Measures for containing an increase in pipes’ dose-equivalent rate in the hydrogen-injected environment at the Shimane Nuclear Power Station Unit 1 １ Tomohiro

Measures for containing an increase in pipes’ dose-equivalent rate in the hydrogen-injected environment at the Shimane Nuclear Power Station Unit 1

１

Tomohiro Minami The Chugoku Electric Power Co., Inc.

Shimane Nuclear Power Station

All Right Reserved. Copyright © 2006 ,THE CHUGOKU ELECTRIC POWER CO., INC.

Table of Content

○ Outline of Shimane Nuclear Power Station

○ Hydrogen injections performance at Shimane Nuclear Power Station

○ Transition of PLR piping dose-equivalent rate

○ Management of gradual hydrogen injection termination

○ Current piping dose-equivalent rate

○ Future tasks

２


Niigata

TokyoFukuoka

Hiroshima

Osaka

Sendai

Kyoto

CHUGOKU

REGION

Sapporo

SHIMANE NUCLEARPOWER STATION

Shimane Prefecture

Yamaguchi Prefecture

Hiroshima Prefecture

Okayama Prefecture

Tottori Prefecture

Hiroshima

Matsue

Yamaguchi

Yonago

Okayama

★

Outline of Shimane NPS(1/2)

３


Outline of Shimane NPS(2/2)

Unit No. Capacity(MW)

ReactorType

Commercial

Operation

1 460 BWR Mar.1974

2 820 BWR Feb.1989

Unit 2

Unit 1

４


Hydrogen injections performance at Shimane Nuclear Power Station

５

Year Outage/Cycle

Feed-waterhydrogen

concentration (ppm)

Description

January 1998 20th outage 　　－・ Installed a hydrogen injection facility (Trailer system)

February 1998 21st cycle 0 ～ 0.70.50

・ Gradual injection test (increment of 0.1ppm)・ Started continuous injection

March 1999 22nd cycle 0.45 ・ Conducted gradual injection and regular termination・ Changed hydrogen concentration due to influence on the MS monitor

May 1999 - May 2000

22nd outage －・ Conducted shroud replacement(Chemical decontamination inside the reactor in the HOP method)

April 2000 23rd cycle 0.40 ・ Changed hydrogen concentration due to influence on the MS monitor

December 2001 24th cycle 0.40 ・ Conducted gradual injection and regular termination

February 2005 25th outage－

・ PLR piping repair work(Chemical decontamination of PLR pump inlet and outlet piping in the HOP method)

August 2005 26th cycle －・ Preliminary oxidative operation・ Conducted gradual injection and regular termination


Transition of PLR piping dose-equivalent rate (Pump A (21th outage))

PLR(A) inlet vertical piping

0.0E+0

1.0E+5

2.0E+5

3.0E+5

4.0E+5

5.0E+5

17th 18th 19th Interim Stoppage 20th 21st

Am

ount

of

nucl

ide

depo

sit(

Bq/

cm2)

0

1

2

3

4

5

dose

-equ

ival

ent

rate

(mSv/

h)

Co- 58Co- 60Mn- 54Fe- 59dose- equivalent rate

PLR(A) outlet vertical piping

0.0E+0

1.0E+5

2.0E+5

3.0E+5

4.0E+5

5.0E+5

18th 19th iInterim Stoppage 20th 21st

Am

ount

of

nuclid

ede

posi

t(B

q/cm

2)

0

1

2

3

4

5

dose

-equ

ival

ent

rate

(mSv/

h)Co- 58

Co- 60

Mn- 54

Fe- 59

dose- equivalent rate

６


Transition of PLR piping dose-equivalent rate (Pump B (21th outage))

PLR(B) inlet vertical piping

PLR(B) outlet vertical piping

0.0E+0

1.0E+5

2.0E+5

3.0E+5

4.0E+5

5.0E+5

18th 19th Interim Stoppage 20th 21st

Am

ount

of

nuclid

e d

epo

sit(

Bq/

cm

2)

