ML16148A577
| ML16148A577 | |
| Person / Time | |
|---|---|
| Site: | Oconee  |
| Issue date: | 11/25/1991 |
| From: | Belisle G, Binoy Desai, Harmon P, Poertner W NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| To: | |
| Shared Package | |
| ML16148A576 | List: |
| References | |
| 50-269-91-30, 50-270-91-30, 50-287-91-30, NUDOCS 9112090101 | |
| Download: ML16148A577 (9) | |
See also: IR 05000269/1991030
Text
kREG(Z
UNITED STATES
NUCLEAR REGULATORY COMMISSION
REGION II
101 MARIETTA STREET, N.W.
ATLANTA, GEORGIA 30323
Report Nos.:
50-269/91-30, 50-270/91-30 and 50-287/91-30
Licensee:
Duke Power Company
P. 0. Box 1007
Charlotte, NC 28201-1007
Docket Nos.:
50-269, 50-270, 50-287, 72-4
License Nos.:
DPR-38, DPR-47, DPR-55, SNM-2503
Facility Name: Oconee Nuclear Station
Inspection Conducte * Se tember 9 - November 2, 1991
Inspectors:
P. E. Harmon, Se ior es d n Inspector
Date Signed
B.Date
Signed
W..K.Poertner
esi ent In
or
Date Signed
Approved by:
6
/5
G. A. glisle, Se6*Q6n Chief
aeSgd
Date Signed
Division of Reactor Projects
SUMMARY
Scope:
This routine,
resident inspection was conducted in the areas of
- operations,
surveillance testing, maintenance activities,
event
follow-up, system walkdowns, and inspection of open items.
Results:
One violation was identified, concerning the failure to take prompt
corrective action to resolve problems associated with a noncon
servative pressure/level curve that resulted in the letdown storage
tank hydrogen gas potentially being able to expand into the suction
of the high pressure injection pumps under certain small break
accident scenarios (paragraph 6.c).
c112cO9O1O1 91,126
PR- ADOCK& 05000269
REPORT DETAILS
1. Persons Contacted
Licensee Employees
- H. Barron, Station Manager
D. Couch, Keowee Hydrostation Manager
T. Curtis, Compliance Manager
- J. Davis, Technical Services Superintendent
D . Deatherage, Operations Support Manager
B. Dolan, Design Engineering Manager, Oconee Site Office
- W.* Foster, Maintenance Superintendent.
T. Glenn, Engineering Supervisor
- 0. Kohler, Compliance.Engineer
C. Little, Instrument and Electrical Manager
H. Lowery, Chairman, Oconee Safety Review Group
B. Millsap, Maintenance Engineer
- M. Patrick, Performance Engineer
D. Powell, Station Services Superintendent
s*G.
Rothenberger, Integrated Scheduling Superintendent
- R.Sweigart, Operations Superintendent
Other licensee employees contacted included technicians, operators,
mechanics, security force members, and staff engineers.
NRC Resident Inspectors:
e
Harmon
- M. Poertner
- B. Desai
- Attended exit interview.
2. Plant Operations (71707)
S
a. General
The inspectors reviewed plant operations throughout the reporting
period to verify conformance with regulatory requirements, Technical
Specifications (TS), and administrative controls. Control room logs,
shift turnover records
temporary modification log and equipment
removal and restoration records were reviewed routinely. Discussions
were conducted with plant operations, maintenance, chemistry, health
physics, instrument & electrical (I&E), and performance personnel.
Activities within the control rooms were monitored on an almost daily
basis.
Inspections were conducted onday and on night shifts, during
weekdays and on weekends.
Some inspections were made *during shift
change in order to evaluate shift turnover performance.
Actions
2
observed were conducted as required by the licensee's Administrative
Procedures.
The complement of licensed personnel on each shift
inspected met or exceeded the requirements of TS.
Operators were
responsive to plant annunciator alarms and were cognizant of plant
conditions.
Plant tours were taken throughout the reporting period on a routine
basis. The areas toured included the following:
Turbine Building
Auxiliary Building
CCW Intake Structure
Independent Spent Fuel Storage Facility
Units 1, 2 and 3 Electrical Equipment Rooms
Units 1, 2 and 3 Cable Spreading Rooms
Units 1, 2 and 3 Penetration.Rooms
Units 1, 2 and 3 Spent Fuel Pool Rooms
Station Yard Zone within the Protected Area
Standby Shutdown Facility
Keowee Hydro Station
During the plant tours, ongoing activities, housekeeping, security,
equipment status, and radiation ,control practices were observed.
