ML20199K392
| ML20199K392 | |
| Person / Time | |
|---|---|
| Site: | Vogtle  |
| Issue date: | 04/02/1986 |
| From: | Youngblood B Office of Nuclear Reactor Regulation |
| To: | Conway R GEORGIA POWER CO. |
| References | |
| TASK-2.K.3.05, TASK-TM GL-85-12, NUDOCS 8604100098 | |
| Download: ML20199K392 (14) | |
Text
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Docket Nos.: 50-424 and 50-425 Mr. Richard E. Conway
-Senior Vice President and Project Director Georgia Power Company Rt. 2, Box 299A Waynesboro, Georgia 30830
Dear Mr. Conway:
Subject:
Request for Additional Infonnation on Generic Letter 85-12, "TMI Item II.K.3.5" The staff has reviewed your response to Generic Letter 85-12, "TMI Item II.K.3.5,"' dated February 17, 1986 and discussed our questions with your staff in a telephone conference call on March 18, 1986. The enclosure documents the conference call agenda items and our understanding of responses obtained from your staff during the call. We request that you confirm the information in the enclosure or correct it as necessary and also.that you provide the supplementary information as requested. This
. information should be detailed enough for the staff to complete its re-view. We request that you provide this information by April 18, 1986.
This schedule will allow the staff to review the information prior to SER Supplement 2 issuance.
If your response is unsatisfactory, Generic Letter 85-12 will be listed as a new open item in SER Supplement 2.
If there are any questions regarding this matter contact the Project Manager, Melanie Miller at (301) 492-7357.
Sincerely, g
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- p. Hood
. J. Youngblood, Director PWR Project Directorate #4 Division of PWR Licensing-A
Enclosure:
As stated cc: See next page DISTRIBUTION:
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APR O 2 $86 Mr. R. E. Conway Georgia Power Company Vogtle Electric Generating Plant m
cc:
Mr. L. T. Gucwa Resident Inspector Chief Nuclear Engineer Nuclear Regulatory Commission Georgia Power Company P. O. Box 572 P.O. Box 4545 Waynesboro, Georgia 30830 Atlanta, Georgia 30302 Mr. Ruble A. Thomas Deppish Kirkland, III, Counsel Vice President - Licensing Office of the Consumers' Utility Vogtle Project Council Georgia Power Company /
Suite 225 Southern Company Services, Inc.
32 Peachtree Street, N.W.
P.O. Box 2625 Atlanta, Georgia 30303 Birmingham, Alabama 35202 James E. Joiner Mr. Donald O. Foster Troutman, Sanders, Lockerman, Vice President & Project General Manager
& Ashmore Georgia Power Company Candler Building Post Office Box 299A, Route 2 127 Peachtree Street, N.E.
Waynesboro, Georgia 30830 Atlanta, Georgia 30303 Douglas C. Teper Mr. J. A. Bailey Georgians Against Nuclear Energy Project Licensing Manager 1253 Lenox Circle Southern Company Services, Inc.
Atlanta, Georgia 30306 P.O. Box 2A25 Birmingham, Alabama 35202 Billie Pirner Garde Citizens Clinic Director Ernest L. Blake, Jr.
Government Accountability Project Bruce W. Churchill, Esq.
303 10th Street Shaw, Pittman, Potts and Trowbridge Augusta, Georgia 30901 1800 M Street, N.W.
Washington, D. C.
20036 Mr. G. Bockhold, Jr.
Vogtle Plant Manager Georgia Power Company Route 2, Box 299-A Waynesboro, Georgia 30830 Regional Administrator, Region II U.S. Nuclear Regulatory Commission 101 Marietta Street, N.W., Suite 2900 Atlanta, Georgia 30323
Enclosure g 3y g PRELIMINARY REVIEW OF V0GTLE REACTOR COOLANT PUMP (RCP) l TRIP CRITERIA MARCH 20, 1986 INTRODUCTION Listed below are the evaluation criteria the staff is applying to RCP trip review and our preliminary appraisal of whether sufficient information was provided by the Georgia Power Company for the staff to complete its review.
The information covered in the evaluation includes that submitted by the applicant in Reference 1, and the results of a telephone conference call conducted between applicant and NRC personnel on March 18, 1986.
Participants in the conference call from Georgia Power were Dennis Hudson, Ken Kopecky, Greg Lee, Larry Prill, and John Bowles.
