[Federal Register Volume 70, Number 162 (Tuesday, August 23, 2005)]
[Notices]
[Pages 49324-49331]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: E5-4597]
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NUCLEAR REGULATORY COMMISSION
[Docket Nos. 50-348 and 50-364]
Southern Nuclear Operating Company, Joseph M. Farley Nuclear
Power Plant, Units 1 and 2; Exemption
1.0 Background
The Southern Nuclear Operating Company (SNC, the licensee) is the
holder of Renewed Facility Operating License Nos. NPF-2 and NPF-8 which
authorizes operation of Joseph M. Farley Nuclear Power Plant (FNP),
Units 1 and 2. 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 two pressurized-water reactors located in
Houston County, Alabama.
2.0 Request/Action
Title 10 of the Code of Federal Regulations (10 CFR) Part 50,
Section 50.48, ``Fire Protection,'' requires that each operating
nuclear power plant have a fire protection plan that satisfies General
Design Criterion (GDC) 3, ``Fire Protection,'' of appendix A to part
50. Section 50.48(b) also references Appendix R, ``Fire Protection
Program for Nuclear Power Facilities Operating Prior to January 1,
1979,'' to part 50, which establishes fire protection features required
to satisfy GDC 3 with respect to certain generic issues for nuclear
power plants licensed to operate before January 1, 1979. On December
29, 1986, the NRC staff granted SNC Exemption Request 1-3, ``Service
Water Intake Structure--Fire Area 72,'' from certain requirements of
Appendix R, Section III.G.2.c that requires fire detection and fire
suppression capabilities and the enclosure of cables, equipment and
associated non-safety circuits of one redundant train of safe shutdown
equipment in a one-hour rated fire barrier. The Exemption issued on
December 29, 1986, listed a total of ten items specific to Fire Area 72
that were part of Exemption Request 1-3. Exemption Request 1-3 was
included in SNC's request, dated March 13, 1985, as supplemented, and
is applicable to Fire Area 72 for the Service Water Intake Structure
(SWIS) which is common to FNP, Units 1 and 2.
By letters dated August 28, 2003, December 28, 2004, and June 9,
2005, SNC submitted a proposed revision to Exemption Request 1-3. SNC
stated in its August 28, 2003, letter that the proposed revisions to
Exemption Request 1-3 would clarify FNP's fire protection licensing
basis, delete unnecessary attributes of the prior approved exemption,
and revise the remaining prior exemption attributes to remove
references to one-hour Kaowool fire barrier material. SNC also stated
that the proposed revision to Exemption Request 1-3 is part of SNC's
comprehensive plan to respond to concerns about Kaowool fire barrier
material. SNC's August 28, 2003, letter re-listed the Exemption Request
1-3 items and numbered them as 1 through 9 and ``Addendum to Request''
for ease of reference. The August 28, 2003, letter also added an item
designated as ``Other'' that was not explicitly addressed in the
December 29, 1986, NRC Safety Evaluation. Therefore, a total of 11
items (1 through 9, ``Addendum to Request'', and ``Other'') comprise
the revised exemption request in SNC's August 28, 2003, letter.
3.0 Discussion
Pursuant to 10 CFR 50.12, ``Specific Exemptions,'' 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 special circumstances are described in 10 CFR
50(a)(2)(ii), in that the application of these regulations in this
circumstance is not necessary to achieve the underlying purpose of the
regulations.
The underlying purpose of Appendix R, Section III.G, ``Fire
protection of safe shutdown capability,'' is to provide features
capable of limiting fire damage so that: (1) one train of systems
necessary to achieve and maintain hot shutdown conditions from either
the control room or emergency control station(s) is free of fire
damage; and (2) systems necessary to achieve and maintain cold shutdown
from either the control room or emergency control
[[Page 49325]]
station(s) can be repaired within 72 hours.
In SNC's letter dated August 28, 2003, SNC stated that they
recognize FNP, Unit 1 was licensed to operate prior to January 1, 1979,
is subject to Appendix R to 10 CFR Part 50 and requires an exemption
for any deviation to the rule, but that FNP, Unit 2 was licensed to
operate after January 1, 1979, and would require a deviation from any
commitment to comply with the rule. SNC stated that they did not
distinguish between an exemption request and deviation request (license
amendment) in their August 28, 2003, letter for the two units because
the subject matter of the original Exemption Request 1-3 and this
revised exemption is located in an area of the plant that services both
units, and because the original Exemption Request 1-3 did not
separately provide for a deviation (license amendment).
Overview of Approach Used by Licensee
For this specific fire protection application, SNC proposes plant
and fire protection program modifications under FNP's current license
conditions, and has performed deterministic re-analyses and a risk-
informed, performance-based evaluation to revise existing Exemption
Request 1-3 for the SWIS Fire Area 72.
The changes proposed by SNC to Exemption Request 1-3 will (1)
Remove some conditions in the 1986 Exemption Request 1-3; (2) eliminate
some manual actions; (3) define new fire areas; (4) modify the success
criterion for the ability to remove decay heat and safely shutdown in
the event of a fire in the SWIS; and (5) remove reliance on FNP, Unit 1
lube and cooling water pumps associated with the service water pumps.
