[Federal Register Volume 76, Number 82 (Thursday, April 28, 2011)]
[Notices]
[Pages 23846-23848]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2011-10282]
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NUCLEAR REGULATORY COMMISSION
[Docket No. 50-338; NRC-2010-0246]
Virginia Electric Power Company, LLC, North Anna Power Station,
Unit No. 1; Exemption
1.0 Background
Virginia Electric Power Company (VEPCO, the licensee) is the holder
of Facility Operating License No. NPF-4, which authorizes operation of
North Anna Power Station (NAPS), Unit No. 1. The license provides,
among other things, that the facility is subject to all rules,
regulations, and orders of the Nuclear Regulatory Commission (NRC, the
Commission) now or hereafter in effect.
The facility consists of a pressurized-water reactor located in
Louisa County, Virginia.
2.0 Request/Action
Title 10 of the Code of Federal Regulations (10 CFR), Part 50,
Section 50.48(b) requires nuclear power plants licensed before January
1, 1979, to meet 10 CFR Part 50, Appendix R, Section III.O. NAPS Unit
No. 1 was licensed on April 1, 1978. Appendix R, Section III.O requires
a reactor coolant pump (RCP) oil collection system (OCS) that is
capable of collecting lube oil from all potential pressurized and
unpressurized leakage sites in the reactor coolant pump lube oil
system.
The licensee requested an exemption from the requirements to the
extent that minor oil misting may not be captured within the OCS. This
applies to all three Unit 1 RCPs.
In summary, by letter dated April 23, 2010 (Agencywide Documents
Access and Management System (ADAMS), Accession No. ML101160376), as
supplemented by letters dated May 13, 2010 (ADAMS Accession No.
ML101380270), October 11, 2010 (ADAMS Accession No. ML102870109), and
November 15, 2010 (ADAMS Accession No. ML103200451), the licensee
requested an exemption from 10 CFR Part 50, Appendix R, Section III.O
because small amounts of oil from the RCP were misting, were being
transported by the ventilation system, and were condensing on the RCP
motor stator coolers (hereafter referred to as coolers). The exemption
would allow the licensee to install features to collect any oil that
accumulates on the coolers instead of preventing the oil mist from
escaping the OCS.
3.0 Discussion
Pursuant to 10 CFR 50.12, the Commission may, upon application by
any interested person or upon its own initiative, grant exemptions from
the requirements of 10 CFR Part 50 when (1) the exemptions are
authorized by law, will not present an undue risk to public health or
safety, and are consistent with the common defense and security; and
(2) when special circumstances are present. These circumstances include
the special circumstances that application of the regulation is not
necessary to achieve the underlying purpose of the rule.
Authorized by Law
This exemption would allow the licensee to install features to
collect any oil that accumulates on the coolers from oil mist
condensation instead of preventing the oil mist from escaping the OCS.
As stated above, 10 CFR 50.12 allows the NRC to grant exemptions from
the requirements of 10 CFR Part 50. The NRC staff has determined that
granting of the licensee's proposed exemption will not result in a
violation of the Atomic Energy Act of 1954, as amended, or the
Commission's regulations. Therefore, the exemption is authorized by
law.
No Undue Risk to Public Health and Safety
The underlying purposes of 10 CFR Part 50, Appendix R, Section
III.O is to ensure that failure of the RCP lube oil system will not
lead to fire during normal or design basis accident conditions and that
there is reasonable assurance that the system will withstand the Safe
Shutdown Earthquake. The regulation intends licensees to accomplish
this by extending the concept of defense-in-depth to fire protection in
fire areas important to safety, with the following objectives:
(1) To prevent fires from starting;
(2) To rapidly detect, control, and extinguish promptly those fires
that do occur;
(3) To provide protection for structures, systems, and components
important to safety so that a fire that is not promptly extinguished by
the fire suppression activities will not prevent the safe shutdown
(SSD) of the plant.
