ML17299A660
| ML17299A660 | |
| Person / Time | |
|---|---|
| Site: | Palo Verde  |
| Issue date: | 10/02/1985 |
| From: | Thompson H Office of Nuclear Reactor Regulation |
| To: | Van Brunt E ARIZONA PUBLIC SERVICE CO. (FORMERLY ARIZONA NUCLEAR |
| References | |
| TAC-56648, NUDOCS 8510110216 | |
| Download: ML17299A660 (8) | |
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UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D. C. 20555 Ot;T g 1S85 Docket Nos.:
50-528, 50-529, and 50-530 Hr. E.
E.
Van Brunt, Jr.
Executive Vice President Arizona Nuclear Power Project Post Office Box 52034 Phoenix, Arizona 85072-2034
Dear Mr. Van Brunt:
On September 12, 1985, Arizona Nuclear Power Project (ANPP) conducted a
loss-of-load test on Palo Verde Nuclear Generating Station Unit 1 from approximately 55% power.
The plant did not perform as expected.
The test resulted in an event involving loss of all offsite power to non-essential loads (including the reactor coolant pumps), turbine trip and reactor trip.
During the recovery phase of the event, overcooling of the reactor coolant system (RCS) ooc0rred to the extent that the emergency core cooling systems were automatically initiated, followed by the associated automatic initiation of containment isolation.
The following two sequences occurred during the event that caused the loss of all three charging pumps:
(1)
When the safety injection actuation signal (SIAS) occurred, power to certain suction valves for the charging pumps was lost since the motor control center for these valves was classified as non-essential
- and, accordingly was designed to be automatically shed from the safety related electric buses.
(2)
Because of a malfunction of the single water level instrument channel for the volume control tank (VCT), automatic control action was lost which would have transferred the suction of the charging pumps from the VCT to other water sources.
Also, after the containment isolation signal was received, all makeup flow to VCT was isolated.
Due to the above sequences, the VCT emptied, the charging pumps became bound on VCT hydrogen cover gas and the pumps were tripped.
This produced a potentially hazardous situation when, to re-establish charging pump flow, the lines from the pumps were 'vented to remove gas.
One of the charging pumps is required to provide auxiliary spray to the pressurizer.
In addition, the charging system may be needed to satisfy General Design Criteria (GDC) 26 and 33.
To assure that specified acceptable fuel design limits are not exceeded, (1)
GDC 26 requires that the plant design include a redundant reactivity control system (e.g.,
boron addition) and (2) 85iOii02i6 85i002 PDR ADOGN, 05000M8 8
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GDC 33 requires that a system be provided to supply reactor coolant makeup for protection against small breaks in the reactor coolant pressure boundary (i.e., when the reactor coolant system is at operating pressure).
As a result of this event, the Region V Office of the NRC 'issued a Confirmatory Action Letter, dated September 17, 1985, confirming an ANPP commitment not to restar t Palo Verde Unit I until the issue of appropriate design criteria for the auxiliary spray system was resolved to the satisfaction of the NRC staff.
Your letter of September 18, 1985 discussed the September 12, 1985 event and briefly addressed concerns relating to the auxiliary spray system.
At a meeting on September 20, 1985, your staff provided a more indepth discussion of the events and further discussed the auxiliary spray system.
At the conclusion of the September 20, 1985 meeting, ANPP coomitted to certain additional short term compensatory measures which justified continued operation of the facility while the long term corrective actions were developed.
The staff found these compensatory measures sufficient to allow restart of Palo Verde Unit I pending the resolution of the design criteria issue for the auxiliary 'spray system.
On the basis of your commitments to the agreed to compensatory mea'sures, the Region V Office of the NRC issued a followup Confirmatory 'Action Letter, dated September 20, 1985, describing the commitments and stating that adequate short term compensatory measures are in place for restart of Palo Verde Unit 1.
The letter also stated that long term measures to assure the reliability of the auxiliary spray system would be the subject of future correspondence.
In a November 3, 1982 letter, you stated that the safety-grade auxiliary spray system provides a depressurization capability of the primary system when the reactor coolant pumps are not running.
In a July 28, 1983 letter, you stated that the safety. grade auxiliary spray system is used to depressurize the plant to shutdown cooling entry conditions following a steam generator tube rupture (SGTR) accident without exceeding offsite dose limits.
As discussed in NUREG-1044, "Evaluation of the Need for a Rapid Depressurization Capability for Combustion Engineering Plants",
the staff's acceptance of the auxiliary spray system in lieu of PORVs was based on its understanding that the auxiliary spray system was safety grade.
