Information Notice 1997-60, Incorrect Unreviewed Safety Question Determination Related to Emergency Core Cooling System Swapover from the Injection Mode to the Recriculation Mode
v>
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF NUCLEAR REACTOR REGULATION
WASHINGTON, D.C. 20555-0001
August 1, 1997
INCORRECT UNREVIEWED SAFETY QUESTION
DETERMINATION RELATED TO EMERGENCY
CORE COOLING SYSTEM SWAPOVER FROM THE
INJECTION MODE TO THE RECIRCULATION
MODE
Addressees
All holders of operating licenses or construction permits for pressurized-water reactors.
Purpose
The U.S. Nuclear Regulatory Commission (NRC) is issuing this information notice to alert
addressees to an instance in which a licensee has incorrectly determined that changes to its
emergency core cooling system (ECCS) swapover procedures that resulted in interruption of
flow and a consequent core heatup in the long-term cooling phase of a potential loss-of- coolant accident (LOCA) did not involve an unreviewed safety question (USQ). 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 contained in this
information notice are not NRC requirements; therefore, no specific action or written response
is required.
DescriDtion of Circumstances
On May 1, 1989, a license amendment was issued approving a semi-automatic ECCS swap- over procedure for Salem Nuclear Unit 2. This procedure provided the plant with the
capability to switch the ECCS suction from the refueling water storage tank (RWST) to the
containment sump (i.e., from the injection mode of operation to the recirculation mode of
operation) without interruption of ECCS flow to the core. It further provided continuous
suction to the high-head safety injection (HHSI) and intermediate-head safety injection (IHSI)
pumps. The semi-automatic swapover design provided this capability by automatically com- pleting the following steps: (1) opening the suction line valves between the residual heat
removal (RHR) pump and the sump; (2) starting component cooling water to the RHR heat
exchangers; (3) opening the suction crosstie valves between the HHSI and IHSI pumps; and
(4) when the sump line valves are fully open, closing the suction line to the RWST. Manual
,
PPI
4-fE NoTV 9qq -060 '70 'O0
I a1.1111111111111
7I3 II
7 lI
'R
C\\-
August 1, 1997 operator action was still required to align the suction of the HHSI and IHSI pumps to the
discharge of the RHR pumps (i.e., the piggyback mode of operation) and to trip the con- tainment spray pumps. Subsequently, both the licensee's individual plant examination and
the NRC technical evaluation report on Salem human reliability analysis issued in August
1995 identified ECCS swapover as one of the most risk-significant operator actions for
Salem.
For Salem Unit 2, ECCS swapover is initiated when the level in the RWST reaches the low- level alarm setpoint. In addition, to prevent vortexing in the RWST and to protect the ECCS
pumps, emergency operating procedures (EOPs) direct operators to trip all ECCS pumps
taking suction from the RWST if the RWST low-low level alarm setpoint is reached. There- fore, the maximum time available for successful completion of ECCS swapover is the time
that it would take the RWST to drain from the low-level alarm setpoint to the low-low level
alarm setpoint. In 1995 and 1996 the licensee performed evaluations that consiaered: (1)
uncertainties in specific operator action times, (2) the introduction of "three-point"
communications, (3) higher than previously assumed containment spray pump flow, and (4)
the identification of more limiting single-failure scenarios. The licensee concluded that
under certain accident conditions, the operators may not be able to complete the swapover
before reaching the low-low level alarm setpoint. For such scenarios, the operators would
be directed to trip the ECCS pumps taking suction from the RWST, thereby interrupting
ECCS flow to the core.
