ML17195A979
| ML17195A979 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 09/23/1985 |
| From: | Wright G NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| To: | |
| Shared Package | |
| ML17195A978 | List: |
| References | |
| 50-010-85-14, 50-10-85-14, 50-237-85-31, 50-249-85-27, NUDOCS 8510080518 | |
| Download: ML17195A979 (5) | |
See also: IR 05000010/1985014
Text
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U. S. NUCLEAR REGULATORY COMMISSION
REGION III
Report Nos. 50-010/85014(DRP); 50-237/8503l(DRP); 50-249/85027(DRP)
Docket Nos.50-010; 50-237; 50-249
License Nos. DPR-02; DPR-19; DPR-25
Licensee:
Commonwealth Edison Company
P. 0. Box 767
Chicago, IL 60690
Facility Name:
Dresden Nuclear Power Station, Units 1, 2, and 3
Inspection At:
Dresden Site, Morris, IL
Inspection Conducted:
August 16 through August 28, 1985
Prepared By:
T. M. Tongue, Senior Resident Inspector
Dresden Nuclear Station
J. H. Neisler, Reactor Inspector
D. E. Miller, Reactor Inspector
Approved By:#.~.~~
Projects Section 2C
Inspection Summary
~
9/ 13/ <tS
DHe
Ins ection on Au ust 16 throu h Au ust 28, 1985 (Re ort Nos. 50-10/85014(DRP);
50-237/85031 DRP ; 50-249/85027 DRP
Areas Inspected: This special report is a summary of the loss of offsite power
event experienced on Dresden Unit 2 on August 16, 1985, a review of the
licensee's prompt and long term actions, and the NRC response.
The inspection
involved a total of 82 inspector-hours onsite by NRC personnel including 46
inspector-hours onsite during off-shifts.
Results: No violations were identified during the inspection .
8510080518 850927
ADOCK 05000010
G
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DETAILS
1.
~ersons Contacted
Commonwealth Edison Company
D. Galle, Vice President and General Manager - Nuclear Stations
- D. Scott, Station Manager
- J. Wujciga, Production Superintendent
R. Flessner, Services Superintendent
T. Ciesla, Assistant Superintendent - Operations
R. Zentner, Assistant Superintendent - Maintenance
- J. Brunner, Assistant Superintendent - Technical Services
R. Christensen, Unit 1 Operating Engineer
J. Kotowski, Unit 3 Operating Engineer
W. Pietryga, Unit 3 Operating Engineer for Recirc. Piping Replacement
J. Achterberg, Technical Staff Supervisor
S. McDonald, Radiation Chemistry Supervisor
J. Mayer, Station Security Administrator
W. Johnson, Chemistry Supervisor
P. Lau, Q.A. Supervisor
R. Stobert, Q.A. Inspector
J. Williams, Sr., Q.A. Inspector
NRC Personnel on Site
J. Keppler, Regional Administrator
N. Chrissotimos, Chief, Division of Reactor Projects Branch 2
W. Guldemond, Chief, Division of Reactor Safety, Operational Progress
Section and Regional Duty Officer
- T. Tongue, Senior Resident Inspector, Dresden Nuclear Station*
- J. Neisler, Reactor Inspector
S. Stasek, Resident Inspector, Dresden Nuclear Station
M. Jordan, Senior Resident Inspector, LaSalle County Station
G. Christoffer, Security Specialist
J. Belanger, Security Specialist
D. Miller, Radiation Specialist
- Indicates those persons present at the Exit Meeting on August 28, 1985.
- Indicates those persons present at the Exit Meeting on August 20, 1985.
The inspectors also talked with and interviewed several other licensee
employees, including members of the technical and engineering staffs,
reactor and auxiliary operators, shift engineers and foremen, electrical,
mechanical and instrument personnel, and contract security personnel.
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2.
Event Description
On August 16, 1985, at 12:21 a.m., Dresden Unit 2 experienced a scram
from low reactor water level from about 70% power.
The trip resulted
from a loss of offsite power that caused a running 2B reactor feed pump
(RFP) to trip and the standby 2C RFP failed to start due to the loss of
power.
The associated auxiliary Buses 22 and 24 had failed to transfer
to the unit auxiliary transformer (UAT) TR21 source of power resulting in
the loss of RFP power.
When the scram occurred, the turbine-generator tripped causing a loss of
power to the UAT resulting in a complete loss of auxiliary power.
The
Unit 2 and 2/3 emergency diesel generators (E D/G) started as designed
and provided power to their respective Buses 24-1 and 23-1.
This
provided power to the ECCS and shutdown systems as necessary; however,
none were required during the event.
Containment Group I, II, and III isolations occurred and reactor pressure
was controlled through use of the isolation condenser and level was
controlled through use of the control rod drive system.
Other associated effects were a loss of power to in-plant radio
transmitters and some telephones including the nuclear accident reporting
system (NARS).
Power was also lost to various reactor protection system
(RPS) components, and the process computer alarm memory which resulted in
the loss of the event alarm history. The reactor building ventilation
system tripped and the standby gas treatment system,started as designed.
At about 12:45 a.m., the licensee declared a GSEP "Alert" and notified
appropriate personnel and agencies.
