ML20032E326
| ML20032E326 | |
| Person / Time | |
|---|---|
| Site: | Rancho Seco |
| Issue date: | 11/16/1981 |
| From: | Mattimoe J SACRAMENTO MUNICIPAL UTILITY DISTRICT |
| To: | Stolz J Office of Nuclear Reactor Regulation |
| References | |
| GL-81-21, TAC-47170, NUDOCS 8111200409 | |
| Download: ML20032E326 (4) | |
Text
-_
' e..suuo SACRAMENTO MUNICIPAL UTILITY DISTRICT C 6201 S Street, Box 15830, Sacramento, rahfornia 95813: (916) 452 3211 November 16, 1981 4
I DIRECTOR OF NUCLEAR REACTOR REGULATION ATTENTION JOHN F STOLZ CHIEF NOW 019s;5
( {' ""- Qftgroa OPERATING REACTORS BRANCH N0 4 U S NUCLEAR REGULATORY COMMISSION s
p g.
p WASHINGTON D C 20555 7C1 k
DOCKET 50-312 RANCHO SEC0 NUCLEAR GENERATING STATION UNIT N0 1 NATURAL CIRCULATION C00LDOWN, GENERIC LETTER NO 81-21 The Sacramento Municipal Utility District has reviewed your letter of May 5,1981, Generic Letter No. 81-21, concerning natural circulation cooldown. We do not feel that the events described in your letter provide i
a safety concern.
It is highly unlikely that Rancho Seco Unit 1 would be cooled down without the use of the reactor coolant pump.
For any event other than a small break LOCA, the plant would be shut down by normal means using forced circulation by the reactor coolant pumps.
If a natural circulation cooldown were required, the cooldown would be controlled by the rate of cooldown of the pressurizer and would be of long duration. Any voiding in the reactor vessel head or top of the hot leg wculd be indicated by a rapid increase in pressurizer level.
Since this event is not considered to be of safety significance, the District does not intend to perform the analyss or tests discussed in your letter.
However, Rancho Seco Unit 1 operators have been trained to recognize the event and operating procedures have been revised to address the possibility of void formation.
Our licensed operators were first made aware of this problem when IE Circular 80-15 was issued as a reading assignment in July of 1980. Since that time, all licensed operators have been trained on this event as part of their requali-1 fication training.
In addition, training for the mitigation of core damage including simulator training at the B &W simulator addresses this issue. The Limits and Precautions, Section of Operating Procedure B.4, Plant Cooldown and Shutdown, restricts the rate of pressurizer cooldown to 100 degrees per hour.
Section 6 of this procedure addresses natural circulation cooldown and Step 6.1.7.6 provides a caution to the operator to monitor the pressurizer and makeup tank level during ccoldown and informs him that a sudden increase in level indicates flashing in the reactor coolant system. This same section of the procedure instructs the operator to depressurize gradually and 75 to 100 psi steps to reduce the effects of metal heating.
j i
8111200409 811116 PDR ADOCK 05000312 kii*bl[
P PDR 40
't IN of tr '
JOHN F STOLZ CHIEF November 16, 1981 We feel that all licensed operators at Rancho Seco have been made adquately aware of the consequences of void formation during plant cooldown.
If we can provide any additional inforrnation, please advise.
hYwg t
/
/
- ohn U. Mattimoe J
Assistant General Manager and Chief Engineer Sworn to me and subscribed before me this /6IA day of November,19 f/.
bLu 0LMh]
Notary Roblic mm=c ->
m g%
surAny restic-cas.ironsta p 9
ParNCIPAL OFFICE IN SACRAMENTO COUNTY S
l My Commission Espires June 28, 1982 l
+ mamuacuu.anuummumomanuuoumaneummmmmmmo
.