ML20138A225
| ML20138A225 | |
| Person / Time | |
|---|---|
| Site: | Hatch  |
| Issue date: | 11/29/1985 |
| From: | Walker R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| To: | Kelly R GEORGIA POWER CO. |
| References | |
| TAC-54150, NUDOCS 8512110615 | |
| Download: ML20138A225 (23) | |
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Georgia Power Company jATTN: Mr. R. J. Kelly Executive Vice President P. O. Box 4545 Atlanta, GA 30302 Gentlemen:
SUBJECT:
MEETING
SUMMARY
- HATCH, DOCKET NOS. 50-321 AND 50-366 This refers to the management meeting conducted at our request in the NRC Region II Office on November 8, 1985. The meeting was held to discuss the Unit I nitrogen inerting and purge line crack (discovered on Decenber 15, 1984) as it relates to the actions taken by Georgia Power Company (GPC) in response to. the recommendations of service information letter (SIL) 402, " Wet Well/Drywell Inerting." A summary of the meeting topics is provided in Enclosure 1.
A list of attendees at the meeting is shown in Enclosure 2.
It is our opinion that this meeting was beneficial in that it provided us a better understanding of the system evaluations and inspections that were utilized in your response to SIL 402, as well as the specifics associated with the crack found in the Unit I nitrogen inerting and purge line. We do believe, however, that had you initially put forth the same effort into the crack event a, you apparently did in preparation for this meeting, the associated licensee event report could have better addressed the scope and depth of the concern.
In accordance with Section 2.790 of NRC's " Rules of Practice," Part 2, Title 10, Code of Federal Regulations, a copy of this letter and its enclosures will be placed in the NRC Public Document Room.
Should you have any questions concerning these matters, we will be pleased to discuss them.
Sincerely, Original signed by R. D. Walker Roger D. Walker, Director Division of Reactor Projects
Enclosures:
1.
Meeting Summary 2.
Meeting Attendees 3.
Meeting Outline Submitted by Georgia Power Company cc w/encls:
(See page 2)
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_g. _Gucwa, Chief, Nuclear Engineer cc w/encis:
RC Resident Inspector ugh S. Jordan, Executive Secretary Document Control Desk Sr. ate of Georgia
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ENCLOSURE 1 MEETING
SUMMARY
On November 8, 1985, representatives of Georgia Power Company (GPC) met with the NRC, at NRC's request, in the NRC Regional office in Atlanta, Georgia. The topic of discussion was the Unit I nitrogen inerting and purge line crack (discovered on December 15,1984) with respect to:
the evaluations and inspections performed by GPC in response to SIL 402; the exclusion of the nitrogen makeup system and its temperature monitoring device from SIL 402 design evaluations; and containment integrity.
Regarding SIL 402, GPC stated that their response to recommendation 4 (inspect nitrogen injection line) was based on the earlier (post Unit 2 vent header crack) inspection conducted in February 1984.
At that time, a visual inspection and limited magnetic particle testing (MT) was performed on the welds of the Units 1 and 2 nitrogen injection lines from the contair. ment penetrations to the inboard isolation valves; no indication of cracking was found.
The licensee explained that this surface inspection, in lieu of the recommended ultrasonic testing (UT),
was sound and met the intent of recommendation 4, since:
false indications common to unbaselined UT was avoided; MT has good sensitivity for outside surface cracks; and cold nitrogen causes rapid crack growth to the surface. Subsequent inservice inspection MT conducted on December 15, 1984, revealed a crack in the weld of the Unit 1 18-inch nitrogen inerting and purge line.
This weld only received a visual inspection in February 1984.
GPC stated that due to the close proximity o1 the 2-inch nitrogen makeup line connection point to the subject weld, the possibility of thermally induced stresses was subsequently precluded by raising the nitrogen makeup line's temperature alarm setting (from 0F to 10 F) and providing procedural instructions to stop nitrogen makeup flow if the alarm is actuated.
Additional followup actions included:
RT of the next weld in line and the subject weld after its repair; MT of 5 additional Unit I welds in the same 18-inch line; and MT of welds similarly located in Unit 2.
The 2-inch nitrogen makeup line, which connects the makeup system (20 SCFM) and the containment atmospheric dilution (CAD) system (100 SCFM) to the 18-inch nitrogen inerting and purge line, was not considered by GPC to be covered under SIL 402 as a source of cold nitrogen (less than 40'F) into containment systems, because of:
the use of relatively low flow rates; and the long run of bare piping inside the warm reactor building between the atmospheric vaporizer and the vent header.