The licensee's analyses for the small break loss-of-coolant accident (SBLOCA) and
accumulator line break accidents allotted the operators 11.8 minutes and 12.9 minutes, respectively, for completing the ECCS swapover procedure from the point that the RWST
level reaches the low-level alarm setpoint. Licensee calculations showed that the low-low
level alarm setpoint would be reached at 10 minutes for the SBLOCA and 7.9 minutes for the
accumulator line break. As discussed above, this is the point at which the operators are
directed to stop all ECCS pumps taking suction from the RWST, thereby interrupting ECCS
flow to the core. Therefore, for the balance of the time allotted for completing the swapover
procedure (i.e., 1.8 minutes for the SBLOCA and 5 minutes for the accumulator line break),
core cooling would have to be provided without ECCS flow. The licensee evaluated these
changes to the swapover procedure, including the introduction of interruption of ECCS flow, pursuant to 10 CFR 50.59 and determined that the changes did not involve a USQ. Accord- ingly, the licensee implemented the changes without NRC staff approval.
The NRC became aware of the above-described changes to Salem Unit 2's semi-automatic
ECCS swapover procedure during a special NRC inspection conducted between March 24 and April 17, 1997. The inspectors were concerned with the introduction of interruption of
flow into the ECCS swapover procedure as the NRC staff had not reviewed this approach fcr
Salem Unit 2. Additionally, the inspectors were concerned about the potential for such
scenarios to violate the requirement contained in 10 CFR 50.46(b)(5), "Long term cooling."
August 1, 1997 Discussion
Pursuant to 10 CFR 50.59, a licensee may make changes in its facility and procedures as
described in the safety analysis report (SAR) without prior Commission approval, unless
the proposed change involves a USQ. In part, 10 CFR 50.59 states that changes shall be
deemed to involve a USQ if the probability of occurrence of a malfunction of equipment
important to safety previously evaluated in the SAR may be increased, or if a possibility
for a malfunction of a different type than any evaluated previously in the SAR may be
created.
The changes to the swapover procedure in the Salem case introduced reliance on manual
operator actions, where such actions were not previously required to stop and restart
ECCS pumps, and reliance on ECCS pumps to restart shortly after being stopped during an
accident.
This was contrary to the intent of the 1989 design change, which was to increase the
reliability of ECCS swapover by automating ceirain features, so that the RHR pumps would
not have to be stopped and restarted, and reduce susceptibility to human error in ECCS
swapover. As a result of the inspection findings, the staff evaluated these changes and
found them to have increased the probability of a malfunction of equipment important to
safety in that the changes provide additional opportunities for operator error, especially
considering the conditions and the time constraints under which the operators would be
working. In addition, restarting ECCS pumps shortly after they have been stopped involves
uncertainties as to whether the pumps will restart and is not recommended by pump vendors.
Therefore, an increase in the probability of malfunction of the ECCS pumps was also
introduced. On the basis of the above discussion, the staff concluded in Inspection Report
50-311/97-11 that these changes did involve a USQ.
In addition, the interruption of flow during ECCS swapover could potentially result in another
fuel uncovery following the initial blowdown and reflood phase of a LOCA. Consequently, the
fuel could reheat during that phase of the accident. Therefore, such an interruption of ECCS
flow could violate the long-term cooling requirement of 10 CFR 50.46 (b)(5). Additional
cycling of the fuel (i.e., introduction of heatups in the long-term cooling phase of the accident)
also increases the probability of cladding failure and therefore involves a USQ as defined in
10 CFR 50.59. For the Salem case, the licensee evaluated the effects of the interruption of
flow on the core. The licensee wanted to maximize the time available to the operators to
complete the swapover. The allowable times for flow interruptions as noted above were
calculated on the basis of maintaining the core under water to avoid core heating. The
licensee has since implemented EOP changes to allow operators to complete the swapover
without interruption of flow. In addition, the licensee verified through simulator exercises
that all operating crews could perform the revised EOPs well within the time frame required
to prevent interruption of flow. The NRC found the licensee's actions to resolve these issues
to be acceptable.