After removing TR-12 from the 138 KV system, power was restored on those
buses and auxiliary power was restored to Unit 2 through TR-22 at 4:32
a.m.
This resulted in the licensee restoring normal power, securing the
E D/Gs and continuing with a normal plant cooldown.
When auxiliary power was restored to Unit 2, the "Alert" was down-graded
- to an Unusual Event.
When the condensate system was restored to normal
for cooldown purpose the Unusual Event was secured.
3.
NRC Response
Upon receipt of the ENs notification that the site was in an
11Alert
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condition, the Senior Resident Inspector and the site response team
reported to the site. In addition, the regional incident response center
was activated and the headquarters operations center was placed in a
standby condition.
Licensee activities were evaluated and observed for verification that
appropriate actions were carried out.
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At the time of the event, two regional security specialists were on site
for a routine inspection and one witnessed the arc in the transformer 12
bus duct.
Her observation and passing of information on to appropriate
personnel was very helpful in identifying the location of the electrical
fault and reduced the time to restore auxiliary power.
Communications between the site, Region III and Headquarters were
established and maintained throughout the alert.
Throughout the event, licensee personnel showed a high degree of
competence in their actions in the control room and through evaluations
and directions given in the Technical Support Center. This was also
verified by regional personnel in the !RC and headquarters personnel in
the O.C. with respect to the accuracy and promptness of answering
questions on the event.
Subsequently, the Senior Resident Inspector followed the recovery
and return to power operation.
He also reviewed all associated
correspondence generated during the inspection from the licensee
and within the NRC and found no inconsistencies.
4.
NRC Review of Corrective Action
The licensee's investigation revealed that the cause of the failure of
Buses 22 and 24 to auto-transfer from transformer 22 to transformer 21
was due to the transformer 22 lockout relay contacts in the tie breaker
closing circuits being open.
These contacts only close when there is a
lockout condition in transformer 22 and since the fault was not in
transformer 22 there could be no auto-transfer to transformer 21.
Subsequent to the event, the lockout relays in the feeder breakers to
4160 volt Buses 21, 22, 23, and 24 were modified to permit the closing
circuitry in the breaker to auto-transfer from transformer 22 to
transformer 21 on any 138 KV Bus, section 3, differential conditions
instead of limiting auto-transfers to internal faults on transformer 22.
- The inspector observed the post-modification test of the auto-transfer
of the 4 KV Buses from transformer 22 to transformer 21 as a result of a
simulated differential on the 138 KV Bus, section 3.
The auto-transfer
test was acceptable. In addition, the inspector reviewed ECN D-85E-08,
modification test procedure M12-2-85-10 and procedure DOP-8500-8,
Revision 0, dated October 1914, Bus 24-1 to Bus 34-1 Tie Breaker Operation.
Based on examination of the engineering change notice, modification test
procedures, work requests and test results, observation of the test of
the auto-transfer function test, and review of operating procedures for bus
transfer, the inspector determined that the licensee's corrective action
to prevent loss of power to safety-related electrical circuits on a
differential trip of the 138 KV Bus, section 3, was adequate .
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5.
Radiological Aspects of Isolation Condenser Release Event
After the loss of offsite power at 12:21 a.m. about 90,000 gallons of
contaminated condensate storage water was fed to the isolation
condenser until 2:46 a.m. when the clean demineralized storage water
feed to the condenser was restored.
The condensate storage tank
is on emergency power; the clean demineralized storage is not.
The activity in the water was 1.1 E-5 microcuries per cubic centimeter
of cobalt 60.
Assuming all of the activity was released, the total
activity released was 3.7 millicuries.
The licensee roped off and controlled access to outdoor areas that
potentially could be contaminated, including the employee parking
lots.
When the release diminished, the licensee began surveying
the outdoor areas.
At about 7:00 a.m. the main parking lot was
released; no activity was found.
At about 10:00 a.m. the majority
of the remaining roped off areas were released.
Several puddles
inside the security fence, and near the Unit 2 turbine building,
showed detectable activity; these puddles were absorbed with floor
dry and put in containers.
A concrete pad beneath the isolation
condenser exhaust was found to be slightly contaminated.
The pad
was later decontaminated.
The licensee properly quantified the release and determined offsite
dose in accordance with technical specification requirements.
There
were no inplant airborne radioactivity or direct radiation problems.
The inspector asked the licensee to determine if there are alternate
methods of feeding clean water to the isolation condenser using emergency
power.
The licensee stated that the matter would be reviewed.
This will
be followed under existing open item No. 237/85005-03 and 249/85004-03.
No violations or deviations were noted.
6.
Open Items
Open items are matters which have been discussed with the licensee, which
will be reviewed further by the inspectors, and which involve some action
on the part of the NRC or licensee or both.
Open items discussed during
the inspection are discussed in Paragraph 5.
7.
Exit Interview
The inspectors met with licensee representatives on August 20, 1985 and
at the conclusion of the inspection on August 28, 1985. The inspector also
discussed the likely informational content of the inspection report with
regard to documents or processes reviewed by the inspector during the
inspection.
The licensee did not identify any such documents/processes
as proprietary.
The licensee acknowledged the findings of the inspection .
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