[Federal Register Volume 75, Number 128 (Tuesday, July 6, 2010)]
[Notices]
[Pages 38845-38850]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2010-16352]


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NUCLEAR REGULATORY COMMISSION

[Docket No. 50-289; NRC-2010-0221]


Exelon Generation Company, LLC; Three Mile Island Nuclear 
Station, Unit No. 1; Exemption

1.0 Background

    Exelon Generation Company, LLC (Exelon, the licensee) is the holder 
of Facility Operating License No. DPR-50 which authorizes operation of 
the Three Mile Island Nuclear Station, Unit 1 (TMI-1). The license 
provides, among other things, that the facility is subject to all 
rules, regulations, and orders of the U.S. Nuclear Regulatory 
Commission (NRC, the Commission) now or hereafter in effect.
    The facility consists of a pressurized-water reactor (PWR) located 
in Dauphin County, Pennsylvania.

2.0 Request/Action

    Title 10 of the Code of Federal Regulations (10 CFR) part 50, 
Section 50.48, requires that nuclear power plants that were licensed 
before January 1, 1979, must satisfy the requirements of 10 CFR part 
50, appendix R, section III.G, ``Fire protection of safe shutdown 
capability.'' TMI-1 was licensed to operate prior to January 1, 1979. 
As

[[Page 38846]]

such, the licensee's Fire Protection Program (FPP) must satisfy the 
established fire protection features of 10 CFR part 50, appendix R, 
section III.G.
    TMI-1 proposes to utilize an operator manual action (OMA) in lieu 
of meeting the circuit separation and/or protection requirements 
contained in 10 CFR part 50, appendix R, section III.G.2 (III.G.2), 
which requires ensuring that one of the redundant trains of systems 
necessary to achieve and maintain hot shutdown is maintained free of 
fire damage. In this case, the OMA is proposed for a fire occurring in 
Fire Zone 6 of the plant's Auxiliary Building (AB-FZ-6). The prescribed 
action involves opening a breaker and manually opening valve MU-V-36 
within 40 minutes to support maintaining a makeup pump minimum 
recirculation path. By letter dated December 30, 1986 (ADAMS Legacy 
Library Accession No. 8701090216), this OMA was previously approved by 
the NRC; however, the time requirement has been shortened, 
necessitating this exemption.
    In summary, by letter dated March 3, 2009 (Agencywide Documents 
Access and Management System (ADAMS) Accession No. ML090630134), as 
supplemented by letter dated March 15, 2010 (ADAMS Accession No. 
ML100750093), Exelon requested an exemption for TMI-1 from certain 
technical requirements of III.G.2 for the use of an OMA in lieu of 
meeting the circuit separation and/or protection requirements contained 
in III.G.2 for AB-FZ-6.