As reflected in 10 CFR 50.48(c), the NRC has adopted National Fire
Protection Association Standard 805, 2001 Edition (NFPA 805), with a
few exceptions, as a risk-informed, performance-based alternative to
NRC fire protection requirements in 10 CFR 50.48(b) and as an optional
new licensing basis for plants licensed after 1979. Licensees who
propose to maintain a complete fire protection program that complies
with 10 CFR 50.48(c) as an alternative to 10 CFR 50.40(b) must complete
their implementation of the methodology outlined in NFPA 805 for the
entire plant and submit a application for a license amendment in
accordance with the regulations. Although SNC has not proposed to
revise its complete FNP fire protection program in accordance with 10
CFR 50.48(c) and NFPA 805, SNC has used the methodology of NFPA 805 for
certain specific issues in its proposed revision to Exemption Request
1-3, as discussed below. The NRC had also previously issued Regulatory
Guide (RG) 1.174 (Revision 1), ``An Approach for Using Probabilistic
Risk Assessment in Risk-Informed Decisions on Plant-Specific Changes to
the Licensing Basis''. SNC has used risk-informed, performance-based
analysis tools and has used RG 1.174 for the risk acceptance criteria.
In general, SNC conducted a review of the SWIS which included
deterministic re-analyses and an analysis using the risk-informed,
performance-based methods. SNC concluded that the review and analysis
showed that some of the conditions in existing Exemption Request 1-3
were unnecessary, that the licensee would no longer rely upon some
conditions in the exemption by upgrading a dividing wall and defining
new fire areas, by modifying lubrication and cooling support for
Service Water pumps and other program changes, and that, by plant
modifications and re-analysis, show that by performing the above
modifications, removal of the reliance on Kaowool would maintain or
enhance safety while reducing unnecessary regulatory burden. The review
and analysis conducted by SNC reflected a combination of planned
modifications to FNP, deterministic re-analyses, and combined risk-
informed and fire modeling analyses.
Area Description
The SWIS structure is located outside of the nuclear main power
block and its support buildings. It is common to FNP, Units 1 and 2 and
contains cables, pumps, valves, and other equipment necessary for the
service water system. The SWIS supplies cooling water from the Service
Water pond to the various essential components in both the nuclear main
power block and balance of plant systems which require heat removal for
proper operation during normal and accident conditions including the
cooling certain plant equipment needed to achieve and maintain safe
shutdown in the event of a fire. Each reactor unit has five pumps, two
each in redundant Trains A and B, and a swing pump that can be aligned
to either train. These pumps are spaced between five and six feet
apart, on centers, and are protected by automatic fire suppression and
detection systems. Redundant Train A and Train B cables supply power
and controls to the pumps and support equipment. These cables are in
close proximity where they enter the SWIS in the northeast corner of
the building. Motor operated valves located in the strainer pit direct
the pump flow for Trains A and B. These valves are horizontally
separated 6 feet 6 inches on center on the FNP, Unit 1 side and 5 feet
on center on the FNP, Unit 2 side of the strainer pit.
In its letter dated August 28, 2003, SNC stated that power cables
in the SWIS are contained in conduit and all cables in the SWIS are
qualified to the Institute of Electrical and Electronics Engineers
(IEEE) 383 standard. In its letter dated December 28, 2004, SNC further
stated that power and control cables have jacket and insulation
materials that are qualified to the IEEE-383 standard and utilize
thermoset materials. SNC stated that nearly all cables in the SWIS have
thermoset plastic jacket and insulation material. SNC identified eight
low-voltage polyvinyl chloride (PVC) PVC/PVC cables in a tray along the
north and west wall that are thermoplastic. These cables are not
located in trays and SNC stated that portions of the cable will be
removed to meet the fire model analysis.
SNC will upgrade the nominal 18 inch concrete wall between Fire
Zone 72A and Fire Zones 72B, C, D and E to meet the requirements of
FNP's Fire Protection Program for a minimum 3-hour fire area boundary.
The upgrade to the wall includes sealing penetrations and replacing un-
rated doors with 3-hour rated fire doors. Three new fire areas will be
defined, 72A, 72B/72C and 72D/72E. These changes will improve fire
safety and defense-in-depth by reducing potential fire propagation
paths between the pump deck and switchgear rooms, as well as between
redundant switchgear rooms.
Fire Areas 73 and 74 remain unchanged with respect to this
exemption request revision. On the FNP, Unit 1 side of the SWIS pump
deck, floor curbs are located between the B- and C-Pumps and the C- and
D-Pumps. SNC will provide a new floor curb to be located between the
FNP, Unit 1 E-Pump and the east wall of the SWIS. On the FNP, Unit 2
side of the SWIS pump deck, floor curbs are located between the B- and
C-Pumps and the C- and D-Pumps. These floor curbs and the slope of the
floor help to confine a lubricant spill from one of the Service Water
pumps and limit fire damage to adjacent pumps.
A concrete wall from floor to ceiling is located between the FNP,
Unit 1 and FNP, Unit 2 Service Water pumps at the pump deck level.
Radiant heat shields are provided on each side of the FNP, Unit 1 and
FNP, Unit 2 swing Service Water pumps (C-Pump) to provide radiant heat
shielding to and from adjacent Service Water pumps.
[[Page 49326]]
Fire Protection Equipment
The SWIS is provided with an area-wide smoke detection system
located in all areas of the SWIS including the pump motor area, under
the pump motor deck, in the battery rooms, in the stairways, and in the
strainer area. The smoke detection system provides a local alarm and
annunciates in the control room. In addition, activation of any smoke
detector trips the clappers for all three preaction sprinkler systems.
