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Nuclear power holds the promise of a sustainable, affordable, carbon-friendly source of energy for the twenty-first century on a scale that can help meet the world's growing need for energy and slow the pace of global climate change. However, a global expansion of nuclear power also poses significant challenges. Nuclear power must be economically competitive, safe, and secure; its waste must be safely disposed of; and, most importantly, the expansion of nuclear combination of technical, political, and institutional measures.

Introduction

Fire situations pose one of the most serious problems in

an industrial establishment with the potential loss of lives

& property as well as damage to the environment. Careful

pre planning, implementation of well-planned &

engineered fire prevention measures and proper response

by trained personnel can minimize the risk & damage

caused by fire. However, in spite of several advances

made in fire detection and fire fighting, fire continues to

be highly unpredictable and hence the best course of

action is to put the maximum emphasis on fire

prevention.

A ‘fire protection programme’ is an integrated

effort involving equipment, procedures and personnel

necessary to conduct all fire protection activities. It

includes system and facility design and analysis; fire

prevention, detection, annunciation, confinement and

extinguishing; administrative controls; fire brigade

organization; training; inspection, maintenance and

testing; and quality assurance. Structures, systems and

components (SSCs) important to safety are required to be

designed and located, consistent with other safety

requirements, so as to minimize the likelihood and effects

of internal fires and explosions caused by external or

internal events. The capability for shutdown, removal of

residual heat, confinement of radioactive material and

monitoring of the state of the plant is required to be

maintained. The consequences of fire can be more severe

in a nuclear installation due to the added risk of release of

radioactivity. Hence there is a need for regulating the fire

protection system in nuclear facilities and strengthen the

fire safety aspects to ensure nuclear and radiological

safety. Fire safety aspects of nuclear facilities include fire

prevention, detection & protection systems along with

other considerations such as personnel safety,

environmental safety and property protection. Fire safety

system aims to achieve a defence-in-depth concept and

provides direction to select the optimum combination of

the three levels - prevention, detection & suppression and

mitigation to ensure safety.

Fire safety is important throughout the lifetime of a

plant, from design to construction and commissioning,

throughout plant operation and in decommissioning. Fire

protection systems, including fire detection systems and

fire extinguishing systems, fire containment barriers and

smoke control systems, shall be provided throughout the

nuclear power plant, with due account taken of the results

of the fire hazard analysis. A typical fire protection

system should have following requirement:

a) The fire protection systems installed at the nuclear

power plant shall be capable of dealing safely with

fire events of the various types that are postulated.

b) Fire extinguishing systems shall be capable of

automatic actuation where appropriate. Fire

extinguishing systems shall be designed and located

to ensure that their rupture or spurious or inadvertent

operation would not significantly impair the

capability of items important to safety.

c) Fire detection systems shall be designed to provide

operating personnel promptly with information on

the location and spread of any fires that start.

Fire detection systems and fire extinguishing systems that

are necessary to protect against a possible fire following a

postulated initiating event shall be appropriately qualified

to resist the effects of the postulated initiating event.

Defence in depth

To ensure adequate fire safety in a nuclear power plant in

operation, an appropriate level of defence in depth should

be maintained throughout the lifetime of the plant,

through the fulfilment of the three principal objectives

identified in:

1) Prevention of fire to start;

2) Detecting fires quickly, suppressing those fires that

occur, putting them out

3) Designing plant safety systems, so that a fire that

starts in spite of prevention programme shall not

prevent essential plant safety functions from being

performed.

It should be ensured by means of the above approach that

the probability of a fire occurring is reduced to as low as

reasonably practicable and safety systems are adequately

protected to ensure that the consequences of a single fire

will not prevent those systems from performing their

required function. The three objectives of defence in

depth can be achieved through a combination of: design,

installation and operation of fire prevention and

protection systems; management of fire safety; fire

prevention and fire protection measures; quality

assurance; and emergency arrangements.

Fire Hazard Analysis

A detailed fire hazard analysis should be carried out

during initial plant design to reflect the proposed

construction arrangements, materials and facilities. This

analysis should be revised periodically as design and

construction progress and before and during major plant

modifications.

The fire hazard analysis should be a systematic study of

(a) all elements of the fire protection programme being

proposed to ensure that the plant design has included

adequate identification and analysis of potential fire

hazards (b) the effect of postulated fires relative to

maintaining the ability to perform safe shutdown

functions and minimizing toxic and radioactive releases

to the environment and (c) suggest remedial measures.

The fire risk can be quantified for the process industries

based on the indices like Dow index (Fire & Explosion

Index) and Mond index. The indices are comprehensive

and give a realistic value to the risk of individual process

unit due to potential fires and explosion. Facilities

handling and storing flammable liquids are exposed to a

potential fire risk. The fires due to flammable liquid may

be a Pool Fire, Jet Fire, Flash Fire or a Boiling Liquid

Expanding Vapour Explosion (BLEVE) depending on the

containment, type of release and source of ignition.

