ML13331B173
| ML13331B173 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 05/03/1989 |
| From: | Baskin K Southern California Edison Co |
| To: | NRC/IRM |
| References | |
| NUDOCS 8905080003 | |
| Download: ML13331B173 (12) | |
Text
Southern California Edison Company P.O. BOX 800 2244 WALNUT GROVE AVENUE ROSEMEAD, CALIFORNIA 91770 KENNETH P. BASKIN TELEPHONE VICE PRESIDENT May 3, 1989 818-302-1401 U. S. Nuclear Regulatory Commission Attention:
Document Control Desk Washington, D. C. 20555 Gentlemen:
Subject:
Docket No. 50-206 Supplement 1 to Amendment Application No. 165 San Onofre Nuclear Generating Station Unit 1 Representatives from SCE met with members of the NRC staff on May 1, 1989 to discuss the restart of San Onofre Unit 1 from its current outage. Items discussed at the meeting included,
- 1) staff requirements for an inspection of the thermal shield at a mid Cycle outage, 2) acceptance criteria for the inspection,
- 3) changes to the proposed license condition on thermal shield monitoring, and 4) SCE's reasons for selecting the modifications proposed for the Cycle XI refueling outage. In order to address the NRC staff requirements for a mid-cycle inspection of the reactor thermal shield, SCE hereby commits to performing such inspection during a mid-cycle outage no later than June 30, 1990. As discussed during the meeting, SCE will propose acceptance criteria for the inspection and will provide these acceptance criteria to the NRC staff for their review. We will submit these criteria within 45 days following return to service from this outage and request a meeting with the staff shortly thereafter in order to reach final approval.
In our previous discussions with members of the NRC staff, comments on our proposed thermal shield monitoring program were provided.
The thermal shield monitoring program was proposed as a license condition by SCE Amendment Application No. 165, dated February 17, 1989 and was modified by our letter dated March 21, 1989.
This letter provides Supplement 1 to that Amendment Application. provides a revision to the thermal shield license condition which incorporates informal NRC staff comments. also provides responses to a set of NRC staff positions which were provided informally to SCE.
In addition, revisions have been made to indicate that monitoring will continue throughout Cycle X until the thermal shield is repaired, the definition of full power has been revised to 85% from 90% to allow for uncertainty in the maximum power attainable for this cycle, the words "channel functional test" have been changed to "channel test" to reflect the terminology used in the technical specifications, and the need to perform loose parts/neutron noise monitoring prior 890508000. '390504 h3oo FDR ADOCIK 05000206 PDC
Document Control Desk
-2 to plant shutdown following a seismic event of 0.25g or greater has been removed. The basis for the latter revision is that the need for plant shutdown, either plant trip or controlled shutdown, may not allow time to obtain the data required by the previous version of the license condition. The wording of condition (6) continues to require demonstration of no additional thermal shield damage due to the seismic event. For this reason, and since the other changes involve only minor revisions to reporting requirements and surveillance frequency contained in the previous version of the proposed condition, it is bounded by the significant hazards analysis (10CFR50.92) included with that proposed change. provides a description of the location of the accelerometers used for loose parts monitoring and the impact testing which was performed to demonstrate acceptability of data collected with these instruments. This information was requested by the NRC staff as part of their review of the thermal shield issue.
Another topic of discussion at the meeting was SCE's plans and schedules for implementation of other pending modifications.
Specifically a list of modifications proposed to be implemented during the Cycle XI refueling outage (or at the mid-cycle outage should it be extended as a result of the thermal shield inspection) was presented. The staff requested that SCE provide the rationale for selection of the Cycle XI modifications. We will be providing the staff with these details by separate correspondence as soon as possible after restart. It is important to note that SCE's schedule is aggressive and will require rapid NRC staff agreement so that engineering activities will not be disrupted.
If you require additional information, please contact me.
Subscribed on this 3 $
day of 2 L,
1989.
Respectfully submitted, SOUTHERN CALIFORNIA EDISON COMPANY By:
Kenneth P. Baskin Vice President Subscribed and sworn to before me this 3AM day of OFFICIAL SEAL AGNES CRABTREE Notary Public-California LOS ANGELES COUNTY Nota Public in and for the County of My Comm. Exp. Sep. 14,1990 Los Angeles, State of California
Document Control Desk
-3 Charles R. Kocher James A.Beoletto Attorneys for Southern California Edison Company By:
iiU'
~ '
J A. Aeoletto1 Enclosures cc:
J. B.Martin, Regional Administrator, NRC Region V F. R. Huey, NRC Senior Resident Inspector, San Onofre Units 1, 2 and 3
UNITED STATES OF AMERICA NUCLEAR REGULATORY COMMISSION In the Matter of SOUTHERN
)
CALIFORNIA EDISON COMPANY
)
and SAN DIEGO GAS & ELECTRIC
)
Docket No. 50-206 COMPANY San Onofre Nuclear
)
Generating Station Unit No. 1
)
CERTIFICATE OF SERVICE I hereby certify that a copy of the enclosed Supplement 1 to Amendment Application No.