0

1

2

3

4

5

dose

-equ

ival

ent

rate

(mSv/

h)Co- 58Co- 60Mn- 54Fe- 59dose- equivalent rate

７

0.0E+0

1.0E+5

2.0E+5

3.0E+5

4.0E+5

5.0E+5

18th 19th Interim Stoppage 20th 21st

Am

ount

of

nucl

ide

depo

sit(

Bq/

cm2)

0

1

2

3

4

5

dose

-equ

ival

ent

rate

(mSv

/h)Co- 58

Co- 60Mn- 54Fe- 59dose- equivalent rate


Dose-equivalent rate distribution in the axis / circumferential directions at the PLR pump outlet piping

21st outage 　　 Dose-equivalent rate of the A-PLR pump outlet piping

0.00

1.00

2.00

3.00

4.00

5.00

6.00

ＫＪＩＨＧＦＥＤＣＢＡposition

pipi

ng d

ose-

equi

vale

nt r

ate(

mSv/

h)

0°90°180°270°

flow

８

The fluctuation of dose-equivalent rate in the axis and circumferential directions was evaluated as attributable to cladding buildup and the increase of dose-equivalent rate.


Base material Base material

In the HWC environment (low hydrogen peroxide), reactor water is in reductive atmosphere, oxidizing chromium acid forms clad deposits on piping internal surfaces.

In the NWC environment, chromium oxide clad on piping's internal surfaces ionizes and elutes into the reactor water.

　 Chromium forms under the HWC / NWC environment

９

HWC environment NWC environment

Cr2O3 (Insoluble)

CrO42-(Soluble)


Hydrogen injection termination/start pattern (21st cycle)

Hydrogen injection termination/start pattern in the 21st cycle

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

Feed

-wate

r h

yd

rog

en

con

cen

trati

on

（p

pm

）

Continuous injectionstarted at the feed-waterhydrogen concentration of0.5ppm

Termination of hydrogen injection associated with CR patternadjustment

Feed-water hydrogen concentration0.5ppm→0.1ppm(maintained for 24 hours )→Termination

21st cycle 21st outage

February

1998

Start of injection

0.5ppm

0.1ppm

Continuous operation for

around 300 days

１０

（ day）


Transition of reactor-water conductivity and chromium acid concentration (21st cycle)

21cyc

0

5

10

15

20

25

0:00 12:00 0:00 12:00 0:00 12:00 0:00 12:00 0:00 12:00

Con

duct

ivity

μS/

m（

）

21cyc

0.5ppm 0.1ppm 0.0ppm21cyc

05

1015202530

0:00 12:00 0:00 12:00 0:00 12:00 0:00 12:00 0:00 12:00

Chro

miu

m a

cid

conc

entr

atio

npp

b（

）

21cyc

１１

（ Time ）

（ Time ）


External layer (Ferrite)Internal

layer(Chromite)

Clad deposit (Fe, Cr)

Base material

Radioactive ion

Shimane Unit 1 21st outage

Continuous 300-day HWC operation increased the amount of chromium deposit from reactor water. The change of environment (HWC -> NWC) eluted chromium, causing uneven piping's internal surfaces, thereby increasing the amount of cladding.

Mechanism of how the dose-equivalent rate of PLR outlet piping increased (21st outage)

１２


Mechanism of how hot spots developed at the PLR pump outlet

PLR pump outlet piping

Swirls at the PLR pump and elbow outlets disturbed the flow significantly.

Environmental change and flow disturbance at the pump outlet increased partial dissolution of Chromium oxides on piping's internal surfaces and aggravated surface unevenness.

The amount of clad deposits at the PLR pump outlet piping showed a localized increase.

Increase of dose-equivalent rate at the PLR pump outlet piping

１３

After extended stable operation with hydrogen injection (around 300 days), terminated hydrogen injection and resumed the injection upon changing the pattern (12/1998).Reactor water environmentReductive→ Oxidative

Reactor water’s radioactive concentration increased upon termination of hydrogen injection.