Computer models are available to simulate the fire

conditions and estimate the potential consequences. The

fire hazard analysis should separately identify hazards

and provide appropriate protection in locations where

safety related losses could occur as a result of:

a) Concentrations of combustible materials, including

transient fire loads due to combustibles expected

to be used in normal operations;

b) Configuration of combustible contents, furnishings,

building materials, or combinations thereof

conducive to fire spread;

c) Exposure to fire, heat, smoke, steam that may

necessitate evacuation from areas that are required to

be attended for safety functions;

d) Fire in control rooms or other locations having

critical safety related functions;

e) Lack of adequate access or of smoke removal

facilities that impede fire extinguishment in safety

related areas;

f) Lack of explosion prevention measures;

g) Loss of electric power and

h) Inadvertent operation of fire suppression systems

The possibility of a fire spreading from one unit to the

other unit should be taken into account in the fire hazard

analysis. i.e. The analysis of consequences of the

postulated fire on safety of the plant should be conducted

by the persons trained and experienced in the principles

of industrial fire prevention & control and in fire

phenomena from fire initiation through its propagation

into adjoining spaces and it should be done in

consultation with the Fire Protection Engineer. The Fire

Hazard Analysis report is reviewed by the regulatory

body prior to the commissioning of the facility. Any

changes emerged from review are appropriately

incorporated by the facility.

Design measures for fire prevention

In any nuclear power plant, every effort should be made

to minimize fire risk by design. In general, the fire

containment approach is preferred, since it emphasizes

passive protection and thus the protection of safety

systems does not depend on the operation of a fixed fire

extinguishing system.

NPPs contain a range of combustible materials, as part of

the structure, equipment, cabling or miscellaneous items

in storage. Since fire can be assumed to occur in any

plant area where combustible materials are present,

design measures for fire prevention should be applied to

all the fixed and transient fire loads. Such measures

include minimization of fixed fire loads, prevention of

accumulation of transient combustible materials and

control or (preferably) elimination of sources of ignition.

The design of fire prevention measures should commence

in the early stages of the design process. All such

measures should be fully implemented before nuclear fuel

arrives on the site.

Control of combustible materials by design

In order to reduce the fire load and minimize the fire

hazard, the following aspects should be considered in

plant design:

a) The use of non-combustible construction materials

(e.g. structural materials, insulation, cladding,

coatings and floor materials) and plant fixtures as far

as practicable;

b) The use of air filters and filter frames of non-

combustible or low combustible construction;

c) The use of a protected pipe or double pipe design for

lubricating oil lines;

d) The use of hydraulic control fluid of low

flammability for the control system of steam turbines

and other equipment;

e) The selection of dry type transformers for interior

applications;

f) The siting of large oil filled transformers in external

areas where a fire would not cause undue hazards;

g) The use of non-combustible materials in electrical

equipment such as switches and circuit breakers, and

in control and instrumentation cubicles;

h) The separation of switchgear boards from each other

and from other equipment by means of fire barriers

or fire compartments;

i) The use of fire retardant cabling.

There should provide adequate provisions for separation

of areas containing high fire loads of electrical cables

from other equipment by means of fire barriers or fire

compartments. Also, it should use non-combustible

scaffolding and staging materials. Electrical systems

should be designed neither to cause a fire nor, as far as

practicable, to support a fire. Storage allowances for

flammable liquids and gases inside plant buildings should

be minimized. Storage areas for bulk supplies of any

flammable or combustible materials should be located in

areas or buildings that do not contain items important to

safety. Systems containing flammable liquids or gases

should be designed with a high degree of integrity in

order to prevent leaks. They should be protected from

vibration and other destructive effects.

Control of ignition sources

Potential ignition sources arising from plant systems and

equipment should be controlled. Systems and equipment

should be made safe through design so as not to provide

any ignition source, separated from combustible

materials, isolated or enclosed. Electrical equipment

should be selected and classified for occupancy

conditions. Equipment for dispensing flammable liquids

or gases should be properly earthed. Hot pipework near

combustible materials that cannot be moved elsewhere

should be shielded and/or insulated. In the construction or

operation of a multiunit power plant, steps should be

taken to ensure that a fire in a unit under construction or

in operation would not have any safety consequences for

a neighbouring operating unit. Temporary fire separations

should be used if necessary to protect the operating units.

The main control rooms should be adequately separated

from possible sites of fire. Consideration should be given

to the possibility of fires involving facilities shared

between units.

Control of explosion hazards

At NPPs where there is a potential hazard due to

hydrogen in plant operations, provisions should be made

to control the hazard by the use of hydrogen monitors,

recombiners, adequate ventilation, controlled hydrogen

burning systems, equipment designed for use in an

explosive atmosphere or other appropriate means. Where

inerting is used, fire hazards arising during maintenance

and refuelling should be considered, and care should be

taken to ensure that gas mixtures remain within the limits

of non-flammability.