In their request, as supplemented, the licensee described elements
of their fire protection program that provide their justification that
the concept of defense-in-depth that is in place in the affected
important to safety fire area (FA), FA 1-1, is consistent with that
required by the regulation. The licensee states in their request, as
supplemented, that the modification to install oil collection trays on
the coolers with piping connected to the RCP OCS is scheduled to be
installed during the next Unit 1 refueling outage. Operating experience
based on a similar design for Unit 2 has indicated that the oil mist
primarily condenses on the coolers and the oil collection tray collects
oil dripping from the coolers. This will reduce the potential for
significant quantities of oil pooling to occur outside the OCS. The
remaining oil sheen that may develop due to misting does not present a
safety
[[Page 23847]]
concern due to the small volume of oil. The licensee further states in
their request, as supplemented, that the purpose of their request was
to address expected, minor RCP oil misting. The collection of the oil
in the tray below the coolers and the piping to the OCS is in addition
to the protective measures installed to meet Section III.O of 10 CFR
Part 50, Appendix R.
In the licensee's request, as supplemented, an analysis was
provided that described how fire prevention, detection, control,
extinguishment and preservation of safe shutdown capability is
addressed for FA 1-1 in the Unit 1 containment, as summarized below.
Fire Prevention
The licensee states that administrative controls are in place to
control combustibles in the plant. No transient combustible materials
are normally allowed in the containment while the unit is at power.
This is ensured by implementing a Unit 1 containment checklist prior to
placing the unit into operation. Hot work does not occur within the RCP
cubicles during power operations. The RCP cubicles are concrete
compartments that are open to the containment on the top and house the
RCPs, the steam generators and the reactor coolant system piping.
NRC Information Notice 94-58, ``Reactor Coolant Pump Lube Oil
Fire'' (ADAMS Accession No. ML031060498), alerted industry that a
credible ignition source for RCP oil is hot RCS piping. Ignition has
typically occurred due to the oil soaking fibrous insulation.
Inadequately designed oil collection systems and oil leaking onto RCP
piping insulation was identified as a cause.
The licensee's April 23, 2010, letter proposes to modify the OCS to
further eliminate the potential for oil pooling outside the OCS. The
modification will also prevent oil from collecting on three sections of
fiberglass cloth covered Tempmat insulation under the RCP motors.
Tempmat insulation is noncombustible and is not an Appendix R concern
with respect to combustible loading. The licensee states that the
modifications to the OCS are scheduled to be installed during the next
refueling outage.
The licensee states that additional defense-in-depth at NAPS Unit
No. 1 is achieved through the physical properties of the oil itself
combined with the limited amount of ignition sources within the area.
The flashpoint of the oil currently used is 374 [deg]F, with an auto-
ignition temperature of 608 [deg]F. Nominal temperatures of the RCP
motor and pump flange are approximately 220 [deg]F and 550 [deg]F,
respectively. These temperatures would not be sufficient to cause auto-
ignition of the oil. However, given the flashpoint of the oil, it is
conceivable that the oil could be ignited in the presence of an
ignition source. A review of equipment in the area has identified one
potential ignition source in addition to the RCPs themselves. The RCP
is protected from being an ignition source by the installed OCS. The
other potential ignition source is the cold leg loop stop valve (LSV)
motor operated valve (MOV), which is in close proximity to the RCP. Due
to the size of the LSV MOV actuator motor, it could also be considered
an ignition source. However, power is removed from the cold leg LSV
MOVs by opening the supply breakers prior to startup and
administratively verified open throughout the cycle. Therefore, the
ignition source is effectively eliminated. In addition, guidance in the
``Station Lubrication Manual'' outlines the procedural controls that
ensure that RCP oil of different properties is not used. The Station
Lubrication Manual is procedurally controlled and requires
authorization to be changed.
With the exception of the oil contained within the RCP motor,
combustibles within each cubicle and loop room are negligible.