165 dated May 3, 1989 was served on the following by deposit in the United States Mail, postage prepaid, on the 3rd day of May
, 1989.
Benjamin H. Vogler, Esq.
Staff Counsel U.S. Nuclear Regulatory Commission Washington, D.C. 20555 David R. Pigott, Esq.
Samuel B. Casey, Esq.
Orrick, Herrington & Sutcliffe 600 Montgomery Street San Francisco, California 94111 L. G. Hinkleman Bechtel Power Corporation P.O. Box 60860, Terminal Annex Los Angeles, California 90060 Michael L. Mellor, Esq.
Thelen, Marrin, Johnson & Bridges Two Embarcadero Center San Francisco, California 94111 Huey Johnson Secretary for Resources State of California 1416 Ninth Street Sacramento, California 95814 Janice E. Kerr, General Counsel California Public Utilities Commission 5066 State Building San Francisco, California 94102
-2 C. J. Craig Manager U. S. Nuclear Projects I ESSD Westinghouse Electric Corporation Post Office Box 355 Pittsburgh, Pennsylvania 15230 A. I. Gaede 23222 Cheswald Drive Laguna Niguel, California 92677 Frederick E. John, Executive Director California Public Utilities Commission 5050 State Building San Francisco, California 94102 Docketing and Service Section Office of the Secretary U.S. Nuclear Regulatory Commission Washington, D.C. 20555 mes Beoletto 05830 Revision 1 to Proposed License Condition 3.M 3.M Cycle X Thermal Shield Monitoring Program The neutron noise/loose-parts detection system shall be used to monitor the condition of the reactor vessel thermal shield throughout Cycle X or until repair. Periodic monitoring of both neutron noise and loose-parts vibrations confirms that no long term unacceptable trend of degradation is occurring. The details of this program are described below.
(1) The unit will be shut down no later than June 30, 1990 to inspect the condition of the thermal shield.
(2) During the first 7 days of > 85% power, interim acceptance criteria for neutron noise/loose-parts monitoring will be developed. These interim criteria will be utilized until the final acceptance criteria is developed.
Final acceptance criteria for neutron noise/loose-parts monitoring will be established by performing baseline evaluations for 45 calendar days at > 85% power following return to service for Cycle X operation. The base line data will be established by recording a minimun of 16 -20 minute data information segments at > 85% power. Adjustments to the acceptance criteria will be made for cycle burnup and boron concentration changes throughout the cycle.
(3) The neutron noise/loose-parts monitoring system shall be OPERABLE in MODE 1 with:
a)
At least two horizontal loose-parts detectors monitored for at least five (5) minutes 2 times per day; and, b) at least three (3) neutron noise inputs monitored for at least five (5) minutes once a week.
(4) The data provided by the loose-parts/neutron noise monitor shall be analyzed once per week and compared with the established criteria. If the data exceeds the acceptance criteria:
a)
Within 1 day the NRC will be informed of the exceedance.
b)
Within 14 days the conditions will be evaluated and a report provided to the NRC documenting future plans and actions.
Page 2 of Enclosure 1 c)
The plant will be shutdown should the remaining flexure be demonstrated failed.
(5) Each channel of the loose-part detection system shall be demonstrated OPERABLE in MODE 1 by performance of a:
a)
CHANNEL CHECK at least once per 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> b)
CHANNEL TEST test at least once per 31 days The surveillance requirments for neutron noise monitor are covered by the Appendix A Technical Specification 4.1.1 for the Power Range Neutron Flux.
(6) With the neutron noise/loose-parts detection instrumentation inoperable for more than 30 days, prepare and submit a Special Report to the Commission pursuant to Appendix A Technical Specification 6.9.2 within the next 10 days outlining the cause of the malfunction and the plans for restoring the system to operable status.
(7) In the case of a seismic event of 0.25g or greater as indicated on site sensors, a controlled shut down shall be initiated. Before operations are resumed, it will be demonstrated that no thermal shield damage has occurred due to the seismic event.
(8) The provisions of Appendix A Technical Specification 3.0.4 are not applicable to this license condition.