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 the application of the regulation is not 
necessary to achieve the underlying purpose of the rule.
    In its March 15, 2010, letter, the licensee discussed financial 
implications associated with plant modifications that may be necessary 
to comply with the regulation. If such costs have been shown to be 
significantly in excess of those contemplated at the time the 
regulation was adopted, or are significantly in excess of those 
incurred by others similarly situated, this may be considered a basis 
for considering an exemption request. However, financial implications 
were not considered in the regulatory review of their request since no 
substantiation was provided regarding such financial implications. Even 
though no financial substantiation was provided, the licensee did 
submit sufficient regulatory basis to support a technical review of 
their exemption request in that the application of the regulation in 
this particular circumstance is not necessary to achieve the underlying 
purpose of the rule.
    In accordance with 10 CFR 50.48(b), nuclear power plants licensed 
before January 1, 1979, are required to meet section III.G, of 10 CFR 
part 50, appendix R. The underlying purpose of 10 CFR part 50, appendix 
R, section III.G is to ensure that the ability to achieve and maintain 
safe shutdown is preserved following a fire event. The regulation 
intends for licensees to accomplish this by extending the concept of 
defense-in-depth to:
    (1) Prevent fires from starting;
    (2) Rapidly detect, control, and extinguish promptly those fires 
that do occur;
    (3) 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.
    The stated purpose of III.G.2 is to ensure that one of the 
redundant trains necessary to achieve and maintain hot shutdown 
conditions remains free of fire damage in the event of a fire. Section 
III.G.2 requires one of the following means to ensure that a redundant 
train of safe shutdown cables and equipment is free of fire damage, 
where redundant trains are located in the same fire area outside of 
primary containment:
    (1) Separation of cables and equipment by a fire barrier having a 
3-hour rating;
    (2) Separation of cables and equipment by a horizontal distance of 
more than 20 feet with no intervening combustibles or fire hazards and 
with fire detectors and an automatic fire suppression system installed 
in the fire area; or
    (3) Enclosure of cables and equipment of one redundant train in a 
fire barrier having a 1-hour rating and with fire detectors and an 
automatic fire suppression system installed in the fire area.
    Exelon has requested an exemption from the requirements of III.G.2 
for TMI-1 to the extent that one of the redundant trains of systems 
necessary to achieve and maintain hot shutdown is not maintained free 
of fire damage in accordance with one of the required means, for a fire 
occurring in Fire Zone AB-FZ-6 in the Auxiliary Building. In its March 
15, 2010, response to the NRC's request for additional information, the 
licensee stated that the purpose of its request was to credit the use 
of an OMA, in conjunction with other forms of defense-in-depth, in lieu 
of the separation and protective measures required by III.G.2 for a 
fire in Fire Zone AB-FZ-6. Specifically, Fire Zone AB-FZ-6 is not 
protected throughout by an automatic fire suppression system and rated 
fire barriers or 20 feet of spatial separation are not provided between 
the redundant equipment. The OMA entails locally opening a feeder 
breaker (1P 480V Switchgear Unit 4C) located in Fire Zone CB-FA-2a and 
a valve (MU-V-36), which is located in Fire Zone AB-FZ-3, to establish 
a makeup pump recirculation flow path.
    In summary, TMI-1 does not meet the requirements of III.G.2 for a 
fire in Fire Zone AB-FZ-6 and an OMA may be necessary to achieve and 
maintain hot shutdown capability. The licensee also indicated that the 
only credible scenario for a fire in Fire Zone AB-FZ-6 that may require 
the need to manually open valve MU-V-36 is as follows: the fire must 
initiate within the MU-V-36 breaker compartment of the 1A Engineered 
Safeguards Valve (ESV) motor control center (MCC), cause a fault on an 
energized circuit to make MU-V-36 close, cause power failure of the 1A 
ESV MCC, spread to and damage the instrument air tubing causing valves 
MU-V-18 and MU-V-20 to close, and cause failure of the 1B ESV MCC power 
circuit, which is contained within a 4-inch galvanized steel conduit.
    See Section 3.3 below for additional details addressing the spatial 
separation between cables and instrument air tubing. In addition, the 
TMI-1 analysis assumes that fire damage may occur immediately upon 
first detection of the fire to all components in the fire area. The 
licensee stated that after confirmation of a fire, the fire abnormal 
operating procedure (AOP) for Fire Zone AB-FZ-6 would be entered.
    The licensee has described in its initial request, and subsequent 
documents, elements of the fire protection program that provide 
justification that the concept of defense-in-depth that is in place in 
Fire Zone AB-FZ-6 is consistent with that intended by the regulation. 
To accomplish this, the licensee provides various forms of protection 
in order to maintain the concept of defense-in-

[[Page 38847]]

depth. The licensee's approach is discussed below.

