ML19321A672
| ML19321A672 | |
| Person / Time | |
|---|---|
| Site: | Cooper  |
| Issue date: | 06/20/1980 |
| From: | Seyfrit K NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| To: | Pilant J NEBRASKA PUBLIC POWER DISTRICT |
| References | |
| NUDOCS 8007240051 | |
| Download: ML19321A672 (1) | |
Text
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CENTRAL FILES p** "'% ',(o, UNITED STATES PDR:HQ NUCLEAR REGULATORY COMMISSION LPDR
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611 RYAN Pt.AZA oRIVE, SulTE 1000 "n
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June 20, 1980 States Dockat No.
50-298 Nebra :E Public Power District ATTN:
J. M. Pilant, Director Licensing & Quality Assurance Post Office Box 499 Columbus,. Nebraska 68601 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, please contact this office.
Sincerely,
'/. bf f6 Karl V.
yfrit
/&
Directo
Enclosures:
1.
IE Circular No. 80-15 2.
List of Recently Issued IE Circ 11ars cc:
L. C. Lessor, Superintendent Cooper Nuclear Station Post Office Box 98 Brownv111e, Nebraska 58321 i
I 800724005I l
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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 cooliag 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, 1980 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 Jackcon 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 auxili - =nrav line.
Pressurizer level increased rapidly around 0700 while p-Pressurizer level continued variatio
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l the cooldown and depressurization c
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DUPLICATE DOCUMENT RCS loops, pressurizer level decrea increase in level when charging thr Entire document previously two minute interval while charging j
at 88 gpm, pressurizer level rose a j
entered into system under:
i than the charging flowrate.
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