Within the areas reviewed, licensee activities were satisfactory.
b. Plant Status
Unit 1 entered the reporting period in a refueling outage.
On
September 30,
1991,
the generator was tied on the grid ending the
refueling outage.
On October 2, the unit tripped from 73% power due
to a turbine trip/reactor trip.
The problem was corrected and the
unit was returned to power operation on October 3.
Unit 2 operated at power the entire reporting period. On October 11,
1991, the unit reduced power and secured the 2B1 reactor coolant pump
due to a low oil pot level alarm.
A Reactor Building entry was made
to add oil to the oil pot, the pump was restarted and the unit was
returned to 100% power.
Unit 3 operated at power the entire reporting period.
c. Unit 1 Reactor Trip
On October 2, 1991, at 3:55 p.m., Unit 1 tripped from 73 percent
power due to a generator lockout signal.
The generator lockout
signal generated a turbine trip and subsequent anticipatory reactor
trip.
The Turbine-Generator protective relaying sensed that the
generator field breaker had opened and that the generator output
breakers were closed, although the generator field breaker had not
actually opened.
3
During the recovery an emergency feedwater start signal was initiated
when the "A" main feedwater pump (MFP)
tripped after the "B" MFP was
secured.
The "A" MFP tripped due to high discharge pressure caused
by a feedwater swing.
The "B" MFP was restarted and the emergency
feedwater system was secured.
Intermediate Range Nuclear Instrument
NI-3 failed to decrease below 10E-10 amps as expected after the unit
trip. The licensee believes that the detector is in the early stages
of failure and that the detector will become progressively worse due
to saturation at power.
The licensee declared NI-3 inoperable and
decided not to replace the detector prior to unit restart.
The
Oconee Technical Specifications do not require that both intermediate
range nuclear instruments be operable prior to criticality.
The
inspectors discussed this item with Operations Management and
expressed concern that only one intermediate range nuclear instrument
would be operable during the restart of the unit.
The detector
operated properly when power level increased above 10E-10.amps.
The generator lockout signal was determined to be caused by.loose
connectors and terminals that caused a loss of DC power to relay
41 MXA. When 41 MXA deenergized, the protective relaying sensed the
generator field breaker open with the generator output breakers
closed.
The loose connectors and terminals had been disconnected
during the refueling outage to allow removal of the Alterex housing.
The connectors and terminals were repaired/tightened and the unit was
restarted on October 3, 1991.
d. Keowee Unit 2 Failure to Start
On October 4, 1991,
Keowee Hydro Unit.2 failed to start when the
Keowee hydro operator attempted to load the unit on the grid at the
request of the load dispatcher. The Keowee hydro operator contacted
the control room and the hydro unit was declared. inoperable and
Keowee unit 1 was verified operable per the requirements of Technical.
Specification 3.7.2(a)(1) within one hour.
Subsequent investigation
by the licensee determined that a set of contacts in the normal start
protective circuitry were dirty and prevented the local start signal
from initiating a start of the hydro unit. The licensee determined
that the hydro unit would still have started from an emergency start
signal.
The dirty contacts were cleaned and the hydro unit was
tested and returned to service.
No violations or deviations were identified.
3. Surveillance Testing (61726)
Surveillance tests were reviewed by the inspectors to verify procedural
and performance adequacy. The completed tests reviewed were examined for
necessary test prerequisites, instructions, acceptance criteria, technical
content, authorization to begin work,
data collection,
independent
4
verification where required, handling of deficiencies noted, and review of
completed work.
The tests witnessed, in whole or in part, were inspected
to determine that.approved procedures were available, test equipment was
calibrated, prerequisites were met,
tests were conducted according to
procedure,
test results were acceptable and system restoration was
completed.
Surveillances reviewed and witnessed in whole or in part:
PT/1/A/230/1B
HPSW to HPI Motor Cooler Flow Test
PT/2/A/600/12
TDEFW Pump Performance Test
Within the areas reviewed, licensee activities were satisfactory.
No
violations or deviations were identified.
4. Maintenance Activities (62703)
a. Maintenance activities were observed and/or reviewed during the
reporting period to verify that work was performed by qualified
personnel and that approved procedures in use adequately described
work that was not within the skill of the trade.
