distinguishing fission and fusion -safety of fusion plant

7th IAEA DEMO Programme Workshop

17,Nov., 2021

Virtual event

S. Konishi

Kyoto University

Photo by K. Okano

Distinguishing Fission and Fusion

-Safety of Fusion plant and its

control -

introduction

• We will soon have to go through the licensing process for fusion reactors that has energy extraction function.

• Each country may have their own regulations but it is preferred to have international standard.

• Radiation safety of the fusion experiments have been well controlled so far, but

• Licensing fusion power plant will need additional consideration.

• Fusion licensing will follow either ;

- existing fission plant standard and regulation

- existing radio-isotopes and radiation facilities

(reprocessing, accelerator, or RI production, etc.)

- totally new regulation dedicated for fusion plants.

Institute of Advanced Energy, Kyoto University

• Nuclear Plant Safety (both fission and fusion) is controlled by

environmental EMISSION that lead to public dose.

• Both accidents and normal release are evaluated.

-Fission mainly accidental risk, while fusion normal emission

will be an issue.

• Public will evaluate Fusion from its environmental impact.

• Adding to licensing, public acceptance is realized to be

essential for any nuclear facilities.

- Dose is NOT always the best measure.

- Contamination or public/social risk, mainly reputational issues

are found to be more serious from the Fukushima event.

Introduction 2Institute of Advanced Energy, Kyoto University

Generalized model

plasma blanketＳＧ

turbine

Heat rejection

Tritium recovery

Reactor hall

divertor

Fuelsystem

building

Tritium removal

Generation process is the dominant release pathway

12

3Tritium

remov

detritiation



Fusion generation plants reject large amount of heat.

• Main paths are:

1) Coolant contamination coming from blanket.

2) Driver of turbine with tritium contamination

3) minor leaks, spills, secondary confinements

• Stuck, effluents and drain.

• Heat rejection through cooling tower or sea water

• Airborne plume diffusion or migration in the sea

• Isotopic dilution in the environments

Release Path from Fusion Plants

How fusion affects?

Plasma

BlanketFacility

Environment,Society

Fuel, Material

(D,Li6,..)

Generation Plant

Heat Transfer

Wastes

(Solid nuclides,

T,C-14)

Exhausts

(T,heat)

(Recycle)Energy

(Electricity)

Fusion will be evaluated

- what it consumes

- what it exhausts

- what it generates , and

- what it leaves

Environmental tritium is

The key for acceptance

Of fusion

Economy



Drain/

cooling tower

Stack

/scrubber

Tritium migrates with heat. Blanket concepts have major impacts.

Coolants, heat exchanger, energy conversion…

Emission from Normal Operation

Fuel cycle

Heat rejection

Heat exchanger(SG/IHX)

ADS

TRS

Reactor hall Plant

Turbine & Generator/

TRS

Sea Water


Drain/

cooling tower

Stack

/scrubber

Fuel cycle

Heat rejection

Heat exchanger(SG/IHX)

ADS

TRS

Reactor hall Plant

Turbine & Generator/

TRS

Sea Water

Emission from Accidental Events

Tritium processing with equipment for normal operation.

Institute of Advanced Energy, Kyoto UniversityHeat exchange and tritium flow

breeder coolant Tritiumrecovery

IHX Genera-tion

Detri-tiation

solid Water / He

Isotopic/chemical

Steam generator

Rankine IsotopicWDS

Solid gas chemical Steam generator

Rankine IsotopicWDS

Liquidmetal

metal physical Steam generator

Rankine IsotopicWDS

Liquidmetal

gas chemical g-g IHX Brayton

metal physical Metal-gasIHX

hybrid

Heat transfer media is a possible problem for workers.


breederTritium recovery

coolantHeat

exchangeEnergy

conversion検討例

Solid + He sweep water SG Steam turbine SlimCS

Solid + He sweep He IHX Gas turbine PPCS-B

Liquid metal water SG Steam turbine PPCS-A

Liquid metalHe + LM

IHX, Recuperator

Gas turbine ARIES-ST

Liquid metal IHX Fuel production GNOME (kyoto)

Liquid metal IHX Gas turbine ARIES-AT

Liquid metal He IHX Gas turbine

Blanket type and energy conversion

SlimCS with PWR generation condition

plant

Fuel cycle

Condenser

Steam generator

ADS

TRS

Reactor hallPlant

Turbine & Generator

WDS WDS

Breeding blanket

2.0e12 Bq/s

permeation

1.4e10 Bq/s

Water

Water/

steamHe

Steam generator

3.4e8 Bq/s

Environmental emission：2.8e6 Bq/sHTO to air

Coolant to

ocean

Water cooled plant

With DT<7K,

20 ton/s

Discharged

To the sea

100Bq/kg

?


