Part 21 Report - 1998-121
ACCESSION #: 9803100298
LICENSEE EVENT REPORT (LER)
FACILITY NAME: Point Beach Nuclear Plant, Unit 1 PAGE: 1 OF 5
DOCKET NUMBER: 05000266
TITLE: Emergency Diesel Generator Air Start Motor Solenoid
Valves Found with Springs not in Accordance with Design
EVENT DATE: 02/03/98 LER #: 98-008-00 REPORT DATE: 03/05/98
OTHER FACILITIES INVOLVED: Unit 2 DOCKET NO: 05000301
OPERATING MODE: N POWER LEVEL: 84
THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR
SECTION:
50.73(a)(2)(ii)
LICENSEE CONTACT FOR THIS LER:
NAME: James Knorr, Regulation & TELEPHONE: (920) 755-6863
Compliance Manager
COMPONENT FAILURE DESCRIPTION:
CAUSE: SYSTEM: COMPONENT: MANUFACTURER:
REPORTABLE NPRDS:
SUPPLEMENTAL REPORT EXPECTED: NO
ABSTRACT:
On January 26, 1998, with Unit 1 at 84 percent power and Unit 2 in cold
shutdown, a 10 CFR 21 notification was received from Engine Systems, Inc.
The letter discussed a defect with the air start solenoid valves used on
Emergency Diesel Generators (EDGs). The solenoid valves do not meet the
minimum DC voltage requirements when inlet pressures below 200 psig are
applied to the valve. Seven of the valves were sold to Wisconsin
Electric. On February 3, 1998, the valves were found on all four EDGs at
Point Beach Nuclear Plant. Calculations performed to assess available DC
voltage at the air start solenoid valves concluded that only one of the
EDGs (G03) had sufficient post-accident voltage. Since G03 was only
connected to one of the safeguards buses, the plant was considered to be
outside the design basis. The valves have been modified or replaced and
EDGs G02, and G04 have been returned to service. G03 will be modified to
maintain similar design between air start systems. G01 will be modified
as part of its overhaul effort.
END OF ABSTRACT
TEXT PAGE 2 OF 5
Event Description:
Engine Systems, Inc. (ESI) issued a 10 CFR Part 21 report on January 26,
1998 that notified Point Beach Nuclear Plant (PBNP) of a defect with the
air start solenoid valves [EK:FSV] used on the Emergency Diesel
Generators (EDGs)(EMD #9513134/Graham-White #712-015 and #712-065)
[EK:DG]. At the time of the notification, Unit 1 was operating at 84
percent power, and Unit 2 was in the cold shutdown condition. The valves
do not meet the minimum DC voltage requirements when inlet pressures
below 200 psig are applied to the valve. The list attached to the Part
21 report indicated that Wisconsin Electric (WE) had purchased seven (7)
of these valves. The solenoid valve relies on system air pressure to
assist the coil in overcoming the force of the spring and thus operating
the valve plunger. The original valve design assumed air pressure at 200
psig and therefore, a weaker spring than now supplied with the 275 psig
rated valve. The EDG air start motor solenoid valves operate with air
pressure under the seat at a minimum of 165 psig for G01 and G02 (Train
A)and for G03 and G04 (Train B). The valves are supplied with DC control
power [EJ]. The voltage at the valve is dependent on the battery load
during an accident scenario that uses the battery [EJ:BTRY] alone under
assumed accident load conditions. In the case of these valves, the
recommended minimum voltage for the valves was 105 V DC. Therefore, the
effect of control power voltages less than that recommended by the vendor
would not assure the valve would open due to the stronger spring in the
275 psig rated valve if the air pressure at the valve was less than 200
psig. Initial calculations for the expected voltage at each air start
assuming accident DC load conditions resulted in voltages less than 105 V
DC for G01, G02 and G04.
Based upon the information supplied by the vendor of the airstart
solenoid valves for EDGs G01, G02 and G04, each was declared inoperable
at 2030 CST on February 3, 1998. Since "03 was aligned to supply power
to only a single safeguards bus (1A06 - Train B vital power), the plant
was in a condition outside its Technical Specification requirements.
This condition lasted for approximately 30 minutes. An operability
determination was prepared for G03. A Wisconsin Electric calculation
dated 3/15/95 shows that terminal voltage in the G03 start circuit does
not fall below 108.7 V DC during the time when the air start solenoids
are required to operate in response to a design basis accident. The
minimum calculated accident voltage available at the solenoid valves for
each of the remaining emergency diesels is, G01:92.93 V DC, G02:93.52 V
DC, G04:102.13 V DC.
G04 was removed from service to 2A06, and G03 was then aligned as the
standby emergency power supply to 1A06 and 2A06. This action restored
standby emergency power for Train B and returned the plant to its
Limiting Condition for Operation (LCO) for a maximum of seven days by
Technical Specification 15.3.7.B.1.h. G02 was declared inoperable but
considered available and aligned to supply 1A05 and 2A05 (Train A),
TEXT PAGE 3 OF 5
while G04 was declared inoperable but functional and removed from service
to 2A06 (Train B).