The staff was represented by Melanie Miller and Warren Lyon.
The general organization of the material which follows is a staff provided statement, either guidance or a statement of an evaluation criterion, generally followed by a staff statement in regard to the initial applicant submittal (Ref.
1).
The staff perception of the telephone conference call is then summarized.
The staff plan to complete the review, as described to the applicant, is to document the results of the preliminary review and the telephone conference call, and to provide the documentation to the applicant.
(This Enclosure is that documentation.) Then the applicant can provide a written response regarding the accuracy of the staff perception of the telephone conference call,,
together with any desired corrections and supplemental information.
This will allow the staff to complete the review and prepare a Safety Evaluation Report (SER).
An alternate, if the applicant desires (and which is not presently contemplated), is for the staff to prepare formal questions for applicant consideration.
l OVERALL GUIDANCE PERTINENT TO RCP TRIP During a small break accident in certain break size ranges, there exists a l
window in time during which tripping RCPs will make the accident worse.
Therefore, in a small break situation, one must trip RCPs prior to entering 1
(
3 i.h2 window.
If cne wish2s to d;psnd up::n canual trip, two criteria are applicable:
1.
One must show that at least 2 minutes exist within which to trip RCPs following " receipt of a trip signal" using licensing calculations as a basis.
2.
One must show that at least 10 minutes exist within which to trip RCPs following " receipt of a trip signal" using best estimate calculations as a basis.
If, for some reason, the RCPs have not been tripped within 10 minutes of the time at which plant conditions indicate trip should be performed, they are to be left running until after the window is closed.
Closure can be indicated by parameters such as regaining both adequate subcooling margin and pressurizer level after they have been lost.
Analyses are required to establish timing relative to items 1 and 2, as well as to establish the dimensions of the window.
It is desirable to leave pumps running for control purposes during other transients and accidents, including steam generator tube rupture accidents of sizes up to one tube broken.
Therefore, insofar as is practical, procedures and criteria should be developed to attain this goal.
Note that leaving pumps running during "non-break" transients and accidents is not a 100% requirement, as contrasted to the small break, where trip must be accomplished to remain in compliance with the regulations.
(Failure to trip as required could lead to exceeding Appendix K specified temperatures.) For "non-break" transients and accidents, RCPs may be tripped when desirable.
If in doubt, the small break criteria are to be applied.
1 New plants coming on line should have dealt with RCP trip prior to power operation.
Note much of the work pertinent to the above criteria has been done on a generic basis, and is applicable to individual plants. Where this is the case, it is sufficient to establish.spplicability, and the generic work need not be repeated on a plant specific basis.
1
SPECIFIC EVALUATION CRITERIA AND COMMENTS The evaluation criteria are generally those provided in Reference 2, including the Safety Evaluation and its appendices, which were an enclosure to Reference 2.
A.
Determination of RCP Trip Criteria Demonstrate and justify that proposed RCP-trip setpoints are adequate for small-break LOCAs but will not cause RCP trip for other non-LOCA transients and accidents such as SGTRs. This is to include performance of safety analyses to prove the adequacy of the setpoints.
Consider using partial or staggered RCP-trip schemes.
Staff Evaluation. The applicant has selected Reactor Coolant System (RCS) pressure as the criterion for tripping the RCP. This option was previously identified by the staff as the least desirable of the three options described by the Westinghouse Owners Group (WOG) in their evaluation of RCP trip. This selection was discussed during the March 18 telephone call.
The additional information provided to the staff is covered in the following subsection.
Applicant Supplemental Infonnation. Georgia Power personnel reviewed the Emergency Response Guidelines (ERGS), evaluated plant specific data, performed calculations pertinent to RCP trip, evaluated each of the three RCP trip approaches recommended by the Westinghouse Owners Group (WOG) and generically approved by the staff, and obtained the accident discrimination characteristics for each of the three RCP trip criteria. They then studied the control room display indicators, and marked the locations of the RCP trip points on drawings of the instruments. This provided information pertinent to operator ability to recognize RCP trip requirements from the control room indicators. At this point, RCS subcooling and pressure were concluded to be the most desirable.
Next, considerations of possible confusion and redundancy were applied.
