FIRE SAFETY SIMULATION OF

CABLE FIRE IN NUCLEAR

POWER PLANT ROOM BASED

ON FLAMMABILITY DATABASE

OF CABLES

Akihiro Matsuda

Department of Engineering Mechanics and Energy

University of Tsukuba

SMiRT23 Manchester UK 2015

CONTENTS

• Objectives

• Flammability tests of electrical cables

• Evaluation by the Arrhenius equation

• CFD analysis with FDS

• Conclusion

This research was supported by research fund from Japan Nuclear Energy Safety Organization(JNES -> NRA,Japan)

OBJECTIVE

• Develop the safety evaluation method of nuclear

power plant cables in fire accidents

• Flammability test of cables in high temperature to

verify electrical performance of cable

• Effect of cable temperature on insulation

resistance and short circuit time

• CFD simulation of switchgear room in fire accident

• Temperature distribution of switchgear room was

computed

• Flammability test machine

• Develop by modifying cone-calorimeter machine

• Temperature of cone heater was controlled digitally

• 1~5 cables on cable tray are possible to test

• Maximum temperature of cone heater is 800℃

TEST FACILITIES

Heat chamber

Heat release rate

PC

• Cable specimens for flammability test

• Cable tray specimen with electrical cables are applicable to

flammability test

• Surface temperature of cable was controlled by laser type

temperature sensor

• Length of cables was 620mm

CABLE SPECIMENS FOR TEST

Cone heater

Cable tray

Cable

INSULATION RESISTANCE IN

FLAMMABILITY TEST

• Insulation resistance in flammability test

• Between insulators, insulator and tray

• Hyper electrical resistance measurement machine

• Capacity of insulation resistance from 2.0 to 1.0x107M

• Ignition of cables were observed in high temperature

Ω

Heater Cable

SM-8215 HIOKI Corp. Japan

CABLES FOR FLAMMABILITY

TESTS

• Cables used in nuclear plants were applied to

flammability test

• SHCVV

• SPVV

• FR-STP

• CCSHV

SPECIFICATION OF CABLES

Name of cable Sheath Insulator

Number

Of

Conductor

DiameterIEE

E383

1.SHCVV HR-vinyl HR-vinyl 8 14mm

2.SPVVPolyvinyl

chloride

Polyvinyl

Chloride2 9mm

3.FR-STP FR-EP rubber FR-HR vinyl 2 10.5mm ○

4.CCSHVCross linked

polyethyleneVinyl 2 9mm

IEEE383: Vertical flame tray test

101

102

103

104

105

106

107

108

Insu

lati

on

res

ista

nce

(MΩ

)

120100806040200

Time (min)

200℃ 220℃ 240℃ 280℃ 340℃ 400℃ 460℃ 550℃

800

600

400

200

Cab

le t

emper

ature

(℃

)

80006000400020000

Time (sec)

200℃ 220℃ 240℃ 280℃ 340℃ 400℃ 460℃ 550℃

TEST RESULTS OF SHCVV

Name of cable Sheath Insulator

Number

Of

Conductor

Diameter

1.SHCVV HR-vinyl HR-vinyl 8 14mm

200℃

800

600

400

200

Cab

le t

emper

ature

(℃

)

120100806040200

Time (min)

220℃ 240℃ 260℃ 320℃ 380℃ 440℃ 530℃

101

102

103

104

105

106

107

108

Insu

lati

on r

esis

tance

(MΩ

)

120100806040200

Time (min)

220℃ 240℃ 260℃ 320℃ 380℃ 440℃ 530℃

Name of cable Sheath Insulator

Number

Of

Conductor

Diameter

2.SPVVPolyvinyl

chloride

Polyvinyl

Chloride2 9mm

TEST RESULTS OF SPVV

220℃

Name of cable Sheath Insulator

Number

Of

Conductor

Diameter

3.FR-STP FR-EP rubber FR-HR vinyl 2 10.5mm

TEST RESULTS OF FR-STP

800

600

400

200

Cab

le t

emp

erat

ure

(℃

)

120100806040200

Time (min)

310℃ 330℃ 390℃ 450℃ 540℃ 590℃

101

102

103

104

105

106

107

108

Insu

lati

on

res

ista

nce

(MΩ

)

120100806040200

Time (min)

310℃ 330℃ 390℃ 450℃ 540℃

310℃

Name of cable Sheath Insulator

Number

Of

Conductor

Diameter

4.CCSHVCross linked

polyethyleneVinyl 2 9mm

TEST RESULTS OF CCSHV

800

600

400

200

Cab

le t

emp

erat

ure

(℃

)

120100806040200

Time (min)