3.1 Fire Prevention

    The licensee has stated that it has an administrative controls 
program in place to control ignition sources, hot work activities 
(activities such as welding or grinding), in situ and transient 
combustibles, and fire system impairments. The administrative controls 
program is described in the TMI-1 Updated Final Safety Analysis Report 
(UFSAR) and in the Fire Hazards Analysis Report (FHAR), which is 
incorporated by reference into the UFSAR. Transient combustibles are 
restricted in Fire Zone AB-FZ-6 and particularly in the 1A ESV MCC 
area.
    In addition to these measures, the licensee has stated that the 
power and control cables with voltages up to 480V AC and 480/120V in 
the fire zone are thermoset (Kerite with ethylene propylene rubber 
(EPR) insulation). Thermoset cables are resistant to self-ignited cable 
fires and are not considered to represent an ignition source. Other 
ignition sources in the area consist of control power transformers 
inside the 1A ESV MCC. The licensee also stated that the transformers 
are contained within the metal-clad MCC housing and contain no 
combustible or flammable liquids and that the control cables are 
located in open trays while the 480V power cables are in conduit or use 
armor jacketed cable. Therefore, due to limited ignition sources and 
the cables installed in conduit and armored jacketed cables, flame 
propagation is not expected to present a hazard.

3.2 Detection, Control and Extinguishment

    Fire Zone AB-FZ-6 is provided with a ceiling-mounted photoelectric 
smoke detection system, which is connected to the Auxiliary Building 
fire detection panel, located near the 1A ESV MCC. The licensee has 
indicated that if smoke is detected, a local horn and strobe light are 
actuated at the fire alarm panel as well as in the control room. There 
are two smoke detectors located within a few feet horizontally and 
approximately 13 feet vertically above the 1A ESV MCC. The smoke 
detection system is designed and installed in accordance with National 
Fire Protection Association (NFPA) 72D (1975), ``Proprietary Protective 
Signaling Systems for Guard, Fire Alarm and Supervisory Service,'' and 
NFPA 72E (1978), ``Automatic Fire Detectors.''
    A hose reel, with at least 100 feet of hose, is provided in 
adjacent Fire Zone AB-FZ-9. The hose reel is less than 100 feet from 
the 1A ESV MCC area or any other area in Fire Zone AB-FZ-6. The hose 
reels were designed and installed in accordance with NFPA 14 (1978), 
``Standpipe and Hose Systems,'' and have electrically-safe fog nozzles 
installed, which make them safe to use in the vicinity of electrical 
equipment. Portable dry chemical and carbon dioxide fire extinguishers 
are also permanently mounted in Fire Zone AB-FZ-6 and adjacent fire 
zones. These extinguishers have been installed in accordance with NFPA 
10, ``Standard for Portable Fire Extinguishers.'' The licensee stated 
that all fire protection equipment is maintained in accordance with the 
site FPP to ensure operability.
    A water curtain is provided for fire protection of the zone 
boundary between Fire Zones AB-FZ-6 and AB-FZ-7. The pre-action water 
curtain system between Fire Zones AB-FZ-6 and AB-FZ-7 is actuated by 
the cross-zone smoke detection system but is not credited for fire 
suppression within Fire Zone AB-FZ-6. The water curtain is only 
provided for fire protection of the zone boundary between Fire Zones 
AB-FZ-6 and AB-FZ-7 and all other openings are sealed with material 
having at least a 1-hour fire rating.
    The remaining zone boundaries consist of reinforced concrete walls, 
floors and ceilings. The south boundary and portion of the ceiling are 
not adjacent to any other plant areas. The remainder of the ceiling 
adjacent to the chemical addition area and Emergency Safeguards 
Features (ESF) Ventilation Room is a 3-hour fire barrier. Most of the 
north boundary is adjacent to Fire Zone AB-FZ-7 with an open passage, 
discussed above, between the zones. The remainder of the north boundary 
is adjacent to the Reactor Building, which is a 3-hour rated fire 
barrier. The east boundary is adjacent to Fire Zones FH-FZ-1 and FH-FZ-
2 and is made of reinforced concrete. A 3-hour rated fire barrier is 
provided on the floor where this zone is adjacent to Fire Zones AB-FZ-
2a, AB-FZ-2b and AB-FZ-2c. An automatic pre-action system is located in 
Fire Zone AB-FZ-4 where the floor of Fire Zone AB-FZ-6 is adjacent to 
Fire Zone AB-FZ-4.