Because of the above considerations, we are concerned about the pressurizer auxiliary spray system for the following reasons and are requesting additional information as discussed in the enclosure:
(I)
The degree to which the design, installation and operational capabilities of the auxiliary spray system meets its licensing basis.
(2)
The Palo Verde accident analyses, in particular the SGTR analysis, takes credit for the auxiliary spray system.
(3)
The Palo Verde plant design also relies on the auxiliary spray system as a means of rapid depressurization of the primary system under certain accident scenarios since the plant does not include PORVs.
Staff evaluation on the need for PORVs in the CE System 80 design was based on the understanding that a safety grade auxiliary spray system would be part of the design.
In order for the staff's conclusion to remain valid, we require that the auxiliary spray system be highly reliable.
Our original review equated this high reliability with meeting safety grade requirements.
(4)
The September 12, 1985 event demonstrated the operators'oncern with getting the charging pumps operable.
Pursuant to 10 CFR 50.54(f), you are requested to furnish in writing, under oath or affirmation within 20 days of the date of this letter, your plans, program and schedule to bring the auxiliary spray system into conformance with the plant's licensing basis.
Your submittal should address the resolution of the concerns identified above and respond to the specific questions in the enclosure.
If you desire, we are prepared to meet with you to discuss your response when it is sufficiently developed to make such a meeting useful.
Sincerely,
Enclosure:
As stated cc:
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Mr. E. E.
Van Brunt, Jr.
Arizona Nuclear Power Project Palo Verde CC:
Arthur C. Gehr, Esq.
Snell
& Wilmer 3100 Valley Center Phoenix, Arizona 85073 Mr. James M. Flenner, Chief Counsel Arizona Corporation Commission 1200 West Washington Phoenix, Arizona 85007 Charles R. Kocher, Esq. Assistant Council James A. Boeletto, Esq.
Southern California Edison Company P. 0.
Box 800
- Rosemead, California 91770 Mr. Mark Ginsberg Energy Director Office of Economic Planning and Development 1700 West Washington - 5th Floor Phoenix, Arizona 85007 Mr. Wayne Shirley Assistant Attorney General Bataan Memorial Building Santa Fe, New Mexico 87503 Mr. Roy Zimmerman U.S. Nuclear Regulatory Commission P. 0.
Box 239 Arlington, Arizona 85322 Ms. Patricia Lee Hourihan 6413 S. 26th Street Phoenix, Arizona 85040 Regional Administrator, Region V
U. S. Nuclear Regulatory Commission 1450 Maria Lane Suite 210 Walnut Creek, California 94596 Kenneth Berlin, Esq.
Winston 5 Strawn Suite 500 2550 M Street, NW Washington, DC 20037 Ms.'ynne Bernabei Government Accountability Project of the Institute for Policy Studies 1901 Que Street, NW Washington, DC 20009 Ms. Jill Morrison 522 E.-Colgate Tempi, Arizona 85238 Mr. Charles B. Brinkman, Manager Washington Nuclear Operations Combustion Engineering, Inc.
7910 Woodmont Avenue Suite 1310
- Bethesda, Maryland 20814 Mr. Ron Rayner P. 0.
Box 1509
- Goodyear, AZ 85338
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ENCLOSURE RE VEST FOR ADDITIONAL INFORMATION CONCERNING THE SEPTEMBER 12, 1985 EVENT AT PALO VERDE UNIT 1 1.
The Palo Verde design includes a safety grade auxiliary pressurizer spray system.
As a result of the September 12, 1985 event at, Palo Verde Unit 1, it is our view that the auxiliary pressurizer spray system does not meet safety. grade standards and that the'alo Verde design is not consistent with the docketed information describing the system design.
Therefore, describe the design modifications you intend to make to upgrade the auxiliary spray system to safety grade standards and provide the schedule by which this effort will be accomplished.
A justification for operation until the modifications have been completed should be provided.
2.
The auxiliary spray system was stated to be safety grade on the Palo Verde docket and then later determined to have single failure vulnerabilities and other deficiencies.
Provide a detailed explanation of how the,'gA process, which should include an independent review and verification of design
- adequacy, did not detect these deficiencies in the auxiliary spray system.
Also provide a description of the corrective actions you intend to take to. remedy any weaknesses identified in the gA process.
3.
Provide a detailed description of what you consider to be safety grade design requirements and how you apply these requirements to systems and components that are specified as safety related.
In particular, discuss how these requirements were applied to the auxiliary spray system and whether the identified deficiencies in auxiliary spray system were due to a failure to apply them to the system.