Activities,
procedures,
and work requests were examined to verify; proper
authorization to begin work, provisions for fire, cleanliness, and
exposure control, proper return of equipment to service, and that
limiting conditions for operation were met.
Maintenance reviewed and witnessed in whole or in part:
WR 94608C
Repair 3PR-34
Within the areas reviewed, licensee activities were satisfactory.
No violations or deviations were identified.
b. Inadequate Post Modification Test
During the Unit 1 refueling outage, valve 1MS-89 was replaced by the
station modification process.
Valve 1MS-89 is the downstream
isolation valve for the main steam pressure control valve to the
turbine driven emergency feedwater pump turbine.
The weld on the
upstream side of the valve is required to be hydrostatically tested
(hydroed) to the main steam pressure requirements,
1313 psig and the
weld on the downstream side of the valve is required to be hydroed to
the auxiliary steam pressure requirements,
720 psig, per the system
drawing.
While preparing to hydro the downstream side of 1MS-89,
operations decided to open 1MS-89 and use the upstream isolation
valve for the pressure control valve (1MS-86) as the hydro boundary.
Subsequent to the hydro,
the post modification testing package
associated with 1MS-89 was signed off as being complete based on the
valve being hydroed to 720 psig.
Subsequent review of the
modification package-by the licensee after the unit was returned to
power identified that the upstream weld on 1MS-89 should have been
5
hydroed to 1313 psig.
Therefore, the post modification test was
inadequate.
Valve 1MS-89 is a normally locked open valve and had
remained locked open throughout the unit startup.
Subsequent to
determining that 1MS-89 had not been tested to the proper hydro test
pressure, a white tag was placed on the valve to ensure that the
valve would remain open until the upstream weld could be properly
tested.
The inspectors expressed concern that the modification
package had been completed and signed off without an adequate post
modification hydro test being performed; however,
the valve was
adequately tested assuming that the valve remained locked open
throughout the operating cycle.
The licensee identified this item
and based on the fact that an adequate post modification test was
performed if the valve remained.in the open position, no enforcement
action will be pursued.
The licensee plans to perform the required
hydro test the next time the unit is brought to a cold shutdown
condition.
No violations or deviations were identified.
5. Low Pressure Service Water (LPSW) System Walkdown (71710)
The inspectors performed a system walkdown on the accessible portions of.
the Unit 3 LPSW system.
The LPSW system provides normal and emergency
cooling. for components in the Turbine Building, Reactor Building and
Auxiliary Building.
The Unit 3 LPSW system consists of two LPSW pumps
that take a suction off the condenser circulating water system and two
supply headers that are crossconnected at the LPSW pump discharge. The
LPSW system is designed such that one LPSW pump should be able to provide
all the required cooling during accident conditions.
The LPSW pumps
receive an automatic start signal on an Engineered Safeguards (ES) signal.
However,
the non-safety portions of the LPSW system outside the Reactor
Building do not isolate on an ES signal.
The inspectors determined that
the Unit 3 LPSW system was aligned correctly, but discrepancies were noted
on the system drawing., the operating procedure valve lineup checklist and
the operating procedure electrical checklist. The discrepancies were not
significant in nature and were discussed with the licensee. The.licensee
is scheduled to perform a Design Basis Document (DBD) review on the LPSW
system as part of the DBD program. This effort had not started as of this
inspection period. The licensee has performed a Self Initiated Technical
Audit (SITA) on the LPSW system previously. The inspectors did not review
the LPSW SITA during the inspection period but plan to review the SITA
results during the next inspection period.
No violations or deviations were observed.
6
6. Inspection of Open Items (92700)(92701)(92702)
The following open items were reviewed using licensee reports, inspection,
record review, and discussions with licensee personnel, as appropriate:
a. (Closed) LER 269/91-02:
Licensed Operator Improperly Exempted From
Requalification Exam Due to a Management Deficiency, Results in TS
Violation.
This LER was submitted to the NRC on May 3, 1991.
Immediate corrective actions taken involved taking the licensed
operator off the active duty roster and notifying the NRC that this
license was not considered current.'
Subsequent corrective actions
included the successful completion of a makeup exam by the operator
and notification to the other Duke Power nuclear stations to assure
proper testing of facility representatives.
In addition,
ETQS
Standard 2306.0 was revised on September 1, 1991.
