THE EFFECTS OF ZINC INJECTION FROM HOT …2014/03/04  · THE EFFECTS OF ZINC INJECTION FROM HOT FUNCTION TEST AT TOMARI UNIT 3 Presented by ：Keisuke Sasaki Hokkaido Electric Power

THE EFFECTS OF ZINC INJECTION FROM HOT FUNCTION TEST AT TOMARI UNIT 3

Presented by：Keisuke Sasaki Hokkaido Electric Power Co., Inc.

2014 ISOE Asian ALARA Symposium September 23-24,2014

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Contents

- Introduction to TOMARI NPS - Zinc injection - Experiences of 1st cycle - Experiences of 1st refueling outage(RFO) - Experiences of 2nd refueling outage(RFO) - Conclusion

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Introduction to TOMARI NPS

Hokkaido

Japan

Letdown flow

Unit 1 Unit 2 Unit 3

Rated Electric Output

Reactor type Commercial Operation SG

579ＭＷ 579ＭＷ 912ＭＷ

ＰＷＲ

1990

20m3/h

1992 2009

600TT 600TT 690TT

54m3/h

Unit1 Unit2

Unit3

3

Operated History of Unit 3

Introduction to TOMARI NPS

Unit 3

Output

2015 2014 2013 2012 2011 2010 2009 2008 2007 FY

1st CYCLE 378 days

2nd CYCLE 424 days

1st RFO 2nd RFO ▲HFT ▲Core loading

▲Commercial Operation

Zn injection

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Zinc injection

Substitution of zinc for Co

Zinc injection during power operation

Suppression Co uptake into the inner oxide layer

Co

5

Zinc injection Zinc injection from HFT

Suppression Co uptake into the inner oxide layer

Corrosion suppression

Ni

Co

6

EXPERIENCES OF 1st CYCLE

0

5

10

0 50 100 150 200 250 300 350 400

Zn Concentration（

ppb）

Commercial Operation Time(day)

Control Band

Zinc concentration was controlled with the target concentration (5±3ppb).

Zn concentration in the primary coolant

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EXPERIENCES OF 1st CYCLE

Ni concentration was higher than that of the reference plant.

Ni concentration in the primary coolant

⇒ Ni releases from corrosion products and the base metal of SG tube.

0

0.5

1

1.5

2

0 50 100 150 200 250 300 350 400

Ni Concentration (ppb)

Commercial Operation Time (day)

Tomari 3

Reference

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EXPERIENCES OF 1st CYCLE

The Co-58 concentration was higher than that of the reference plant.

Co-58 concentration in the primary coolant

1E-2

1E-1

1E+0

1E+1

1E+2

1E+3

0 100 200 300 400

Co-58 Concentration (Bq/ml)

Commercial Operation Time(day)

Ion (Tomari 3) Ion (Reference)

Crud (Tomari 3) Crud (Reference)

⇒ Suppression Co uptake into inner oxide layer

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EXPERIENCES OF 1st RFO

1E+0

1E+1

1E+2

1E+3

1E+4

1E+5

1E+6

-24 0 24 48 72 96 120 144 168 192 216

Co-58 Concentration (Bq/ml)

Time from Shutdown (hr)

Ino (Tomari 3)

Ion (Reference)

Crud (Tomari 3)

Crud (Reference)

The particulate Co-58 was higher than that of the reference plant. The ionic Co-58 was at the same level as that of the reference plant.

Concentrations of radioactive Co-58（Ion,Crud） in the primary coolant

⇒ The amount of the corrosion product with a higher specific radioactivity has decreased.

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The amount of Ni removal was about 20% less than that of the reference plant.

EXPERIENCES OF 1st RFO

Tomari unit 3 Reference plant Ni（g） 3039 3639

Co-58（Bq） 1.3×1014 1.2×1014

Co-60（Bq） 8.0×1011 5.2×1011

Amount of Ni,Co-58,and Co-60 removal

The amount of Co-58 removal was about equal to that of the reference plant.

⇒ Corrosion suppression effect

⇒ Suppression Co uptake into the inner oxide layer and decreasing Ni inventory

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EXPERIENCES OF 1st RFO

The dose-rates at SG , RV inside and MCP were about over 40% less than those of the reference plant.

Dose-rates on SG tube, SG CH,RV Inside, and MCP

0

10

20

30

40

50

60

70

80

SG Tube SG CH Hot SG CH Cold RV Inside

Dose

Rat

e (

mS

v/h)

Reference

TOMARI 3

0

0.05

0.1

0.15

0.2

Hot Leg Cold Leg Crossover Leg

Dose

Rat

e (

mS

v/h)

Reference

TOMARI 3

⇒ The dose-rate reduction effect with zinc injection is about 40-60% at the 1st RFO.

TLD with Pb cover Ionization chamber

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Tomari unit 3 Reference plant

Co-58 inventory 22.2 43.2

Co-60 inventory 0.9 2.1

Radiation source inventory 24.2 48.1

EXPERIENCES OF 1st RFO

The Co-58, Co-60 and radiation source inventory were about 50% less than those of the reference plant.

Evaluation of Radiation Source Inventory [TBq]

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⇒ These are in good consistency with the actual dose-rates on the main components.

EXPERIENCES OF 2nd RFO

The dose-rates on SG tube, SG CH and RV Inside at the 2nd

RFO were about 50-60% less than those at the 1st RFO.

The dose-rates on MCP at the

2nd RFO were about 20-60% less than those at the 1st RFO.

0

0.01

0.02

0.03

0.04

0.05

Hot Leg Cold Leg Cross Over Leg

Dose

Rat

e (

mS

v/h)

1st RFO

2nd RFO

0

10

20

30

40

50

SG Tube SG CH Hot SG CH Cold RV Inside

Dose

Rat

e (

mS

v/h)

1st RFO

2nd RFO

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CONCLUSION

At the 1st RFO, the dose-rates at the main components are about 50% less than that of the reference plant,

as a similar trend to the radiation source inventory. Considerable dose-rate reduction at the 2nd RFO was

confirmed compared to the 1st RFO. From now on, further dose-rate reduction effect is

expected.

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Thank you for your Attention.