Provisions for Fire Detection

NPPs should have competent fire detection equipment to

ensure early detection of incipient fire or potential causes

for fire. Their capability of detection should not be

hampered due to fire induced secondary effects such as

smoke. Fire detection equipment should be based on

diverse working principals. Fire detection system should

be reliable and provide distinct alarm and detailed

information on location of fire ,major equipment in the

vicinity of fire, degree and spread of fire. To ensure an

adequate level of protection for fire compartments and

fire cells, the following elements should be considered in

the design of the plant:

a) Where detection or extinguishing systems are

credited as active elements of a fire cell or fire

compartment, arrangements for their design,

procurement, installation, verification and periodic

testing should be sufficiently stringent to ensure their

permanent availability. A fire extinguishing system

should be included in the assessment against the

single failure criterion for the safety function it

protects.

b) Where detection systems or fixed fire extinguishing

systems are relied upon as protection against a

potential fire following a postulated initiating event

(PIE) (e.g. an earthquake), they should be designed

to resist the effects of this PIE.

c) The normal or the spurious operation of fire

extinguishing systems should not impair safety

functions.

Fire detection and alarm systems

Each fire compartment and fire cell should be equipped

with fire detection and alarm system. The detection

system should provide detailed annunciation in the

control room about the location of the fire (i.e. at the fire

cell level) by means of audible and visual alarms. All

detection and alarm systems should be energized at all

times and should be provided with non-interruptible

emergency power supplies, including fire resistant supply

cables where necessary, to ensure functionality in the

event of a loss of normal power. Individual detectors

should be sited so that the flow of air due to ventilation or

pressure differences necessitated for contamination

control does not cause smoke or heat energy to flow away

from the detectors and thus unduly delay actuation of the

detector alarm. Fire detectors should also be placed in

such a way as to avoid spurious signals due to air currents

generated by the operation of ventilation system. This

should be verified by in situ testing. In the selection and

installation of fire detection equipment, account should

be taken of the environment in which the equipment will

function.

Wiring for fire detection systems, alarm systems or

actuation systems should be protected from the effects of

fire by a suitable choice of cable type, proper routing, a

looped configuration or by other means, protected from

mechanical damage, constantly monitored for integrity

and functionality.

Fire Extinguishing

The licensee should ensure that fire fighting systems

(FFS) should be able to reach all areas of NPP to

effectively extinguish the fire. It should ensure operability

of FFS during all operating states by inspecting these

periodically.

Moreover, FFS should have provisions for minimizing

adverse effects on items important to safety as well as on

people and environment. Their operation should not

hamper the operability of SSCs important to safety and

should not induce common cause failure in redundant

system. Also, design of FFS should ensure their mal-

operation does not jeopardize protection against PIEs.

Fixed provisions for fire extinguishing

NPPs should be provided with fixed fire extinguishing

equipment. This equipment should include provisions for

manual fire fighting, such as fire hydrants and fire

standpipes. The fire hazard analysis should determine the

need to provide automatic extinguishing systems such as

sprinklers, spray systems, foam, water mist or gaseous

systems, or dry chemical systems. The design criteria for

fire extinguishing systems should be based on the

findings of the fire hazard analysis, so as to ensure that

the design is appropriate for each fire hazard that is being

protected against. There are three different extinguishing

systems:

1. Water based extinguishing systems should be

permanently connected to a reliable and adequate

supply of fire fighting water, and these systems

include automatic sprinkler, water spray, deluge,

foam and water mist systems. Automatic water

sprinkler (or spray) protection should be provided at

all locations where one of the following factors

applies, subject to the findings of a fire hazard

analysis:

a) A high fire load is present.

b) A potential for rapid spread of fire exists.

c) A fire could compromise redundant safety

systems.

d) An unacceptable hazard for fire fighters could be

created.

e) An uncontrolled fire would make access for fire

fighting difficult.

2) Gaseous extinguishing systems use carbon dioxide.

3) Dry powder and chemical extinguishing systems

consist of a stored quantity of powder or chemical

suppression agent, a source of compressed gas

propellant, an associated distribution network,

discharge nozzles and provisions for detection and/or

actuation. The systems can be either manually

operated at the hazard, or remotely or automatically

actuated by a detection system. These systems are

usually used to protect against flammable liquid fires

and certain fires involving electrical equipment.

These extinguishing agents should not be used on

sensitive electrical equipment since they generally

leave a corrosive residue.

Manual Fire Fighting

Portable and mobile fire extinguishers of a type and size

suitable for the hazards being guarded against should be

provided for use in manual fire fighting by plant

personnel. The entire plant should be equipped with a

sufficient number of portable and mobile extinguishers of

the appropriate types as well as spares or facilities for

recharging. All fire extinguisher locations should be

clearly indicated. Fire extinguishers should be placed

close to the locations of fire hoses and along the escape

and access routes for fire compartments.

Portable and mobile extinguishers filled with water or

foam solution and other extinguishing agents with a

neutron moderating capability should not be used in

locations where nuclear fuel is stored, handled or

transported unless an assessment of the criticality hazard

has demonstrated that it is safe to do so. Manual fire

fighting forms an important part of the defence in depth

strategy for fire fighting. The design of the plant should

allow for access by fire teams and fire brigades using

heavy vehicles. Suitable emergency lighting should be

provided for all fire compartments.

Fire brigade for manual fire fighting

A fixed wired emergency communication system with a

reliable power supply should be installed at preselected

stations. Alternative communication equipment such as

two way radios should be provided in the control room

and at selected locations throughout the plant. In addition,

portable two way radios should be provided for the fire

fighting team. Prior to the first fuel loading, testing

should be carried out to demonstrate that the frequencies

and transmitter powers used does not cause spurious

operation of the protection system and control devices.