340℃ 360℃ 380℃ 400℃ 490℃ 540℃

101

102

103

104

105

106

107

108

Insu

lati

on

res

ista

nce

(MΩ

)

120100806040200

Time (min)

340℃ 360℃ 380℃ 400℃ 490℃ 540℃

340℃

RELATIONSHIPS BETWEEN SHORT-

CIRCUIT TIME AND CABLE

TEMPERATURE (CABLE 1~4)

700

600

500

400

300

200

100

0

Cab

le t

emp

erat

ure

(℃

)

12 3 4 5 6 7 8 9

102 3 4 5 6 7 8 9

1002

Short circuit time (min)

SHCVV

SPVV

FR-STP

CCSHV

• Relationships between short circuit times and surface

temperature of cables were summarized

• θ= θ∞+(θb -θ∞) exp(α・t)

• θb : Temperature of ignition

• θ∞ : Temperature which reach

2h without short-circuit

• α: Parameter of each cables

Test results of every cables showed faster short circuit time as temperature higher.

Fundamental behavior of electrical characteristics and effects of temperature were obtained.

EVALUATION BY ARRHENIUS

EQUATION

• Applicability of the Arrhenius equation to flammability

test was investigated

• Plot the relation ships between ln(TR) and reciprocal of

θ(1/θ(K)) in same insulation resistance

• Short circuit, 10MΩ, 100MΩ were selected

101

102

103

104

105

106

107

108

Insu

lati

on

res

ista

nce

(MΩ

)

120100806040200

Time (min)

200℃ 220℃ 240℃ 280℃ 340℃ 400℃ 460℃ 550℃

100MΩ

10MΩ

TR

θ

Short circuit

ARRHENIUS PLOT OF SHCVV

AND SPVV

• Plots of SHCVV and SPVV show linear relationships between

ln(TR) and 1/θ(K)

6

5

4

3

2

1

0

-1

ln(T

R)

2.52.01.51.0

1/θ (10-3

/K)

短絡10MΩ100MΩ

○ short circuit

□ 10MΩ

△ 100MΩ

5

4

3

2

1

0

-1

-2

-3

ln(T

R)

2.01.51.0

1/θ (10-3

/K)

短絡10MΩ100MΩ

○ short circuit

□ 10MΩ

△ 100MΩ

SHCVV SPVV

3

2

1

0

ln(T

R)

1.61.41.2

1/θ (10-3

/K)

短絡10MΩ100MΩ

5

4

3

2

1

0

-1

ln(T

R)

2.01.51.0

1/θ (10-3

/K)

短絡10MΩ100MΩ

ARRHENIUS PLOT OF FR-STP

AND CCSHV• Arrhenius plot of FR-STP and CCSHV show linear

relationships between ln(TR) and 1/θ(K)

• The Arrhenius equation was applicable to flammability

test○ short circuit

□ 10MΩ

△ 100MΩ

○ short circuit

□ 10MΩ

△ 100MΩ

FR-STP CCSHV

CFD ANALYSIS BY FDS

• FDS: Fire Dynamics Simulator

• Developed by NIST(National Institute of Standards and Technology, USA)

• Solve the Navire-Stokes equation

• Large Eddy simulation for turbulence flow

• Input heat release rate for fire source

• In this simulation, an electrical cabinet fire was supposed

• A switchgear room was selected

• Specification of room was based on Nuclear Power Plant Fire Modeling

Application Guideline(NPP FIRE MAG), NUREG-1934( 2011)

SWITCH GEAR ROOM FOR

SIMULATION

• Mesh model for switchgear room was created in FDS

• Switchgear room and cable tray were applied to CFD model

• Ventilation was supposed as design value

• Fire from electrical cabinet was assumed

NUREG-1934( 2011) CFD model

• For fire-source, burning test results of electrical cabinet

were applied.

• 0.3m x 0.6m of the upper surface of electrical cabinet was

supposed as the fire-source, duration time was 40min.

HEAR RELEASE RATE FOR

NUMERICAL ANALYSIS

1000

800

600

400

200

0

Hea

t re

leas

e ra

te(k

W)

25002000150010005000

Time(s)

Nuclear Power Plant Fire Modeling Application Guideline(NPP FIRE MAG), NUREG-1934( 2011)

SNAPSHOTS OF CFD ANALYSIS

1000

800

600

400

200

0

Hea

t re

leas

e ra

te(k

W)

25002000150010005000

Time(s)

• Time of snapshot was 1100sec.

