperature differe'.itial of AT=3200F may occur when the Reactor Coolant Syst.ta (RCS) operating temperature is less than 1350F.
l The staff's concern is that this condition has not been considered.in the bounding evaluation and that the l
thermal loads assumed by.CE in the stress and fatigue analysis. may not bound Maine Yankee's operations fc.* RCS l
loop temperature of T<1350F.
The licensee's position is that Operations usually i
maintains a sufficient margin, based on systen pressure, to assure that the maximum AT does not' exceed 3200F.
This statement could not be verified.
l The staff requested additional information on this issue i
to justify the higher systen 0
AT of 340 F at Maine s
Yankee.
The CEN:387-P report table 3.6 predicted an elastic Cumulative Usage Factor (CUF) for fatigue of 0.36 when the travel limitations of 0.06" waro imposed on SL-SH-i 11.
This factor-is larger than the 0.27 of.the Palo Verde analysis.
CEN-387-P report indicates that the Palo Verde analysis is the the worst case and Maine Yankee is enveloped by the Palo Verde inelastic evalua-tion.
The staff's concern.is that Maine Yankee may not be bound by the Palo Verde analysis since it appears that Maine Yankee has a larger CUF than Palo Verde.and.the potential for additional constraints.
- The licensee's review of,the CEN 387-P. report identified' and transmitted the same concern to CE.-
Based on a tele-con memorandum of 9/15/89 which was presented to staff, it was indicated that CE' reconfirmed that the Palo Verde shakedown and fatigue analysis envelopes l
Maine Yankee's PSL.
It was also-indicated that CE will provide a'more detailed explanation in future revisions of the CEN 387-P report why Maine Yankee is enveloped by the Palo Verde analysis.
The same concern has also been presented to CE at a meeting with the staff on september 25 and 26, 1989.
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ENCLOSURE
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The staff requested a copy of the spring hanger calcula-tions for SL-SH-10, ~11,
& 12 which are the only sup-i ports on the PSL. -The licenst ' indicated that since I
these are vendor supplied items, calculations were not i
available on site.
The staff disagrees with the licens-l ee's position and feels that calculations need to be prepared to verify adequacy of the supports.
The staff's concern is that due to thermal stratification,-
the loads may increase and therefore, support re-evalua-i tion is required.
CE predicted that the loads.on hang-ers SL-SH-10 and -12 increased by 74 and 24 respectively above their respective design loads, when.the stratifi-cation effects were included.
The licensee agreed to prepara a calculation for SL-SH-11 which is the support having the largest anticipated movement based on the i
l CE's analysis.
l The staff reviewed Calc. no. NYC-1237 Rev.
0, dated 9-l 26-89, for support SL-SH-11, which was transmitted to staff on 10-11-89 and had the following consentet a)
The pipe clamp type is unknown.
Field verification is required in order to. verify clamp capacity.-
b)
Recent editions of the ITTG catalog (pH-87) indi-cate that there was a change in the-rod size, from 1-1/8" to 1-1/4", for spring size 14,.from the previously published data.
SL-SH-11 is a $14 Fig B-268.
Field verifications is required to verify which rod size exist (1-1/8" or 1-1/4").
If.a 1-1/4" rod diameter exists, documentation is re-quired to show how this change was made from the 1-1/8" to 1-1/4" rod size.
l c)
Unsymmetrical-bending of the structural angles was not considered.
d)
Since baseplate is not rigid, the top row center.
bolt will resist higher loads that the outermost top row anchor bolts.
e)
Support was evaluated for 5200 lbs which is the rated load of the spring can and assumes that no bottoaing out of the spring occurs when the thermal stratification and seismic effects are considered.-
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ENCLOSURE l
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l The staff feels that-further evaluation is required to assess the impact of above-mentioned concerns.
In addition, the staff feela that calculations need to be generated for hangers SL-SN-10 and -12 to evaluate load increases due to thermal stratification and seismic, 3.3 The staff reviewed correspondence relating to the inter-rttlationship between efforts of the licensee and CE as l
l they pertain to the PSL stratification issues.
The licensee presented to the staff memorandua NY-PO-53731 dated September 26, 1989 concerning the " Applicability j
of Pressuriser Surge Line Generic Analysis for Maine Yankee".
The purpose of the meno was to documents a)
The information/ drawings submitted to the CEOG by i
the licensee.
k b)
The licensee's review of the CEN-387-P analysis critical input, assumptions and conclusions specif-ically relating to Maine Yankee.
j c)
Visual inspection results and'as-built drawings of l
the PSL and associated supports.
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A number of other concerns were also identified to CE by
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the licensee's review of the report and were listed on this memorandum.
The staff agrees with all the comments made by the licensee.on the CE CEN-387-P report.
The.
j staff requests that future revisions / enhancements to the-i l
CEN-387-P report be reviewed by the' licensee and docu -
mented as required.
i The staff feels that the licensee has made acceptable j
efforts to provide CE with the-pertinent information related to the stratification-issue, review the analysis' critical input and assumptions and assess the i
reports' conclusion.as they pertain specifically to Main Yankee's operations.
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ENCLOSURE
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i Page 8 of 8
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Based on our review, we conclude that the licer.see of Maine i
Yankee had made generally acceptable efforts to meet certain I
requested actions as ~ delineated in item 'la and ib of the NRC i
However, in order to close out the Bulletin issue, the licensee should perform-the followings.
a)
Provide further justification to demonstrate why the inelastic analysis performed for Palo Verde in document CEN 387-P is applicable to Maine Yankee.
f (This request was also made at the 9/25/89.and 9/26/89 meetings with CE.)
b)
Provide additional information detailing how the l
loads unique to Maine Yankee such as seismic, dead-weight and thermal transients, were included in the stress resultant compared to ASME code allowables.
(Request was also made to CE on 9/27/89 through a conference call.)
c)
Clarify the loading considered in-identifying the various stress values in the CEN 387-P report.
d)
For the 3 PSL supports:
i 1)
Assess the impact of restraining the PSL movement during a seismic event where the i
larger movements are anticipated, and deter-mine the additional loads / stresses on the PSL l
due to likely insufficient clearances with the
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l adjacent 1" and the 10" lines.
Consideration should be given to the effects of seismic displacements on the proposed modifications-in response to DR-842-89.
2)
Assess the impact of the maximum temperature differential of AT*340cF vs. the AT=3200F l
which was assumed in the generic bounding evaluation.
3)
Generate calculations for spring supports.SL-SH-10 and -12, including the integral welded attachments and evaluate impact of the load increases when the stratification effects are included.
4)
Address the comments listed in section 3.2.a, 3.2.b, 3.2.c, 3.2.d, and 3.2.e concerning spring support SL-SH-ll.
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EMCLOSURE i
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ENCIDEURE 1 l
AGENDA j
NRC AUDIT OF BULLETIN 88-11 ISSUES AT MAINE YANKEE l
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I.
AUDIT DISCUSSION ITEMS A.
Surge Line Inspection Results and Corrective Actions B.
NRC Staff Questions Related to CEOG Report CEN 387-P.
C.
Inter-relationship Between Efforts of Maine Yankee and CEOG.
k II.
DOCUMENT REVIEWS A.
Inspection Reports and Results.
B.
Surge Line Design Drawings.
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Analysis Supporting Acceptability of Corrective Ac-tions.
D.
Analysis Verifying code compliance.
E.
Other Pelevant Licensee or CE Reports.
III. WALKDOWN l
A.
Inspection of Surge Line (If accessible).
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Distribution:
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