Self-contained breathing apparatus, including spare

cylinders and a facility for recharging, should be provided

at appropriate locations for the emergency response team.

Provisions for smoke and heat venting

An assessment should be carried out to determine the

need for smoke and heat venting, including the need for a

dedicated smoke and heat extraction system, to confine

the products of combustion and prevent the spread of

smoke, to reduce temperatures and to facilitate manual

fire fighting. In the design of a smoke and heat extraction

system, the following criteria should be taken into

account: fire load, smoke propagation behaviour,

visibility, toxicity, fire brigade access, the type of fixed

fire extinguishing system used and radiological aspects.

Confinement of fire

The licensee should ensure that appropriate provisions

have been installed for confining fire to the place at

which it had originated. It should put fire barriers

penetration seals, water curtains, fire and/or smoke

dampers, fire doors, etc., of sufficient fire resistant

capability to prevent its progression. Fire detection

systems, fire extinguishing systems and support systems

should be independent of their counterparts in other fire

compartments to maintain their operability during fire in

the compartment. Early in the design phase, the plant

buildings should be subdivided into fire compartments

and fire cells. The purpose is to segregate items important

to safety from high fire loads and to segregate redundant

safety systems from each other. The aim of segregation is

to reduce the risk of fires spreading, to minimize

secondary effects and to prevent common cause failures.

A fire compartment is a building or part of a building that

is completely surrounded by fire resisting barriers (all

walls, floor and ceiling). The fire resistance rating of the

barriers should be sufficiently high so that the total

combustion of the fire load in the compartment can occur

(i.e. total burnout) without breaching the fire barriers.

Confinement of fire within the fire compartment is

intended to prevent the spread of fire and its effects (e.g.

smoke and heat) from one fire compartment to another,

and thus prevent the failure of redundant items important

to safety. The separation provided by fire barriers should

not be compromised by temperature or pressure effects of

fires on common building elements such as building

services or ventilation systems. The fire resistance rating

of the barriers that form the boundaries of a fire

compartment should be established in the fire hazard

analysis. Further, a minimum resistance rating of one

hour should be adopted. National regulations may require

higher values for the minimum resistance rating of fire

compartment boundaries.

Procedures should be established for the purpose of

ensuring that amounts of combustible materials (the fire

load) and the numbers of ignition sources be minimized

in areas containing items important to safety and in

adjacent areas that may present a risk of exposure to fire

for items important to safety. Effective procedures for

inspection, maintenance and testing should be prepared

and implemented throughout the lifetime of the plant with

the objective of ensuring the continued minimization of

fire load, and the reliability of the installed features for

detecting, extinguishing and mitigating the effects of

fires, including established fire barriers .

Emergency arrangements

Written emergency procedures that clearly define the

responsibility and actions of staff in responding to any

fire in the plant should be established and kept up to date.

The emergency procedures should give clear instructions

for operating personnel on immediate actions in the event

of a fire alarm. These actions should be primarily directed

to ensuring the safety of the power plant, including

shutdown of the plant if necessary. The procedures should

set out the role of operating personnel in relation to the

role of the fire fighting team taking immediate action, the

plant fire brigade and outside emergency services such as

local authority fire brigades. Special attention should be

paid to cases for which there is a risk of release of

radioactive material in a fire. It should be ensured that

such cases are covered in the emergency arrangements for

the plant. Appropriate measures should be taken for

radiation protection for fire fighting personnel. Regular

fire exercises should be held to ensure that staff have a

proper under- standing of their responsibilities in the

event of a fire. Records should be maintained of all

exercises and of the lessons to be learned from them. Full

consultation and liaison should be maintained with any

off-site organizations that have responsibilities in relation

to fire fighting. Plant documentation should provide a

clear description of the manual fire fighting capability

provided for those areas of the plant identified as

important to safety. The manual fire fighting capability

may be provided by a suitably trained and equipped on-

site fire brigade, by a qualified off-site service or by a co-

ordinated combination of the two, as appropriate for the

plant and in accordance with national practice

Fire safety considerations in a typical NPP

(1) Fire Protection Measures for Mechanical

Components and Systems

Components containing flamable liquid and gases

1) Oil supplies shall be designed such that possible

leakage oil will not come into contact with plant

components having a surface temperature higher than

200 °C. The heat insulation in the vicinity of oil

supplies shall be designed such that autoxidation

from leakage oil seeping into the heat insulation is

prevented.

2) Only non-combustible materials shall basically be

used. Exceptions are permissible in the case of

sealants and gas kets, provided, they are protected

against direct flames in the event of fire.

Combustible hoses shall normally be completely

3) surrounded by metal sheathing.

4) The systems containing flammable liquid or gaseous

materials shall normally be provided equipment for

leakage detection, e.g., filling level monitors in the

case of liquid mate rials and pressure monitors in the

case of gaseous materials, and, if applicable, for the

draining off of leakages.

5) Vessels containing larger amounts of flammable

liquids shall be provided with collecting facilities.

