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.