G01 was out of service for routine inspection when the Part 21 report was
received. G02 was aligned to Train A buses 1A05 and 2A05 but was
declared inoperable. Therefore, after G03 was tied to both 1A06 and 2A06
standby emergency power was considered to be in a seven (7) day limiting
condition of operation (LCO) per Technical Specification 15.3.7.B.1.h.
G01 air start solenoid valves are currently being worked in concert with
the G01 overhaul/inspection. WO 9801735 documents work performed on the
solenoid valves. This work will be completed prior to returning G01 to
service.
G02 air start solenoids were modified in accordance with the instructions
provided in 10CFR21-0077. Work was performed per WO 9801736. Both
valves were tested per criteria provided in the Part 21 report. G02 was
subsequently returned to service to 1A05 and 2A05, and the LCO exited on
February 6, 1998.
G04 air start solenoid valves were modified in a similar fashion to G02,
except there was no LCO constraint since G03 was aligned to the Train B
buses. Work was completed per WO 9801738, and G04 restored to service to
bus 2A06.
G03 air start solenoid valves will be modified via WO 9801737. Since the
G03 valves satisfy the Part 21 voltage criteria, this WO is
discretionary. The valves will be modified to be consistent with the
other EDGs, and the work will be scheduled with the next scheduled G03
inspection.
Component and System Description:
The Train A EDGs (G01 and G02) are automatically started by either one of
two pairs of air motors. Each EDG has its own independent starting
system including two banks of three air storage tanks fed by two air
compressor systems. Each bank of air receivers has sufficient storage to
crank the engine five times for the normal cranking duration of three
seconds. The starting system is completely redundant for each EDG.
Starting air for each Train A EDG is admitted from the storage tanks at a
nominal working pressure of 175 psig to the starting systems through the
subject solenoid valves.
The control voltage for the air start system is backed up by a manually
switched 125 V DC power supply for the alternate station battery.
TEXT PAGE 4 OF 5
The Train B emergency diesels are automatically started by two pairs of
air motors. Each bank Unit has its own independent starting system,
including two banks of two air storage tanks and two compressors. Each
bank of air receivers has sufficient storage to crank the engine five
times for the normal cranking duration of five seconds. The starting
system is completely redundant for each diesel generator.
Starting air for each Train B EDG is admitted from the storage tanks to
the starting systems through the subject solenoid valves through a 200
psi pressure regulator.
The control voltage for the diesel starting system is backed up by a
manually switched 125 VDC power supply from an alternate station battery.
Cause:
The cause of the event is the use of a 275 psig solenoid valve which does
not meet the minimum DC voltage available during an accident relying on
the station batteries for control power. This deficiency was reported to
the Commission via a 10 CFR Part 21 notification by Engine Systems, Inc.
Report No. 10CFR21-0077, on January 22, 1998. Wisconsin Electric
received notification as of January 26, 1998 and discovered the valves
installed on the EDGs on February 3, 1998.
Corrective Actions:
1. G02 start solenoids were modified in accordance with the
instructions provided in the Engine Systems, Inc. Report No.
10CFR21-0077. Work was performed per WO 9801736. Both valves were
tested per criteria provided in the Part 21 report. G02 was
subsequently returned to service to 1A05 and 2A05, and the LCO was
exited on February 6, 1998.
2. G04 solenoid valves were modified in a similar fashion to G02,
except there was no LCO constraint since G03 was aligned to the
Train B buses. Work was completed per WO 9801738, and G04 aligned
to bus 2A06.
3. G03 solenoid valves will be modified to ensure that the four EDGs
remain the same in this respect during its next scheduled
inspection.
4. G01 solenoid valves are currently being worked in concert with the
G01 overhaul/inspection. WO 9801735 documents work performed on the
solenoid valves. This work will be completed prior to G01 being
returned to service from its presently ongoing overhaul outage.
TEXT PAGE 5 OF 5
Reportability
On February 3, 1998 at 2130 CST a notification to Commission was made in
accordance with 10 CFR 50.72(b)(1)(ii)(B) at 2130, "Any event or
condition that resulted in the condition of the nuclear plant, including
its principal safety barriers, being seriously degraded; or that resulted
in the nuclear power plant being in a condition that was outside the
design basis of the plant." This report is being filed in accordance with
10 CFR 50.73(a)(2)(ii)(B), "Any event or condition that resulted in the
condition of the nuclear power plant being ... in a condition that was
outside the design basis of the plant."
Safety Assessment:
Based upon calculation, the DC voltages reached during an accident would
have resulted in voltages less than the 105 V DC which has been concluded
to be the acceptable limit at which the valve would work with a high
degree of assurance. The air pressures under the valve seat assumed in
the vendor testing of the 275 psig rated valves were as low as 125 psig.
The lowest pressure allowed for the EDGs is 165 psig. The valves were
modified in accordance with the Part 21 recommendations and tested
satisfactorily at 100 psig and 90 V DC. Therefore, the diesels would be
expected to start with voltages less than the 105 V DC.
Similar Occurrences:
LER Description
266/98-006-00 TDAFWP Low Suction Pressure Trip (Seismic) outside Design
Basis
System and Component Identifiers
The Energy Industry Identification System component function identifier
for each component or system referred to in this Licensee Event Report
are designated as [EIIS System Code:Component Identifier}
*** END OF DOCUMENT ***
Page Last Reviewed/Updated Wednesday, March 24, 2021