Information Notice 1989-90, Pressurizer Safety Valve Lift Setpoint Shift
| ML031190006 | |
| Person / Time | |
|---|---|
| Issue date: | 12/28/1989 |
| From: | Rossi C Office of Nuclear Reactor Regulation |
| To: | |
| References | |
| IN-89-090, NUDOCS 8912210146 | |
| Download: ML031190006 (7) | |
1 UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF NUCLEAR REACTOR REGULATION
WASHINGTON, D.C. 20555 December 28, 1989 NRC INFORMATION NOTICE NO. 89-90: PRESSURIZER SAFETY VALVE LIFT SETPOINT
SHIFT
Addressees
All holders of operating licenses or construction permits for pressurized water
reactors (PWRs).
Purpose
This information notice is to alert addressees to potential problems resulting
from operating pressurizer safety valves (PSYs) in an environment different from
that used to establish the PSV lift setpoint. It is expected that recipients
will review this information for applicability to their facilities and consider
actions, as appropriate, to avoid similar problems. However, suggestions-con- tained in this information notice do not constitute NRC requirements; therefore, no specific action or written response is required.
Description of Circumstances
In October 1989, Westinghouse informed its plant owners of a potential deviation
of the PSV set pressure from the ASME Code and the plant technical specification
(TS) requirements for plants having loop seals upstream of the PSYs. Recent
plant operating experience and test data indicate that the PSV lift pressure
changes by more than 1 percent from the original set pressure when the valve
is operated at conditions different from those used during the establishment
of the lift setpoint. Westinghouse observed a shift of 4 to 8 percent on
Crosby PSVs when setpoints were initially established using a loop seal with
300OF water, draining the loop seal, and checking the lift set pressure with
steam. As ASME Code Section III requires a safety valve setting with a toler- ance of +1/-1 percent of the set pressure and the plant TSs typically specify
the PSV lift setting of 2485 psig +1/-1 percent,. some plants may be operating
with PSV setpoints not in compliance with their TSs or the ASME Code if they
are operating in an environment different from that used to establish the valve
setpoints. In addition, some plant TSs have a footnote which states, *The lift
setting pressure shall correspond to ambient conditions of the valve at nominal
operating temperature and pressure."
The Westinghouse letter specifically identified a potential safety issue with
setting the PSY setpoint with steam and operating the valves in a loop seal
containing water. Because the actual lift set pressure could be 4 to 8 percent
higher than the 2485 psig +1% set pressure, this increased PSV lift setpoint
December 28, 1989 could result in primary system overpressurization for certain
Thus, plant-specific analyses of those scenarios in which the event scenarios.
availability of
the PSV was used in the licensing basis criteria for the facility
that the appropriate pressure limit is exceeded for the pressurizer may show
sociated piping. and as- The PSY loop seals may be uninsulated or insulated and may or
heaters. Water temperatures in the uninsulated and insulated may not have
loop seals are
approximately 140°F and 300OF to 400°F, respectively. The temperature
loop seal water affects the PSV temperature and the lift pressure. of the
pressure setpoints of the PSYs with loop seals are not established The lift
by the industry. A survey showed that the inlet conditions consistently
lift setpoints were established include steam, nitrogen, and under which the PSV
water conditions. As a result, the actual PSY lift pressure actual loop seal
too high or too low, depending on the method of PSY setting could be either
fluid condition upstream of the PSVs. and the actual
Discussion:
Inconsistencies in the conditions at which the PSY lift pressure
established, compared to actual operating conditions of the is actually
implications and affect compliance with the plant TSs. It is PSY, have safety
the PSYs be operable with proper lift pressure settings that essential that
-for-accepItabue-piuuverpressur-oetn-butmh enoucts are low enough
of the PSYs at a pressure approaching the reactor coolant system prevent-ttfting
conditions. If the lift pressure for a PSY is set on steam (RCS) operating
and is operated
with loop seal water, the actual lift setpoint may be too high
and
noncompliance with the TSs as well as possible overpressurization result in
system in excess of the acceptance limit of 110 percent of of the primary
design pressure for
certain accidents. On the other hand, if the PSY setpoint is
loop seal water, a loss of loop seal water will result in a established with
lift pressure. This situation may result in noncompliance withlower actual PSY
and also may cause the PSY to lift at a pressure approaching the plant TSs
the
pressure, increasing the probability of a challenge to the PSYs. RCS operating
Item II.K.3.2, addresses the need for reducing challenges to NUREG-0737, or frequent challenges to the PSYs may prevent the PSVs from PSYs. Repetitive
reseating with a
potential for an unisolable small-break loss-of-coolant accident
effect on the actual lift pressure of a PSV that is set with (LOCAS. The
nitrogen and
operated with loop seal water has not been determined.
