Progress of the Zinc Injection in Tsuruga NPP Unit 2

1ISOE/ATC ALARA ISOE/ATC ALARA Symposium Symposium 2006 2006

The Japan Atomic Power CompanyThe Japan Atomic Power Company

Progress of the Zinc Injection in Tsuruga NPP Unit 2

October 12, 2006October 12, 2006

THE JAPAN ATOMIC POWER COMPANYTHE JAPAN ATOMIC POWER COMPANYNobuaki NAGATA, Hideaki ICHIGE, Eiichi KADOINobuaki NAGATA, Hideaki ICHIGE, Eiichi KADOI

HOKKAIDO ELECTRIC POWER CO., INC.HOKKAIDO ELECTRIC POWER CO., INC.Yoshifumi WATANABEYoshifumi WATANABE

THE KANSAI ELECTRIC POWER CO., INC. THE KANSAI ELECTRIC POWER CO., INC. Hideya IKOMAHideya IKOMA

SHIKOKU ELECTRIC POWER CO., INC. SHIKOKU ELECTRIC POWER CO., INC. Tsuyoshi SEMBATsuyoshi SEMBA

SHIKOKU RESEARCH INSTITUTE INC. SHIKOKU RESEARCH INSTITUTE INC. Toshiaki HAMAGUCHIToshiaki HAMAGUCHI



Objectives

• Effect of water chemistry during zinc injection

• Effect of decreasing dose equivalent rate on primary equipment and pipes after zinc injection

• Evaluation of the fuel performance by observing the external appearance and thickness of oxide film on the fuel installed in core during zinc injection

To evaluate followings of the zinc injection for Japanese PWR plants by using Tsuruga-2



0

20

40

60

80

100

1 2

Zn- 64Zn- 66,67,68,70 Isotope

Abundance(%)

RadioIsotope

RadioactiveHalf-life

Zn-64 48.6 Zn-65 244 D

Zn-66 27.9 －－Zn-67 4.1 －－

Zn-68 18.8Zn-69 56 M

Zn-69m 13.8 H

Zn-70 0.6 Zn-70m 4 HNatural Zn Depleted Zn

Isot

ope

Ab

un

dan

c e( %

)General idea for dose reduction by application of Zn injection

Suppression of the dissolution of corrosion products

Suppression of redeposition

Outer layer （ Ferrite ）： NiFe2O4

Inner layer （ Chromite:CoCr2O4

） : Oxygen :Zinc

:Co, （ Ni ）: Cr

Pip

e

Pip

ePrimary Water

FuelDeposition

Accumulation RadioactivationCo（Ni）

58Co, 60CoZnZn

ZnZn

Redeposition58Co, 60Co

Depleted Zn : Suppression of dose increase due to reducing the abundance of Zn-64 below 1%

Accumulation and radioactivation of the corrosion products



Zn Injection Equipment designing, manufacturing, setting

Fuel Performance 　　　　　　　

FY 2004 FY 2005 FY 200615/12～ 25/2 22/4～ 22/5

# 14

Planning and Pre-adjustment

Zn Injection

Evaluation Water Chemistry

Dose equivalent rate

# 15Outage (Tsuruga-2)

The Application Study Schedule of Zn Injection

Depleted Zn Purchase

Start of Zn Injection(10/8) ▼



Zinc Injection System in Tsuruga-2

Tsuruga-2　　 4 loops PWR　　 Start Operation : Feb. 1987　　 Electric Power : 1160 MWe　　　　　

Charging pump Reactor vessel

Steam generator(SG)

Zn injectionequipment

Demineralizer

Volume control tank(VCT)

Samplingrack

Sample Water Return Injection Pump

Zinc acetatetank

Chemical VolumeControl System

Sampling Roomfor Primary Water

Pressurizer

Primary Loop

※

※



Zn Injection Equipment

Equipment Configuration・ Chemical Tanks : 2 (10 little)・ Concentration of Zinc Acetate : about 5～ 12（ g/little）Safety Precaution・ Chemical tank : low level detection・ injection pressure : high detection・ Leakage : detection・ check valve in sampling sink

Automatic stop

Connection Point

Sampling Sink


Zn injection equipment was downsized with making consideration to safety precaution, and was connected to the sampling return line.

Chemical Tanks

Drain Line




Zn Injection Plan

Zn injection had been performed in Tsuruga-2 for eight months within a range of 5-7 ppb based on the European experience. (Upper limit : 10 ppb)

Zi C

once

ntr

atio

n in

Pri

mar

y W

ater

(ppb

)

Nov., 2005 Jan., 2006 Mar., 2006 May, 2006Jul., 2005 Aug., 2005

21

0May, 2005

6543

10987

About 5 ppb

About 7 ppb

Detection Limit : １ｐｐｂ

Start of Zn Injection

Outage #15

Incubation Period ※

※　 Because most of the Zinc is incorporated in the oxide layers on primary equipment and piping , zinc concentration of primary water is not detected in a early stage of Zn injection.



Primary Water Chemistry during the Zn Injection

Although concentration of the radioactive Co was increased by a factor of ten with Zn injection than before, the increase was expected based on the European experience. RCS purity, pH and conductivity, was not affected.