The subcooling monitor is located in the midst of other displays, and only
4 two chann21s ar2 available. Tha RCS pressure displays are a part of the Reactor Vessel Level Instrumentation System (RVLIS), are directly in front of the normal operator and shift supervisor stations, and there is additional redundancy available from non-RVLIS indicators.
Finally, the applicant reviewed data uncertainties and performed an operator oriented overview. Concern was expressed relative to in-core thermocouple uncertainty, and if a differential pressure technique were to
.be applied, the uncertainty in steam generator secondary side pressure would also contribute to overall uncertainty. Application of the staff recommended pressure difference technique would also require the operator to read additional instruments, and to perform a subtraction.
These steps led to a clear choice of RCS pressure as the most desirable RCP trip criterion.
Staff Coment. This is sufficient information for completion of the review.
A1.
Identify the instrumentation to be used to determine the RCP trip set point, including the degree of redundance of each parameter signal needed for the criterion chosen. Establish the quality level for the instrumentation, identify the basis for the sensing-instruments' design features, and identify the basis for the degree of redundance.
Staff Evaluation. The applicant has identified that four redundant channels of wide range pressure instrumentation (tag numbers provided) are available to support the selected RCP trip criterion. Pressure is sensed from the hot legs of loop 1 and 4 of the Reactor Coolant System (RCS).
There are two pressure sensing lines, each of which has two transmitters.
The instrument piping is seismically qualified and the transmitters, cabling and indicators are all Class 1E and environmentally qualified for local adverse conditions.
The instrumentation is identified, as is its classification and the bases for redundancy and qualification. This information is sufficient for staff evaluation.
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S d2.
Identify the instrumentatien uncertainties for both normal and adverse containment conditions.
Describe the basis for the selection of the adverse containment parameters. Address, as appropriate, local conditions, such as fluid jets or pipe whip, which might influence instrumentation reliability.
Staff Evaluation.
Instrument uncertainties associated with the four RCS pressure instrument channels are stated to be 3% of span (90 psi), and are stated to be applicable to both normal and adverse containment conditions since the wide range pressure transmitters are located outside of containment. This uncertainty is stated to cover readout on both the control board indicators and the plant safety monitoring system display.
The applicant also stated that since two transmitters are connected to each of two pressure sensing lines, a postulated single failure of an impulse line due to accident conditions would affect only one pair of pressure measurements.
The applicant further conducted an engineering review of sensing lines and instrumentation layout, and concluded that adverse local effects would not result in the unavailability of the instrumentation.
The reported results are not consistent with staff experience, which leads to an expectation of significantly different uncertainty for normal as contrasted to adverse containment conditions.
The value of 90 psi for adverse conditions appears low.
The staff would further expect an influence of temperature upon the sensing lines, which could affect all lines roughly equally, or conversely, could cause instrumentation to behave differently due to localized effects.
Is the reported behavior due to use' of pressure sensors connected to the hot legs as opposed to the pressurizer? More broadly, justification for the applicant conclusions would be helpful.
Operator response to instruments under normal and abnormal conditions when one instrument is inoperative should be addressed.
Emphasis should be upon abnormal conditions if these are found to provide a larger uncertainty.
Applicant Response.
As explained above, the selected displays utilize the RVLIS system, and transmitters for this system are located outside containment where they are not exposed to an adverse containment
. ~
6 atmosph;re. Georgia Power personnel evaluated the pressure lines within containment, taking into account that line temperature is monitored by RTDs at selected locations, and found there was no significant perturbation due to adverse containment conditions.
Georgia Power personnel evaluated conditions outside coniainment and found there was no adverse condition reasonably possible due to the RVLIS system component locations. There is no major piping which could affect the system.
(This was not the case for the pressure differential RCP trip approach, where a significant adverse condition existed outside containment for steam line breaks due to the location of pressure instrumentation.)
There are two wide range pressure transmitters available which provide the operator with backup information, and which can be used to supplement the primary RCP trip indicators. Operator training provides emphasis on potential instrument malfunctions and the obtaining of confimation from alternates when such actions are indicated.
Staff Response. The only additional information that is needed is instrument response time. What is the lag associated with the long pressure lines leading from the RCS to the transmitters?
A staff observation is that the operator should be aware that adverse containment condition can affect wide range pressure instrumentation, which is a potential source of confusion if there is a question pertinent to pressure as indicated by RVLIS.
A3.