1 Cooling tower

• Heat rejection by evaporation, with the vapor pressure or

less, at ambient temperature.

• Air (plume) diffuses and diluted. Vapor also diluted with

moisture.

• Vapor diluted with air.

• Airborne emission control applied.

• Rainfall immediately cause wet deposition

2 Cooling water

• 7K limit applied. 100 ton/s water needed.

• Extremely large isotopic dilution

• Large water mass makes environmental dilution slower

Institute of Advanced Energy, Kyoto UniversityEnvironmental concentration

• Tritiated water approaching 1x106 ton, containing 106 Bq/kg.

(cf. typical CANDU heavy water 1011~12 Bq/kg.

• Regulation limit 6x104 Bq/kg. (~100x dilution requested)

• Total 1015 Bq was decided be released.

(cf reprocessing plant 1.4x1016 Bq/y)

Required control level is far lower than legal limit.

Tritiated water in Fukushima

0 200 400 600 8001000elapsed days

radio

actio

vity (B

q/g

)1 year 2 years

calculated withsource term

calculated without source term

: measured

a) 137 Cs b) Tritium

calculated withsource term

0 200 400 600 8001000elapsed days

calculated without source term

1 year 2 years

: measured 107

106

105

104

103

102

104

103

102

101


Environmental tritium, history

1.Natural production by cosmic ray

Discovered in 1949 in the environment

2.Atmospheric nuclear tests in 1950s to 1960s

First bomb in 1945（Nevada）、first fusion bomb in 1954

Atmospheric nuclear test ban treaty in 1963

（global fallout, tracer for air mass, seawater etc）

3.Peaceful use of unclear energy

Nuclear power station in Japan（55）、world（434）、nuclear fuel treatment facility

4.Nuclear fusion reactor （a huge amount, local emission）

14Prof. Momoshima Kyushu University


EBq=1018

1000MW

(～5kg)

4. Fusion

reactor

Environmental tritium

O+n —> H+

1．Cosmic ray

1-1.3 EBq

14N+n —> 3H+12C 16 3 14N

15

3. Nuclear stations

0.02 EBq y-1

(0.01-0.02)

Earth crust

6 Li+n—> 3 H+ 4 He

238 U+n—> 3 H+Products

2. Nuclear bomb

240 EBq (185-240)

3. Consumer products

0.4 EBq y-1

(0.3-0.4)

Natural T≒2.7 kg

World inventory (2010)

1-1.3 EBq (1) + 17 EBq (13-17)

Prof. Momoshima Kyushu University

0

50

100

150

200

250

1960 1970 1980 1990 2000 2010

Bq/L

Tritium in the Water in Japan

16

Fallout from nuclear detonation

We experienced

200 times high

Tritium level.0.0

0.5

1.0

1.5

2.0

2.5

1980 1985 1990 1995Trit

ium

co

nce

ntr

atio

n(B

q/L

)

Fukuoka, Japan

year



• HT : 12.5 ± 6.9 mBq/m3 (H2: 0.5 ppm)

• CH3T : 9.0 ± 8.2 mBq/m3 (CH4: 1.4 ppm )

• HTO : 6.7 ± 5.4 mBq/m3

0.69 ± 0.35 Bq/L (Rain 0.35 Bq/L)

◼ HT: 2.6x105 TU

◼ CH3T: 3.4x103 TU

◼ HTO: 5.8 TUTUT/H=1x10-18

Tritium in the Air

Airborne tritium is

Suspected to come from

Artificial sources.

And we will have hundreds plants for long years

to go.



Effect is evaluated as dose

(Sv)

e.g. 1 mSv/y

Facility controls

Tritium emission

(g/y)

Emission control

Groundwater

soilplant

plume

environment

confinement

facility dose

Background

Site boundary


Institute of Advanced Energy, Kyoto UniversityNuclides from fission/fusion

• Behavior of radio-nuclides is well understood forfission facilities

• Major concern is accident

• Nuclides diffuses as “plume” and deposit and go away.

• Some nuclides are enriched by biological process and food chain.

• Dose is easily estimated from the activity.

• Isotopic contents in the environment is not usually a problem.---All different for FPs from fission vs. tritium from fusion!

Impact pathway of tritium

Cause cancer?



Tritium in the environment

• Tritiated water is a major concern

• Many of the facilities discharge by normal operation.