There were two instances (on May 17 and August 25, 1989) at
plant in which the loop seal was lost as a result of the PSV the V. C. Summer
the setpoint of the V.C. Summer PSY was established with hot leakage. Because
lift setpoint decreased as a result of the absence of water water, the actual
piping. The PSY opened prematurely, resulting in a partial in the loop seal
of the reactor coolant system. PSY leakage also occurred at depressurization
the Diablo Canyon
plant, where the PSY setpoint was also established with hot
water.
past the PSV was detected by the PSY tailpipe temperature monitoring Leakage
and the acoustic leak monitors and subsequently resulted in devices
a plant shutdown.
I
December 28, 1989 In the case of the PSYs at Summer, the PSV lift setpoints are still based upon
a loop seal configuration. The licensee has taken steps to maintain the loop
seal. They have installed thermocouples in the PSV loop seals to monitor the
PSY body inlet and loop seal temperatures. If the valve body inlet temperature
exceeds a predetermined temperature, this is considered indicative of an im- pending loss of the loop seal and the licensee will then take action to shut
down the plant to restore the loop seal. The licensee is considering removing
the PSY loop seals at the next refueling outage.
In October 1989, the Surry Station Unit 2 PSVs were shipped to the Westinghouse
Western Service Center to undergo testing after leakage was observed from one
of the valves. The setpoints of the Surry PSVs had been established with steam.
The test results showed that the as-found lift pressure setpoints differed signi- ficantly when tested under steam vs loop seal water conditions. The licensee
reset the Unit 2 PSYs under water conditions to comply with the TS requirements.
However, during a subsequent post-maintenance pressure test, the "C" PSV lifted
at an RCS pressure of 2335 psig and reclosed at 2255 psig, apparently from a
loss of loop seal water. As a result of this event, the licensee decided to
return to the previous method of establishing the PSY lift pressure with steam
to avoid challenges to the Unit 2 PSYs. On November 10, 1989, the licensee re- quested a TS change for Units 1 and 2 for the remainder of Cycle 10 operation
to increase the PSV setpoint tolerance to the value observed in the Unit 2 PSY
test data. This TS shange request was-supported-by a safety analysis showing---
that the reactor system pressure remains below the 110-percent design pressure
limit for the limiting pressurization events if the PSY setpoint is increased
provided a power-operated relief valve (PORV) is operable. The:TS change was
approved with the provision that the licensee take compensatory measures to
ensure operability of at least one of the PORts and also ensure the operability
of the direct reactor trip upon a turbine trip.
This information notice requires no specific action or written response. If
you have any questions about the information in this notice, please contact one
of-the technical contacts listed below or the appropriate NRR project manager.
-i :: Krt.s s~,~r`t
Division of Operational Events Assessment
Office of Nuclear Reactor Regulation
Technical Contacts: Y. (Gene) Hsii, NRR
(301) 492-0887 W.Jensen, NRR
(301) 492-1190
Attachment: List of Recently Issued NRC Information Notices
.1 -
Attachment
. December 28, 1989 Page I of I
LIST OF RECENTLY ISSUED
PRC INFOR'MATION NOTICES
........
AffS
n9 n
Ub I WU
_._ __
UaIe o_
Notice No. SubJect Issuance Issued to
89-89 Event Notification 12/26/89- All holders of OLs
Worksheets or CPs for nuclear
power reactors.
89-88 Recent NRC-Sponsored 12/26/89 All holders of OLs
Testing of Motor-Operated or CPs for nuclear
Valves poaer reactors.
89-87 Disabling of Emergency 12/19/89 All holders of OUs
Diesel Generators by or CPs for nuclear
Their Ueutral Ground-Fault power reactors.
Protection Circuitry
89-45. Mstalclad, Low-Voltage 12/1/89 All holders of OLs
Supp. 2 Power Circuit Breakers or CPs for nuclear
Refurbished with power reactors.
Substandard Parts
89-86 Type Ht Circuit Breakers 12/15/89 All holders of OLE
Nissing Close Latch Anti- or CPs for nuclear
Shock Springs. power reactors.
894E5 EPA's Interim Final Rule 12/15/89 All medical. academic.
on Redical Waste Tracking industrial, waste
and Management broker, and waste
disposal site licensees.
89-84 Failure of Ingersoll Rand 12/12/89 All holders of OLE
Air Start Motors as a Result or CPs for nuclear
of Pinion Gear Assenbly pawer reactors.