Page 3 of Enclosure 1 SCE RESPONSE TO NRC COMMENTS REGARDING THERMAL SHIELD LICENSE CONDITION NRC Position Establish a monitoring program able to: (a) Determine thermal shield-core barrel changes due to potential breakage of the 120 degrees flexure and/or further degradation of the thermal shield supports and (b) determine with some degree of certainty the presence of loose parts in the lower part of the vessel. The existing program should be expanded to include:
"The neutron noise monitoring program should include as a minimum the following features:
(a) At least 16 to 20 minute segments of data at 100% power should be taken for the initial data base."
REPLY:
Included in program, see Rev. 1 Proposed License Condition (b) The data should be analyzed for cross spectral correlations as well as for phase and coherence.
REPLY:
Cross Power Spectral Density Correlations will be incorporated in the data reduction and analysis program.
(c) The data will be,updated for cycle burnup and boron concentration through the cycle.
REPLY:
Cycle Burnup and Boron Concentration factors will be considered in establishing the acceptance criteria for Neutron Noise Monitoring. Included in Rev. 1 of Proposed License Condition.
(d) A level of "internal consistency" will be estimated and used to define the "alarm level" through the cycle monitoring.
REPLY:
Internal Consistency is taken to mean "an average range of signal amplitudes," which will be established as part of the Baseline data evaluation to be developed during the first 45 days of full power operation.
(e) The licensee will submit this program for staff review.
REPLY:
The baseline data and acceptance criteria for both the interim and final programs will be submitted to the NRC staff.
Page 4 of Enclosure 1 NRC Position The loose parts monitoring will include either:
Accelerometers mounted on the area of the bottom of the pressure vessel or instrument tubes or similar locations where acoustical noise at the lower part of the vessel can be detected or; Impact testing should be performed at the lower part of the vessel (for a variety of mV values) in order to record a spectrum of corresponding signatures at the accelerometers mounted on the vessel flange. The licensees should justify its reasons to the staff.
If the Licensee finds it impossible to implement the loose parts monitoring program, the Licensee should submit the justification to the staff.
REPLY:
The location of the accelerometers and the impact testing performed are described in Enclosure 2 to this submittal.
Discussion of the Physical Placement of the Accelerometers with Respect to the Magnitude of Their Signal Output This enclosure discusses the physical placement of the accelerometers, and presents conclusions from response testing of the accelerometers in order to show that good response is obtained with the accelerometers placed orthogonally around the Rx vessel flange.
Four accelerometers have been placed orthogonally around the circumference of the vessel flange. These locations were selected primarily due to being at the same elevation as the core barrel seating surface (the thermal shield is supported from the core barrel).
Impact testing was performed with all accelerometers installed. Response spectra for each of the accelerometers was recorded for each of three different size ball bearings. Response spectra of the accelerometers to the ball bearing impacts was overlaid on the response spectra recorded when the RCS was at full power operation. A visual comparison of the two levels results in a high confidence factor that the loose-parts impact response is significantly higher in amplitude than the normal noise floor of the RCS at full operating conditions.
When the amplitude of the impact signal from a ball bearing impact at the North accelerometer location was recorded on the South accelerometer, there was no attenuation in amplitude as a function of distance from the accelerometer.
A centrally mounted accelerometer on the lower vessel head was considered, but later dismissed because (1) response signatures of the flange mounted accelerometers indicated sufficient sensitivity to be able to identify loose-parts impact on the bottom head, and (2) high radiation exposure and high smearable contamination exist at lower head locations that would exceed ALARA guidelines.
Lending support to the decision not to install accelerometers on the bottom head were the following facts (see attached figure):
- 1.
Access to the bottom on the Rx vessel, although not entirely prohibited, is restricted by a 1/4" thick tank cover welded for 3600 into the imbed surrounding the vessel.
Page 2 of Enclosure 2
- 2.
If the tank cover was removed, sand tanks, also welded in place, would have to be cut out to provide access.
- 3.
The four accelerometers placed on the vessel flange were deemed sufficient to identify any change in loose-parts impacts should they occur.
- 4.
The thermal shield is attached to the core barrel which in turn is supported at the top of the vessel. This is directly opposite the installed accelerometers.
In conclusion, the existing placement of the accelerometers around the vessel flange has been evaluated and deemed to be adequate to monitor the trend of loose parts noise for the duration of the fuel cycle prior to implementing the thermal shield repair.
Attachment to Enclosure 2 ENCLOSURE FOR REACTOR CAVITY 1/4" PIPE SEAL RING PLATE PLUG COVER SAND TANK NOZZLE INSULATION ENCLOED-,REACTOR CONCRETE VSE