distinguishing fission and fusion -safety of fusion plant
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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
Institute of Advanced Energy, Kyoto University
Institute of Advanced Energy, Kyoto University
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
Institute of Advanced Energy, Kyoto University
Institute of Advanced Energy, Kyoto University
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
Institute of Advanced Energy, Kyoto University
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.
Institute of Advanced Energy, Kyoto University
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
?
Institute of Advanced Energy, Kyoto University
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
Institute of Advanced Energy, Kyoto University
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
Institute of Advanced Energy, Kyoto 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
Prof. Momoshima Kyushu University
Institute of Advanced Energy, Kyoto University
• 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.
Prof. Momoshima Kyushu University
Institute of Advanced Energy, Kyoto University
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 University
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?
Institute of Advanced Energy, Kyoto University
Institute of Advanced Energy, Kyoto University
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.
Institute of Advanced Energy, Kyoto University
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
Institute of Advanced Energy, Kyoto University
・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.
Institute of Advanced Energy, Kyoto University
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
Institute of Advanced Energy, Kyoto University
However, if fusion will be a viable energy source
In the world, tritium background will eventually
Higher than ever.
Fusion needs social understanding.
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