Tripping the clappers charges the preaction sprinkler systems with fire
water.
The SWIS is also protected by automatic preaction sprinkler
systems. Two preaction systems provide coverage to the entire pump
deck, the area in the strainer pit beneath the pump deck, and to
safety-related cabling in the upper northeast corner of the Service
Water pump room. In addition, a third preaction 'spray' system for
local application protects the Service Water pumps. Local carbon
dioxide fire suppression systems are provided in the switchgear and
transfer switch panels in Fire Zones 72B, 72C, 72D and 72E.
Upon receipt of an alarm, the Control Room would dispatch the Fire
Brigade to the SWIS. Manual fire fighting equipment consisting of hose
stations and portable fire extinguishers is available inside the SWIS.
In addition, two fire hose/hydrant houses are located directly outside
of the SWIS within the security fence. Therefore, all areas of the SWIS
can be reached with an effective hose stream.
Operability and surveillance requirements for fire protection
systems, including those provided for the SWIS are provided by the FNP
Final Safety Analysis Report . The operability of the SWIS fire
protection systems will continue to ensure defense-in-depth is
maintained.
Combustible Controls
Processes and procedures are in place at FNP to address
housekeeping and control of combustible loading throughout the plant.
This includes housekeeping and combustible loading control in the SWIS.
The procedures provide guidance for bringing combustibles into a fire
area for any plant activity including guidance for determining the
amount and type of fire extinguishing equipment in the event of
temporary increases in potential fire loading.
SNC will implement additional specific transient combustible
controls to restrict transient combustibles from being stored/located
in the northeast corner and in the vicinity of the Service Water pumps.
Configuration control will be maintained (from a fire protection
program perspective) over the type and quantity of lubrication oil used
in the Service Water pump motors. SNC will implement precautions to
limit the amount of lubricant in the vicinity of the Service Water
pumps during lubricant changes by removing the drained lubricant from
the area prior to bringing the new (unused) lubricant into the area.
This will provide additional assurance that the conditions of the
risk-informed, performance based evaluation are met and that defense-
in-depth is maintained in the area.
Fire Modeling
SNC's evaluation uses the concepts from NFPA 805 for fire modeling.
NFPA 805 presents two concepts, the maximum expected fire scenario
(MEFS) and limiting fire scenario (LFS). The MEFSs or worst case
credible scenarios are identified by considering the fire types that
have a reasonable likelihood of occurrence. The LFSs are developed by
altering one or more input parameters to MEFSs to determine the
threshold at which a target would exceed the critical temperature or
radiant heat flux. The purpose of determining an LFS was to perform a
sensitivity analysis and demonstrate adequate margin between parameters
when determining MEFS and LFS.
Three scenarios were evaluated by the licensee, (1) transient
combustible material fire in the northeast corner of the SWIS, (2) FNP,
Unit 1 Service Water pump fire, and (3) FNP, Unit 2 Service Water pump
fire. These scenarios were chosen since they were believed to be the
most likely to affect multiple trains of systems. Consolidated Model of
Fire Growth and Smoke Transport (CFAST) (Peacock et al., 2004), HEATING
Version 7.3 (Childs, 1998), and empirical correlations (thermal plume
and radiant heat flux) were used to model the fires. The hot gas layer
temperature and radiant heat flux exposure to the safety-related cable
trays and junction boxes were determined for the MEFSs. The licensee
evaluated other fire scenarios such as smaller quantities of lubricant
oil, motor windings, and other cable trays and concluded that the MEFS
for these fire scenarios would not have resulted in target damage.
The preaction sprinkler system actuation was evaluated for each
fire scenario although sprinkler actuation was not directly credited in
the fire modeling analysis except for defense-in-depth considerations.
In Scenario 1, transient combustible material fire in the northeast
corner of the SWIS (Item 4 and Item ``Other'' of the revised Exemption
Request 1-3), CFAST was used to calculate the maximum hot gas layer
temperature and layer height above the floor. Localized target exposure
temperatures to cable tray targets (Train A and Train B cables in the
northeast corner) were calculated using thermal plume correlations.
This simulation assumed there was no Kaowool fire barrier protecting
the Train A or B cable trays. The results of the CFAST fire simulation
for an MEFS indicate that the maximum hot gas layer temperature would
be below the cable damage temperature and that there would be no
significant radiant exposure to targets located in the SWIS. Based on
the fire modeling results, SNC concluded that the modeled SWIS targets
would not be adversely impacted by an MEFS.
In Scenario 2, FNP, Unit 1 pump fire scenario (Item 9 of the
revised Exemption Request 1-3), the effects of a lubricant oil pool
fire, located between the FNP, Unit 1 Service Water pumps and the south
wall of the SWIS were modeled. CFAST was used to calculate the maximum
hot gas layer temperature and layer height above the floor, and thermal
radiation heat transfer correlations were used to calculate target
exposure to radiant heat flux. The targets evaluated in this scenario
are cable trays (Train-A), using hot gas layer information from CFAST
and pump motor junction boxes using thermal radiation from the heat
transfer correlations. The results of the CFAST fire simulation
indicate that the local targets on the Pump Deck would be immersed by
the hot gas layer. However, the calculated hot gas layer temperature is
lower than the damage temperature of the cable. The radiation heat
transfer calculation shows that the fire originating from a lubricating
oil spill could cause the incident heat flux at a second tier pump
(i.e., pump adjacent to the pump where the spill occurs) or the Train A
cable trays along the east wall to exceed critical heat flux levels;
however, the duration of the fire is not sufficient for the flux to
cause the target surface temperature to exceed the critical cable
temperature based on the analysis using the HEATING7 model. Therefore,
based on this analysis at least one Service Water pump would not be
adversely impacted by this fire scenario.
