ML17191A673
| ML17191A673 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 05/13/1998 |
| From: | Grant G NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| To: | Kingsley O COMMONWEALTH EDISON CO. |
| Shared Package | |
| ML17191A674 | List: |
| References | |
| 50-249-98-15, NUDOCS 9805270267 | |
| Download: ML17191A673 (3) | |
See also: IR 05000249/1998015
Text
UNITED STATES
NUCLEAR REGULATORY COMMISSION
REGION Ill
Mr. Oliver D. Kingsley
President, Nuclear Generation Group
Commonwealth Edison Company
ATTN: Regulatory Services
Executive Towers West Ill
1400 Opus Place, Suite 500
Downers Grove, IL 60515
801 WARRENVILLE ROAD
LISLE, ILLINOIS 60532-4351
May 13, 1998
SUBJECT:
NRC INSPECTION REPORT NO. 50-249/98015(DRP)
Dear Mr. Kingsley:
On April 17, 1998, a special inspection was completed at the Dresden Nuclear Power Station.
The purpose of the inspection was to assess information regarding the April 9, 1998, inadvertent
closure of all Unit 3 main steam isolation valves and the subsequent reactor scram. The
enclosed report presents the results of that inspection.
On April 9, 1998, Dresden Unit 3 experienced a full closure of all main steam isolation valves
(MSIVs) from full power which resulted in a reactor scram. Initially, the cause of the MSIV
closure was unknown. Dresden Station's Root Cause Analysis Team, established to evaluate
this event, concluded that the most probable cause for the MSIV closure and resultant scram
was a combination of two factors. The first factor was the discovery of a failed main steam line
high flow switch during surveillance testing. Technical Specifications then required* the MSIV trip
channel associated with this failed flow switch be placed in a trip condition. Therefore, the
A portion of the MSIV trip system was placed in the tripped condition, thus satisfying one half of
the MSIV closure logic. The second factor involved a loss of continuity for a contact associated
with a time delay relay in the B MSIV trip system. This satisfied the second half of the MSIV
closure logic and resulted in all MSIVs closing. The inspectors concluded the root cause effort
was thorough and agreed with the licensee's conclusion.
During recovery from the scram, reactor water level reached +60 inches on medium range
indication and subsequently entered the steam lines for the high pressure coolant injection
(HPCI) system. Operators closed the steam isolation valve to the HPCI system, making the
system inoperable. This consequence of scram recovery, water in the HPCI steam lines, was
experienced following the Unit 2 scram in December 1997, and resulted in the development of
. feedwater level control contingencies to prevent recurrence. The contingencies did not prevent
recurrence of water entering the HPCI steam lines during this event, partly due to the specific
circumstances of the event. We understand modifications to the feedwater level control system
to prevent recurrence of this condition have been installed on Unit 2 and are planned for Unit 3.
While the safety consequences were minimal in this case, overfill of the reactor vessel following
a scram resulting in an inoperable HPCI system is an undesirable condition. You should carefully
re-examine your feedwater level control contingencies until the modifications are installed and
monito'r performance following installation of the modifications to ensure actions to prevent
recurrence are effective.
9805270267 980513
ADOCK 05000249
G
0. Kingsley
-2-
In accordance with 10 CFR 2.790 of the NRC's "Rules of Practice," a copy of this letter and its
enclosure will be placed in the NRC Public Document Room.
Sincerely,
/s/ G~ E. Grant
Geoffrey E. Grant, Director
Division of Reactor Projects
Docket No.: 50-249
License No.: DPR-25
Enclosure:
Inspection Report
.
No. 50-249/98015(DRP)
cc w/encl:
M. Wallace, Senior Vice President
D: Helwig, Senior Vice President
G. Stanley, PWR Vice President
J. Perry, BWRVice President
D. Farrar, Regulatory
- Services Manager
I. Johnson, Licensing Director
DCD - Licensing
M. Heffley, Site Vice President
P. Swafford, Station Manager
F. Spangenberg, Regulatory Assurance
Manager
Richard Hubbard
Nathan Schloss, Economist
Office of the Attorney General
. State Liaison Officer
Chairman, Illinois Commerce
Commission
DOCUMENT NAME: G:\\DRES\\DRE98015.DRP
To receive a copy of this document, indicate in the box "C" = Copy without attachment/enclosure "E" = Copy with attachment/enclosure
"N" = No co
OFFICE
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DATE
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OFFICIAL RECORD COPY
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Distribution:
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Project Mgr., NRR w/encl
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J. Caldwell w/encl
B. Clayton w/encl
SRI Dresden w/encl
DRP w/encl
TSS w/encl
DRS (2) w/encl
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PUBLIC IE-01 w/encl*
Docket File w/encl
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