Based on these
actions, thi.s item is closed.
b. (Closed) LER 269/90-09:
Inappropriate Operator Actions to Control
and Maintain Minimum Level in Emergency Feedwater Inventory Tank
Resulted in a TS Violation.
As part of the planned corrective
actions, training, described in training package 90-12, was given to
all licensed operators concerning control of condensate inventory
when operating in the feedwater. cleanup mode of operation.
The
licensee reviewed the upper surge tank low level computer alarm
setpoint and raised from seven feet decreasing to eight feet
decreasing.
Also, after review of operating procedures, it was
decided not to change the procedure controlling feedwater cleanup
activities.
Instead, the licensee placed a tag near the controller
for the auxiliary steam supply to the 'E' heaters cautioning the
operators to monitor UST level while in the feedwater cleanup mode of
operation. Based on these actions, this item is closed.
C. (Closed) Unresolved item 269,270,287/91-26-02:
LDST .Pressure/Level
Curve.
This item identified that the existing operating curve
defining maximumletdown storage tank (LDST) pressure and level was
nonconservative and that the potential. existed for hydrogen intrusion
into the suction of the high pressure injection pumps under certain
small break .loss of coolant accidents as level in the borated water
storage tank (BWST)
decreased.
This item was identified as an
unresolved item pending further review by the NRC and licensee. The
inspectors determined that the licensee was aware that the LDST
pressure/level curve was nonconservative as early as the December
1990 timeframe when the High Pressure Injection (HPI) System Design
Basis Document was issued.
The licensee at that time carried this
item as an open item on a design engineering punchlist.
The
inspectors had also questioned the adequacy of the curve as a result
of the routine inspection program around this same timeframe and had
been told that Design was reviewing the basis of the curve and would
document its adequacy but based on preliminary reviews the curve
appeared acceptable.
The inspectors continued to question the
adequacy of the curve and in April of 1991 when the licensee again
7
stated that the official calculation had not yet been performed but
that the curve was probably acceptable, the inspectors were shown an
unofficial calculation performed by Design in January of 1991 that
showed there was a 1 psi margin before hydrogen intrusion could occur
at the HPI pump suctions.
The inspectors questioned the margin
available in the calculation and also questioned the assumptions on
which the unofficial calculation was based.
The licensee stated in
the April timeframe that the unofficial calculation was a very rough
calculation with overly conservative assumptions and methodology.
The inspectors were again assured that Design would perform an
official calculation to document the adequacy of the
LDST
pressure/level curve.
However, a timeframe for completion was not
given.
Subsequent to these events,
the licensee performed the official
calculation in September 1991 and determined that the existing LOST
pressure/level curve was inadequate and that the HPI system had been
operated since initial power operation in a condition that was
outside the design basis of the HPI system.
This calculation was
performed as. a result of corrective action for an April 1991 event
where the operators exceeded the the original pressure/level curve
during hydrogen addition to the LDST. The inspectors are not
convinced .that.the review of the pressure/level curve would have
occurred in September for any other reason except for the corrective
action as a result of exceeding the. original curve.
As a result of
this review, the licensee determined that hydrogen intrusion into the
suction of the HPI pumps would have occurred during a small break
LOCA, assuming no operator action if .a
HPI BWST suction valve failed
to open on an ES signal and all three HPI pumps started.
The
licensee also determined that the HPI system had operated on a
routine basis in a condition where hydrogen intrusion into the
suction of the HPI pumps could have occurred even if both HPI BWST
suction valves opened during a small break LOCA assuming no operator
action. The inspectors consider that the licensee actions to resolve
this issue were untimely and that the unofficial calculation was
inadequate in identifying the operability concern and should have
identified to the licensee the importance of completing the review of
the pressure/level curve in an expeditious manner.
The failure to
take prompt corrective action to resolve the LOST pressure/level
curve issue is identified as Violation 269,270,287/91-30-01:
Inadequate Corrective Action to Resolve Operability Concern.
8
7.
Exit Interview (30703)
The inspection scope and findings were summarized on November 1, 1991,
with those persons indicated in paragraph 1 above.
The inspectors
described the areas inspected and discussed in detail the inspection
findings.
The licensee did not identify as proprietary any of the
material provided to or reviewed by the inspectors during this inspection.
Item Number
Description/Reference Paragraph
VIO 269,270,287/91-30-01
Inadequate Corrective Action to
Resolve Operability Concern (paragraph
6.c).