In Scenario 3, FNP, Unit 2 pump fire scenario (Item 9 of the
revised Exemption Request 1-3), the effects of a lubricant oil pool
fire, located between the FNP, Unit 2 Service Water pumps and the south
wall of the SWIS were modeled. The targets evaluated in this scenario
are pump motor junction
[[Page 49327]]
boxes. There are no cable tray targets modeled in this fire scenario.
Scenario 3 is bounded by Scenario 2 because the pumps on FNP, Unit 2
contain less oil and would define a fire of shorter duration than in
Scenario 2. Therefore, based on this analysis at least one Service
Water pump would not be adversely impacted by this fire scenario.
A sensitivity analysis was performed for Scenarios 1, 2, and 3 to
demonstrate the sensitivity of the results of the calculations to
variations in the MEFSs input parameters. The sensitivity analysis of
the results to the assumptions regarding the composition of the
transient fuel package and the impact of ventilation conditions in the
SWIS was examined. The results clarify the degree of conservatism
inherent in the calculation and the margin between the MEFS and the
LFS. The calculations were compared over a parameter spread that
included conditions that would result in failure of the target. The
licensee concluded that the sensitivity analysis demonstrates that the
results and conclusions would not change with the exception of adjacent
pump motor junction box targets. As a result, these targets are assumed
to fail in the analysis.
Risk Assessment
RG 1.174 specifies that the risk associated with a plant change be
determined by considering the change in Core Damage Frequency (CDF) and
Large Early Release Frequency (LERF) that result from the plant change.
These changes in CDF and LERF are calculated by comparing the CDF and
LERF values for the pre- and post-change locations within the fire area
that will be affected by the change to ensure that all contributors to
risk are included. Thus, the fire risk analysis focused only on
elements of the SWIS that had been or were proposed to be changed from
SNC's current licensing basis. These elements were associated with
pump/motor lubricant fires (one for each pump or ten cases in all).
The FNP plant-specific Level 1 and Level 2 Probabilistic Risk
Assessment (PRA) Model was used, with modifications, to evaluate the
impacts on plant risk of postulated fires originating in the SWIS. The
modifications involved two changes that are summarized below. The
analysis did not add any fire specific operator actions or recoveries
to the base plant PRA Model.
The scope of analyses that were performed by SNC for the changes to
Exemption Request 1-3 included a re-analysis of the service water
system performance. SNC's re-analysis concluded that a single service
water pump per unit was sufficient to satisfy the system performance
requirements for fire protection safe shutdown. The re-analysis results
were incorporated into the PRA Model by lowering the number of Service
Water pumps per train required for system success from two to one. The
total plant CDF from internal events that is reported below reflects
this change in the success criterion.
The licensee modified the plant PRA model to take advantage of
recent vendor data related to reactor coolant pump (RCP) seal
performance. The specific data is related to seal performance given
loss of motor bearing cooling. The licensee stated their model assumed
increased seal leakage will begin at 15 minutes after loss of all RCP
seal cooling based on information in WCAP-16141, ``RCP Seal Leakage PRA
Model Implementation Guidelines for Westinghouse PWRs'' and that they
credit recovery of RCP seal injection using the standby train of
Component Cooling Water and charging through operator action done by
procedures and performed from the main control room. Leakage due to
loss of motor bearing cooling is an additional contribution to CDF with
respect to the RCP seal loss-of-coolant accident (LOCA) PRA model. When
these two leakage models are combined, the resultant CDF contribution
slightly exceeds that from an equivalent application via the Rhodes RCP
seal LOCA model, i.e., it is conservative. The total plant CDF from
internal events that is reported below reflects this change in the
success criterion.
The performance of the PRA quantifications with the changes
described above applied the same techniques and processes as used for
the Fire IPEEE. This basically involved the setting of certain model
basic events to ``TRUE'' by translating the fire modeling results for
the MEFS into plant equipment damage states. SNC developed a fire
ignition frequency for each fire scenario by partitioning the generic
fire frequencies from the Electric Power Research Institute Fire Events
Database. The resulting CDF for each of the fire scenarios was
aggregated to obtain the cumulative risk for the proposed change. A
separate calculation for the ``baseline'' CDF was not developed.
Instead, the CDF for the changed configuration was taken as a
conservative surrogate for the increase in risk.
The total plant CDF from internal events for FNP, Unit 1 and 2 is
3.86E-05/yr and 5.81E-05/yr, respectively based on one Service Water
pump as the success criterion. A comparison of the Fire IPEEE results
with the internal events PRA results that were applicable at that time
shows that the FNP, Unit 1 Fire CDF was approximately 20 percent higher
than the corresponding FNP, Unit 1 internal events CDF. This would
result in an estimated total plant risk of 8.5E-05/yr.
The FNP, Unit 2 Fire CDF was approximately 10 percent less than the
corresponding Unit 2 internal events CDF. This would result in an
estimated total plant risk for FNP, Unit 2 of 1.1E-04/yr.