KJ
August 1, 1997 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 Office of Nuclear Reactor Regulation (NRR) project manager.
ary e
. Slosson, Acting Dire
r
Division of Reactor Program Management
Office of Nuclear Reactor Regulation
Technical contacts:
Mohammed A. Shuaibi, NRR
301-415-2859 E-Mail: mas4@nrc.gov
Thomas Koshy, NRR
301-415-1176 E-mail: txk@nrc.gov
Frank R. Orr, NRR
301-415-1815 E-Mail: fro@nrc.gov
Doug Dempsey, RI
(610) 337-5347 E-mail: dadl@nrc.gov
Attachment: List of Recently Issued NRC Information Notices
L~t
/
e
A
T
B-A
.
IK
do:
Attachment
August 1, 1997 LIST OF RECENTLY ISSUED
NRC INFORMATION NOTICES
Information
Date of
Notice No.
Subject
Issuance
Issued to
97-59
97-58
97-57
Fire Endurance Test
Results of Versawrap
Fire Barriers
Mechanical Integrity of
In-Situ Leach Injection
Wells and Piping
Leak Testing of Packaging
Used in the Transport of
Radioactive Material
Possession Limits for
at the Environcare of
Utah Low-Level Radioactive
Waste Disposal Facility
Calculation of Surface
Activity for Contaminated
Equipment and Materials
08/01/97
07/31/97
07/30/97
07/28/97
07/23/97
All holders of OLs or CPs
for nuclear power reactors
Holders of and Applicants
for Licenses for In-Situ
Leach Facilities
Suppliers and users of
packaging for the trans- portation of radioactive
material required to per- form packaging leak tests
All licensees authorized
to possess special nuclear
material
All Uranium Recovery
Licensees
97-56
97-55
97-54
NRC Licensed Operators
at Six Non-Power Reactor
Facilities Allow their
Operator Licenses to
Expire
07/18/97
All holders of OLs or CPs
for test and research
reactors and all licensed
operators at test and
research reactor facilities
97-53
Circuit Breakers
Left Racked Out in
Non-Seismically
Qualified Positions
07/18/97
All holders of OLs or CPs
for nuclear power reactors
OL = Operating License
CP = Construction Permit
. .
S
August 1, 1997 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 Office of Nuclear Reactor Regulation (NRR) project manager.
original signed by S.H. Weiss for
Marylee M. Slosson, Acting Director
Division of Reactor Program Management
Office of Nuclear Reactor Regulation
Technical contacts:
Mohammed A. Shuaibi, NRR
301-415-2859 E-Mail: mas4@nrc.gov
Thomas Koshy, NRR
301-415-1176 E-mail: txk@nrc.gov
Frank R. Orr, NRR
301-415-1815 E-Mail: fro@nrc.gov
Attachment: List of Recently Issued NRC Information Notices
Tech Editor has reviewed and concurred on 06/19/97
- SEE PREVIOUS CONCURRENCE
DOCUMENT NAME: 97-60.1N
Doug Dempsey, RI
(610) 337-5347 E-mail: dadl@nrc.gov
To receive a copy of this document, Indicate In the box: "C' - Copy wtut enclosures "E - Copy with enclosures "N" u No copy
OFFICE
-TEC
(A)C:SRXB
-C:OGCC:PECB
(A)D:DRPM
i
CONTACT
S
I.I
I
r
NAME
MShuaibi*
JLyons*
MRafky*
AChaffee*
MSlosson
FOrr*
GGalleti*
EMcKenna*
TKoshy
DATE
7/97*
7/15/97
07/22/97
07/23/97
074f /97
OFFICIAL RECORD COPY
-t
K>
IN 97-xx
July xx, 1997 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 Office of Nuclear Reactor Regulation (NRR) project manager.
