ML19317G844
| ML19317G844 | |
| Person / Time | |
|---|---|
| Site: | Rancho Seco |
| Issue date: | 01/05/1976 |
| From: | Mattimoe J SACRAMENTO MUNICIPAL UTILITY DISTRICT |
| To: | Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8004010671 | |
| Download: ML19317G844 (4) | |
Text
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_ f R C, TRICUTION FOR PART 50 DOCl i M ATERI AL
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CONTROL NO: /I FILE:
F ROM: SMUD DATE OF DOC DATE REC'D LTR TWX RPT OTHER Sacramento, Calif.
1-5-76 1-9-76 XXX T T: w H e
ORIG CC OTHER*
SENTl:RC PDR dX NRC 1 Signed SENT LOCAL PDR
- CLASS UNCLASS PROPINFO INPUT NO CYS REC'D DOCKET NO:
XXX 1-50-312 DESCRIPTION:
ENCLOSURES:
Ltr. re our ltr. d td 5-8-75...Trans the folicw
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ing.... describing 3 modes of operation regard-ACKNOT 1p"gG[h, ing loss-o f-Coolant-accident......W/ Attachment 99 gon.=&
PLANT NAME: Rancho Seco 7
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N-Re:
Docket No. 50-312 Rancho Seco Nuclear Generating Station Unit 1
Dear Sir:
In a letter to Mr. Robert A. Purple dated May 8,1975, the Sacramento Municipal Utility District presented operator actions for long-term cooling and described the analysis which demonstrates th3t boron precipitation will not occur during long-term cooling following a loss-of-coolant accident.
Attachment No. I to this letter described three modes of operation which could be implemented following a loss-of-coolant acci-dent to assure that boron precipitation would mot compromise long-term core cooling capability. The third mode of operation required the addition of two motor operators to valves inside the reactor containment. The District has ordered these motor operators; however, delivery will not occur for one year.
The temperature indicator for full implementation of Mode 2 operation has been installed at Rancho Seco Unit No.1.
Therefore, Modes 1 and 2 have been fully implemented.
In order to implement Mode 3 at the present time, the District has developed a revised 'ethod of opera-tion to replace Mode 3 as described in our letter of May c, 1975 Mode 3 would be implemented if Mode 2 is not successful. This mode of operation will route dilute injection to the area above the core.
The flow path is from the makeup pump, through a new line to be installed between a drain valve in the makeup line outside the containment to a drain valve in the pressurizer liquid sample line also outside the con-tainment, into the pressurizer through the liquid sample line, out of the pressurizer through the surge line into the hot leg, and then into the reactor vessel.
This mode of operation is shown as a dashed line on Figure 1.
The details of Mode 3 operation are as follows:
a.
Ttis operating mode will be used if Mode 2 is not successful.
b.
Close main pressurizer spray line EM0 Valve VI or V2, or both.
154 AN ELECTRIC SYSTEM S E RVIN G MORE THAN 600.000 IN THE HEART OF C ALIF0 R N I A
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.n U.S. Nuclear Regulatory Commission January 5, 1976 c.
Line up the makeup pump to pump to the pressurizer liquid sample line, taking suction from an operati.~.g LPI string.
This will require manually opening the drain valves in both the makeup line and liquid sample line.
(These valves are physically located approximately thirty feet apart in one rocm of the auxiliary building.) Open the two EMO valves in the pressurizer liquid sample line inside the containment. The EM0 valve downstream of the drain valve in the makeup line is a safety features valve and would have been closed upon initiation of the safety features system.
d.
Flow indication is provided on the makeup line enabling the operator to determine if this mode is successful.
Calculations indicate that a flow greater than 40 gpm would be available to the pressurizer under this mode of operation.
If Valve SFV-23604, which is the motor-operated valve downstream of the makeup line drain valve, were to open during long-term cooling, flow would be reduced to the pressurizer. However, there is a manual valve immediately downstream of SFV-23604 which could be closed.
There are two motor operated valves inside the containment in the pressurizer liquid sample line which are required to be open in this mode of operation.
If either of these valves were to fail closed this would prevent Mode 3.
However, Modes 1 and 2 would be unaffected.
The District feels this is an acceptable mode of operation to i
assure that boron precipitation would not compromise long-term core cooling following a loss-of-coolant accident.
Operating procedures will be revised to incorporate this third mode of operation as soon as the line connecting the makeup line drain valve and liquid sample line drain valve is installed.
We will inform you when this third mode of operation has been incorporated into the operating procedures.
Please advise us if we can provide further information.
Sincerely ya rs, WY i
.[.Mattimoe Assistant General Manager and Chief Engineer Attachment l
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