The CDF and LERF for the changed configuration was taken as a
conservative surrogate for the increase in risk, i.e. the baseline CDF
and LERF was assumed to be zero such that delta CDF and LERF was
conservatively estimated as the total CDF and total LERF for the
changed contribution (no subtraction of baseline value). As a result,
the licensee's risk analysis determined that a conservative estimate of
the CDF associated with the ten cases would be approximately 6.5E-07/yr
per unit. The licensee reports that the CDF for the cases ranged from
2.08E-08/yr per unit to 1.34E-07/yr per unit with no one case
dominating as a contributor relative to the rest. Based on the estimate
for total CDF, this places the proposed change in Region III of the RG
1.174 acceptance criteria for CDF.
In order to gain further insights, the fire areas that were the
dominant contributors to risk from the Fire IPEEE were requantified
using the current plant PRA model. This re-quantification of dominant
fire areas provided a cumulative CDF of 4.98E-05/yr and 5.87E-05/yr for
FNP, Units 1 and 2, respectively. Using these updated values, the
estimated total plant risk for FNP, Units 1 and 2 is 8.84E-05/yr and
1.17E-04/yr, respectively.
The licensee stated that the contribution to LERF from a SWIS fire
is the result of core damage combined with failure of containment
isolation. The conditional probability of containment isolation failure
(crediting only check valves and fail closed air-operated valves) is
2.13E-4. The licensee stated that this resulted in a total LERF
contribution from the seven SWIS fire scenarios analyzed for FNP, Unit
1 of 1.38E-10/yr per unit. This indicates the same LERF for FNP, Unit 2
since both units have the same CDF. SNC concluded that the LERF
associated with the proposed change is negligible given the acceptance
criteria of RG 1.174. RG 1.174, Section 2 also requires consideration
of five key principles that the change is expected to
[[Page 49328]]
meet. SNC concluded that all of the five principles have been met.
Defense-in-Depth
10 CFR Part 50, Appendix R, section II states that a licensee's
fire protection program extend the concept of defense-in-depth to fire
protection with the following objectives:
I. To prevent fires from starting,
II. To detect rapidly, control, and extinguish promptly those fires
that do occur, and
III. 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 of
the plant.
RG1.174 also identifies factors to be considered when evaluating
defense-in-depth for a risk-informed change.
SNC has evaluated defense-in-depth and stated the following:
Fire prevention is strengthened by SNC's commitment to enhance the
transient combustible control program in the SWIS northeast corner and
in the vicinity of the Service Water pumps.
SNC proposes no changes to the existing fire detection and
automatic fire suppression systems in the SWIS and will continue to
control these systems to maintain defense-in-depth. Protection for
structures, systems and components is weakened by the elimination of
the reliance on the Kaowool fire barrier in the northeast corner of the
SWIS and the strainer pit. However, the elimination of the reliance on
Kaowool has been evaluated by SNC in accordance with RG 1.174 or by
deterministic re-analysis. Protection for structures, systems and
components is strengthened by reducing the population of equipment
requiring protection due to deterministic re-analyses (i.e., single
Service Water pump and motor operated valve circuit analysis) and plant
modifications (FNP, Unit 2 elimination of lube and cooling pumps); and
by modifying the existing barriers between the pump deck and switchgear
rooms and between disconnect switch rooms to 3-hour fire rated
barriers; and by installing a floor curb on the FNP, Unit 1 side of the
pump deck to limit fire exposure to the Train A cables along the east
wall.
Safety Margins
RG 1.174 provides acceptable guidelines to ensure sufficient safety
margins are maintained. RG 1.174 states that the proposed change
provide sufficient margin to account for analysis and data uncertainty.
The licensee concluded that for Scenario 1, a heat release rate to four
times that modeled in the MEFS is needed to reach the LFS; for Scenario
2 an increase in combustible oil lubricant volume of 75 percent for a
C-pump fire scenario and an increase four times the volume of
combustible oil lubricant for an A-,B-,D-or E-pump fire scenario are
needed to reach the LFS; and for Scenario 3 a minimum increase five
times the volume of combustible oil lubricant to reach the LFS.
SNC addressed uncertainty for Exemption Request 1-3, Item 9 and
Item ``Other'' by considering the degree to which the fire models/
calculations used bound the uncertainty in the input parameters. The
licensee conducted an evaluation on the input parameters and concluded
that the models/calculations that were used bounded the uncertainty
except for the limiting oxygen index (LOI) parameter. However, the
licensee concluded that the LOI assumption below a certain threshold is
not possible for the temperatures predicted and is therefore not
credible.
Uncertainty was further addressed by determining an LFS for each
fire scenario. The LFS was determined by increasing one or more of the
parameters that characterize the fire used for the MEFS until a failure
condition is attained.
A sensitivity analysis was also conducted to determine that the
conclusions would not be altered. In the case of the SWIS fire
scenarios, sensitivity was conducted on the natural and forced
ventilation conditions, the composition of the transient Class A fuel
package (for Scenario 1) and the absorptance of the targets. As a
result of the sensitivity analysis, SNC determined that some adjacent
pump motor targets could be heated to the critical temperature. SNC
then conservatively concluded that these targets would fail despite the
results of the MEFS to the contrary. SNC concluded that other targets
were not affected.