3.3 Preservation of Safe Shutdown Capability

    The licensee has stated that the postulated fire event that may 
require the OMA to open MU-V-36 would include at least four independent 
failures to occur; two of which are sequence dependent (i.e., MU-V-36 
hot short occurs prior to loss of MCC) as described below:
     While 1A ESV MCC is energized, the fire causes a hot short 
(within 1A ESV MCC), which establishes proper voltage in the closing 
circuit and causes MU-V-36 to travel closed (MU-V-36 control cable 
CQ232A).
     After MU-V-36 is closed, the fire causes loss of 1A ESV 
MCC (cable LP8 within MCC), which is located in the fire zone. This 
eliminates remote control of MU-V-16A and MU-V-16B and would isolate 
the `A' train emergency makeup (High Pressure Injection [HPI]) flow 
path (valves normally closed).
     The fire causes a loss of integrity of the \1/4\-inch 
outside diameter copper tubing which causes a sufficient reduction in 
the Auxiliary Building instrument air supply pressure for MU-V-18 to 
close and eventually for MU-V-20 to close. Loss of control of MU-V-18 
eliminates the use of the normal Reactor Coolant System (RCS) makeup 
flow path and depressurization of the MU-V-20 actuator would cause seal 
injection flow to the RCP to be isolated.
     Fire causes loss of power to 1B ESV MCC (cable LS7A). This 
eliminates remote control of MU-V-16C and MU-V-16D and would eliminate 
the `B' train emergency makeup (HPI) flow path as an alternate means of 
RCS makeup (valves normally closed).
    In order for a fire to cause MU-V-36 to close, the licensee has 
indicated that `` * * * the fire must cause an intra-cable hot short 
between a normally energized conductor in multi-conductor cable CQ232A 
and the conductor that picks up the closing coil. This would short out 
the remote control switch and energize the closing coil for MU-V-36. 
The fire must maintain this hot short without grounding the circuit and 
blowing the control power fuses or otherwise causing a loss of control 
power, such as loss of the main 1A ESV MCC power cable LP8. The MU-V-36 
circuits of concern are located within the MCC breaker compartment 
along with the control power fuses. It is unlikely that a fire could 
sufficiently damage cable CQ232A insulation and short the proper 
conductors to energize the closing coil for MU-V-36 prior to blowing 
the control power fuses. Because the fire must cause a hot short to 
close MU-V-36 prior to loss of control power, the most likely fire 
ignition location within Fire Zone AB-FZ-6 is in the MU-V-36 breaker 
compartment. Fires in other areas of 1A ESV MCC would be likely to trip 
the main bus breaker or otherwise damage the 1A ESV MCC power cable LP8 
prior to affecting MU-V-36 circuits.''
    Next, the licensee has indicated that ``[t]he primary combustible 
in Fire Zone AB-FZ-6 is 1A ESV MCC and

[[Page 38848]]

