ML20212F758
| ML20212F758 | |
| Person / Time | |
|---|---|
| Site: | Vogtle  |
| Issue date: | 12/23/1986 |
| From: | Rice P GEORGIA POWER CO. |
| To: | Grace J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| References | |
| REF-PT21-86, REF-PT21-87-003-000 GN-1258, PT21-87-003-000, PT21-87-3, NUDOCS 8701120151 | |
| Download: ML20212F758 (5) | |
Text
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vwe Proret December 23, 1986 United States Nuclear Regulatory Commission Region II, Suite 2900 File: X7BG03-M129 101 Marietta Street, Northwest Log:
GN-1258 Atlanta, Georgia 30323
Reference:
Vogtle Electric Generating Plant-Units 1 & 2; 50-424, 50-425; Containment Cooling Unit Manifold Nozzles Letter GN-1125, dated October 21, 1986 Letter GN-1197, dated November 25, 1986 Attention:
Mr. J. Nelson Grace In previous correspondence, Georgia Pcwer Company notified the NRC of a reportable condition concerning the containment cooling unit manifold nozzles.
At that time, Georgia Power Company provided a summary of the engineering portion of its evaluation and indicated that the NRC would be advised of the results of the evaluation for a quality assurance program breakdown upon its completion.
Georgia Power Company has completed its evaluation of the quality assurance program of CVI and concluded that a significant breakdown has not occurred.
Additionally, the previous engineering evaluation summary indicated that the pipe support configurations for the containment cooling units (CCOs) and the auxiliary cooling units (ACUS) had insufficient l
flexibility due to excessive thermal stresses and that corrective I
action modifications for Unit I had been completed.
In fact it was only necessary*tio make modifications to the CCUs.
Originally the vendor stated that an analysis for the CCUs and ACUS indicated that pipe support modifications were required and the details of these modifications were discussed at a
jobsite meeting.
Subsequently, CVI completed a detailed analysis which indicated that l
these modifications were no longer required for the ACUS.
Due to l
a delay in communication, this information was not incorporated into our earlier response.
Confirmation of completed corrective actions for Unit I was misinterpreted to include both the CCUs and ACUS when, in fact, only the piping supports for the CCUs required modifications.
Thus, this revision does not change the results of the previous evaluation but does clarify the corrective action.
A summary of our evaluation, including the quality assurance program breakdown evaluation and revised corrective action, is attached.
I g 8701120151 861223 PDR ADOCK 05000424 I
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2-This response contains no proprietary information and may be placed in the NRC Public Document Room.
Yours truly,
~.
P. D. Rice CWH/PDR/kmc Attachment xc:
U. S. Nuclear Regulatory Commission Document Control Desk Washington, D. C.
20555 H. G. Baker D. R. Altman L. T. Gucwa J. P. O'Reilly J. A. Bailey C. W. Hayes G. F. Head G. Bockhold G. A. McCarley R. E. Conway J. F. D'Amico R. W. McManus R. H. Pinson W. D. Drinkard Sr. Resident (NRC)
B. M. Guthrie C. C. Garrett (OPC)
J. E. Joiner (TSLA)
R. A Thomas D. Feig (GANE)
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EVALUATION OF A POTENTIALLY REPORTABLE CONDITION CONTAINMENT COOLING UNIT MANIFOLD N0ZZLES (Revised 12/18/86)
Initial Report:. On September 24, 1986, Mr. R. E. Folker, Vogtle ' Quality Assurance Engineer, notified Mr. M. Sinkule of the USNRC-Region II of a potentially reportable condition associated with the inadequate consideration of thermal stresses in the design of the manifold nozzles for the containment' cooling units.
This concern was initially identified during an audit by the NRC Seismic Qualification Review Team (SQRT) and the Pump and Valve Operability Review Team (PVORT).
In subsequent correspondence, Georgia Power Company indicated that the NRC could expect to be informed of the results cf the evaluation of this condition by November 24, 1986.
Background Information: There are four separate. types of. cooling units provided by CVI, Incorporated, under specification X4AJ16.
They are: (1) containment cooling units (CCU), (2) the piping penetration area coolers (PPAC), (3) auxiliary cooling units (ACU) and (4) reactor cavity cooling units (RCCU).
The principal function of the CCU (tag numbers 1/2-1501-A7-001 through 008) is to reduce the containment temperature following a design basis accident (DBA),
loss of. coolant accident (LOCA), or main steam line break (MSLB) inside the containment.
These cooling units also function during normal operation to maintain the containment temperature within a minimum-maximum range of 60* to 120'F.
The PPAC (tag numbers 1/2-1561-E7-001 and 003) are provided to serve the piping penetration filter exhaust system (FPES).
