Fire Protection Program 

for Operating Reactors

NUREG/BR-0522

August 2014

FIRE PROTECTION PROGRAM 

RESOURCES

Alternate Fire Protection Rule

NFPA 805, Performance-Based Standard for 

Fire Protection for Light-Water Reactor Electric 

Generating Plants

http://www.nrc.gov/reactors/operating/opsexperience/fire-protection/protection-rule.html 

NRC Regulatory Guide 1.189 

Fire Protection for Nuclear Power Plants 

http://pbadupws.nrc.gov/docs/ML0925/

ML092580550.pdf 

Plant Exemption Requests 

10 CFR 50.12

http://www.nrc.gov/reading-rm/doccollections/cfr/part050/part050-0012.html 

Separation and Fire Walls

NUREG-1552, Fire Barrier Penetration Seals in 

Nuclear Power Plants 

http://www.nrc.gov/reading-rm/doccollections/nuregs/staff/sr1552/ 

Fire Wrapped Cabling

NUREG-1924, Electrical Raceway Fire Barrier 

Systems in U.S. Nuclear Power Plants

http://www.nrc.gov/reading-rm/doccollections/nuregs/staff/sr1924/ 

National Fire Protection Association

www.nfpa.org

Underwriters Laboratory

www.ul.com

NRC Fire Protection Program 

at Nuclear Power Plants

http://youtu.be/MuRwxP3Sq5A 
In some 

cases, 

equipment 

sets had 

to be less 

than 20 feet 

apart, but 

the plant 

could still 

meet the 

overall goal of keeping one set free of fire damage. 

In these cases, the licensee applied for and in many 

cases were granted an exemption by the NRC.

The NRC’s regulations allow plants to request 

exemptions if the plants can show specific special 

circumstances. The NRC only grants exemptions 

if they do not present an undue risk to health and 

safety and if other relevant requirements are met. 

A plant operating with an approved exemption and 

other regulatory requirements complies with the 

NRC’s regulations.

RISK-INFORMED, PERFORMANCEBASED FIRE PROTECTION

In 2004, the NRC modified its fire protection 

regulations in Title 10 of the Code of Federal 

Regulations (10 CFR) 50.48, “Fire Protection,” 

to give U.S. reactors the choice of using an 

updated, scientifically sound way of reducing fire 

risks. Plants can adopt National Fire Protection 

Association Standard 805 (NFPA 805) in place of 

their existing fire protection approach. 

NFPA 805 uses computer models of fire 

progression and other ways of quantifying fire risk. 

This approach focuses fire protection resources 

where they’re most needed. The standard 

establishes a fundamental fire protection program, 

as well as requirements for fire protection systems 

and features, including prevention, fire detection 

and suppression, and safe shutdown. This effort 

is part of how the NRC enhances safety by 

incorporating risk information into regulations and 

oversight. The risk-informed approach relies on a 

required outcome rather than requiring a specific 

process or technique to achieve that outcome. 

DEFENSE-IN-DEPTH

The NRC’s approach to fire protection includes 

the multi-layered concept of defense-in-depth to 

keep the public safe from the effects of fires at 

nuclear power plants. A proper defense-in-depth 

fire protection program will:

• Prevent fires from starting;

• Rapidly detect, control, and extinguish 

promptly those fires that do occur;

• Protect the reactor’s ability to safely shut 

down if a fire is not promptly extinguished.

The NRC’s requirements incorporate the work 

of experts such as the National Fire Protection 

Association and Underwriters Laboratory. 

Prevention: Keeping combustibles and 

potential fire starters out of the plant as much 

as possible to reduce the chances of a fire. 

Prevention features and activities involve:

• Fire Marshal—Nuclear power plant staff 

monitor fire hazards such as the storage of 

combustibles, and control ignition sources such 

as metal cutting and welding. 

OVERVIEW 

The U.S. Nuclear Regulatory Commission (NRC) 

requires every U.S. nuclear power plant to reduce 

the chances of a fire and be able to safely handle the 

consequences of any fires that might occur. Each 

plant owner, or licensee, must maintain a robust 

fire protection program and ensure the reactor can 

shut down safely in the event of a fire. The NRC 

uses operational experience and information about 

fires in making regulatory decisions about U.S. 

commercial nuclear power plants. Only the March 

1975 fire at the Browns Ferry plant near Decatur, 

AL., has affected the safe operation of a U.S. 

reactor. Even in that case, plant personnel were 

able to safely shut down the Browns Ferry reactors. 

DETERMINISTIC FIRE PROTECTION

The 1975 fire at one of the Browns Ferry reactors 

in Alabama prompted the NRC to establish 

deterministic fire protection requirements. Since 

that time, U.S. plants have always shut down safely 

following a fire. Every plant’s fire protection plan 

must meet NRC requirements to outline the overall 

fire protection program and installed fire protection 

systems, as well as the means to ensure safe 

reactor shutdown in the event of a fire. 