associated cables * * * [t]he tubing closest to 1A ESV MCC is \1/4\-
inch outside diameter tubing used for testing reactor building pressure 
switches. This tubing is at least 6 feet from the MCC with no 
intervening combustibles. The loss of integrity of these \1/4\-inch 
outside diameter tubing lines may not be sufficient to exceed the 
capacity of the instrument air supply and reduce the instrument air 
supply pressure to MU-V-18 (normal RCS makeup isolation valve) below 60 
psig [pounds per square inch gauge]. Both instrument air compressors 
are unaffected by a fire in Fire Zone AB-FZ-6 and would attempt to 
maintain the instrument air supply to MU-V-18. The loss of instrument 
air system integrity occurs in a section supplied through \3/8\-inch 
regulators and \1/4\-inch outside diameter tubing. The main instrument 
air system distribution headers are 2-inch lines. This specific failure 
may not be sufficient to reduce the air supply pressure to MU-V-18 
enough to prevent adequate RCS makeup flow. The next closest copper 
tubing in Fire Zone AB-FZ-6 is against the containment wall. This 
tubing is further separated from 1A ESV MCC by at least 10 feet of 
distance with no intervening combustibles. Based on the existing 
separation with no intervening combustibles and outside diameter of the 
instrument air lines within Fire Zone AB-FZ-6, it is unlikely that a 
fire in 1A ESV MCC would cause a loss of Auxiliary Building instrument 
air pressure.''
    The licensee further indicated that ``[t]he power cable for 1B ESV 
MCC (LS7A) is routed through Fire Zone AB-FZ-6. The cable comes through 
the 1-hour-rated wall (similar to UL-tested configuration U-410) 
separating Fire Zones AB-FZ-6a and AB-FZ-6 in 4-inch galvanized steel 
conduit as it passes through the area near 1A ESV MCC. As it turns away 
from 1A ESV MCC (at least 6 feet of separation with no intervening 
combustibles), it exits the conduit and enters a tray (via a splice 
box). There is at least 12 feet of vertical separation with no 
intervening combustibles between the top of 1A ESV MCC and the 4-inch 
conduit that holds LS7A. Based on the existing separation and conduit 
protection, it is unlikely that the 1B ESV MCC power cable would be 
damaged, even if 1A ESV MCC were fully consumed in a fire.''
    Additionally, the Auxiliary Building ventilation system is not 
credited for smoke removal. If the primary safe shutdown (SSD) operator 
becomes aware of smoke in the Auxiliary Building, the operator will don 
a self-contained breathing apparatus (SCBA) to perform actions when 
directed by the control room. Two SCBAs are staged near the primary 
operator station on Auxiliary Building 305' elevation. All operators 
assigned to fire brigade or SSD duties are qualified to use a SCBA. 
Validation exercises have been performed to demonstrate that operators 
can reliably don a SCBA in less than 3 minutes.
    Given the lack of combustibles, separation of cables described 
above, and the sequence of events required, it is unlikely that the OMA 
to open MU-V-36 would be required. It is also likely that a fire would 
be detected and suppressed before the sequence of events and failures 
described above fully evolved. In the unlikely occurrence that the 
sequence does fully evolve, the OMA is available to provide assurance 
that safe shutdown can be achieved.

3.4 Feasibility and Reliability of the OMAs

    This analysis postulates that the features described in Sections 
3.1, 3.2 and 3.3, are not sufficient to assure safe shutdown 
capability. The licensee has proposed an OMA to be performed in 
addition to the above discussed fire protection features.
    NUREG-1852, ``Demonstrating the Feasibility and Reliability of 
Operator Manual Actions in Response to Fire,'' provides criteria and 
associated technical bases for evaluating the feasibility and 
reliability of post-fire OMAs in nuclear power plants. The following 
provides the TMI-1 analysis of these criteria for justifying the OMA 
specified in this request for Fire Zone AB-FZ-6.
3.4.1 Bases for Establishing Feasibility and Reliability
    The licensee's analysis addresses factors such as environmental 
concerns, equipment functionality and accessibility, available 
indications, communications, portable equipment, personnel protection 
equipment, procedures and training, staffing and demonstrations.
    In their March 3, 2009, letter, and further supported by their 
March 15, 2010, letter, the licensee stated that environmental 
considerations such as radiological concerns, emergency lighting, 
temperature and humidity conditions and smoke and toxic gases were 
evaluated and found to not represent a negative impact on the 
operators' abilities to complete the OMA. The licensee stated that 
radiation levels expected during travel to or at the OMA location in 
the Auxiliary Building are minimal with dose rates that would be less 
than 10 millirem per hour. The licensee also confirmed that sufficient 
emergency lighting exists at the areas where actions are performed and 
along the travel routes to the areas. The licensee has stated that 
operators also have access to 8-hour battery-powered portable lights, 
as well. The licensee also has confirmed that temperature and humidity 
conditions will not challenge the operators performing the OMA. The 
licensee stated that radio and page communications are available for 
this OMA. Additionally, the licensee indicated that heat and smoke or 
gas generation from the fire will not impact the operator performing 
the OMA. This is further supported by the fact that the location of the 
postulated fire event is in a different fire zone than the locations 
for where actions are performed.
    The licensee stated that the functionality of equipment and cables 
needed to perform the required OMA is documented in the OMA procedures, 
which reflect equipment availability and provide specific direction 
where functionality of equipment and cables may be compromised by fire. 
In addition, in-plant OMA walk downs were performed and demonstrated 
that the OMA equipment was accessible. The physical location of the 
components where the OMA is to be performed is identified in the fire 
AOPs and where components cannot be operated from the floor, installed 
ladders or portable ladders are provided. Other than keys, portable 
lighting, and portable ladders, the operators use no other additional 
support equipment. The fire AOPs identify when a key is required to 
perform the OMA. Keys required by operators are in the possession of 
the operator and the specific key number required for the OMA is 
identified in the fire AOP.
    With regard to available indications, the licensee has stated that 
available diagnostic instrumentation is listed in the fire AOP for each 
fire area; however, instrumentation or indications are generally not 
relied upon to perform the OMA. Explicit steps in the fire AOPs direct 
the operators on how to perform the OMA such that one train of 
available indications is always available for a fire in a given fire 
area or zone. The licensee stated that the OMA does not require any 
indication to support completion of the OMA; however, lack of 
indication may be used to initiate an action and that successful 
accomplishment of the OMA is directly observable by the operator 
performing the OMA. The successful completion of the action is then 
reported to the Control Room operators. Additionally, emergency

