dose rate reduction experiences of piping replacement atfukushima daiichi unit 4 and 5atsutoshi...

7/31/2019 Dose Rate Reduction Experiences Of Piping Replacement AtFukushima Daiichi Unit 4 and 5Atsutoshi MakihiraALALA Mini-WorkshopNov.9, 2005 Hamaoka NPS

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Dose Rate Reduction Experiencesof Piping Replacement at

Fukushima Daiichi Unit 4 and 5

Atsutoshi Makihira

ALALA Mini-WorkshopNov.9, 2005 Hamaoka NPS


2/13

Removal Work Scope of Equipment and

Floor Drain Piping

4(BWR4)

Schedule

Unit

Work

Nov.22, 2002 May 21,2003

Removal:415m

Installation:556m

Reactor Building Suppression Pool Area

West East

Reactor Building Suppression Pool Area

West East

5(BWR4)Jan.20, 2003 Sep.26, 2003

Drain PipingDrain Piping

Working AreaWorking Area

Removal:446m

Installation:446m


3/13

Dose Rate at Piping Before Replacement Work

Unit 4Unit 4

West

Contact (max)Contact (max)

mSv/hmSv/h

Field (max)Field (max)

mSv/hmSv/h

RHR pipingRHR piping

Work areaWork area

East East

ContactContact projectionprojection

mSv/hmSv/hFiledFiledprojectionprojection

mSv/hmSv/h

Unit 5Unit 5


4/13

RHR and Drain Piping at West Part

of Suppression Pool Area

Unit 4Unit 4

West East

RHR PipingRHR Piping

Drain PipingDrain Piping


5/13

(1)Filed Dose Rate and Estimated Working Time per Person-Day

(2) Estimated Working Time per Person with Annual Dose Limit


6/13


7/13

Proposals for Improvement

2. FlushingUnit 4

High dose rate at RHR-4, RHR-41, RHR-23

because of RHR operation in shutdown Flushing RHR-4, RHR-41 by using RHR(C) pump which

circulates water in suppression pool

Flushing RHR-23 by opening MO-23 valve when RHR(C)pump running

Unit 5

High dose rate at RHR-3, RHR-7, RHR-27 because

of RHR operation in shutdown

Flushing by using RHR pumps which circulates water insuppression pool


8/13

RHR-Hx(B)

PLR-5 PLR-2

MO

MO

MO

MOB

MOB

MOD

MO

MO

RHR-22 RHR-21RHR-1

MO

MO

RHR-2

MO

MO

MO

MO

MOB

RHRRHR--4141

MOB

RHR-3

RHR-3

RHR-55RHR-53

RHR-55

RHR-1RHR-21

RHR-7

PLR-1PLR-4RHR-23

RHR-41

RHR-27

RHR-23

RHRRHR--2323

RHR-53

MO

MO

MO

RHR-23

RHR-26

RHR

-24

RHR-

3

RHR

-4

RHR-6

RHR-3

RHR-53RHR-3

RHR-7RHR-8RHR-27

RHR-28

MO67MO57RHR-52

RHR-44

RHR-44

RHR-47 RHR-51

RW

RHRRHR--33

MO

MO

MO

MO

Flushing line

High Dose Pipng

MO

MO

RHR-Hx(A)

Flushing by use of RHR(C)

pumps which circulate

system water

Open VMO-20 valve when

circulate system water

2.Flushing(example)


Unit 4Unit 4


9/13

3.Temporary ShieldingInstalling temporary shielding at high radiation piping after RHR flushing

Unit 5

Unit 4

Installing temporary shielding at projected high radiation piping during operationInstalling temporary shielding at high radiation piping after RHR flushing

RW-1C Lead

covered with SSEquipment Drain

Lead covered with

SS

RW-209

lead blanket

Installing during operation

RHR-27

lead blanket

Installing after flushing

RHR-23

lead blanket



10/13

Reactor water drained because of RRSreplacement work

High dose rate was projected at RHR-Hx,RHR pumps, suppression pool area


4.Blow Down Water Treatment at Unit 4

R/B B floor suppression pool areaR/B B floor suppression pool area R/B 1R/B 1stst floorfloor RHRRHR--HxHx roomroom R/B B floorR/B B floor RHR pump areaRHR pump area


11/13

Planned reactor water blow down twice

First blow down water drained tosuppression pool so as to second blowdown which contains higher activity can

be transferred to radwaste (because ofcapacity)

Removing crud deposited on RPVbottom by temporary pump and filters

Fill up RHR-44 with water before blowdown for preventing crud deposition

4.Blow Down Water Treatment at Unit 4



12/13

5.Remote Monitoring

Dose indicator

Wireless APDWireless APD

Remote monitoring

of individual dose

TransmittanceTransmittance

Dose indicator

Individual dose can be

monitored even on cloths

Unit 5 Unit 4 &5



13/13

RHR-27

N

EW

S

Equipment Drain

vertical

Equipment

Drain

horizontal

VerticalPiping

Horizontal Piping

CUW-19 Contact dose rate: 36.0%

RW-1C Contact dose rate: 44.4%

Field dose rate:20.0%

Results for Improvement

Equipment drain piping

Contact:66.7%

Field:88.7%

Dose Rate Reduction Effectiveness after Installing Temporary Shielding

RW-209 pipings

Contact:66.7%

Field:86.7%

Unit 4Unit 4

dose rate reduction experiences of piping replacement atfukushima daiichi unit 4 and 5atsutoshi...

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