IR 05000155/1976011
| ML20002D549 | |
| Person / Time | |
|---|---|
| Site: | Big Rock Point File:Consumers Energy icon.png |
| Issue date: | 06/17/1976 |
| From: | Cook R, Little W NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| To: | |
| Shared Package | |
| ML20002D547 | List: |
| References | |
| 50-155-76-11, NUDOCS 8101210333 | |
| Download: ML20002D549 (7) | |
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UNITED' STATES NUCLEAR' REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT
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REGION III-
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Report'of Operations Inspection'
IE Inspection Report No'. 050-155/76-11
- Licensee:
Consumers Power Company 212 West Michigan Avenue.
Jackson, Michigan 49201 Big Rock Point Nuclear Plant
. License No. DPR-6 Charlevoix, Michigan
. Category:
'C~
Type of Licensee:
BWR GE 240 MWt Type of Inspection:
Special. Announced Dates of Inspection: May 6-7 and l'-22',
19,76
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Principal Inspector:
R. J. Coo [
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'(Date)
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Accompar.ying Inspectors: None Other Accompanying Personnel:
None
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Reviewed By:
W. S. Lit e, Chief
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Nuclear Support Section (Dat'ei '
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SUMMARY OF FINDINGS
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t Inspection Summary-
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Inspection of May 6-7, and 19-22, 1976 (76-11):
Examined code-b safety valve components.
Reviewed procedures,1 lue. prints and pertinent documentation for the safety valve nozzle replacemen'.
and refurbishing. Witnessed hydrostatic testing of installed replacement nozz1cs, safety valve assembly and set point testing.
Enforcement Itemsi None.
Licensee AcElon on Previous'ly Identified Enforcement -Items
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None inspected.
Other Significant Items A.
Systems and Components ~
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None.
B.
Facility Items (Plans and Procedures)
Nonc l'nspected.
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C.
Managerial Items
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D.
i!oncompliance Identified and Corrected by L insee-None.
E.
Deviations None.
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Status of Previously Identified Unresolved Items None inspected.
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Management' Interview 1 1 A management' interview wa's conducted with Mr. Hartman, Plant Superintendent and other members of :he-staff including members
- of the corporate staff on May 21, 1976. The'following items
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were discussed:
A.
Inadequacies in the safety valve assembly'and testing i;
procedures were discussed. The 1icensee acknowledged the-
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(Paragraphs-5 and 6' Report Details)
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B.
The physical condition.of the valves was discussed. The:
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inspector stated that the inspection would continue until
more valves were assembled and set.
The licensee acknowledged the commenta.
(Paragraph 3, 4 and 6, Report Details)
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REPORT DETAILS ~
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Persons Contacted C. Hartman, Plant Superintendent-
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J. Fynn,, Maintenance Superintendent G. Szczotka, Quality Assurance Superintendent-J.-Popa, Maintenance Engineer H. Black, Maintenance Supervisor
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D. Wilks, Assistant Maintenance Supervisor R. Brzezinski,~ Associate Engineer
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E. Dziedzic, Quality Control Inspector.
C. Kellogg, Machinist J. Leja, Crosby Valve and' Cage Company, Field Representative C. Ansorge,11artford Boiler Inspector 2.
General During' inservice inspection of the six installed drum rode safety valves, crack indications were noted in the pro.:imity of the nozzle seal weld heat af fected zone when the area was dye penetrant tested. One nozzle had crack indications in the throat area about 1 inch to 2 inches below the seating surface. All nozzles, including the nozzle from the spare valve were removed and replacement nozzles installed.
When the replacement nozzles were seal welded crack indications were noted (by dye penetrant testing) in the valve body base
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metal in the proximity of the heat affected zone.
An inspection was performed to review licensee efforts pertinent to the repair, refurbishing and testing of the code safety valves.
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Removed nozzles with crack indications have been sent to laboratory facilities for metallographic examinations and
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further testing. A future inspection is planned to review the results of these examinations.
3.
Valve Body cracks
The crack indications in the valve body base metal were all primarily located in the same quadrant when viewing the valve from the inlet side.
Using a quadrant reference and with the valve outlet pointed downward with the flange face parallel to a horizontal plane, the body c:cck indications were located at nominally the one_to r!.cce o' clock position
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and near the fillet seal weld.
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The following is a cummary of the cite quality records showing the relative size of the body cracks and the final disposition
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for each valve.
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a.
Valve Number 5000
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This valve is designated as the spare valve.
A replacement nozzle wos not installed in this valve as complete certification and traceability of nozzle material could not be established for the nozzle intended for this valve.