[[Page 38849]]

makeup flow indication is available for a fire in Fire Zone AB-FZ-6.
    With regard to communications, the licensee stated that TMI-1 has 
portable radio and installed phones available as part of the normal 
plant communications available between the Control Room and the 
operators and the radio and phone systems are robustly designed such 
that they should be available following most fire scenarios. If the 
various communication systems are not available, the method of 
communication will be face-to-face or using radios via line-of-sight 
(i.e., no repeaters). The licensee simulated face-to-face communication 
was simulated by having operators start the manual action from directly 
outside the Control Room. Task completion is normally reported by 
portable hand held radio or installed phones but may also be reported 
by face-to-face communication if plant communication systems are not 
available. The General Announcing System, Operations Radio System, 
Plant Telephone System, Sound Powered Phone System, and Face-to-Face 
Communications are all available to Control Room operators and 
operators performing OMAs.
    The licensee stated that operators performing the OMA are provided 
with standard personal protective equipment (PPE), including hardhat, 
gloves, and protective glasses. In the unlikely event that smoke 
conditions would require SCBAs to be worn, the plant equipment 
operators are qualified to wear SCBAs and the SCBAs are staged at 
strategic locations in the plant with additional SCBAs in the fire 
brigade locker.
    The licensee stated that fire AOPs have been developed for each 
fire area or zone and that the fire AOPs are staged in certain 
strategic locations that are easily accessible to the operators. The 
individual procedures are presented in a standardized procedure format 
that the operators are familiar with. The fire AOPs contain both 
preventive actions to prevent potential adverse fire effects, as well 
as reactive actions to direct timely action if a fire causes a 
particular adverse condition (i.e., valve spuriously opens or closes). 
The procedures for individual fire areas are used in conjunction with 
the symptom-based (reactive) Emergency Operating Procedures (EOPs) and 
other symptom-based AOPs to provide a combined preventive (fire AOPs) 
and reactive (EOPs and all AOPs, including fire) approach to achieve 
safe shutdown following a fire. The individual fire area shutdown 
procedures provide the operators with information as to the available 
equipment (including instrumentation) that can be relied upon following 
a fire. The fire AOP procedures provide specific guidance to the 
operators as to what equipment could be affected by the fire and are 
written in order of time criticality (i.e., the most time critical 
actions are in the front of the procedure) to ensure that the actions 
are taken within the analyzed time required in the safe shutdown 
analysis.
    With regard to staffing and demonstrations, the licensee stated 
that three qualified operators are available to perform the manual 
action at all times and that demonstrations were performed in the TMI-1 
plant simulator and in the plant by operator walk downs to show that 
the OMAs can be performed within the times as described in the safe 
shutdown analysis.
3.4.2 Feasibility
    The licensee's analysis demonstrates that, for the expected 
scenario, the OMAs can be diagnosed and executed in 19 minutes while 
the time available to complete them is 40 minutes. The licensee stated 
that the 40-minute time limit itself is a conservative measure since 
recent testing on the MU-V-20 backup air supply demonstrated that MU-V-
20 would only stay open for approximately 75 minutes. The licensee's 
analysis also demonstrates that various factors, as discussed above, 
have been considered to address uncertainties in estimating the time 
available. Therefore, the OMA included in this review is feasible 
because there is adequate time available for the operator to perform 
the required manual actions to achieve and maintain hot shutdown 
following a fire in Fire Zone AB-FZ-6.
3.4.3 Reliability
    The stated completion time of 19 minutes provides reasonable 
assurance that the OMA can reliably be performed under a wide range of 
conceivable conditions by different plant crews because it, in 
conjunction with the 21-minute margin and other installed fire 
protection features, accounts for sources of uncertainty such as 
variations in fire and plant conditions, factors unable to be recreated 
in demonstrations and human-centered factors. Therefore, the OMA 
included in this review is reliable because there is adequate time 
available to account for uncertainties not only in estimates of the 
time available, but also in estimates of how long it takes to diagnose 
a fire and execute the OMAs (e.g., as based, at least in part, on a 
plant demonstration of the actions under nonfire conditions).