Hydrogen injection termination/ start pattern in the 22nd cycle

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

Feed

-wat

er h

ydro

gen

conc

entr

atio

npp

m（

）

22nd Cycle

Management of gradual hydrogen injection termination (reflection to the 22nd cycle)

Pattern of hydrogen injection termination / start

Termination patternFeed-water hydrogen concentration0.45ppm→0.2ppm (maintained for 24 hours) → Termination (3 days)→0.2ppm (maintained for 24 hours)→0.45ppm

Maintained for 24 hours

0.45ppm

0.2ppm

0ppm

0.45ppm

0.2ppm

Hydrogen injection termination once every three months

１４

Operation for around 3 months

Operation for around 3 months

3 day stoppage


05

1015202530

0:00 12:00 0:00 12:00 0:00 12:00 0:00 12:00 0:00 12:00

Chro

mium

acid

con

cent

ratio

npp

b（

）

21cyc

22cyc(J un)

22cyc(Sep)

22cyc(Nov)

22cyc(Mar)

0

5

10

15

20

25

0:00 12:00 0:00 12:00 0:00 12:00 0:00 12:00 0:00 12:00

Cond

uctiv

ityμ

S/m

（）

21cyc

22cyc(J un)

22cyc(Sep)

22cyc(Nov)

22cyc(Mar)

0.45ppm 0.2ppm 0.0ppm

0.5ppm 0.1ppm 0.0ppm21cyc

22cyc

Transition of reactor-water conductivity and chromium acid concentration (21st and 22nd cycles)

１５

（ Time ）

（ Time ）


0.0E+0

1.0E+5

2.0E+5

3.0E+5

4.0E+5

5.0E+5

20th 21st 22nd

Am

ount

of

nucl

ide

depo

sit(

Bq/

cm2)

0

1

2

3

4

5

Dos

e-eq

uiva

lent

rat

e(m

Sv/h

)Co- 58Co- 60

Mn- 54Fe-59dose- equivalent rate

Transition of PLR piping dose-equivalent rate (Pump A (22nd outage))



１６

0.0E+0

1.0E+5

2.0E+5

3.0E+5

4.0E+5

5.0E+5

20th 21st 22nd

Amou

nt o

f nuc

lide

depo

sit(B

q/cm

2)

0

1

2

3

4

5

dose

-equ

ivale

ntra

te(m

Sv/h

)

Co-58Co-60

Mn- 54Fe- 59

dose-equivalent rate


0.0E+0

1.0E+5

2.0E+5

3.0E+5

4.0E+5

5.0E+5

20th 21st 22nd

Am

ount

of

nucl

ide

depo

sit(

Bq/

cm2)

0

1

2

3

4

5

Dos

e-eq

uiva

lent

rate

(mSv

/h)

Co- 58Co- 60Mn- 54Fe- 59Dose- equivalent rate

0.0E+0

1.0E+5

2.0E+5

3.0E+5

4.0E+5

5.0E+5

20th 21st 22nd

Amou

nt o

f nuc

lide

depo

sit(B

q/cm

2)

0

1

2

3

4

5

Dose

-equ

ivale

ntra

te(m

Sv/h

)


Transition of PLR piping dose-equivalent rate (Pump B (22nd outage))



１７


Transition of PLR piping dose-equivalent rate (Pump A (23rd outage))


0.0E+0

1.0E+5

2.0E+5

3.0E+5

4.0E+5

5.0E+5

20th 21st 22nd After decontamination 23rd

Am

ount

of

nucl

ide

depo

sit(

Bq/

cm2)

0

1

2

3

4

5

Dos

e-eq

uiva

lent

rat

e(m

Sv/

h)



0.0E+0

1.0E+5

2.0E+5

3.0E+5

4.0E+5

5.0E+5


Am

ount

of nuclid

e d

epo

sit(

Bq/

cm

2)

0

1

2

3

4

5

Dose

-equ

ival

ent

rate

(mSv/

h)