In addressing criterion selection, provide consideration of uncertainties associated with the WOG supplied analyses values. These uncertainties are to include uncertainties in computer program results and uncertainties resulting from plant specific features not representative of the generic data group.
If a licensee (or applicant) detemines that the WOG alternative criteria are marginal for preventing unneeded RCP trip, it is recommended that a more discriminating plant-specific procedure be developed. Licensees (or l
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applicant) should take credit for all equipment (instrumentation) available to the operators for which the licensee has sufficient confidence that it will be operable during the expected conditions.
j Staff Evaluation.
Analyses with the licensed Westinghouse LOFTRAN computer code are referenced as the basis for Vogtle under non-LOCA conditions.
l The computer program result uncertainties evaluation is based on the assumption of no changes in initial plant conditions (such as full power, pressurizer level, all Safety Injection (SI) pumps running, and all
{
Auxiliary Feed Water (AFW) pumps running).
The major contributors to j
uncertainty are stated to be break flow rate, SI flow rate, decay heat generation rate, and AFW flow rate.
Parametric studies are summarized in which the major uncertainties are stated to be due to the break flow model and SI flow inputs.
The calculated overall uncertainty in the analyses is stated to be 150 psi on each side of the trip point.
l The applicant has not directly addressed such topics as the accuracy of the
{
numerical solution scheme or of nodalization.
Further, there is no determination of the influence of equipment or operational failures.
Information pertinent to the former result from comparisons of the LOFTRAN code to operational and experimental data, and as a result was included i
in the 150 psi number. Detemination of equipment or operational failures is not a necessity as long as the expected configuration of the plant is l
addressed since the objective of RCP trip is to provide reasonable j
assurance of not tripping for transients for which a trip is undesirable.*
j It is not necessary to establish that one will never trip since the plant is capable of being safely controlled if an unnecessary trip does occur.
Thus, no additional information is needed for the staff to complete review of this item.
i B.
Potential Reactor Coolant Pump Problems j
j Bl. Assure that containment isolation, including inadvertent isolation, will l
not cause problems if it occurs for non-LOCA transients and accidents.
j Demonstrate that, if water services needed for RCP operations are i
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terminated, they can be restored fast enough once a non-LOCA situation is confirmed to prevent seal damage or failure.
Confirm that containment isolation with continued pump operation will not lead to seal or pump damage or failure.
Staff Evaluation.
A non-safety related, seismic Category 1 Auxiliary Component Cooling Water (ACCW) system is used to provide cooling water to RCP oil coolers, motor coolers, and thermal barrier heat exchangers.
Seal injection water is provided by the Chemical Volume and Control System (CVCS). Containment penetrations for these systems are designated as
" essential", and the isolation valves associated with the penetrations are remote-manual without automatic isolation provisions.
The valves fail "as is" if electrical power to the motor operators is lost. The running ACCW pump continues to function if a Safety Injection (SI) signal is received with off site power available.
If off site power is lost coincident with the SI signal, power to the ACCW pumps is terminated.
They can be manually restarted by the operator once the Class 1E bus sequencer has completed its function.
Clarification is necessary with respect to isolation.
Does containment isolation result in loss of CVCS provided seal water to the RCPs? Does containment isolation result in loss of ACCW water to the RCP thermal barrier heat exchangers? If ACCW pump operation is terminated, how long does it take for the pump to be restarted and flow restored to the thermal barrier heat exchangers and other RCP associated components? Where is the information pertinent to timing of loss of cooling or injection and the protection against RCP seal LOCA? Information should be provided pertinent to trip of the RCPs under conditions such as loss of seal injection or ACCW, and restart of the RCPs following restoration of services leading to the trip.
Items such as trip parameters, operator response and timing of operations should be identified.
Applicant Response.
Seal injection is always maintained with respect to containment isolation operations.
The only way one loses seal injection is l
if there are equipment failures, such as loss of all charging pumps.
9 If ACCW is lost fer more than 10 cinut:s, or if b:aring temperatur:s exce2d specified limits, whichever occurs first, then the RCPs are tripped.
Detailed procedures exist pertinent to restart which require that transient criteria are met to guard against thermal stresses during RCP restart.
Staff Response.
Continued discussion revealed that significant information and planning exist, and it was clear that these points are adequately addressed.
No further infomation is necessary.
82.
Identify the components required to trip the RCPs, including relays, power supplies and breakers.