3.5 Defense-In-Depth Summary

    In summary, the defense-in-depth concept for a fire in Fire Zone 
AB-FZ-6 provides a level of safety that results in the unlikely 
occurrence of fires; rapid detection, control, and extinguishment of 
fires that do occur; and the protection of structures, systems, and 
components important to safety. As discussed above, in the unlikely 
event of a fire that challenges safe shutdown capability, the licensee 
has provided preventative and protective measures in addition to a 
feasible and reliable OMA that together demonstrate the licensee's 
ability to preserve or maintain safe shutdown capability at TMI-1 in 
the event of a fire in Fire Zone AB-FZ-6.

3.6 Authorized by Law

    This exemption would allow TMI-1 to utilize an OMA, in conjunction 
with the other installed fire protection features, to ensure that at 
least one means of achieving and maintaining hot shutdown remains 
available during and following a postulated fire event, as part of its 
fire protection program, in lieu of meeting the circuit separation and/
or protection requirements specified in III.G.2 for a fire in Fire Zone 
AB-FZ-6. 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.

3.7 No Undue Risk to Public Health and Safety

    The underlying purpose of 10 CFR part 50, appendix R, section III.G 
is to ensure that at least one means of achieving and maintaining hot 
shutdown remains available during and following a postulated fire 
event. Because the use of the specific OMA, in conjunction with the 
other installed fire protection features, only impacts the response to 
the specific Fire Zone AB-FZ-6 scenario described above, 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.

3.8 Consistent With Common Defense and Security

    The proposed exemption would allow TMI-1 to utilize a specific OMA, 
in conjunction with the other installed fire protection features, in 
response to a fire in Fire Zone AB-FZ-6 in lieu of

[[Page 38850]]

meeting the requirements specified in III.G.2. This change, to the 
operation of the plant, has no relation to security issues. Therefore, 
the common defense and security is not diminished by this exemption.

3.9 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 purpose of 10 CFR Part 50, Appendix R, Section 
III.G is to ensure that at least one means of achieving and maintaining 
hot shutdown remains available during and following a postulated fire 
event. Therefore, since the underlying purpose of Appendix R, Section 
III.G is achieved, the special circumstances for granting an exemption 
from 10 CFR Part 50, Appendix R, Section III.G exist, as required by 10 
CFR 50.12(a)(2)(ii).

4.0 Conclusion

    Accordingly, the Commission has determined that, pursuant to 10 CFR 
50.12(a), 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 Exelon an exemption from the 
requirements of section III.G.2 of appendix R of 10 CFR part 50, to 
TMI-1 for the OMA discussed above.
    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 (75 FR 36700).
    This exemption is effective upon issuance.

    Dated at Rockville, Maryland, this 28th day of June 2010.
    For The Nuclear Regulatory Commission.
Joseph G. Giitter,
Director, Division of Operating Reactor Licensing, Office of Nuclear 
Reactor Regulation.
[FR Doc. 2010-16352 Filed 7-2-10; 8:45 am]
BILLING CODE 7590-01-P