Shroud replacement work

(Chemical decontamination inside the reactor)

↓



↓

１８


Transition of PLR piping dose-equivalent rate (Pump B (23rd outage))



0.0E+0

1.0E+5

2.0E+5

3.0E+5

4.0E+5

5.0E+5


Am

ount

of

nucl

ide

depo

sit(

Bq/

cm2)

0

1

2

3

4

5

Dos

e-eq

uiva

lent

rate

(mSv

/h)


0.0E+0

1.0E+5

2.0E+5

3.0E+5

4.0E+5

5.0E+5


Am

ount

of

nucl

ide

depo

sit(

Bq/

cm2)

0

1

2

3

4

5

Dos

e-eq

uiva

lent

rat

e(m

Sv/

h)


１９



↓



↓


Base material Base material

Mechanism of how radioactive deposits built up in the HWC environment (23rd outage onward)

２０

HWC Environment

NWC Environment

Radioactive ion Radioactive ion

Clad deposits(Fe 、 Cr)External layer

(Ferrite)Internal layer (Chromite)

The HWC environment (low hydrogen peroxide) encourages a buildup of the external layer (ferrite) with low protective property, and an internal layer (chromite) that readily captures Co, thereby increasing the amount of Co-60 deposit.

Operation under the NWC environment forms a dense external layer. This reduces elution of metal ions from the base, and contains the growth of the external layer (ferrite) and internal layer (chromite), thereby decreasing Co-60 deposits.


Current PLR piping dose-equivalent rate (Pump A (25th outage))


0.0E+0

1.0E+5

2.0E+5

3.0E+5

4.0E+5

5.0E+5

20th 21st 22nd Afterdecontamination

23rd End of 23rd 24th 25th

Am

ount

of

nuclid

ede

posi

t(B

q/cm

2)

0

1

2

3

4

5

Dose

-equ

ival

ent

rate

(mSv/

h)



0.0E+0

1.0E+5

2.0E+5

3.0E+5

4.0E+5

5.0E+5



Am

ount

of

nuclid

e d

eposit(B

q/cm

2)

0

1

2

3

4

5

Dose-equiv

ale

nt

rate

(mSv/h)



(Chemical decontamination inside

the reactor)



PLR piping repair work(Chemical

decontamination)


decontamination)

２１


Current PLR piping dose-equivalent rate (Pump B (25th outage))



0.0E+0

1.0E+5

2.0E+5

3.0E+5

4.0E+5

5.0E+5



Am

ount

of

nuclid

ede

posi

t(B

q/cm

2)

0

1

2

3

4

5

Dose

-equ

ival

ent

rate

(mSv/

h)


0.0E+0

1.0E+5

2.0E+5

3.0E+5

4.0E+5

5.0E+5



Am

ount

of

nuclid

ede

posi

t(B

q/cm

2)

0

1

2

3

4

5

Dose

equ

ival

ent

rate

(mSv/

h)

Co- 58Co- 60Mn- 54Fe- 59Dose equivalent rate




(Chemical decontamination inside

the reactor)

２２


decontamination)


decontamination)


PLR piping dose-equivalent rate after chemical decontamination (comparison with other plants)

２３

0.00

0.50

1.00

1.50

2.00

-2 -1 0 1 2 3 4Outage No. counted from the outage when decontamination was conducted

PLR

pip

ing

dose

rat

e(m

Sv/h

)

Shimane Unit 1BBBCBEJ AGBGD


Future tasks

Dose-equivalent rate assessment after preliminary oxidization operation

Application to Shimane Unit 2

Introduction of a startup hydrogen injection facility at Shimane Unit 1

２４


Thank you.

Measures for containing an increase in pipes’ dose-equivalent

rate in the hydrogen-injected environment at the Shimane Nuclear Power Station Unit 1

２５

Documents

Measures for containing an increase in pipes’ dose-equivalent rate in the hydrogen-injected environment at the Shimane Nuclear Power Station Unit 1 １ Tomohiro