• Tritium is diluted by natural water.

• Biological processes changes chemical forms. i.e.H2 – HTO – OBT (organically bound tritium)

• Natural background and environmental recycling

• Specific for food, environment, culture and habits

• Dose may not be a good measure of damage--range of beta is very short. (~5mm)

Yearly change of tritium concentration

0.1

1

10

0 20 40 60 80 100

Operatinf time (year)

Atm

osph

ere

HTO

conc

entr

atio

n

(Bq/

m3)

0.001

0.01

0.1

1

10

100

-100 -80 -60 -40 -20 0 20 40 60 80 100

Distance from fusion plant (km, -West, +East)

Atm

osp

here

HTO

Cocentr

atio

n (B

q/m

3)

1st year 2ndyear4th year 10th year20th year 40th year60th year 80th year100th year

Change on the tritium concentration in the atmosphere

during prolonged operation is analyzed.

5.7 km west

100 km west

•Tritium concentration increase for about 60 years on land.

•Tritium concentration on the sea surface is low and dose

not show accumulation

Emission rate: 1.35x1014 Bq/year

0.01

0.1

1

0 20 40 60 80 100

Operatinf time (year)A

tmos

pher

e H

TO

conc

entr

atio

n

(Bq/

m3)

Atmosphere HTO concentration after 100 years operation.


1.0E-03

1.0E-02

1.0E-01

1.0E+00

0 20 40 60 80 100

Operating time (year)

Atm

osp

here

HT

O

conc. (B

q/m

3)

1.0E-04

1.0E-03

1.0E-02

1.0E-01

0 20 40 60 80 100

Operating time (year)

Atm

osp

here

HT

O

conc. (B

q/m

3)

5.7 km west

100 km west

Operating time: 1 yearOperating time: 2 yearsOperating time: 4 yearsOperating time: 10yearsOperating time: 20 yearsOperating time: 40 yearsOperating time: 60 yearsOperating time:80yearsOperating time: 100 years

•Considerably increases for 20 years

•Still negligible from dose, but easy to detect.

- If 100 plants will be operated for 100 years?

Emission rate: 1.35x1014 Bq/year

Accumulation in the environment

Annual emission accumulates in the environment


・Environmental models converts emission to dose.

・Major dose from normal operation comes from ingestion

・mSv per person, per year per 1 gram emission.

foods will be contaminated.

Total tritium dose during 1 year

operation calculated by NORMTRI.

Structure of NORMTRI model

Accumulation in the environment

Acknowledge W. Raskov and D. Galeriu

Institute of Advanced Energy, Kyoto UniversityTritium dose by fusion

0.0

2.0

4.0

6.0

8.0

10.0

12.0

0.15 0.21 0.32 0.5 0.68 1 1.5 2 3.2 5 6.8 10 15 21 32 46 68 100

Distance from the plant (km)

Effective

Dos

e Eq

uiva

lent

( mSv

/yea

r)

Drinking water

Meets and milk

Grain and rice

Vegetables

Inhalation

After 100 years operation

•Total tritium dose is about 10 mSv/year or less.

•Approximately 15 times increased after 1 year operation.

Tritium dose: 1 year operation

Tritium dose: 100 years operation

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.145 0.21 0.32 0.5 0.68 1 1.5 2 3.2 5 6.8 10 15 21 32 46 68 100

Distance from the plant (km)

Effe

ctive Dos

e Equ

ivalen

t

( mSv

/yea

r)

Drinking water

Meets and milk

Grain and rice

Vegetables

Inhalation

UNSCEAR 2008report

Tritium emission to the ocean environment

UK

CANADA

Argentina

France

Japan

Spain

Germany

USA

Conclusion

Legal limits are common for fission and fusion, but..

• Normal tritium release to the environment dominates thepublic acceptance of fusion.

• Environmental tritium behavior should be well understood for safety design as well as social acceptance.

• Tritium in the environment is visible an detectable.(while fission risks are usually hypothetical and virtual)

• Fusion acceptance is thus subject to the double standard.

Environmental tritium concentration limit will be negotiable but needs

mutual agreement among stakeholders.


Social concern is the most important factor in

radiation control for nuclear (both fission and fusion)

Conclusion

Fusion tritium emission control will be different

from fission case

regulation mutual understanding with public

dose environmental concentration

legal scientific


However, if fusion will be a viable energy source

In the world, tritium background will eventually

Higher than ever.

Fusion needs social understanding.

distinguishing fission and fusion -safety of fusion plant

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