The volume of the collecting facilities shall be

specified under consideration of the maximum

possible non-isolatable leakage amount of the largest

6) individual vessel and, in the case of the presence of a

stationary fire extinguishing system, also of the

accumulated fire suppres sant; measures shall be

taken to enable a controlled draining off of the

accumulated fire suppressant and liquid leakage.

7) Combustible materials escaping from safety valves

shall be safely drained or dissipated off.

8) Any hot component parts shall basically be avoided

in the vicinity of components containing combustible

or combustion supporting materials. If this is not

possible for

9) technical reasons, measure shall be taken to prevent

self ignition of the leakages (e.g., insulation,

concentric guard pipe, encapsulation, air exhaust).

10) It is not permissible to use cutting ring fittings for

pressure retaining pipes containing flammable liquid

materials.

Reactor Coolant Pumps

1) In the case of an external oil supply, the oil amount

in the oil tank shall be monitored by suitable means.

As soon as the oil amount falls below a minimum

value to be specified depending on the oil supply, the

oil supply shall automatically be interrupted.

2) In the case of reactor coolant pumps and associated

motors are provided with an integrated oil supply, the

pumps shall be equipped with a collecting facility for

the entire oil amount of the largest individual supply

vessel.

3) In the case of an integrated oil supply with cooling

equipment inside the oil vessel, the level in the oil

vessel shall be monitored. When the maximum

permissible level is reached, the cooling water supply

to the oil cooler shall be shut off.

4) In the case of an external oil tank, the oil tank

including the auxiliary equip-

5) ment in the same room does not need to be designed

against external events, provided, it is validated

analytically that the structural partitions of the fire

sub-compartment of the oil tank compartment will

remain functional even after an external event and

that the oil collection vessel is still leak tight.

Steel Reactor Containment

1) The integrity of the reactor containment in the event

of fire shall be ensured. Therefore, larger fire loads in

the direct vicinity of the containment wall shall

basically be avoided. Exceptions are such fire loads

that are protected by suitable structure related or

equipment-related fire protection measures. In case

such measures cannot be applied, other requirements

shall be specified in each individual case, e.g.,

protective coating of the cables in the vicinity of

cable penetrations.

2) The measures specified under para. 1 shall also

ensure that no fire spreading occurs on account the

influence from direct heat or thermal radiation on the

other side of the con tainment wall.

3) The air locks and air lock annexes shall be kept free

of any fire loads that are not required for the

operation of the locks or for the purpose of personnel

protection.

4) (4)The function of safety-related actuators, valves

and fittings shall be ensured such that even in the

event of fire the necessary safety-related measures

can be taken to the required extent.

Turbine Generator Building

The turbine building should be separated from adjacent

structure containing equipment important to safety by a

fire barrier with a rating of at least 3 hours. The fire

barriers should be designed to maintain structural

integrity even in the event of a complete collapse of the

turbine structure. Openings and penetrations in the fire

barrier should be minimized and should not be located

where the turbine oil system or generator hydrogen

cooling system creates a direct fire exposure hazard to the

barrier. Considering the severity of the fire hazards,

defense in depth may dictate additional protection to

ensure barrier integrity, and the potential effect of a major

turbine building fire on the ability to maintain operator

control of the plant and safely shut down should be

evaluated.

Turbine buildings contain large sources of combustible

liquids, and piping for systems lube oil, seal oil, and

electrohydraulic s includingreservoirs ystems. These

should be separated from systems important to safety by

3-hour rated barriers. Additional protection should be

provided on the basis of the hazard or where fire barriers

are not provided.

Turbine generators may use hydrogen for cooling.

Hydrogen storage and distribution systems should meet

the safety guidelines .Smoke control should be provided

in the turbine building to mitigate potential heavy smoke

conditions associated with combustible liquid and cable

fires.

Emergency power generating facilities with diesel

generator units

1) The fuel oil storage tank of each redundancy shall be

located, and the fuel oil day tank of each redundancy

shall basically be located, in individual fire sub

compartments apart from the diesel generator units.

2) The exhaust gas lines shall be insulated and encased

with non-combustible building materials of Class A 1

, such that the surface temperature even during

continuous operation will not exceed 200 °C. It shall

be ensured that neither fuel oil nor lubrication oil

will penetrate into the insulation.

3) The fuel oil system and the lubrication oil system of

the diesel motor shall be routed or insulated such that

no leakages can come in contact with components

the surface temperatures of which are above 200 °C.

The fuel oil injection lines shall be designed with a

concentric guard pipe or with a comparable

shielding.

4) The pipe connections of fuel oil injection lines shall

be metallically sealing or of an equivalent design.

5) Fuel or oil leakages from the diesel motor, oil day

tank, fuel oil storage tank or supply lines shall be

collected in, or drained into vats or vessels and shall

be moni-

6) tored and displayed. If applicable, a siphoning effect

from the

Storage of Combustible Operating Materials and

Pressurized Gas Bottles

1) It is not permissible to store combustible or

combustion supporting gases, e.g., oxygen, in the

vicinity of safety-related plant components. The

storage of combustible or combustion supporting

gases inside the controlled area shall be limited to the

amounts required for the individual task.

2) The storage of flammable liquids or other

combustible or combustion supporting materials in

the vicinity of safety-related plant components shall

basically be avoided. This storage is only permissible

if a fire of the materials stored cannot endanger any

of the safety-related plant components.

