IR 05000335/1987009
| ML17219A548 | |
| Person / Time | |
|---|---|
| Site: | Saint Lucie  |
| Issue date: | 04/28/1987 |
| From: | Conlon T, Hunt M NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| To: | |
| Shared Package | |
| ML17219A547 | List: |
| References | |
| 50-335-87-09, 50-335-87-9, 50-389-87-08, 50-389-87-8, NUDOCS 8705040196 | |
| Download: ML17219A548 (8) | |
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UNITED STATES NUCLEAR REGULATORY COMMISSION
REGION II
101 MARIETTASTREET, N.W., SUITE 2900 ATLANTA,GEORGIA 30323 Report Nos.:
50-335/87-09 and 50-389/87-08 Licensee:
Florida Power and Light Company 9250 West Flagler Street Miami, FL 33102 Docket Nos.:
50-335 and 50-389 Facility Name:
St. Lucie 1 and
Inspection Conducted:
April 1-3, 1987 I
Inspector:
l~
unt Approved T. E.
Con on, Section Chief Engineering Branch Division of Reactor Safety License Nos.:
DPR-67 and NPF-16 te gne Date Soigne SUMMARY Scope:
This special announced inspection was conducted to examine the conditions surrounding the failure of Unit 1B Low Pressure Safety Inspection (LPSI)
pump to start prior to the unit going from Mode 3 to Mode 4.
Results:
No violations deviations were identified.
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REPORT DETAILS 1.
Persons Contacted Licensee Employees
- K. N. Harris, Vice President, Plant St. Lucie
- D. A. Sager, Plant Manager
- R. E. Dawson, Electrical Department Supervisor
- J. B. Harper, Superintendent, gA
- L. W. Pearce, Operations Supervisor
- R. L. Kulavich, Reliability and Support Engineer
- J. Scarola, Electrical Maintenance
- M. B. Vincent, Power Plant Engineering Other licensee employees contacted included engineers, technicians and oper ators.
NRC Resident Inspectors
- R. V. Crlenjak
- H. E. Bibb
"Attended exit interview 2.
Exit Interview The inspection scope and findings were sumnarized on April 3, 1987, with those persons indicated in paragraph 1 above.
The inspector described the areas inspected and discussed in detail the inspection findings.
No dissenting comments were received from the licensee.
'he licensee did not identify as proprietary any of the materials provided to or reviewed by the inspector during this inspection.
3.
Licensee Action on Previous Enforcement Matters This subject was not addressed in the inspection.
4.
Unresolved Items Unresolved items were not identified during this inspection.
5.
The inspector was dispatched to the St.
Lucie Plant to examine the conditions surrounding the licensee reported failure of the unit LPSI pumps to function properly prior to the unit going from Mode 3 to Mode 4.
During the inspection, the inspector held discussions with various members
of the plant staff, participated in the analysis with a equality Improve-ment Program (gIP) team organized by the licensee to investigate the cause of the event, and observed various tests relating to 4160 kv breaker operations.
The sequence of events developed by the gIP Team is as follows.
Se uence of Events Introduction On April I, 1987, the Unit I plant was preparing to enter Node 4 from Mode 3.
The RCS was being cooled down in preparations for repair of a leak in the Reactor Vessel Head 0-ring seal.
The following chronology was developed from information obtained by the gIP Team from interviews with operating and maintenance personnel, control room log sheets and computer alarm printouts.
The time shown is military time for April I, 1987.
The red and green indicating lights are located both on the main control room panels and the breaker cubicles.
The red light on means that the breaker is closed and the equipment is energized.
The green light on means that the breaker is open.
The amber light located 'at the breaker cubicle when lighted means that the breaker springs are charged and ready to close the breaker when released.
The annunciator R-59 when lighted means LPSI pump 1B can not be started.
Annunciator R-58 applies to LPSI pump 1A.
When either the red or green light is lighted the breaker trip circuit has power to trip the breaker.
Time 0 erational Actions 8 Observations Indications 0211 0211 0214 The lA LPSI pump was started to warm up the Shutdown Cooling piping prior to entry into Mode 4.
Indication:
Red light blinking in control room for approxi-mately 10 seconds.
Attempted start of the 1B LPSI pump.
(Pump did not start).
Indications:
1.
Green light lit.
2.
Alarm R-59 illuminated.
Manually secured (hard stop)
the 1A LPSI pump to preclude possible pump damage.
Indications:
1.
Red light off.
2.
Green light off.
3.
Alarm R-58 illuminate Indicator lights were checked for possible bulb failure.
The Control Room Operator did not attempt a restart of lA LPSI pump due to a
lack of indication of pump breaker trip capability.
The Shift Supervisor for Electrical Maintenance, Nuclear Plant Supervisor and the Nuclear Watch Engineer were dispatched to the 1A LPSI breaker cubicle.
At the breaker cubicle:
Indications:
1.
Amber light lit.
2.
Green light off.
Pulled both sets of control fuses on the lA LPSI breaker.