Evaluation of Exemption Request 1-3 Items
The NRC staff examined the licensee's submittals to determine if
the revised Exemption Request 1-3 in Fire Area 72 of the SWIS would
meet the underlying purpose of the 10 CFR part 50, appendix R rule.
The NRC staff has evaluated each of the revised items of Exemption
Request 1-3 on a case by case basis by ensuring adherence to the fire
modeling approach discussed in NFPA 805, ensuring that RG 1.174
criteria are met, assessing that a reasonable balance among the
elements of defense-in-depth is maintained, and ensuring safety margins
are maintained, where appropriate.
Item 1
SNC proposes to implement modifications to each of the five FNP,
Unit 2 service water pumps by December 2006 that will result in
removing the need for the redundant lubricating oil and coolant pumps,
valves and control stations for FNP, Unit 2. The licensee concluded
that modifications will eliminate the need to consider fire-induced
impacts from a fire on the FNP, Unit 2 lubricating oil and coolant
pumps, valves and their control stations as well as removing these
pumps as ignition sources and combustible loadings. Based on the plant
modifications, SNC concluded that the conditions of Exemption Request
1-3, Item 1 will no longer be applicable following completion of those
plant modifications. On these bases, the NRC staff concludes that, upon
completion of the modifications to the pumps as discussed above, there
will be no further need for the exemption provided in the first
paragraph of Section 2.3 of the NRC staff's December 29, 1986,
exemption and, accordingly, it would be deleted.
Item 2: FNP, Unit 2 Side of Strainer Pit
For the strainer inlet valves and swing pump discharge valves in
the FNP, Unit 2 side of the strainer pit, SNC stated in its December
28, 2004, response to question 26 and in its June 9, 2005, response to
question 2, that it had performed a deterministic re-analysis on the
cables for these valves. SNC's review of the circuitry located in the
strainer pit determined that spurious operation of the valves could not
result if the power cables to the valve motors and control cables to
the valve position switches were subjected to hot shorts, open
circuits, or shorts to ground. SNC stated that power is removed during
normal operation from swing service water pump discharge valves
Q2P16V507-A and Q2P16V506-B and that spurious operation of the valves
due to a 3-phase hot short does not require evaluation in accordance
with the guidance in Generic Letter 86-10, Section 5.3.1. SNC stated
that the main and control power to strainer inlet valves Q2P16V511-A
and Q2P16V508-B is not isolated during normal operation and that open
circuits or short circuits will not result in spurious operation of the
valves and that a 3-phase hot short does not require evaluation in
accordance with the guidance in Generic Letter 86-10, Section 5.3.1.
The licensee further states that for the control cables to limit
switches, hot shorts, open circuits or shorts to ground could not
result in
[[Page 49329]]
spurious operation because the cables do not contain the conductors
necessary to energize the motor starters due to open control room
switch contacts. Based on SNC's analysis, SNC concluded that reliance
on Kaowool as part of the basis for Exemption Request 1-3, Item 2 is no
longer necessary. The NRC staff concludes that on the basis of SNC's
deterministic-based findings that the valves will not be repositioned
due to a fire, the fire detection and suppression features for Fire
Area 72A and the defense-in-depth measures as discussed above, that a
continued exemption from the requirements of appendix R, section
III.G.2.c for this item is acceptable.
Item 3: FNP, Unit 1 side of strainer pit
For the strainer inlet valves and swing pump discharge valves in
the FNP, Unit 1 side of the strainer pit, SNC stated in its December
28, 2004, response to question 26 and in its June 9, 2005, response to
question 2, that it had performed a deterministic re-analysis on the
cables for these valves. SNC's review of the circuitry located in the
strainer pit determined that spurious operation of the valves could not
result if the power cables to the valve motors and control cables to
the valve position switches were subjected to hot shorts, open
circuits, or shorts to ground. SNC stated that power is removed during
normal operation from swing service water pump discharge valves
Q1P16V507-A and Q1P16V506-B and that spurious operation of the valves
due to a 3-phase hot short does not require evaluation in accordance
with the guidance in Generic Letter 86-10, Section 5.3.1. SNC stated
that the main and control power to strainer inlet valves Q1P16V511-A
and Q1P16V508-B is not isolated during normal operation and that open
circuits or short circuits will not result in spurious operation of the
valves and that a 3-phase hot short does not require evaluation in
accordance with the guidance in Generic Letter 86-10, Section 5.3.1.
The licensee further states that for the control cables to limit
switches, hot shorts, open circuits or shorts to ground could not
result in spurious operation because the cables do not contain the
conductors necessary to energize the motor starters due to open control
room switch contacts. Based on SNC's analysis, SNC concluded that
reliance on Kaowool as part of the basis for Exemption Request 1-3,
Item 3 is no longer necessary. The NRC staff concludes that on the
basis of SNC's deterministic-based findings that the valves will not be
repositioned due to a fire, the fire detection and suppression features
for Fire Area 72A and the defense-in-depth measures as discussed above,
that a continued exemption from the requirements of Appendix R, Section
III.G.2.c for this item is acceptable.
