Part 21 Report - 1995-066
ACCESSION #: 9403230211
LICENSEE EVENT REPORT (LER)
FACILITY NAME: Seabrook Station PAGE: 1 OF 4
DOCKET NUMBER: 05000443
TITLE: Operation at Reduced Power Levels with Inoperable MSSVs
EVENT DATE: 02/17/94 LER #: 94-003-00 REPORT DATE: 03/17/94
OTHER FACILITIES INVOLVED: DOCKET NO: 05000
OPERATING MODE: 1 POWER LEVEL: 100
THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR
SECTION:
50.73(a)(2)(ii)
50.73(a)(2)(v)
LICENSEE CONTACT FOR THIS LER:
NAME: James M. Peschel, TELEPHONE: (603) 474-9521
Regulatory Compliance Manager extension 3772
COMPONENT FAILURE DESCRIPTION:
CAUSE: SYSTEM: COMPONENT: MANUFACTURER:
REPORTABLE NPRDS:
SUPPLEMENTAL REPORT EXPECTED: NO
ABSTRACT:
In September 1992, North Atlantic conducted Main Steam Safety Valve
Setpoint testing as required by Technical Specification 4.0.5 and Section
XI of the ASME Boiler and Pressure Vessel Code. During this testing the
plant was in MODE 1, at approximately 65% RTP, with power levels being
gradually reduced in preparation for Refueling Outage 2. North Atlantic
determined on February 17, 1994, that the MSSV setpoint testing conducted
in September 1992 was reportable pursuant to 10CFR 50.72 (b)(1)(ii)(A)
and (B) (unanalyzed condition and a condition outside the design basis)
and made the requisite 1 hour non-emergency notification. This
determination was based on new information contained in Westinghouse
Nuclear Safety Advisory Letter 94-01. NSAL 94-01, "Operation at Reduced
Power Levels With Inoperable MSSVs" provides notification that Technical
Specification Table 3.7-1 which allows plant operation at reduced power
levels as determined by the neutron flux high trip setpoint, may not be
conservative at the reduced power levels. During the MSSV setpoint
testing, North Atlantic operated in the configuration allowed by Seabrook
Station Technical Specification Table 3.7-1. However, on the basis of
the new information provided in NSAL 94-01, operation per Table 3.7-1 may
have resulted in secondary side overpressurization in the event of a Loss
of Load/Turbine Trip transient. Westinghouse concluded in NSAL 94-01
that this issue does not represent a substantial safety hazard and that
there is no loss of safety function to the extent that there is a major
reduction in the degree of protection provided to the public health and
safety.
Short term corrective actions included the calculation of conservative
Technical Specification Table 3.7-1 values. A calculation performed by
North Atlantic using the algorithm provided in NSAL 94-01 to determine
these values and a Technical Clarification TS-011 was approved and issued
to ensure that the values are administratively controlled until such time
that the Technical Specifications are revised.
END OF ABSTRACT
TEXT PAGE 2 OF 4
EVENT DESCRIPTION
In September 1992, North Atlantic conducted Main Steam Safety Valve
Setpoint testing as required by Technical Specification 4.0.5 and Section
XI of the ASME Boiler and Pressure Vessel Code. This testing was
conducted using a Furmanite Trevitest device. During this testing the
plant was in MODE 1, at approximately 65% RTP, with power levels being
gradually reduced in preparation for Refueling Outage 2. During this
testing, all 20 of the MSSVs (5 per steam generator) were tested. North
Atlantic previously submitted LER 92-16 on October 5, 1992, which
reported t 9 MSSVs were discovered to be inoperable with setpoints
outside of the acceptance criteria required by Technical Specification
3.7.1.1.
North Atlantic determined on February 17, 1994, that the MSSV setpoint
testing conducted in September 1992 is reportable pursuant to 10CFR 50.72
(b)(1)(ii)(A) and (B) (unanalyzed condition and a condition outside the
design basis). This determination was based on new information contained
in Westinghouse Nuclear Safety Advisory Letter 94-01 (NSAL 94-01).