1.
The fuse holders were tightened.
2.
The same fuses were replaced in the fuse holders.
The lA LPSI breaker was racked out.
Racked in 1A LPSI breaker.
Inserted fuse holder into breaker.
0250 Indications:
1.
Green light lit.
2.
Amber light lit.
3.
Noted spring charge.
Started 1A LPSI pump.
The E/M supervisor, Nuclear Plant Supervisor (NPS),
and Nuclear Watch Engineer (NWE) moved to the 1B LPSI breaker cubicle.
As they traveled from the 1A to 1B LPSI breaker, they audibly noted the lA breaker closing.
At the 18 breaker cubicle.
Indications:
1.
Green light lit.
2.
Amber light off.
Pull both sets of fuses.
1B breaker racked ou Indication:
Spring discharged as breaker racked out.
Racked in breaker.
Reinstalled fuse holders.
Indications:
1.
Green light lit.
2.
Amber light lit.
3.
Spring charges.
0254 Start 1B LPSI pump.
It should be noted that on other occasions when similar problems had occurred, they were corrected by racking their breakers out and back in.
To accomplish this, it is necessary to remove the control fuses prior to racking the breaker out and back in on the bus.
The construction of the fuse holders is such that the fuses can appear loose in the holder when they are removed; thus, the fuse holders wer e tightened as a corrective measure.
Discussions with maintenance and operating personnel revealed that if a failure of indicating lights (Red and Green)
to light or the breakers to operate properly, it was usually after the breaker had been
"racked out" (as a safety measure)
for maintenance or as a personnel safety measure during pump related maintenance, and the equipment was then being restored to operating status.
Because of the fact that fuse removal and racking the breaker out and back in usually corrected the problem of indicating lights not burning and/or alarm panels lighting, the fuse holders became suspect.
The licensee instituted the following interim corrective actions:
1.
On Unit 1, an inspection was made on all fuse holders in cubicles of non-running equipment.
Fuse holders were examined for unusual wear or markings.
If fuses appeared to be loose in the holder, the holder was tightened.
2.
On Unit 2, an inspection of the indicating lights on the safety-related breaker cubicles was made.
Proper lights were observed to be illuminated.
Safety-related pumps were started and run successfully.
(LPSI, HPSI, AFW, Cont. Spray)
3.
Operations Department personnel initiated a separate sign-off for Non-Licensed Operators to document proper lights that are observed on each safety breaker cubicle on each shift.
This sign-off reinforces the normal Non-Licensed Operator duties in checking status lights on his normal round The gIP team reviewed numerous items which could cause the type of problem encountered, then by the evaluation of each item r educed the number of likely items to the fuse holders and/or the secondary contact block connectors located on the breakers.
The decision was made to try to recreate the conditions that existed at the time that LPSI pump system warmup had been attempted.
The fuses holders were opened to the point that the fuses fell out due to lack of holder tension.
It was determined that fuses this loose would present a personnel safety hazard when attempting installation.
Further inspection of the fuse block revealed that the fuse holders tightened securely around the ends of the fuses when the holder is inserted into the fuse block.
Therefore, good electrical contact would be accomplished if the fuses and holders were properly maintained.
There was no evidence to indicate that proper electrical connections had not been made.
No burned or corroded places were found on the fuse or fuse holders.
I From the above indications, it appears that the fuse holders were not the cause of the problem.
It was determined that by misaligning the breaker secondary contact blocks, conditions similar to those noted by the operating and maintenance personnel at the time of the problem could be recreated.
Examination of the male connecting pins on the breaker secondary contact block was made.
The lengths of the pins on these blocks are such that there appears to be adequate contact surface.
However, it was found that certain pins did not indicate full contact wipe with the female contacts located in the breaker panel housing.
There was a conductive grease applied to the male pins during breaker maintenance which would mask the polishing effects of contact wipe and since this is not a frequent make-break type connection a polishing effect would probably not be created.
By intentional misalignment of these secondary contact connections, it was determined through voltage measurements that various open circuits could be created which would resemble faulty fuse holder connections.
On the basis of the investigation, the possibilities for the LPSI pump starting problem were reduced to the probable misalignment of the breaker secondary contacts.
The licensee has committed to delve further into the secondary contact block condition and develop a report of their findings.
In the meantime, the inspector made the following recommendations for licensee actions:
1.
Continue to log the status of the safety-related equipment breaker indicating lights located on the main control boar ds and on the breaker panel.
Examine the possibility of some type of special maintenance for the breaker secondary contact blocks.
3.
Insure that anytime a piece of safety-related equipment is returned to service (breaker racked in and control fuses installed)
the equipment is adequately surveilled to insure proper operation.
4.
Log any instances in which a breaker had to be re-racked in after being racked out in order to get all indicating lights burning and annunciations cleared.
The above recommendations should create a list of items and conditions which would indicate the extent of the problem associated with these breakers.
Within the areas inspected, no violations or deviations were identified.