3) In the case of storage of flammable liquids, means

for the collection of the maximum possible non-

isolatable amount of leakage from the largest

individual vessel shall be provided for in the direct

vicinity of the place of installation of this

4) vessel; furthermore, means shall be provided to

enable a controlled draining off of the accumulated

fire suppressant and liquid leakage.

5) No stationary pressurized gas bottles, even for non

flammable gases, may be installed in the vicinity of

massive fire loads. Exempted are pressurized gas

bottles for small fire extinguishing systems and for

equipment protection systems.

Insulation, Encasements and Coatings of Components

1) The insulation of pipes and components shall

basically consist of non-combustible materials in

building material class A.

2) In the case of low-temperature insulations it is

permissible to use combustible foam isolation

materials or combustible auxiliary materials.

3) In the vicinity of possible leakages of flammable

liquids, special measures shall be taken to prevent

the penetration of these liquids into the insulation

materials, e.g., by baffles or sheet metal

encasements.

4) The decontaminable coatings of components shall be

at flame retardant.

Exhaust-Gas Systems (Gas Treatment Systems)

1) With regard to exhaust-gas systems, measures shall

be taken that will prevent the occurrence of a fire,

that will ensure fire detection and will limit the

extent of the fire.

2) The exhaust-gas systems in power plants with

pressurized water reactors shall basically be operated

under inert gas atmosphere.

3) In the room of the place of installation, combustible

materials are permissible only in such amounts as are

required for the operation of the activated charcoal

filters.

4) The filter containers shall consist of non-combustible

material .

Fire Protection Measures for Electrical Facilities and

Components

General Requirements

1) A low risk of occurrence of fire and fire spreading in

electrical facilities and components shall be achieved

by the proper choice of materials and by

corresponding protective means. To attain this goal

the fire protection measures in accordance with the

technical standards of VDE and DIN shall be

supplemented by meeting the additional

requirements as specified under this safety standard.

2) The redundancies of electrical facilities and

components shall be protected from each other, either

by sufficiently fire resistant structural elements or the

physical separation or encapsulation of combustible

materials, such that a fire cannot cause the failure of

an impermissible number of redundant equipment.

3) The fire protection measures for electrical facilities

and equipment specified in the following sections

shall be applied with highest priority.

Electric Circuits & Equipment

In closed ventilated areas, where smoke/heat venting is

not possible, for power cables and control cables,

halogen-free, fire-retardant, low smoke (FRLS) materials

shall be used for sheathing. Fire survival cables having

copper conductors with special insulating materials are

capable of maintaining circuit integrity for extended

periods under fire conditions and meets the special Fire

Survival Test as per IEC 331. These cables can safely be

used in essential circuits, which serve plant safety

functions. Placement of power & control cables on the

cable racks should be such that high voltage cables are on

the top rack and low voltage cables are on the bottom

rack as per AERB Fire Standard. Cable routing should be

so chosen to avoid passing

close to equipment such as steam pipe lines, oil pipe

lines, resistor grids and process

equipment which are capable of producing heat. Where

cables are required to be routed for loads located close to

such systems, protection shall be provided to these

cables. The cables shall be protected against oil spillages.

Transformers

All transformers shall meet the requirements of “The

Indian Electricity Rules, 1956 as amended on November

16, 2000 and “The Atomic Energy (Factories) Rules

1996”. Transformers installed inside fire areas containing

systems important to safety should be of the dry type or

insulated and cooled with noncombustible liquid.

Transformers filled with combustible fluid that are

located indoors should be enclosed in a transformer vault.

Outdoor oil-filled transformers should have oil spill

confinement features or drainage away from the buildings

and have a fire rating of at least 3 hours. The transformers

shall be protected by an automatic high velocity water

spray system or by carbon dioxide or Halon alternatives

fixed installation system or Nitrogen injection and drain

method.

Cable Trenches

All cable outlet points in the trench shall be insulated /

sealed with fire resistant materials / fiber wools or light

PCC to prevent spreading of fire. Fire barriers shall be

provided in cable trenches at periodical intervals.

Fire detection and alarm system:

In designing fire detection and alarm systems, it is

important to consider the reliability of the system and

individual components, to always perform their required

functions. For fire detection systems, this reliability may

be affected by the reduction in sensitivity or of sensing

devices leading to non- detection or late detection of a

fire, or the spurious operation of an alarm system when

no smoke or fire hazard exists. The detection system shall

annunciate by audible and visual alarms in the control

room and in-house fire station. Fire alarms shall be

distinctive and shall not be capable or being confused

with any other plant alarm. Reliable & uninterrupted

power supply shall be ensured for the fire detection and

alarm system. To take care of failure of main supply,

emergency power from diesel generating set and back-up

supply from battery system shall be provided. The

selection of detectors shall be based on the nature of

products released by the heating up, carbonization, or the

initial bursting into flame of the materials present in the

fire hazard area. The appropriateness of the detection

system shall be confirmed by Fire Hazard Analysis

(FHA). Selection of fire-detection equipment shall take

into account the environment in which it functions, e.g.

radiation fields, humidity, temperature and air flow.