Westinghouse has submitted a copy of NSAL 94-01 to the NRC. NSAL 94-01,
"Operation at Reduced Power Levels With Inoperable MSSVS" provides
notification that Technical Specification Table 3.7-1 which allows plant
operation at reduced power levels as determined by the neutron flux high
trip setpoint, may not be conservative at the reduced power levels.
Operation per Table 3.7-1 may have resulted in secondary side
overpressurization in the event of a Loss of Load/Turbine Trip (LOL/TT)
transient.
In September 1992, while performing MSSV setpoint testing, the requirements
of Technical Specification Table 3.7-1 were applied. At the initiation of
the testing the neutron flux high setpoint was set at 87% RTP to allow the
use of the Furmanite Trevitest device which restricts the MSSV from
relieving fully and therefore requires the MSSV being tested to be declared
inoperable. Testing of 2 MSSVs was performed concurrently using 2
Trevitest devices (1 device in the east pipechase and 1 device in the west
pipechase on different SG loops). The neutron high flux trip setpoints
utilized during the testing were in accordance with Technical Specification
Table 3.7-1. Table 3.7-1 requires that the neutron high flux setpoint be
reduced to 87% RTP when operating with a maximum of one inoperable MSSV on
any SG (65% RTP with 2 inoperable on any SG, 43% RTP with 3 inoperable on
any SG). Later in the testing, the neutron flux high setpoints were
further reduced per Table 3.7-1 to accommodate the testing of MSSVs on SG
loops with 2 inoperable MSSVs.
NSAL 94-01 provides an algorithm for calculation of conservative Technical
Specification Table 3.7-1 values. A calculation was performed by North
Atlantic to determine these values and a Technical Clarification TS-011 was
approved and issued to ensure that the values are administratively
controlled until such time that the Technical Specifications are revised.
The calculation established a value of 60% RTP for the high flux trip
setpoint when operating with a maximum of one inoperable MSSV on any SG
(42% RTP with 2 inoperable on any SG, 25% RTP with 3 inoperable on any SG).
Therefore during the September 1992 MSSV setpoint testing, the high flux
setpoint utilized were non-conservative relative to the values calculated
using the NSAL 94-01 algorithm. Operation in this condition represents an
unanalyzed condition and a condition outside the design basis of the plant.
TEXT PAGE 3 OF 4
SAFETY CONSEQUENCES
North Atlantic determined on February 17, 1994, that Seabrook Station had
been operated in an unanalyzed condition and a condition outside the
design basis of the plant during September 1992 while conducting MSSV
setpoint testing. This determination was made based on the calculation
of conservative Technical Specification Table 3.7-1 values using the
algorithm provided in NSAL 94-01. During the September 1992 MSSV
setpoint testing, the high flux setpoint utilized were non-conservative
with respect to the NSAL 94-01 algorithm values.
From a licensing basis perspective, this condition may have resulted in
secondary side overpressurization in the event of a loss of load/turbine
trip transient. The Seabrook Station licensing basis for anticipated
operational occurrences (ANS Condition II events) requires that the
secondary side pressure remain below 110% of the design value.
Westinghouse concluded in NSAL 94-01 that this issue does not represent a
substantial safety hazard. This Westinghouse conclusion was based on
"several mitigating factors which provide assurance that there is no loss
of safety function to the extent that there is a major reduction in the
degree of protection provided to the public health and safety". The
following mitigating factors identified by Westinghouse in NSAL 94-01 are
applicable to Seabrook Station:
1. The LOL/TT analysis conservatively assumes that main feedwater flow
to the SGs is lost at the time of the turbine trip. If a LOL/TT
transient occurs at reduced power levels and main feedwater flow is
maintained, operation in accordance with the Technical Specification
Table 3.7-1 will not result in an overpressure condition.
2. In any LOL/TT transient, the atmospheric steam dump valves and/or
condenser steam dump valves actuate to relieve energy from the steam
generators prior to the opening of the MSSVs, and continue to relieve
steam if the MSSVs do open. Since it is not a safety grade function,
steam dump is not assumed to operate in the safety analysis; however
it is reasonable to expect that the steam dump system would function
to protect the secondary system against overpressurization. It is
very improbable that all these components would be non-functional
coincident with inoperable MSSVs.