Fitting Problems
W9-83 Sustained Degraded Voltage 12/11/89 All holders of OLE
- C Por Creactrs.
Grid and Loss of Other poswer reactors.
Generating Stations as
a Result of a Plant Trip
694-2 Recent Safety-Related 12/7/89 All NRClicensees
Incidents at Large authorized to
Irradiators possess and use
sealed sources at
large irradiators.
- Operating License
- Construction Permit
UNITED STATES
NUCLEAR REGULATORY COMMISSION IPOSTAGE &FEES PAID
WASHINGTON, D.C. 20555 JSJVACj
PERMIT No.C.$
OFFICIAL BUSINESS
PENALTY FOR PRIVATE USE, S300
December 28, 1989 In the case of the PSYs at Summer, the PSV lift setpoints are still based upon
a loop seal configuration. The licensee has taken steps to maintain the loop
seal. They have installed thermocouples in the PSV loop seals to monitor the
PSY body inlet and loop seal temperatures. If the valve body inlet temperature
exceeds a predetermined temperature, this is considered indicative of an im- pending loss of the loop seal and the licensee will then take action to shut
down the plant to restore the loop seal. The licensee is considering removing
the PSY loop seals at the next refueling outage.
In October 1989, the Surry Station Unit 2 PSYs were shipped to the Westinghouse
Western Service Center to undergo testing after leakage was observed from one
of the valves. The setpoints of the Surry PSYs had been established with steam.
The test results showed that the as-found lift pressure setpoints differed signi- ficantly when tested under steam vs loop seal water conditions. The licensee
reset the Unit 2 PSVs under water conditions to comply with the TS requirements.
However, during a subsequent post-maintenance pressure test, the "C" PSV lifted
at an RCS pressure of 2335 psig and reclosed at 2255 psig, apparently from a
loss of loop seal water. As a result of this event, the licensee decided to
return to the previous method of establishing the PSY lift pressure with steam
to avoid challenges to the Unit 2 PSVs. On November 10, 1989, the licensee re- quested a TS change for Units 1 and 2 for the remainder of Cycle 10 operation
to increase the PSY setpoint tolerance to the value observed in the Unit 2 PSV
test data. This TS change request was supported by a safety analysis showing
that the reactor system pressure remains below the 110-percent design pressure
limit for the limiting pressurization events if the PSV setpoint is increased
provided a power-operated relief valve (PORV) is operable. The TS change was
approved with the provision that the licensee take compensatory measures to
ensure operability of at least one of the PORVs and also ensure the operability
of the direct reactor trip upon a turbine trip.
This information notice requires no specific action or written response. If
you have any questions about the information in this notice, please contact one
of the technical contacts listed below or the appropriate NRR project manager.
Charles E. Rossi, Director
Division of Operational Events Assessment
Office of Nuclear Reactor Regulation
Technical Contacts: Y. (Gene) Hsii, NRR
(301) 492-0887 W. Jensen, NRR
(301) 492-1190
Attachment: List of Recently Issued NRC Information Notices
- SEE PREVIOUS CONCURRENCES
- EAB:NRR *NRR:SRXB *TECH:EDITOR*EAB:NRR *NRR:DST *C:IEAB:NRR
WJensen:db GHsii DCFWscher AThadani CJiHaughney
12/11/89 12/11/89 12/11/89 12/13/89 12/18/89 12,(20/89
- C:OGCB:NRR D:P>tA~Rh
CHBerlinger
12/20/89
IN 89-XX
December xx, 1989 In the case of the PSVs at Summer, the PSY lift setpolnts are still based upon
a loop seal configuration, and no TS change Is required. The licensee has
taken steps to maintain the loop seal. They have installed thermocouples in
the PSY loop seals to monitor the PSV body inlet and loop seal temperatures.
If the valve body inlet temperature exceeds a predetermined temperature, this
is considered indicative of an impending loss of the loop seal and the licen- see will then take action to shut down the plant to restore the loop seal.
The licensee is considering removing the PSY loop seals at the next refueling
outage.
In October 1989, the Surry Station Unit 2 PSVs were shipped to the Westinghouse
Western Service Center to undergo testing after leakage was observed from one
of the valves. The setpoints of the Surry PSYs had been established with
steam. The test results showed that the as-found lift pressure setpoints
differed significantly when tested under steam vs loop seal water conditions.