The PPES is designed to minimize the release of airborne radioactivity to the outside atmosphere resulting from containment leakage into the piping penetration area during a DBA condition.
The PPAC are located in the auxiliary buildings and provide cooling for the filter units.
These coolers are not req ;r:d during normal operation, but are required to operate following a DBA.
The ACU (tag numbers 1/2-1515-A7-001 and 002) augment the cooling capacity of the containment cooling units during normal operation.
These units are isolated during a DBA and do not perform a safety function, but are required to maintain the integrity of their pressure boundaries.
The RCCU (tag numbers 1/2-1511-E7-001 and 002) are designed to provide cooling air during normal and loss of offsite power conditions to prevent the reactor cavity concrete from exceeding its allowable temperature.
These units are isolated during a DBA and do not perform a safety function, but are required to maintain the integrity of their pressure boundaries.
Although cooling units are manufactured by CVI, the stress analyses for these units ware performed by Karagozian and Case (KC), consultant to CVI.
The pressure boundary components for these cooling units are constructed in accordance with American Society of Mechanical Engineering (ASME) Boiler and Pressure Vessel (B&PV)
Code Section III, Class 2 and 3.
Failure to maintain the pressure boundaries of ACU and RCCU during DBA conditions in conjunction with a single failure of unit isolation valves could result in loss of the nuclear service cooling water (NSCW) inventory and could potentially impact
plant safety.
During the SQRT and PV0RT audit in June 1986, the NRC expressed a concern that th rmal stresses in the header nozzles on the cooling coils of the RCCU were not addressed in the stress analysis.
Engineering Evaluation:
In response to this
- concern, Bechtel Western Power Corporation (BWPC) engineering and the. CVI consultant reviewed the calculations of the cooling units supplied under Specification X4AJ16.
This review concluded that thermal stresses due to temperature difference between the structural frame and the inlet manifolds of these four units had not been properly addressed for:
Piping / manifold / nozzle interfaces Cooling coil tubing During normal plant operation, the four types of units (CCU, PPAC, ACU, and RCCU) ara subject to temperature differentials of about 40* between the cooling unit structural frame and the inlet cooling water piping and tubing.
Under DBA conditions the CCU and PPAC are subject to a temperature differential of about 197*F and 40*F respectively between the cooling unit structural frame and the inlet cooling water piping and tubing.
Containment Cooling Units (CCU):
The pipe support configuration of the CCU was found to provide insufficient flexibility, and as a result calculated piping thermal Stress exceeded the allowable stress limits under both normal and DBA conditions.
Piping Penetration Area Coolers (PPAC):
The impact of the thermal stresses on the PPAC pipe supports as a result of the described temperature differential was considered in the reanalysis.
The reanalysis demonstrated that piping stresses were within allowable stress limits under both normal and DBA conditions. Thus, the present configuration is acceptable.
Auxiliary Cooling Units (ACU):
'The impact of the thermal stresses on the ACU pipe supports as a result of the described temperature differential was considered in the reanalysis.
The result of the reanalysis demonstrated that piping stresses were within allowable stress limits under normal conditions.
Thus, the present configuration is acceptable.
Cooling Coil Tubing (CCT):
l CVI developed a test program in accordance with Appendix II of ASME Section III l
to determine whether failure of the coil tubing would have resulted under the described condition.
The result of the testing demonstrated that the present installation is acceptable for both Units 1 and 2.
Reactor Cavity Cooling Units (RCCU):
The impact of the thermal stresses, on the RCCU pipe support as a result of the
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described temperature differential was considered in the reanalysis.
The result of the reanalysis demonstrated that piping stresses were within allowable stress limits under both normal and DBA conditions.
Thus, the present configuration is 1
acceptable.
Evaluation of Qu'ality Assurance Program Ereakdown: Overlooking a single design input (thermal stresses due to temperature oifferences between frame and inlet I
manifolds) in preparing the cooler stress analysis, does not in itself represent a significant quality assurance program breakdown.
==
Conclusion:==
Based on the above evaluation, the plant safety could have been impacted if the condition associated with inadequate thermal stress analysis for the containment cooling units had gone uncorrected.
Therefore, Georgia Power Company has concluded that a reportable condition as defined by the reporting criteria of Part 10CFR50.55(e) and Part 10CFR21 does exist.
Based on the guidance in NUREG-0302, Revision 1, concerning duplicate reporting of an event, Georgia Power Company is reporting this event per the criteria of Part 10CFR50.55(e).
Corrective Action:
a.
Pipe support modifications for the CCUs have been completed on the Unit 1 pipe supports.
b.
Corrective actions for the Unit 2 Containment Cooling units are tracked under program for completion work (PCW) item no.
2B1587 and will be complete commensurate with Unit 2 construction schedules.