• Maximum temperature was

observed in CFD simulation

Temperature distribution Velocity of air

EVALUATION OF

CABLE TEMPERATURE

800

600

400

200

0

Tem

per

ature

(゜C

)

70605040302010

Distance from fire source(cm)

• Maximum cable temperature showed higher as distance

from the fire source closer

• Duration time of this simulation case was short for long-

time short circuit.

• In this case, 400℃ was supposed as the temperature of

immediate short circuit.

CONCLUSION

• The safety evaluation method of cables in nuclear plant fire accidents was developed

• Electrical performance test of cables in high temperature were conducted

• Relationships between temperature and short circuit time was proposed

• CFD simulation(FDS) to know temperature distribution of cables in nuclear power plant room

• Safety distance from fire source was able to be investigated by CFD simulation

• Performance of cables in high temperature were able to investigate by flammability test and CFD simulation

800

600

400

200

Cab

le t

emp

erat

ure

(℃

)

120100806040200

Time (min)

380℃ 390℃ 410℃ 430℃ 470℃ 490℃

Name of cable Sheath Insulator

Number

Of

Conductor

Diameter

5.Eco-material PolyethyleneFR-

Polyethylene2 10mm

TEST RESULTS OF EMC

380℃

101

102

103

104

105

106

107

108

Insu

lati

on

res

ista

nce

(MΩ

)

120100806040200

Time (min)

380℃ 390℃ 410℃ 430℃ 470℃ 490℃

800

600

400

200

Cab

le t

emp

erat

ure

(℃

)

120100806040200

Time (min)

430℃ 450℃ 470℃ 490℃ 530℃ 550℃ 570℃

Name of cable Sheath Insulator

Number

Of

Conductor

Diameter

6.Non-halogen FR-Polyethylene Polyethylene 2 10mm

TEST RESULTS OF NH

430℃

101

102

103

104

105

106

107

108

Insu

lati

on

res

ista

nce

(MΩ

)

120100806040200

Time (min)

430℃ 450℃ 470℃ 490℃ 530℃ 550℃ 570℃

EFFECT OF HEATED AREA ON

INSULATED RESISTANCE

R1

R2

R3

321

111

1

RRR

R

3

1RR

321 RRR

• Heated area of flammability test was increased

• Heated area was double and triple of normal test

• Insulated resistance was evaluated

RELATIONSHIPS BETWEEN SHORT-

CIRCUIT TIME AND CABLE

TEMPERATURE(EMC AND NHC)

• Relationships between short circuit times and surface

temperature of cables were summarized

• θ= θ∞+(θb -θ∞) exp(α・t)

• θb : Temperature of ignition

• θ∞ : Temperature which reach

2h without short-circuit

• α: Parameter of each cables

Test results of every cables showed faster short circuit time as temperature higher.

Fundamental behavior of electrical characteristics and effects of temperature were obtained.

700

600

500

400

300

200

100

0

Cab

le t

emp

erat

ure

(℃

)

12 3 4 5 6 7 8 9

102 3 4 5 6 7 8 9

1002

Short circuit time (min)

EMC

NHC

SHCVV

0

100

200

300

400

500

600

EMC NHC SHCVV SPVV FR-STP CCSHV

Ca

ble

tem

per

atu

re(℃

)

Cable

安全温度

発火温度

TEMPERATURE Θ∞

AND ΘB

θ∞

θb

θb

θ∞

EFFECT OF HEATED AREA ON

INSULATED RESISTANCE

• Cable specimen was fixed on cable tray

• Length of cable was 1800mm

• Cable was bended and 2 and 3 part of cable were under the heater

Φ180

TEST RESULTS

• Insulated resistance became 1/2 and 1/3, when

heated area were double and triple.

101

102

103

104

105

106

107

108

Insu

lati

on

res

ista

nce

(MΩ

)

120100806040200

Time (min)

直線 2つ折り 3つ折り

○ Straight

□ Double area (x2)

△ Triple area (x3)

Θ＝290℃

101

102

103

104

105

106

107

108

Insu

lati

on

res

ista

nce

(MΩ

)

50403020100

Time (min)

直線 2つ折り 3つ折り

EFFECT OF HEATED AREA ON

SHORT CIRCUIT TIME

• The heated area increases, short circuit time

became shorter

○ Straight

□ Double area (x2)

△ Triple area (x3)

Θ＝390℃

CONCLUSION

• Fire damage testing of electric cables in nuclear

plants was conducted

• Flammability test of cables in high temperature

• Relationships between temperature and short

circuit time was investigated

• Relationships between heated time and

temperature was evaluated by the Arrhenius

equation

FUTURE WORK

• Establish estimation method of insulation

resistance of cable in fire accidents

• Modeling of relationship between insulation

resistance and time under various temperature

would be investigated