The licensee did confirm, however, that the CAD system was in use for an 18h-hour period (subsequent to the February 1984 inspection) when the ambient temperature did not get above 22*F during its 2-day span of operation.
Makeup line nitrogen temperatures during this period of atmospheric vaporizer use were not known by the licensee, nor were there in existence at that time any written alarm instructions associated with the makeup line's temperature annunciator. Although it is possible that this crack was caused by thermally induced stress as indicated in licensee event report (LER) 50-321/84-25, GPC representatives stated that it was more likely the growth of a pre-existing weld E
2 defect.
This second evaluation was based on the small occurrence of failure initiation for carbon steel at the calculated stress level.
In regard to containment integrity, the licensee pointed out that the crack was small (2 and 3/4 - inches long) and was detected through MT, not visual examination. Subsequent GPC analysis indicates that during a loss of coolant accident, the leakage contribution of the crack to the assumed FSAR total leakage rate would be relatively low (0.06% per day).
Consequently, the whole body and thyroid boundary doses resulting from the assumed FSAR leakage combined with the leakage caused by the crack, would not exceed 10 CFR Part 100.11 limits. This analysis was based on a calculated crack opening of 0.01 inz and no further crack propagation. Accordingly, a catastrophic failure of the subject weld, as implied in LER 50-321/84-25, was not considered possible within the bounds of containment.
design pressure.
^
ENCLOSURE 2 MEETING ATTENDEES U. S. Nuclear Regulatory Commission R. D. Walker, Director, Division of Reactor Projects.(DRP)
.V. L. Brownlee, Chief, Reactor Projects Branch 2, DRP
,z A. R. Herdt, Chief. Engineering Branch, Division of Reactor Safety (DRS)
V.' W. Panciera, Chief, Reactor Projects Section 28, DRP J. J. Blake Chief, Materials and Processes Section, DRS P. Holmes-Ray, Senior Resident Inspector, Plant Hatch 2
R. E. Carroll, Jr., Project Engineer, Reactor Projects Section 28, DRP C. E. Rossi, Chief,- Events Analysis Branch, Division of Emergency Preparedness and Engineering Response R. N. Singh, Reactor Systems Engineer, Division of Emergency Preparedness and
. Engineering Response G. W. Rivenbark, Project Manager, Operating Reactors Branch (ORB) 4, Division of Licensing (DL), NRR P. P. Tremblay, Project Manager, Operating Reactors Assessment Branch, NRR l
Georgia Power Company i
.L. T. Gucwa, Manager, Nuclear Safety and Licensing, Georgia Power Company (GPC)
C. T. Jones, Manager of Engineering, Plant Hatch, GPC
.R. D. Baker, Nuclear Licensing Manager, Hatch, GPC W. E. Burns, Nuclear Licensing Manager, Vogtle, GPC J. A. Edwards, Senior Regulatory Specialist, GPC P. P. Norris, Senior Plant Engineer, Plant Hatch, GPC G. D.'M:Gaha, Project Engineer, Plant Hatch, Southern Company Services, Inc.
P. P. Stancavage, Principal Engineer, Mechanical and Safety Engineering, General Electric Company l
M. L. Herrera, Senior Engineer, Structural and Fracture Mechanics, General i '
Electric Company G. A._Kosi, Hatch Project Engineer, Bechtel Power Corporation K. L. Khianey, Mechanical Supervisor, Hatch, Bechtel Power Corporation G. Trassman, Metallurgist, Bechtel Power Corporation t
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MEETING BETWEEN GEORGIA POWER COMPANY AND U. S. NUCLEAR REGULATORY COMMISSION PLANT HATCH UNIT 1 NITROGEN INERTING AND PURGE LINE CRACK ATLANTA, GA NOVEMBER 8, 1985 AGENDA I.
INTRODUCTION L.T. Gucwa II. LICENSEE EVENT REPORT 84-25 C. T. Jones III. PROBABLE CAUSE OF CRACK M. L. Herrera IV.
G. E.
SIL 402 RESPONSE o System Design K. L. Khianey o SIL Basis & Intent / Industry Action P. P. Stancavage o GPC Response C. T. Jones V.
