ML19321A676
| ML19321A676 | |
| Person / Time | |
|---|---|
| Site: | Fort Saint Vrain  |
| Issue date: | 06/20/1980 |
| From: | Seyfrit K NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| To: | Millen C PUBLIC SERVICE CO. OF COLORADO |
| References | |
| NUDOCS 8007240054 | |
| Download: ML19321A676 (1) | |
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States June 20, 1980 Docket No. 50-267 Public Service Company of Colorado ATTN: Mr. C. K. Millen Senior Vice President P. O. Box 840 Denver, Colorado 80201 Gentlemen:
This Circular is forwarded for information. No written response to this IE Circular is required.
If you have any questions related to this matter, 1
please contact this office.
Sincerely, KarlV. Shit w
i Director
Enclosures:
1.
IE Circular No. 80-15 2.
List of Recently Issued IE Circulars cc:
D. W. Warembourg, Nuclear Production Manager Fort St. Vrain Nuclear Station P. O. Box 368 Platteville, Colorado 80651 L. Brey, Manager, Quality Assurance i
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e SSINS No.: 6835 Accession No.:
UNITED STATES 8005050073 NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D. C.
20555 IE Circular No. 80-15 Date:
June 20, 1980 Page 1 of 4 LOSS OF REACTOR COOLANT PUMP COOLING AND NATURAL CIRCULATION C00LDOWN Description of Circumstances:
This Circular contains information on the St. Lucie Unit i response to a total loss of component cooling water (CCW) flow to reactor coolant pumps.
Pres-surizer level and primary system pressure response indicate that voids were formed in the reactor vessel during the ensuing natural circulation cooldown.
The void was believed to have been steam in the area located directly under the reactor vessel head.
At time 0226 on June 11, 1960 with St. Lucie Unit 1 at full power, an electrical short across a solenoid valve terminal board caused one of two series containment isolation valves in the CCW return from all reactor coolant pumps (RCP) to fail shut.
The terminal short resulted from environmental effects of a minor steam leak in the immediate vicinity of the solenoid valve.
After unsuccessful attempts to restore CCW flow, the reactor was tripped manually at time 0233.
Within two minutes, all four RCPs were also manually tripped. A natural circulation cooldown was initiated at approximately 0300.
Component cooling water flow to RCPs was restored at 0400.
The solenoid operated air valve whose terminal board had shorted was bypassed with a temporary air line to reopen the CCW valve (HCV-14-6). Although variations in seal leakoff flowrates were observed, the seals on the four idle RCPs did not fail.
St. Lucie has Byron Jackson reactor coolant pumps with three stage mechanical seals plus a vapor seal.
Controlled reactor coolant bleedoff flow is used for seal cooling and lubrication. The pumps do not have a seal water injection system.
The natural circulation cooldown continued uneventfully until after time 0600.
The highest cooldown rate achieved was approximately 65 to 70 F per hour.
Between 0600 and 0630 RCS pressure was reduced from 1140 to 690 psi by charging water through the pressurizer auxiliary spray line. Pressurizer level increased rapidly around 0700 while charpj Pressurizer level continued variations n%gvjgthguvgrggggdtogymege.
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