Item 4: Discharge Valves to Wet Pit and Storage Pond Flume
For Fire Zone 72A, SNC performed a deterministic re-analysis on the
redundant safe shutdown service water Train A and Train B cables,
associated with service water discharge to the wet pit and storage pond
flume, shared by Unit 1 and Unit 2. The December 29, 1986, exemption,
page 11, first paragraph, reflected SNC's original finding that there
was a potential for these valves to be mis-positioned by fire effects
and that this could be acceptably dealt with by manually realigning the
valves, if needed, within a required 24-hour period. SNC's submittals,
specifically its June 9, 2005, submittal states that the main and
control power to valves QSP16V505-A, QSP16V507-A, QSP16V506-B and
QSP16V508-B is not isolated during normal operation and that open
circuits or short circuits will not result in spurious operation of the
valves and that a 3-phase hot short does not require evaluation in
accordance with the guidance in Generic Letter 86-10, Section 5.3.1.
SNC further states that for the control cables to limit switches, hot
shorts, open circuits or shorts to ground could not result in spurious
operation because the cables do not contain the conductors necessary to
energize the motor starters due to open control room switch contacts.
For the control cables to control room switches and other interlocks,
the licensee concluded from its deterministic analysis that hot shorts
could result in spurious operation of the valves. However, the licensee
used fire modeling, as discussed in the section above on the modeling
of fire scenarios, to demonstrate that fire induced cable damage from a
fire could not result in spurious operation of both trains of valves
and that there would not be a need to perform the long-term manual
operator actions previously relied upon. Based on SNC's analysis, SNC
concluded that reliance on Kaowool as part of the basis for Exemption
Request 1-3, Item 4 is no longer necessary. The NRC staff concludes
that on the basis of SNC's deterministic and fire modeling analysis
results as discussed above, the fire detection and suppression features
for Fire Area 72, defense-in-depth measures as discussed above, and
enhanced combustible controls, that a continued exemption from the
requirements of appendix R, section III.G.2.c for this item is
acceptable.
Items 5 and 6: Swing Service Water Pumps
SNC's compliance strategy is unchanged for these two items.
Therefore, the previous portion of the exemption issued on page 11,
paragraphs two and three, of the December 29, 1986, exemption is
unchanged and remains in effect. Accordingly, there is no further
consideration in this Safety Evaluation for this item.
Item 7: Swing Service Water Pump Cables in Fire Zones 72D and 72E
SNC states in its August 28, 2003, submittal that the current
exemption and its bases (included on page 11, last paragraph, and page
12, first paragraph of the December 29, 2005, exemption) remain
unchanged because they do not involve Kaowool. The previous conditions
for this item discussed in the NRC letter dated December 29, 1986,
remain unchanged and there is no further consideration in this safety
evaluation of those conditions. However, SNC has committed to implement
plant modifications that will upgrade certain fire barriers to 3-hour
fire ratings as previously discussed in this exemption. The creation of
the three hour fire barriers will enhance the overall defense-in-depth
of the SWIS.
Item 8: Swing Service Water Pump Cables in Fire Zones 72B and 72C
SNC states in its August 28, 2003, submittal that the current
exemption and its bases (included on page 12, second paragraph, of the
December 29, 2005, exemption) remain unchanged because they do not
involve Kaowool. The previous condition for this item discussed in the
NRC letter dated December 29, 1986, remains unchanged and there is no
further consideration in this safety evaluation of those conditions.
However, SNC has committed to implement plant modifications that will
upgrade certain fire barriers to 3-hour fire ratings as previously
discussed in this exemption. The creation of the 3-hour fire barriers
will enhance the overall defense-in-depth of the SWIS.
Item 9: Raceways for Train A Service Water Pumps
The exemption for service water pumps that was included on page 12,
third paragraph of the December 29, 1986, exemption was based, in part,
on the raceways servicing the Train A service water pumps for both
units being protected with a Kaowool blanket
[[Page 49330]]
fire barrier. SNC performed an evaluation for these raceways using a
combined fire modeling and risk assessment analysis approach to revise
the conditions for Exemption Request 1-3, Item 9. This approach does
not take any credit for the Kaowool fire barrier and is addressed in
the above Fire Modeling section discussion of scenarios 2 and 3. Based
on SNC's Fire Modeling analysis, SNC concluded that at least one
service water pump would not be adversely impacted by this fire
scenario. As discussed in the above Risk Assessment section, SNC has
also concluded that a single service water pump per unit is sufficient
to satisfy the system performance requirements for fire protection. The
NRC staff concludes that on the basis of SNC's deterministic and fire
modeling analysis results as discussed above, the fire detection and
suppression features for Fire Area 72, defense-in-depth measures as
discussed above, and enhanced combustible controls, that a continued
exemption from the requirements of appendix R, section III.G.2.c for
this item is acceptable.
Addendum to Exemption Request 1-3, Fire Area 72
SNC included an Addendum to Exemption Request 1-3 in its October
18, 1985, submittal wherein SNC noted that adequate coordination was
not provided between certain safe shutdown and non-safe shutdown
circuits. The December 29, 1986, exemption noted that a design change
had been initiated to improve breaker coordination, which would
eliminate the concern. SNC's August 28, 2003, submittal stated that the
design change had been completed. Accordingly, the NRC staff finds that
the conditions requiring the exemption item that begins with the last
paragraph of page 12 of the December 29, 1986, exemption are no longer
present and, accordingly, this part of the exemption is no longer
necessary.