Marylee M. Slosson, Acting Director
Division of Reactor Program Management
Office of Nuclear Reactor Regulation
Technical contacts:
Mohammed A. Shuaibi, NRR
301-415-2859 E-Mail: mas4@nrc.gov
Thomas Koshy, NRR
301-415-1176 E-mail: txkenrc.gov
Frank R. Orr, NRR
301-415-1815 E-Mail: froenrc.gov
Doug Dempsey, Region I
(610) 337-5347 E-mail: dadl@nrc.gov
Attachment: List of Recently Issued NRC Information Notices
- SEE PREVIOUS CONCURRENCE
DOCUMENT NAME: G:\\TXKCFLOWMNT.IN
To receive a copy of this docurnent, Indicate In the box: I"C'
IOFFICE
ITECH
I
I(A)C:SRXB
I
without enclosures "i
= Copy with enclosures "N" - No copy
IN 97-xx
July xx, 1997 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 Office of Nuclear Reactor Regulation (NRR) project manager.
Marylee L. Slosson, Acting Director
Division of Reactor Program Management
Office of Nuclear Reactor Regulation
Technical contacts:
Mohammed A. Shuaibi, NRR
301-415-2859 E-Mail: mas4@nrc.gov
Thomas Koshy, NRR
301-415-1176 E-mail: txk@nrc.gov
Frank R. Orr, NRR
301415-1815 E-Mail: fro@nrc.gov
Doug Dempsey, Region 1
610-337-5347 E-mail: dadl@nrc.gov
Attachment: List of Recently Issued NRC Information Notices
- SEE PREVIOUS CONCURRENCE
DOCUMENT NAME: G:%TXKXFLOWINT.IN
To rarucvi
a mnv of this documetnL Indicate In the box: IC' - Conv without enclosures "E" - CODv with enclosures "N" - No copy
OFFICE
TECH
(A)C:SRXB
C: PECB
(A)
D:FDRPM
l
CONTACT
S
I
I
I
I
NAME
MShuaibi*
JLyons*
MRafky*
AChaffee
MSlosson
FOrr*
GGalleti*
EMcKenna*
l ______ TKoshy
.
.
.
_l
DATE
7/97*
7/15/97
07/22/97
07/ A97
07/ /97
.~~~~~-
- - - - -
- - -v5nras
rr
UII-ILIAL KtUWKU LUY'T
9 Dix No
IN 97-xx
July xx, 1997 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 tp6ihnical contacts
listed below or the appropriate Office of Nuclear Reactor Regulation (N R) project
manager.
Marylee L. Slosson, A
ng Director
Division of Reactor P gram Management
Office of Nuclear
actor Regulation
Technical contacts: Mohammed A. Shuaibi, NRR
/
Thomas Koshy, NRR
301-415-2859 E-Mail mas4@nrc.gov
/
301-415-1176 txk@nrc.gov
Frank R. Orr, NRR
301-415-1815 E-Mail fro@nrc.gov
Doug Dempsey, Region 1
610-337-5347 dad1 @nrc.gov
Attachment: List of Recently Issued NRC Information Notices
DOCUMENT NAME: G:\\TXK\\FLOWINT.IN
To receive a copy of this document, indicate hi the box:
with enclosures
N' - No copy
OFFICE
TECH
(A)C D
CONTACT
S
I
__
NAME
MShuaibi*
JLyon
FOrr*
GGalleti*
EMcKenna*
TKoshy
O70
IN 97-xx
July xx, 1997 ,
This information notice requires no specific action or written response. If
questions about the information in this notice, please contact one of the tE
listed below or the appropriate Office of Nuclear Reactor Regulation (NRF
)u,nave any
Jiinical contacts
project manager.
Marylee)Slosson, A
ng Director
Division of Reactor
ogram Management
Office of Nuclear O actor Regulation
Technical contacts:
Mohammed A. Shuaibi, NRR
301-415-2859 E-Mail mas4@nrc.gov
Thomas Koshy, NRR
301-415-1176 txk@nrc.gov
Frank R. Orr, NRR
301-415-1815 E-Mail fro@nrc.gov
Doug Dempsey, Region 1
610-337-5347 dadi @nrc.gov
Attachment: List of Recently Issued NRC
Notices
DOCUMENT NAME: G:=TXKFLOVMNT.IN
To receive a copy of fths document, Indicate In the box:
with enclosures "N" a No