0

500

1000

1500

発電機出力

(MW

e)

0

2

4

6

8

10 炉水亜鉛イオン

亜鉛イオン濃度

(ppb

)

0

10

20

30

40 pH炉水炉水導電率

pH(-

)，(μ

S/cm

)導電率

0

10

20

30

40

50

60

2003/ 10/ 29 2004/ 2/ 6 2004/ 5/ 16 2004/ 8/ 24 2004/ 12/ 2 2005/ 3/ 12 2005/ 6/ 20 2005/ 9/ 28 2006/ 1/ 6 2006/ 4/ 16

Co58炉水イオン Co60炉水イオン

放射性コバルトイオン

(Bq/

cm3)


#14 Operation cycle #15 Operation cycle

pH

Conductivity

Co-58 Ion

Zinc Ion

Co-60 Ion

Ele

ctri

c P

ower

(Mw

e)C

once

ntr

atio

n(p

pb

)p

H (

-)C

ond

. (μ

S/c

m2 )

Con

cen

trat

ion

(Bq

/ml)



Measurement of the Radioactive Zinc(Verification of the depleted Zinc)

The increase in Zn-65 was not found due to using depleted zinc.

14/1/04 13/4/04 12/7/04 10/10/04 8/1/05 8/4/05 7/7/05 5/10/05 3/1/06 3/4/06

0.001

0.01

0.1

1

10

100

Act

ivit

y C

once

ntr

atio

n (

Bq

/ml)

Zn-65 Crud Zn-69m Crud

Zn-65 Ion Zn-69m Ion

#14 Operation Cycle #15 Operation Cycle




Relative dose equivalent rate on the primary equipment and pipes

The zinc injection reduced the dose rate of primary equipment and pipes to 70-80 % than that of previous outage. This effect of dose reduction is higher than expectation based on the foregoing plants.However, low temperature nonregenerater had no effect due to zinc injection.

Charging pumpReactor Vessel

Steam generator (SG) Nonregenerative heat exchanger (1.1)

Zn injection equipment

Demineralizer

Volume control Tank(VCT)

Sampling Rack

Sample water return

＊Injection Pump

Zinc Acetate Tank

＊

Crossover leg(0.69)

SG channel head(0.64 - 0.78)

Cold leg(0.81)

Hot leg(0.73)

Regenerative heat exchanger (0.3)

RCS pump(0.86) : Dose rate measuring points

(Ratio from the previous outage ）



Behavior of dose equivalent rate in SG Channel head

Dose equivalent rate in SG channel head had increased with age, but was reduced to its about 20-30% thanks to the application of zinc injection.

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100

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Outage #

Dos

e eq

uiv

alen

t ra

te (

mS

v/h

)

SG channel head (Hot)

SG channel head (Cold)

Zn Injection

※

※ ： Radiation source decay due to unscheduled plant shutdown when dose rate was measured



L K J H G F EN M D CP B AR

1

2

3

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15

14

13

12

#13 Operation CycleFuel Burn-up : 13202MWd/tSpecific Power ratio : 0.84

#14 Operation CycleFuel Burn-up : 31265MWd/tSpecific Power ratio : 1.15

#13 Operation Cycle (Zn Injection)Fuel Burn-up : 46365MWd/tSpecific Power ratio : 1.00

# R 08 (46365MWd/t)

# P 02　 (46560MWd/t)

Evaluation of the Fuel Cladding- Visual Inspection of the fuel external appearance -

Fuel surface showed no significant differences with or without zinc injection. (The region looked white on the figure due to difference of growth of the oxide film (thickness, crystal structure) does not show an abnormality for the fuel performance.)

Fuel experienced Zn injection Fuel experienced no Zn injection



Evaluation of the Fuel Cladding- Measured thickness of oxide film -

In the result of the evaluation, it was not considered that zinc injection would affect corrosion on fuel cladding because the measured thickness of oxide film was included in past database.

※　 Sendo et al. AESJ, 2003，Mitsubishi Heavy Industrial,LTD, NHI-NES-1012

Th

ick

nes

s of

oxi

de

film

(μ

m)

Past database ※

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160

0

従来ｽｽﾞｼﾞﾙｶﾛｲｰ 4

低ｽｽﾞｼﾞﾙｶﾛｲ -4 (先行照射 )

低ｽｽﾞｼﾞﾙｶﾛｲ -4 (Vandellos 2) *

低ｽｽﾞｼﾞﾙｶﾛｲ -4 (North Anna 1)

低ｽｽﾞｼﾞﾙｶﾛｲ -4 (高浜３号機 ) **

低ｽｽﾞｼﾞﾙｶﾛｲ -4 (敦賀２号機；亜鉛経験なし )

低ｽｽﾞｼﾞﾙｶﾛｲ -4 (敦賀２号機；亜鉛経験あり )

10 20 30 40 50 60 70 0

*　(財)原子力発電技術機構、平成11年度軽水炉改良技術確証試験　（高燃焼度等燃料に関するもの）に関する報告書、平成12年3月** (財)原子力発電技術機構、平成10年度軽水炉改良技術確証試験　（高燃焼度等燃料に関するもの）に関する報告書、平成11年3月

： Slightly rough surface

Average of fuel burn-up(GWd/t)

Past Data ※

: Zircaloy-4 (No Zn injection): Zircaloy-4 (Zn injection)



SummaryWater Chemistry

・ Concentration of zinc in primary water was controlled well within the target value (5-7 ppb).

・ Although concentration of the radioactive Co was increased by a factor of 10 with Zn injection than before, the increase was included within the expectation based on the European experience.

・ The increase in Zn-65 was not found due to using depleted zinc.

Dose equivalent rate・ The zinc injection reduced the dose equivalent rate of primary equipment

and pipes to 70-80 % than that of previous outage.

Fuel Performance・ It was not considered that zinc injection (eight months) would affect

corrosion on fuel cladding by observing the fuel external appearance and thickness of oxide film on the fuel cladding.

Zinc injection in Tsuruga-2 will continue to be performed.Influence of long-term zinc injection on the plant and fuel performances will be estimated.

Progress of the Zinc Injection in Tsuruga NPP Unit 2

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