Background & Objectives
Implication of Fukushima Event and Its Possible
Impact on Tritium Release from Fusion Facilities
Satoshi Konishi and Ryuta Kasada
Kyoto University, Gokasho, Uji, Kyoto, Japan
Generalized Fusion Plant as Tritium Emitter
Release Path and Impacts
Conclusion
Tritium Rerease and Its Impact
Second IAEA DEMO Programme Workwshop 17-20 Dec.2013, IAEA HQ, Vienna, Austria
Fusion Plant Safety is controlled by environmental EMISSION.
(more accurately, Annual emission) in Normal Operation.
- Accidents may not be serious, but lead to environmental
contamination.
Public will evaluate Fusion from its environmental impact.
- Dose is NOT always the best measure.
- contamination or public concern/threat could be
more important.
Strategy should consider the public evaluation.
- Fukushima events attract serious attention on
detectable increase of tritium level.
EMISSION CONTROL to respond public request needed
2. Questions- Heavy water reactor and reprocessing plants have had good public
understanding so far. Can we expect it for future?
- What is the target of normal tritium emission from fusion plants?
(particularly after Fukushima)
- Compared with other sources, can fusion be accepted?
3. Subjects to study
- To investigate possible tritium release scenario for fusion
- To consider strategy for the environmental tritium level.
1. Previous understanding
Tritiated water in Fukushima
Tritiated water currently 4x105 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 should be released.
(cf reprocessing plant 1.4x1016 Bq/y)
Current background ~1Bq/kg water
detection limit 0.1 Bq/kg or less for experts,
1 Bq/kg even for beginners with good scintillator
・Environmental models converts emission to dose.
・Major dose from normal operation comes from ingestion
・mSv per person, per year per 1 gram emission.
particular concern is a damage for sales of food products.
Total tritium dose during 1 year
operation calculated by NORMTRI.
Structure of NORMTRI model Acknowledge W. Raskov and D. Galeriu
Fukushima Events
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
Release Path from Fusion Plants
breeder coolant Tritium
recovery
IHX Genera-
tion
Detri-
tiation
solid Water
/ He
Isotopic
/chemical
Steam
generator
Rankine Isotopic
WDS
Solid gas chemical Steam
generator
Rankine Isotopic
WDS
Liquid
metal
metal physical Steam
generator
Rankine Isotopic
WDS
Liquid
metal
gas chemical g-g IHX Brayton
metal physical Metal-gas
IHX
hybrid
Heat transfer media is a possible problem for workers.
(tritium production=2.0e12Bq/s)
WDS capacity: ITER (20L/h) Darlington (360L/h)
WDSPermiation
to coolant
permeation to
2nd coolant
Leak to
waste water
20kg/h 1.4e10Bq/s 1.4e9Bq/s 1.2e7Bq/s
360kg/h 1.4e10Bq/s 3.4e8Bq/s 2.8e6Bq/s
Pipe
thickness
Permeation
to coolant
Concentration
in coolant
Permeation to
2nd coolant
Leak to waste
water
1.5mm 1.4e10Bq/s 1.4e11Bq/kg 3.4e8Bq/s 2.8e6Bq/s
2mm 1.0e10Bq/s 1.0e11Bq/kg 2.9e8Bq/s 2.4e6Bq/s
1.5mm,
TPR=1001.4e8Bq/s 1.4e9Bq/kg 3.4e7Bq/s 2.8e5Bq/s
Blanket coolant pipes (permeation barrier)
Trade with WDS plant design
Coolant contaminationCoolant options
• Tritium emission will be controlled by law, regulation, agreement with local community, as well as public acceptance,
regardless of the type of nuclear facility. Fusion is not an
exception.
• If current control for Heavy Water Reactor or Reprocessing plant will be applied, WDS will be needed to handle ca. 2 orders of
magnitude larger capacity. Fusion cannot exceed the current emission from them.
• Tritium in the environment, water and agricultural products can easily be detected. Despite it is far lower than the regulation limit, it
may cause a serious acceptance problem.
• Isotopic dilution in the environment is extremely important.