Assure that RCP trip, when necessary, will occur.
Exclude extended RCP operation in a voided system where pump head is more than 10% degraded unless analyses or tests can justify pump and pump-seal integrity when operating in voided systems.
If necessary, as a result of the location of any critical component, include the effects of adverse containment conditions on RCP trip reliability.
Describe the basis for the adverse containment parameters selected.
Staff Evaluation.
Components associated with RCP trip are identified, but there is no discussion of their location. The applicant should determine that none of the components will be affected by accident conditions such as high energy line breaks inside or outside containment, or other accident conditions which could create an adverse environment in the vicinity of the components.
There is no information pertinent to assurance that RCP trip will occur when necessary, nor is an alternate operator response provided if there is a failure to trip upon operation of control switches in the control room.
RCP operation in a voided system is not mentioned.
Applicant Response. Georgia Power will supply information pertinent to the above.
The staff was requested to provide the origin of the concern with RCP operation in a voided system, namely " Exclude extended RCP
10 operation in a voided system where pump head is more than 10% degraded unless analyses or tests can justify pump and pump-seal integrity when operating in voided systems."
Staff Response. The quoted material in the above paragraph is Item 2, page 3 of Appendix A to the Safety Evaluation Report attached to NRC Generic Letter No. 85-12 (Ref. 2).
The lead-in to the list of items that include item 2 states:
"C.
Consider the following guidelines in developing RCP-trip setpoints." The staff added several items of this type to the wording provided in the Generic Letter when it was felt technical points might be overlooked due to the summary nature of the letter.
C.
Operator Training and Procedures (RCP Trip)
C1. Describe the operator training program for RCP trip.
Include the general philosophy regarding the need to trip pumps versus the desire to keep pumps running.
Also cover priorities for actions after engineered safety features actuation.
Assure that training and procedures provide direction for use of individual steam generators with and without operating RCPs.
Assume manual RCP trip does not occur earlier than two minutes after the RCP-trip set point is reached.
Determine the time available to the operator to trip the RCPs for the limiting cases if manual RCP trip is proposed.
Best Estimate calculational procedures should be used.
Most probable plant conditions should be identified and justified by the licensee, although NRC will accept conservative estimates in the absence of justifiable most probable conditions.
Justify that the time available to trip the RCPs is acceptable if it is less than the Draft ANSI Standard N660.
If this is the case, then address the consequences if RCP trip is delayed.
Also develop contingency procedures and make then, available for the operator to use in case the RCPs are not tripped in the preferred time frame.
i i
11 Staff Evaluation.
References for training are provided as is a list of training topics.
However, the applicant response is general and does not address the above identified points, nor does the response establish that the applicant has an understanding of the need to trip RCPs as contrasted to keeping them running.
Applicant Response.
A brief description of training which addresses the background and tne above points will be provided.
C2.
Identify those procedures which include RCP trip related operation:
(a) RCP trip using WOG alternate criteria (b) RCP restart (c) Decay heat removal by natural circulation (d) Primary system void removal (e) Use of steam generators with and without RCPs operating (f) RCP trip for other reasons J
Ensure that emergency operating procedures exist for the timely restart of the RCPs when conditions warrant.
Staff Evaluation.
The licensee has presented a listing of selected procedures, most of which are stated to be based upon the WOG Guidelines.
This list appears to be sufficient.
It would be helpful to briefly describe the technical requirements to be met for restart.
Staff Comment.
The necessary material was discussed as part of the above.'
No further information is needed for the staff to complete its evaluation.
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12 RE ERENCES 1.
Bailey, J.
A., "NRC Docket Numbers 50-424 and 50-425, Construction Permit Numbers CPPR-108 and CPPR-109, Vogtle Electric Generating Plant - Units 1 and 2, Generic Letter 85-12, TMI Item II.K.3.5, Letter to Director of Nuclear Reactor Regulation from Georgia Power Company, File X78C35, Log GN-806, Feb. 17, 1986.
2.
Thompsun, Hugli L. Jr., " Implementation of IMI Action Item II.K.3.5, ' Automatic Trip of Reactor Coolant Pumps' (Generic Letter No.
85-12)", NRC Letter Addressed to All Applicants and Licensees with Westinghouse {W)DesignedNuclearSteamSupplySystems(NSSSs),Jun.28, 1985.
a