Where the environment (e.g. higher radiation level, high

temperature etc.) does not allow detectors to be placed

immediately in the area to be protected, alternative

methods, such as sampling of the gaseous atmosphere

from the protected area for analysis by remote detectors

with an automatic operation should be considered. Where

spurious operation is detrimental to the plant, activation

shall be by two lines of protection system. Provision for

manually activated fire alarms shall also be made.

Fire detection and alarm system

In designing fire detection and alarm systems, it is

important to consider the reliability of the system and

individual components, to always perform their required

functions. For fire detection systems, this reliability may

be affected by the reduction in sensitivity or of sensing

devices leading to non- detection or late detection of a

fire, or the spurious operation of an alarm system when

no smoke or fire hazard exists. The detection system shall

annunciate by audible and visual alarms in the control

room and in-house fire station. Fire alarms shall be

distinctive and shall not be capable or being confused

with any other plant alarm. Reliable & uninterrupted

power supply shall be ensured for the fire detection and

alarm system. To take care of failure of main supply,

emergency power from diesel generating set and back-up

supply from battery system shall be provided. The

selection of detectors shall be based on the nature of

products released by the heating up, carbonization, or the

initial bursting into flame of the materials present in the

fire hazard area. The appropriateness of the detection

system shall be confirmed by Fire Hazard Analysis

(FHA). Selection of fire-detection equipment shall take

into account the environment in which it functions, e.g.

radiation fields, humidity, temperature and air flow.

Where the environment (e.g. higher radiation level, high

temperature etc.) does not allow detectors to be placed

immediately in the area to be protected, alternative

methods, such as sampling of the gaseous atmosphere

from the protected area for analysis by remote detectors

with an automatic operation should be considered. Where

spurious operation is detrimental to the plant, activation

shall be by two lines of protection system. Provision for

manually activated fire alarms shall also be made.

Fire Water Systems

In selecting the type of suppression system to be

installed, consideration shall be given to speed of

operation, the type of combustible material present as

indicated in the fire hazard analysis, possibility of thermal

shock, its effect on human beings (e.g. asphyxiation) and

on items important to safety (e.g. Reaching criticality

condition during water or foam flooding in the nuclear

fuel storage area). Reliable power supply should be

ensured for electrically operated control valves meant for

automatic suppression systems. Fire suppression systems,

which employ water as means for suppression of fire,

could be principally categorized under fixed water

extinguishing systems as follows:

a) Sprinkler and other water spray systems

b) Fire hydrant or standpipe and hose systems

a) Sprinkler and other water spray system

Complete automatically initiated water sprinkler

protection should be provided as a conservative measure

in all those locations of the plant or facility where

significant amounts of combustible material might be

present, which would result in unacceptable fire damage

in the event of an uncontrolled fire. Such a design

measure may also take into account aspects other than

safety (for example), spread of contamination. Generally,

water systems are preferred in areas containing a high fire

load of electrical cable material and other combustibles

where the possibility exists for deep-seated fires. Water

sprinklers may also be used for large quantities of oil (for

lubrication or transformer cooling). Further, in cases

where gas or other extinguishing systems are provided for

primary fire protection, water systems serve as a good

back-up fire protection. Sprinkler/spray extinguishing

systems shall, as a minimum, conform to requirements of

appropriate standards.

b) Fire Hydrant or Standpipe and Hose systems

Standpipes with hose connections equipped with

approved fire hose and nozzles should be provided for

areas containing or exposing nuclear-safety-related

structures, systems or components and should be spaced

so that these areas are accessible to at least one hose

stream. Water supply and hose capability should be

provided for the containment. Fire hose stations should be

conspicuously located as dictated by fire hazard analysis

and should not be blocked. The fire hose standpipe

system should be used for fire-fighting only. Alternative

hose stations should be provided for an area if the fire

hazard could block access to a single hose station serving

that area. Fire hydrant or standpipe hose system, should,

as a minimum, conform to requirement of appropriate

standards such as NFPA 14, “Standpipe and Hose

systems” or IS: 5714-1970 “Hydrant Standpipe for fire

fighting” for sizing, spacing and pipe support

requirements.

Fire water system of a typical NPP

This system utilizes water to extinguish the fire by

hydrant system and different water spray system.

Personnel protection spray system is provided inside

reactor building to faciliate personnel to exit from reactor

building in case rise of temperature due to LOCA. Fire

water is also used as a backup to end shield cooling and

steam generator cooling during station blackout.

Fresh water supply for this system is fulfilled by two

reservoirs:

1). Reservoir 1 having capacity of 20000 cube meter

2).Reservoir 2 having capacity of 4000 cube meter

Reservoir-2

Divided into two compartments (2000 m3 each)

Water requirement to extinguish fire

1150 m3

8 hydrants operating simultaneously for 2 hours

= 2 х 34 х 8 m3

= 544 m3

Largest water spray for two hours

= 2 х 290 m3

= 580 m3

So, water requirement to extinguish fire

= (544 + 580) m3

= 1124 m3

Water requirement as a backup during

475 m3

station blackout (4 hours) for E/S cooling and SG

cooling

End shield cooling requirement

= 123m3

Steam generator cooling requirement

= 352 m3

Total requirement

= (1150 + 123 + 352)m3

= 1625 m3As such only As such only compartment is

sufficient to cope with the situation.