Furthermore, containment is maintained at a sub-atmospheric pressure
and not routinely occupied during operation. As a result, the
introduction of transient combustibles into this area at power is
negligible.
Each RCP motor has a dedicated OCS tank that is designed to contain
the entire oil inventory of the motor. A vent and flame arrestor are
provided on top of the tank. Operations procedures verify the oil
collection tanks are empty prior to unit start-up from Mode 5. In
addition, tank drain lines were extended in the mid-1990's to allow
draining the tank from outside the loop rooms (lower radiation dose
area).
A design change to enhance the baffled ventilation openings of the
RCP oil lift pump enclosure that ensures that all oil will be contained
in the event of pressurized oil leakage inside these enclosures has
been installed on NAPS Unit No. 1.
A design change to install oil collection trays on the coolers with
piping connected to the RCP OCS tank is scheduled to be installed on
NAPS Unit No. 1 during the next refueling outage. This piping will
direct the oil in the cooler collection trays to the RCP OCS tank. The
oil collection trays will be installed in the areas where the most oil
outside the OCS has been found. Prior to installation of the collection
trays on NAPS Unit No. 2, licensee staff identified oil pooling under
the coolers. Approximately 6 months after the collection trays were
installed, a walkdown of NAPS Unit No. 2 RCP A and B verified that the
oil collection trays were performing as designed.
The licensee states that all preventative maintenance tasks are
controlled by established preplanned work orders under the recurring
task evaluation (RTE) process. Deferral of any of these work orders
will require an RTE that will be evaluated by VEPCO on a case-by-case
basis. The licensee states that they follow the manufacturer's
recommendations for maintenance of the RCPs and that the RCPs are
refurbished every 9 years by an offsite vendor.
Detection, Control and Extinguishment
Fire detection within the NAPS Unit Nos. 1 and 2 containment
consists of linear heat detection on each RCP, smoke and heat detection
within the cable penetration area of containment, heat detection for
the residual heat removal pumps, and duct smoke detection on the outlet
of each of the three containment air recirculation fans. The RCP linear
heat detection alarms at 575 [deg]F. The alarm is received locally in
containment at the local control panel, on the control room vertical
board, and on the control room fire detection panel. System trouble
conditions are annunciated similarly.
Manual fire suppression equipment for containment consists of a 100
lb.-wheeled CO2 unit on each floor of containment, three
CO2 and one dry chemical extinguisher at the personnel
entrance to containment, and a dry standpipe system with hose stations.
Hoses are not normally connected to the hose valves. A fire brigade
equipment locker is provided outside of the personnel entrance to
containment.
The licensee states that the CO2 extinguishers and the
dry chemical extinguisher are rated for a Class B fire (flammable and
combustible liquids). The initial fire fighting attack can be made
using either a CO2 or dry chemical extinguisher. A fire hose
can be used if CO2 is ineffective or does not completely
extinguish the fire. In addition, foam is available and can be applied
if determined necessary by the fire brigade.
Preservation of Safe Shutdown Capability
The licensee states that FA 1-1 is the primary containment for NAPS
Unit No. 1. The area is a multi-level structure. The boundary fire
barriers for containment are of heavy reinforced
[[Page 23848]]
concrete construction with an inherent fire rating in excess of 3
hours. Access is gained into containment through a personnel access
lock. The RCP motor cubicles are located above the associated reactor
coolant system loop room. The floor of the RCP motor cubicle consists
of steel grating with multiple openings between the motor cubicle and
reactor coolant system loop room. The rooms are separated from the
remainder of containment by heavy concrete shield walls, with a
personnel access door for each cubicle and loop room. There are
multiple openings in the ceiling of the motor cubicles. Although not
maintained as rated fire boundaries, the heavy shield walls provide a
degree of separation.