Therefore, no post weld body cracking has occurred in this valve. The licensee plans to refurbish this valve at some later time.
b.
Valve Number 5001 The crack indications required local grinding to a depth of 0.550 inches to remove any indications.
The ground cavity was filled using tungsten inert gas (TIC)
techniques. No cavity traces or crack indications existed after the repair.
c.
Valve Number.5002 The crack indications in this valve were located at the 3 o' clock position and required local grinding to a depth of 0.194 inches to remove any indications. No filling of the ground out cavity was performed.
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Valve Number 5003 The crack indications in the body base initial required local grinding to a depth of 0.190 inches to remove any indications.
No filling of the ground out cavity was performed.
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Valve Number 5004 The crack indications in the body base metal required local grinding to a depth of 0.201 inches to remove any indications.
No filling of the ground out cavity was performed.
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Valve Nurber 5045
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The cra'ck indications required local grinding to a depth of neminally 0.100 inches to remove any indications. No filling of the ground out cavity was performed.
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Valve Number'5046 g-sad u.c U ai
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The fillet seal weld was taken out-by machi. ting.
This increased the inside radius at the fillet weld by 0.520 inches. A crack like indication still; existed w1ich was
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removed by local grinding an additional depth of.0.125 inches. Rewelded the seal weld.using a wider fillet of 5/8 inc.i.
An analysis to evaluate the in1'et minimum wall thickness
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was performed by the safety valve manufacturer.
This analysis states that the, minimum wall thickness must be
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7/8 inch.
The minimum wall thickness was determined to be nominally 1 3/16 inch.
Using a casting quality factor of 0.8 the~allowabic maximum stress for-1700 psig at 614 F is 1400 psi. The maximum encroachment of this allowabic stress was a calculated stress of 12,274' psi in the flange area.
The cause.of the post weld body cracking is attributed to imposing additional residual stresses on the body.
casting from the nozzle seal welding process.
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4.
Safety Valve Assembly During the inspection, essentially all aspects of valve assembly were o'bserved. Some dimensional checks were made to establish conformity of t'ae replacement nozzles with intended design. No indications.of stem extremity thread interference with the adjusting bolt bearing (guide brushing)
were observed. No indications of interference or binding between the guide and disc holdcr were noted when the valve internal components were examined.
The valve manufacturer's representative was involved in assisting the licensee during the assembly of some of the valves.
During the examination of valve components, a full length 0.010 inch longitudinal. crack indication was noted in all the stems.
This was attributed to a manufacturing defect.
All stems were replaced with four stems manufactured from stainless steel and two stems made of Monel. The stems were supplied by the. valve manufacturer. Other replacement parts used in the valves were three disc holders, three discs and all nozzles.
Two of the nozzles were outside the limits of parallelism with the component translational axis'of the valve after the seal welds were completed. The nozzle seating surfaces were-6-f
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'remachined cnd lapped by th2 valve canufacturer's repreeentative.-'
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- Parallelism and concentricity'of thesseating: surface was. brought:
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within manufacturer recommended. tolerances, i.
All the nozzles were hydrostatically testid prior ~to valve-
. assembly at 2380 psig to test boundry integrity. lThe:
hydrostatic tests,on two of the nozzles'(scal welded in the.
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valve body) were witnessed-by the. inspector.
No. leakage or discrepancies.were noted.'
The Hartford Boiler Inspector-
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was'present to witness these hydrostatic tests.
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Assembly Procedure
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The assembly procedure was reviewed and someLsubtle symantic discrepancies'were noted which werel corrected by the licensee..
The severest objections to the procedure wereLin not supplying
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enough detail such'that a' novice could perform a given' step.
The licensee relied heavily onLthe knowledge'and experience-of the plant machinist to perform procedural. steps.- The
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inspector. recommended that.the licensee incorporate more-detailed. instructions in the procedure with the ' details of
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how a given procedural step 1is performed being supplied by
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the plane machinist. Some of these' details were approved and-incorporated into the safety valve assembly and test procedure during the period.that the valves were assembled.
The licensee plans to further improve the safety. valve' assembly.and test procedure during the assembly and testing of'the spare valve.
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. Safety _V _1_ve Set Point Testing'
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The safety valve lift set points were established using nitrogen. The testing rig had the capability of supplying i
i a relatively large ~ volume as an accumulator was changed with nitrogen and chen brought to lif t pressure by pumping water
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into the accumulator.
The setting of four safety valves was
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witnessed by the inspector.
The valve manufacturer's representative assisted in the setting of two of the safety
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' valves., The. valves accepted for service showed sharp opening
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I and closing characteristics without any evidence of seal leakage.
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