Jockey pumps (P-1 and P-2)

(One main duty and another standby duty)

Start 8.5 kg/cm2

Stop 9.5 kg/cm2

Electrical motor driven fire water pump (P-3 and P-4)

Pump-3 start Discharge header pressure reaches 8

kg/cm2 with time delay of 30 sec

Pump-4 start Discharge header pressure reaches 7.5

kg/cm2 with time delay of 30 sec

Once started, pump is to be stopped manually

Diesel engine driven FW pump (P-5 and P-6)

Pump-5 start Discharge header pressure reaches kg/cm2

with time delay of 30 sec

Pump-6 start Discharge header pressure reaches 6.5

kg/cm2 with time delay of 30 sec

Once started, pump is to be stopped manually

Fire Water Supply to Various Equipment Hydrant

System: Total 250

The hydrant system covers the following buildings in

addition to the outdoor area:

a) Reactor Building (RB) nos. 3 and 4

b) Reactor Auxiliary Building (RAB) nos. 3 and 4.

c) Station Auxiliary Building (SAB) nos. 3A, 3B, 4A and

4B

d) Service building, control building

e) Turbine Building (TB) nos. 3 and 4

f) Electrical bay of TB nos. 3 and 4

g) Auxiliary boiler, fuel oil tanks and heavy water

upgrading plant

h) CCW and ASW pump house

i) Non-active process water pump house

j) Service water pump house

k) Demineralizer (DM) plant chlorination plant

h) Diesel storage area

i) Administration building, permanent warehouses

j) Waste management plant

k) Pipe and cable bridge area

l) Switchyard area

Water Spray System: Total 90 DVs

a) Generator transformers

b) Unit auxiliary transformers

c) Startup transformer

d) Turbine oil tanks, lube oil equipment and piping

e) Cable vault in SAB-3A, 3B, 4A, 4B

f) Cable vault in TB no. 3, 7, 4 at EL 107 m and 116.55 m

g) Cable trays in RB (selected areas only)

h) Cable passage between RB and CB and between RB

and SAB

i) Cable passage at EL 104 m in TB up to cable bridge

j) Pipe and Cable Bridge (PCB) at 100 m and 106 m

between RB and TB

k) Vertical cable shaft in CB between EL 97 m and 111 m

l) Cable trenches from CB to switch yard

m) Day oil tanks outside SAB-3A, 3B, 4A, 4B

n) PHT pump motors in RB-3 and 4

o) F/M vaults in RB-3 and 4

p) F/T rooms in RB-3 and 4

q) TG bearing housing and hydrogen seals

r) Cable on raceways on RB OCW

Requirements to be Ensured for Firewater System

A minimum of one out of two diesel driven fire fighting

pump shall always be operable. If a pump is found in

operable condition, the same shall be brought back to

service within seven days.Fire fighting water system shall

be kept filled and pressurized between 6.5 to 9.5 kg/cm2

(g) at all times. If it falls below 5.5 kg/cm2 (g), then

reactor shall be shutdown.Fire deluge system should be in

poised state for all equipments in useFire water pumps

sump level shall be maintained above 96.225 m

(minimum submergible level)

REFERANCES

(1)Safety Standards of the Nuclear Safety Standards

Commission (KTA) KTA 2101.3 (12/2000)

(2) heavy water reactors: status and projected

development;International Atomic Energy Agency

Vienna, 2002

(3)safety systems for pressurised heavy water reactor;

AERB safety guide no. aerb/npp-phwr/sg/d-10

(4)A MONOGRAPH by K. Ramprasad ,Ashis Kumar

Panda and Diptendu Das ;

Industrial Plants Safety Division

(5) Current status of fire risk assessment for nuclear

power plants ; Heinz Peter Berg1, Marina Röwekamp2

1Bundesamt für Strahlenschutz,

Germany

(6)Fire Safety in the Operation of Nuclear Power Plants

safety guide no. Ns-g-2.1 , IAEA

(7) Protection against Internal Fires and Explosions in the

Design of Nuclear Power Plants

safety guide No. NS-G-1.7 , IAEA

(8) Fire protection in pressurised heavy water type

nuclear power reactor, safety guide, no-AERB/SG/D-4

(9)aerb safety guide no. AERB/NPP-PHWR/SG/D-8

Primary heat transport system for pressurised heavy water

reactors

(10) AERB SAFETY GUIDE NO.

AERB/NPP-PHWR/SG/D-20

Safety related instrumentation and control pressurised

heavy water reactor

(11) IAEA-TECDOC-1421

Experience gained from fires in nuclear power plants:

Lessons learned

(12)IAEA-TECDOC-1554

Generic Safety Issues for Nuclear Power Plants with

Pressurized Heavy Water Reactors and Measures for their

Resolution

(13) IAEA-TECDOC-1594

Analysis of Severe Accidents in Pressurized Heavy Water

Reactors

(14)USNRC;regulatory guide

Fire protection for nuclear power plants

(15)SFPE Handbook of Fire Protection Engineering