ML17083B433
| ML17083B433 | |
| Person / Time | |
|---|---|
| Site: | Diablo Canyon  |
| Issue date: | 09/11/1984 |
| From: | Liang C, Liang Chuyu Office of Nuclear Reactor Regulation |
| To: | Sheron B Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML16341A317 | List: |
| References | |
| TAC-51638, NUDOCS 8409250259 | |
| Download: ML17083B433 (10) | |
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UNITED STATES CLEAR REGULATORY COMMISSI WASHINGTON, D. C. 20555 SEP f
1 198 THRU:
MEMORANDUM FOR Brian W. Sheron, Chief Reactor Systems
- Branch, DSI Ledyard B. Marsh, Section 0 Leader /3~
Reactor Systems
- Branch, DSI FROM:
SUBJECT:
Chu-yu Liang Reactor Systems
- Branch, DSI DIABLO CANYON TRIP REPORT L. Marsh and I made a trip to Diablo Canyon Site on August 21 and 22, 1984.
The trip was accompanied by H. Holz of Generic Issues
- Branch, DST and H. Schierling of DL.
The purposes of this staff trip are as follows:
1)
To discuss with the licensee on the design of the interlocks and power supplies to the RHR suction isolation valves; 2)
To discuss with the licensee on the planned natural circulation and boron mixing tests at Diablo Canyon Unit 1 to demonstrate the compliance of the Branch Technical Position RSB 5-1; 3)
To examine the physical arrangement of the components and systems used for plant decay heat removal.
The results of the discussions with PG&E and the staff site visit during this trip are addressed in the enclosed report.
~
~
Chu-yu L'g, Sectio Reactor Systems Branc
, DSI
Enclosure:
As stated
ENCLOSURE 1 DIABLO CANYON TRIP REPORT (August 21 and 22,1984) 1.
Discussions on the desi n of the interlocks and ower su lies to the RHR suction isolation valves:
As a result of the staff evaluation on Diablo Canyon Allegation No. 45, the staff has stated in SSER No.
26 that the staff requested that the technical Specification 3.4.9 '
and Operating Procedure B-2. 11 must be changed within 3 months after the low flow alarm is installed to require power to be available to the RHR hot leg suction isolation valves.
This staff required action was to reestablish the design function of the pressure interlocks on the RHR isolation valves to reduce the I
probability of a LOCA outside containment from occurring.
The licensee in a letter dated August 15, 1984, proposed that the interlocks on the RHR isolation valves be removed before power is made available to the RHR isolation valves.
The basis of this licensee's request is that with the interlock in effect and power restored to the valves, inadvertent valve closures could result in adverse situations such as 1) interruption of decay heat removal, 2)
RHR letdown isolation resulting in RCS pressure spi king and/or PORV challenge, and 3) potential for RHR pump k
damage.
Therefore, PGEE does not feel that restoring power to the RHR suction valves with the interlock installed is in the best interest of plant safety.
On August 21,
- 1984, the staff discussed this issue with PGEE at Diablo Canyon Site.
The merits of the RHR design with or without interlocks to the isolation valves were explored.
In conclusion, the licensee agreed to reinstall power back to the isolation
0
valves within 3 months following the installation of the low flow alarms I
(low flow alarms have been installed on June 6, 1984).
This is to satisfy the requirement stated in SSER No. 26.
However, the licensee will submit a letter requesting the removal of interlocks to the RHR isolation valves with justifications.
The licensee believes that the intersystem LOCA concerns can be resolved by installing alarms to warn the operators if the RHR suction valves are not closed when the RCS pressure is above 450 psig.
These alarms would back up operating procedures and provide additional assurance that both valves will be closed when the RCS is at pressure.
The staff has informed the licensee during the discussion that the staff would give prompt response to this forth coming request.
2.
Discussions. on the lanned natural circulation and boron mixin tests:
In Amendment 60 to FSAR, the licensee has committed to perform natural circulation and boron mixing tests at Diablo Canyon Plant.
In a letter dated October 23,
- 1979, the staff provided a summary of the staff's review of the licensee's draft test procedure No. 42.7 (Natural Circulation Boron Nixing Test) and additional guidance in regard to the supporting analyses required by Branch Technical Position RSB 5-1.
By letter dated Nay ll, 1983, the licensee submitted a copy of the test procedure No. 42.7 revision 2 for staff review.
On August 22,
- 1984, the staff discussed this test procedure with PGKE at Diablo Canyon site.
The staff's major comments to the planned tests are as follows:
a)
The licensee should develop proper criteria for test operation and termination.
b)
Test should include plant cooldown to RHR initiation conditions and to Node 5 using RHR system.
c)
The licensee should verify the effects of potential single failure on loop charging valve to the function of the auxiliary pressurizer spray system during RCS depressurization.
d)
The test should demonstrate the adequacy of the safety related condensate storage capacity for plant cooldown.
e)
The test should demonstrate the adequacy of the safety related nitrogen supply te air operated atmospheric steam dump valves for plant cooldown.
Condenser steam dump should not be operated during the test.
f)
The test should include 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> hot standby time before cooldown to Mode 4.
g)
Justification of manual operation outside the control room during the tests in light of BTP RSB 5-1.
h)
The normal pressurizer spray valves should not be used during the test.
i)
In the proposed test procedure, the RCPs are manually tripped after the reactor trip.
The staff suggested that the time gap between the reactor trip and the RCPs trip should be minimized.
j)
PGEE should submit a post-test report including the necessary analysis to address the c'ompliance of BTP RSB 5-1.
The use of non-safety related equipment in the test should be substantiated in the f'inal report.
During the discussion, the staff agreed that we will issue our formal questions on this issue within 3 weeks.
0
3.
Staff lant tour On August 21, 1984, the staff made a walk through at Diablo Canyon Unit 1.
The staff has observed the equipment arrangement inside and outside the containment in the areas that components used for plant decay heat removal and ECCS are located.
Especially, the staff examined the locations of the RHR hot leg suction isolation valves inside containment and the atmospheric steam dump valves upstream of the MSIVs.
The RHR hot leg suction isolation valves and ADVs are equipped with handwheels which could be used for local manual operation when necessary during plant cooldown.