SAFETY SIGNIFICANCE OF CRACK P. P. Stancavage VI. CONCLUSION L. T. Gucwa LTG/Il-08-85 2321N
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CCOrgia power A MEETING E1 WEEN GEORGIA POWER COMPANY AND U. S. NUCLEAR REGULATORY COMMISSION PLANT HATCH UNIT 1 NITROGEN INERTING AND PURGE LINE CRACK ATLANTA, GA NOVEMBER 8, 1985 LICENSEE ATTENDEES L. T. GUCWA Manager Nuclear Safety and Licensing Georgia Power Company C. T. JONES Manager of Engineering - Plant Hatch Georgia Power Company R. D. BAKER Nuclear Licensing Manager - Hatch Georgia Power Company W. E. BURNS Nuclear Licensing Manager - Vogtle Georgia Power Company J. A. EDWARDS Senior Regulatory Specialist Georgia Power Company P. P. NORRIS Senior Plant Engineer - Plant Hatch Georgia Power Company G. D. McGAHA Project Engineer - Mechanical Southern Company Services, Inc.
P. P. STANCAVAGE Principal Engineer - Mechanical & Safety Engineering General Electric Company M. L. HERRERA Senior Engineer - Structural and Fracture Mechanics General Electric Company G. A. KOSI Hatch Project Engineer Bechtel Power Corporation K. L. KHIANEY Mechanical Supervisor - Hatch Bechtel Power Corporation G. TRASSMAN Metallurgist Bechtel Power Corporation LTG/11-08-85 2321N
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o ADDRESSES MAIN NITROGEN INERTING SYSTEM o
INERTING SYSTEM DESIGN AND OPERATION STEAM VAPORIZER REDUNDANT TEMPERATURE ELEMENTS AUTOMATIC SHUT 0FF ON LOW TEMPERATURES UPGRADED PROCEDURES '
o NITROGEN INJECTION LINE INSPECTION UT 2 PLANTS (PLANNED)
SURFACE 4 PLANTS NONE 5 PLANTS o
CONTAINMENT INTEGRITY ASSURED DESIGN AND OPERATION REVIEW SURFACE INSPECTION IS SOUND l
o AVOIDS FALSE INDICATIONS COMMON WITH UNBASELINED UT f
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MAG PARTICLE HAS GOOD SENSITIVITY FOR OUTSIDE SURFACE' CRACKS j
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o EVALUATE INERTING SYSTEM DESIGN PREVENT INJECTION OF COLD NITROGEN INTO CONTAINMENT EXCLUDES NITROGEN MAKEUP AND CONTAINMENT ATMOSPHERE DILUTION SYSTEMS o
LOW FLOW RATES o
LONG RUN OF BARE PIPE o
INSIDE WARM REACTOR BUILDING o
INJECTION TEMPERATUP.E AB0VE 600F
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INSPECT NITROGEN INJECTION LINE MAIN INERTING PATH FROM CONTAINMENT PENETRATION TO ISOLATION VALVE ULTRASONIC TEST RECOMMENDED BUT-0UTSIDE SURFACE EXAMINATION MEETS. INTENT.
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. CONTAINMENT INTEGRITY ASSURED SYSTEM DESIGN AND OPERATION SURFACE' INSPECTION OF INERTING LINES o
PUBLIC SAFETY PROTECTED SMALL CRACK AREA INCREMENTAL DOSES LESS THAN 0.5% OF LIMITS 9
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LOW LEAKAGE RATE BOUNDING DRYWELL PRESSURE LEAK RATE 2 x 10-3 3
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DESCRIPTION OF NITR0 GEN SYSTEM NITROGEN IS DIRECTED INTO TORUS AND DRYWELL THROUGH 20" AND 18" INJECTION LINES, RESPECTIVELY.
' NITROGEN SYSTEM AT HATCH HAS THREE SUBSYSTEMS:
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INERTING SYSTEM 6" SUPPLY L'INE (START UP) 4000 SCFM APPROXIMATELY 600F USES STEAM VAPORIZER 2.
MAKE UP SYSTEM 2" SUPPLY LINE (NORMAL PLANT OPERATION)
- 20 SCFM APPROXIMATELY 600r USES TANK EVAPORATION Ar..
AMBIENT VAPORIZER
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- 100 SCFM AT OUTSIDE AIR TEM-PERATURE (UP TO 80F)
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