The license states that the only SSD function instruments present
are the three resistance temperature detectors (RTDs) that provide
indication of the RCS hot leg temperature in the control room. There is
no credible means for minor oil misting to impact the safe shutdown
function of the hot leg RTDs. Each RTD is separated from the closest
redundant RTD located in another pump cubicle by two heavy concrete
walls. Therefore, a credible fire in one RCP cubicle would not affect
RCS temperature indication from the other two loops.
Summary of Defense-in-Depth
In summary, the defense-in-depth concept for a fire in FA 1-1
discussed above provides an adequate level of safety through the
prevention of fires, detection, control and extinguishment of fires
that occur and the protection of structures, systems and components
important to safety. As discussed above, the licensee has provided
preventative and protective measures that together demonstrate the
licensee's ability to preserve or maintain SSD capability in the event
of a fire within an RCP cubicle or reactor coolant system loop room.
Based on the above, the NRC staff concludes that the licensee has
met the defense-in-depth objectives and no new accident precursors are
created by the installation of features to collect any oil that
accumulates on the coolers from oil mist condensation instead of
preventing the oil mist from escaping the OCS, thus, the probability of
postulated accidents is not increased. Also, based on the above, the
consequences of postulated accidents are not increased. Therefore,
there is no undue risk to public health and safety.
Consistent With Common Defense and Security
The proposed exemption would allow the licensee to install features
to collect any oil that accumulates on the coolers from oil mist
condensation instead of preventing the oil mist from escaping the OCS.
This change to the plant has no relation to security issues. Therefore,
the common defense and security is not impacted by this exemption.
Special Circumstances
Special circumstances, in accordance with 10 CFR 50.12(a)(2)(ii),
are present whenever application of the regulation in the particular
circumstances is not necessary to achieve the underlying purpose of the
rule. The underlying purposes of 10 CFR Part 50, Appendix R, Section
III.O is to ensure that failure of the RCP lube oil system will not
lead to fire during normal or design basis accident conditions and that
there is reasonable assurance that the system will withstand the Safe
Shutdown Earthquake. As described above, the defense-in-depth concept
for a fire in FA 1-1 discussed above provides an adequate level of
safety through prevention of fires, detection, control and
extinguishment of fires that do occur and the protection of structures,
systems and components important to safety. In addition, the licensee
has provided preventative and protective measures that together
demonstrate the ability to preserve or maintain SSD capability in the
event of a fire in an RCP cubicle and loop room. Allowing the
collection of oil that accumulates on the coolers instead of preventing
the oil mist from escaping the OCS does not impact the ability of the
OCS to withstand the Safe Shutdown Earthquake. Therefore, since the
underlying purpose of 10 CFR Part 50, Appendix R is achieved, the
special circumstances required by 10 CFR 50.12(a)(2)(ii) for the
granting of an exemption from 10 CFR Part 50, Appendix R exist.
4.0 Conclusion
Accordingly, the Commission has determined that, pursuant to 10 CFR
50.12, the exemption is authorized by law, will not present an undue
risk to the public health and safety, and is consistent with the common
defense and security. Also, special circumstances are present.
Therefore, the Commission hereby grants VEPCO an exemption from 10 CFR
Part 50, Appendix R, Section III.O to the extent that minor oil misting
may not be captured within the OCS. This applies to all three RCPs for
NAPS Unit No. 1. Pursuant to 10 CFR 51.32, the Commission has
determined that the granting of this exemption will not have a
significant effect on the quality of the human environment as published
in the Federal Register on July 8, 2010 (75 FR 39285).
This exemption is effective upon issuance.
Dated at Rockville, Maryland this 21st day of April 2011.
For the Nuclear Regulatory Commission.
Robert A. Nelson,
Acting Director, Division of Operating Reactor Licensing, Office of
Nuclear Reactor Regulation.
[FR Doc. 2011-10282 Filed 4-27-11; 8:45 am]
BILLING CODE 7590-01-P