The licensee reset the Unit 2 PSVs under water conditions to comply with the
TS requirements. However, during a subsequent post-maintenance pressure test, the 'C" PSY lifted at an RCS pressure of 2335 psig and reclosed at 2255 psig, apparently from a loss of loop seal water. As a result of this event, the
licensee decided to return to the previous method of establishing the PSV lift
pressure with steam to avoid challenges to the Unit 2 PSYs. However, this
procedure necessitated a TS change. On November 10, 1989, the licensee re- quested a TS change for Units 1 and 2 for the remainder of Cycle 10 operation
to increase the PSV setpoint tolerance to the value observed in the Unit 2 PSV
test data. This TS change request was supported by a safety analysis showing
that the reactor system pressure remains below the 110-percent design pressure
limit for the limiting pressurization events if the PSV setpoint is increased
provided a power-operated relief valve (PORV) is operable. The TS change was
approved with the provision that the licensee take compensatory measures to
ensure operability of at least one of the PORVs and the operability of the
direct reactor shutdown upon a turbine shutdown.
This information notice requires no specific action or written response. If
you have any questions about the information in this notice, please contact one
of the technical contacts listed below or the appropriate NRR project manager.
Charles E. Rossi, Director
Division of Operational Events Assessment
Office of Nuclear Reactor Regulation
Technical Contacts: Y. (Gene) Hsii, NRR
(301) 492-0887 W. Jensen, NRR
(301) 492-1190
Attachment: List of Recently Issued NRC I formation v ices
- SEE PREVIOUS CONCURRENCES [*I
vI (
- EAB:NRR *NRR:SRXB *TECH:EDITOR EAB:NRR NRR:DST C:EABIR R
WJensen:db GHsii DCFischer AT dani JHpughney
)2/11/89 12/11/89 / /89 I0/13/89 MI'z/89 ILiU989 MIJOGCB:NRR D:DOEA:NRR
iC HBerlinger CERossi
PuL tr9,/89 w / /89
J V IN 89-XX
December xx, 1989 upon
In the case of the PSVs at Summer, the PSV lift setpoints are still based has
a loop seal configuration, and no TS change is required. The licensee
in
taken steps to maintain the loop seal. They have installed thermocouples
the PSV loop seals to monitor the PSY body inlet and loop seal temperatures.
this
If the valve body inlet temperature exceeds a predetermined temperature,licen- is considered indicative of an impending loss of the loop seal and the
seal.
see will then take action to shut down the plant to restore the loop
seals at the next refueling
The licensee is considering removing the PSV loop
outage.
In October 1989, the Surry Station Unit 2 PSYs were shipped to the Westinghouse from one
Western Service Center to undergo testing after leakage was observed with
of the valves. The setpoints of the Surry PSYs had been established
steam. The test results showed that the as-found lift pressure setpoints
differed significantly when tested under steam or loop seal water conditions. the TS
The licensee reset the Unit 2 PSYs under water conditions to comply with test, the
requirements. However, during a subsequent post-maintenance pressure
and reclosed at 2255 psig,
"C" PSV lifted at an RCS pressure of 2335 psig the
apparently from a loss of loop seal water. As a result of this event, PSV lift
licensee decided to return to the previous method of establishing the
this
pressure with steam to avoid challenges to the Unit 2 PSVs. However, re- procedure necessitated a TS change. On November 10, 1989, the licensee
remainder of Cycle 10 operation
quested a TS change for Units 1 and 2 for the 2 PSV
to increase the PSV setpoint tolerance to the value observed in the Unit showing
test data. This TS change request was supported by a safety analysis
pressure
that the reactor system pressure remains below the 110-percent design
limit for the limiting pressurization events if the PSV setpoint is increased
or if a power-operated relief valve (PORV) is operable. The TS change wasto
approved with the provision that the licensee take compensatory measuresshutdown
ensure operability of at least one of the PORVs and the direct reactor
upon a turbine shutdown.
If
This information notice requires no specific action or written response. one
you have any questions about the information in this notice, please contact
of the technical contacts listed below or the appropriate NRR project manager.
Charles E. Rossi, Director
Division of Operational Events Assessment
Office of Nuclear Reactor Regulation
Technical Contacts: Y. (Gene) Hsii, NRR
(301) 492-0887 W. Jensen, NRR
(301) 492-1190
Attachment: List of Recently Issued NRC Information Notices
Wie
4tB NRR:A,
- db GHsii
TECH:EDITO
raft
EAB:NRR
DCFischer
NRR:DST
AThadani
C:EAB:NRR
CJHaughney
I2a,(/89 /7-/11/89 Ia/Il / /89 / /89 / /89 C:OGCB:NRR D:DOEA:NRR
CHBerlinger CERossi
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