ML17299A987
| ML17299A987 | |
| Person / Time | |
|---|---|
| Site: | Palo Verde  |
| Issue date: | 01/13/1986 |
| From: | Ebersole J, Reed G Advisory Committee on Reactor Safeguards |
| To: | Palladino N NRC COMMISSION (OCM) |
| Shared Package | |
| ML17299A986 | List: |
| References | |
| TAC-60540, NUDOCS 8602050398 | |
| Download: ML17299A987 (4) | |
Text
January 13, 1986 Honorable Nunzio J. Palladino Chairman U. S. Nuclear Regulatory Commission Washington, D.C.
20555
SUBJECT:
COMMENTS ON OPERATIONAL TEST RESULTS OF PALO VERDE NUCLEAR GENERATING STATION, UNITS 1, 2, AND 3 AND SUGGESTED FOLLOW-UP ACTIONS
Dear Dr. Palladino:
On November 7,
- 1985,
. the Advisory Committee on Reactor Safeguards discussed the operational status of the Palo Verde Nuclear Generating
- Station, Units 1, 2 and 3 regarding the power ascension test program and results at Unit 1 and the completion status of Unit 2.
ACRS reports on these units were issued on December 15, 1981 and May 13, 1985.
A related ACRS report on the need for rapid depressurization capability in newer CE plants (without PORVs) was issued on October 18, 1983.
Based on discussion during the November 1985 meeting, the Committee decided not to provide additional comments regarding these units.
We disagreed with their decision at the time and on further consideration, must inform you that, in our opinion, this ACRS action was a mistake.
Palo Verde is being allowed to get off to a "bad start" in a
somewhat "poli-cy" context.
During the power ascensioh tests at Palo
- Verde, Unit 1,
one of the systems that did not perform as expected was the Auxiliary Pressurizer Spray System (APSS) and thus, ACRS previous concerns in regard to the function of "rapid" depressurization at this plant should be considered as having been poorly resolved, first, by the licensee attempting the use of an existing and "unqualified" system and then, upon discovery of
- problems, invoking the use of another existing (thin) system which was installed (as a
post-TMI requirement) f'r noncombustible g'as venting from the pressurizer.
In essence, the elements of the problem are as follows:
(1)
The "rapid" depressurization function has been elevated (NUREG-1044) to a safety function but a dedicated safety grade system in this new plant has not been provided to perform it.
(Of course, it has not yet been required of the older plants which use nonsafety grade PORVs).
(2)
The utility has now taken credit (after problems with the APSS during the testing program) for an alternate system (the gas vent system) for depressurization.
This would permit very f
8602050398 860121 PDR ADOCK 05000528 P
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Honorable Nunzio J. Palladino January,13, 1986 slow depressurization through a preferred 3/4" line or alter-natively through a 7/32" orifice.
(3)
The systems (APSS and vent) have numerous single failure vulnerabilities.
(4)
The reliability of both of these systems depends on many valves that must open from a normally closed position and on the operability of several air operated valves.
We believe that these current systems at Palo
- Verde, even with the planned modifications and surveillances, may not be adequate to provide for the rapid depressurization need.
As a minimum, the "new" APSS and alternate pressurizer vent should be carefully tested to determine their capabilities and should be subjected to a
mini-PRA to assess their overall reliability.
As a further observation, Arizona Public Service Company admitted that it did not and presumably does not now have an organized, methodical and documented activity for performing system interaction studies at this plant --
a state of affairs which tends
.to produce situations like the one described above.
As you will recall, the companion issue in this design is whether, in the absence of valving of such size and reliability to assure "bleed and-feed" (as 'well as depressurization) capability, decay heat removal can be assured through the single mode of rejection through the secon-dary
- system, a
system supported by a large number of auxiliary func-tions.
The most critical of these is, of course, the Auxiliary Feed-water System which in this plant is somewhat less conservative than "standard" designs which do have bleed-and-feed capability.
Sincerely, sse berso e, retire ea Nuclear Engineer, Tennessee Valley Authority enn ee
, ret)re ant
- Manager, Pt.
Beach Nuclear Power Plant, Wisconsin Electric Power Company
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