SWIS Northeast Corner Raceways
SNC stated in its August 23, 2003, submittal that in addition to
the nine situations that were addressed in the exemption issued on
December 29, 1986, that it had also considered the FNP, Units 1 and 2
redundant Train A and Train B cables near the ceiling of the northeast
corner of the SWIS. The northeast corner of the SWIS includes a
``pinch-point'' where FNP, Units 1 and 2 Train A and Train B cables
approach each other as they run along perpendicular walls from the
corner. The cables are 20 feet above the strainer pit floor. SNC
performed an evaluation using fire modeling as discussed in the above
Fire Modeling section, scenario one, to support the addition of this
condition to the exemptions for Fire Area 72. Based on the fire
modeling results, SNC concluded that the cables would not be adversely
impacted by an SNC's analysis to support this exemption item and SNC's
program modifications, SNC concluded that it is unlikely the cables of
interest would be damaged by a maximum expected fire scenario. The NRC
staff concludes that on the basis of SNC's fire modeling analysis
results as discussed above, the fire detection and suppression features
for Fire Area 72, defense-in-depth measures as discussed above, and
enhanced combustible controls, that an exemption from the requirements
of Appendix R, Section III.G.2.c for this item is acceptable.
Modifications
SNC will implement programmatic and design modifications as
outlined in letters dated August 28, 2003, and December 28, 2004. These
modifications include: (1) Modification of the FNP, Unit 2 service
water pumps to eliminate their reliance on lubrication and cooling
support pumps, (2) upgrading of the nominal 18-inch concrete wall
between Fire Zone 72A and Fire Zones 72B, C, D and E to meet the
requirements of FNP's Fire Protection Program for a minimum 3-hour fire
area boundary. Penetrations will be sealed, un-rated doors will be
replaced by 3-hour rated fire doors, and three new fire areas will be
defined, 72A, 72B/72C and 72D/72E. In addition, the scope of the
barrier surveillance program will be enhanced to ensure that the
conditions of the risk-informed, performance-based assessment are
maintained, (3) installation of a new floor curb on the FNP, Unit 1
pump deck to prevent liquid spill fires associated with the FNP, Unit 1
pumps from pooling beneath the Train A cable tray located near the east
wall, (4) specific transient combustible controls will be implemented
to restrict transient combustibles from being stored or located in the
SWIS northeast corner and in the vicinity of the service water pumps.
Configuration control will be maintained (from a fire protection
program perspective) over the type and quantity of lubrication oil used
in the service water pump motors. Precautions will be implemented to
limit the amount of lubricant in the vicinity of the service water
pumps during lubricant changes by removing the drained lubricant from
the area prior to bringing the new (unused) lubricant into Fire Zone
72A. Transient fuel packages associated with maintenance activities
will be controlled via procedural changes, and (5) SNC identified eight
low-voltage PVC/PVC cables in a tray along the north and west wall that
are thermoplastic. SNC stated that portions of the cable will be
removed to meet the fire model analysis.
The evaluation that SNC prepared assesses the impact of the change.
This evaluation uses a combination of risk-insights and deterministic
methods to show that sufficient safety margins and defense-in-depth are
maintained.
The results of the risk-informed portions of the analysis are
consistent with a change that would be acceptable when compared to the
acceptance criteria described in RG 1.174, ``An Approach for Using
Probabilistic Risk Assessment in Risk-Informed Decisions on Plant-
Specific Changes to the Licensing Basis,'' Revision 1.
The NRC staff examined SNC's rationale to support the changes to
Exemption Request 1-3 and concludes that adequate defense in depth and
safety margins exist and that the underlying purpose of Appendix R,
Section III.G.2.c is met. Fire modeling demonstrates that it is
unlikely that the cables of interest in the northeast corner will be
damaged by a fire and that at least one service water pump for each
unit will not be damaged by a fire. Also, fire detection and automatic
fire suppression systems in the areas of interest remain to provide
defense-in-depth. Based upon the above considerations, the NRC staff
concludes that the revisions to Exemption Request 1-3 meet the
underlying purpose of the rule. Therefore, the NRC staff concludes that
pursuant to 10 CFR 50.12(a)(2) this exemption is acceptable.
4.0 Conclusion
Accordingly, the Commission has determined that, pursuant to 10 CFR
50.12(a), the changes to Exemption Request 1-3 are authorized by law,
will not present an undue risk to the public health and safety, and are
consistent with the common defense and security. Also, special
circumstances are present. Therefore, the Commission hereby grants SNC
a revised exemption 1-3 from the requirements of appendix R, section
III.G.2.c to 10 CFR Part 50 to provide 1-hour fire separation in Fire
Area 72 for the FNP, Units 1 and 2, subject to the full implementation
of the programmatic and plant design modifications discussed above.
Acceptance of this revised Exemption Request 1-3 is based on the
programmatic and plant design modifications, the deterministic re-
analyses, the risk-informed plant change evaluation and its results
specific to the
[[Page 49331]]
SWIS, enhanced controls on transient combustibles, the existing fire
detection and automatic fire suppression capability to maintain
defense-in-depth, and the availability of manual fire fighting and
associated fire fighting equipment.
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 (70 FR 46892).
This exemption is effective upon issuance.
Dated at Rockville, Maryland, this 16th day of August, 2005.
For the Nuclear Regulatory Commission.
Ledyard B. Marsh,
Director, Division of Licensing Project Management, Office of Nuclear
Reactor Regulation.
[FR Doc. E5-4597 Filed 8-22-05; 8:45 am]
BILLING CODE 7590-01-P