The NRC’s requirements assume a serious fire in 

establishing generic criteria for all plants. For some 

operating or proposed plants the generic approach 

was impractical, or the plant demonstrated a better 

approach to achieving the same level of safety. In 

these cases, the NRC reviewed and approved plantspecific exemptions and amendments. 

For example, plants must ensure one of several 

sets of safe shutdown systems will remain free of 

fire damage. The regulation prescribes that the safe 

shutdown equipment sets will:

1. Be separated by a barrier that protects one 

set from fire for 3 hours; or

2. Be at least 20 feet apart and have automatic 

fire suppression and detection systems; or

3. Be separated by a barrier that protects one 

set from fire for an hour and have automatic 

fire suppression detection systems.
• NRC Inspections—The NRC’s resident inspectors 

monitor daily plant activities and perform 

specific fire safety inspections every 3 months, 

plus an additional yearly inspection. Inspectors 

from the NRC’s regional offices inspect a 

plant’s fire protection approach in depth every 

3 years. Engineers and technical staff from 

NRC headquarters review plant changes to 

ensure that fire safety is acceptably maintained. 

Headquarters staff also support the resident 

and regional inspectors.

• Training and Fire Drills—Nuclear power plants 

train their staff on fire safety, including regular 

drills on responding to possible fires. Plants also 

map out the types of fire hazards at the plant and 

the location of firefighting equipment in the event 

of a fire.

Suppression: Detecting and extinguishing fires 

that are not prevented. Suppression involves: 

• Automatic Fixed Fire Sprinklers, Foam—Plants’ 

installed firefighting systems operate 

automatically to control and extinguish plant 

fires. These general area protection systems 

are usually fire sprinklers. Special hazards such 

as oils can require foam-based systems.

• Detection

Fire Detectors—Plant fire detectors, including 

some very high-sensitivity systems, identify fires 

before significant plant damage occurs. The 

detectors alert a constantly staffed location, which 

investigates the alarm and calls the onsite fire 

brigade to respond.

Video Surveillance—Plants may temporarily rely on 

constantly monitored video surveillance to detect 

fires in high-radiation areas.

• Fire Protection Loop

Fire Pump Building—Nuclear power plants have 

several pumps whose only purpose is providing 

firefighting water throughout the plant. These 

pumps can provide up to thousands of gallons of 

water per minute.

Natural Water Supply (Lake, River, or Ocean)—Some 

nuclear plants use the essentially unlimited water 

supply of nearby lakes, rivers, or the ocean for 

their firefighting systems. Plants use filters and 

other precautions to ensure that the water from 

natural supplies does not damage fire protection 

systems through corrosion or due to obstructions.

Peripheral Fire Hydrant—The plant fire pumps and 

water supplies also feed fire hydrants located 

strategically around the plant. Plant fire brigades 

and offsite fire departments use these hydrants 

to supply water to extinguish fires outside of the 

plant.

Water Tank—Many plants dedicate large water 

tanks (hundreds of thousands of gallons) to 

firefighting.

• Offsite Support—Nuclear operators have 

agreements with nearby fire departments to 

support firefighting operations if needed.

• Onsite Fire Brigade—Each nuclear plant’s fire 

brigade (or department) has staff trained and 

equipped for firefighting. These firefighters’ 

training includes understanding the plant layout 

and hazards located in and around the plant site.

Safe Shutdown: Using installed equipment and 

procedures that reasonably ensure the reactor 

can shut down safely if a plant fire is not prevented 

or rapidly suppressed. Safe shutdown features 

include:

• Backup Power Supply—If the plant loses power 

from the transmission grid, reliable alternative 

power sources such as diesel generators power 

equipment to safely shut down the plant. Plants 

also have diesel-powered fire pumps to supply 

firefighting water.

• Redundant Safety Pumps—Multiple sets of 

different pumps can provide cooling water 

to keep the nuclear fuel safe. Fire protection 

programs separate these pump sets to keep 

them from being damaged by a single fire. 

• Separation and Fire Walls—Fire walls separate 

sets of safety equipment, including pumps, into 

areas that would be impacted by a single fire. 

The walls are typically concrete or concrete 

block with fire-resistant sealant protecting the 

openings for pipes and cables. 

• Wrapped Cabling—Fire-resistant material 

protects cables for redundant safe-shutdown 

components located in one fire area. This 

material will have been tested to last 1 to 3 hours, 

depending on the application. 
Prevention

Minimizing the potential for 

fires and explosions

The NRC requires every U.S. nuclear power plant 

to have a robust fire protection program to ensure 

the reactors are safe from plant fires. Plants can 

manage their fire safety with either a deterministic 

or a risk-informed, performance-based approach. 

Both methods use the “defense in depth” concept to 

meet fire protection objectives.

The NRC’s Fire Protection Regulations, Inspections, And Research Activities Focus On:

Suppression

Rapidly detecting, controlling, and 

extinguishing fires that do occur 

Safe Shutdown

Ensuring operators can shut down 

the reactor safely despite a fire