3. The primary coolant heatup resulting from the LOL/TT transient would
tend to drive the MTC negative, which would reduce the core power and
heat input to the coolant. This would result in a lower required MSSV
capacity to prevent secondary overpressurization. The safety analysis
does not credit the reduction of MTC during the transient.
ROOT CAUSE
The root cause of this event is the failure of the UFSAR LOL/TT analysis
to bound the operating configurations permitted by Technical
Specification Table 3.7-1 since the neutron high flux trip setpoints
specified in this table for a corresponding number of MSSVs may not be
low enough to preclude a secondary system overpressurization condition.
TEXT PAGE 4 OF 4
CORRECTIVE ACTIONS
NSAL 94-01 provides an algorithm for calculation of conservative Technical
Specification Table 3.7-1 values. A calculation was performed by North
Atlantic to determine these values and a Technical Clarification TS-011
was approved and issued to ensure that the values are administratively
controlled until such time that the Technical Specifications are revised.
North Atlantic will submit a license amendment request containing proposed
revisions to Technical Specification Table 3.7-1.
PLANT CONDITIONS
This event occurred in September 1992 while North Atlantic was conducting
Main Steam Safety Valve setpoint testing as required by Technical
Specification 4.0.5 and Section XI of the ASME Boiler and Pressure Vessel
Code. During this testing the plant was in MODE 1, at approximately 65%
RTP, with power levels being gradually reduced in preparation for Refueling
Outage 2.
PREVIOUS OCCURRENCES
This is the third condition of this type at Seabrook Station where
non-conservative Technical Specification values have been determined to
exist. Licensee Event Report 92-02 dated March 13, 1992, and Supplement
1 to LER 92-02 dated April 8, 1993, identify a non-conservative value for
RHR flow and a non-conservative figure depicting reactor core safety
limits.
ATTACHMENT TO 9403230211 PAGE 1 OF 2
P.O. Box 300 N
North Seabrook, NH 03874
Atlantic Telephone (603) 474-9521
Facsimile (603) 474-2987
Energy Service Corporation
Ted C. Feigenbaum
Senior Vice President and
Chief Nuclear Officer
NYN- 94028
March 17, 1994
United States Nuclear Regulatory Commission
Washington, D.C. 20555
Attention: Document Control Desk
Reference: Facility Operating License No. NPF-86, Docket No. 50-443
Subject: Licensee Event Report (LER) 94-03-00: "Operation at
Reduced Power Levels with Inoperable MSSVs"
Gentlemen:
Enclosed please find Licensee Event Report (LER) No. 94-03-00
for Seabrook Station. This LER addresses Main Steam Safety Valve
(MSSV) setpoint testing which was conducted in September 1992. North
Atlantic determined on February 17, 1994, on the basis of new information
received from Westinghouse that plant operation during the MSSV testing
in September 1992 was reportable pursuant to 10CFR50.72(b)(1)(ii)(A) and
(B). This LER is being submitted pursuant to 10CFR50.73(a)(2)(ii) and
10CFR50.73(a)(2)(v).
Should you require further information regarding this matter, please
contact Mr. James M. Peschel, Regulatory Compliance Manager at (603)
474-9521 extension 3772.
Very truly yours,
Ted C. Feigenbaum
TCF:ALL/act
Enclosures: NRC Forms 366/366A
a member of the Northeast Utilities system
ATTACHMENT TO 9403230211 PAGE 2 OF 2
United States Nuclear Regulatory Commission March 17, 1994
Attention: Document Control Desk Page two
cc: Mr. Thomas T. Martin
Regional Administrator
United States Nuclear Regulatory Commission
Region 1
475 Allendale Road
King of Prussia, PA 19406
Mr. Albert W. De Agazio, Sr. Project Manager
Project Directorate 1-4
Division of Reactor Projects
U.S. Nuclear Regulatory Commission
Washington, DC 20555
Mr. Antone C. Cerne
NRC Senior Resident Inspector
P.O. Box 1149
Seabrook, NH 03874
INPO
Records Center
700 Galleria Parkway
Atlanta, GA 30339-5957
*** END OF DOCUMENT ***
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