JAEABlanket technology group

Hisashi Tanigawa, T. Hirose, Y. Kawamura and M. Enoeda

Strategy of WCCB-TBM Testing in ITER

Third IAEA DEMO Programme Workshop

13 May 2015Hefei, China

Outline

2/18

DEMO blankets developed in Japan

WCCB (Water Cooled Ceramic Breeder) TBM and demonstration tests in ITER

Issues in Blanket development and relationship with TBM testing

Actions to solve the issues

Summary

DEMO concepts developed in JapanJapan has been developing the DEMO conceptswith water-cooled ceramic breeder blankets.

3/18

SlimCS (JAEA) SSTR (JAERI) DEMO-CREST (CRIEPI)

Why is water selected as coolant?

He with Brayton Cycle

He with combined cycle

supercritical-water

power generation efficiency

22.1% 35.3% 41.4%

Coolant conditions

in 220℃,out 500℃

in 250℃,out 500℃Steam turbinein 130℃,out 470℃

in 280℃, out 500℃

25 MPa

BOP study in DEMO2001Fusion power: 2.3 GW, Total power: 2.91 GWHeat removal in Blanket: 2.42 GW (83%)Heat removal in Divertor: 0.49 GW (17%)

Water with PWR conditions

～30%

in 290℃, out 325℃

15.5 MPa

Water-cooling is selected with considerations that; maximum allowable temperature of RAFM is about 550℃, early realization of electric power is important. 4/18

BOP study in the present DEMO

Major specification of blanket in JapanPebble bed of tritium breeder (Li2TiO3, Li4SiO4, Li2O)

Container and inner structures（RAFM F82H)

Coolingwater

Pebble bed of neutron multiplier (Be or Be12Ti)

With minor difference in breeder or multiplier materials and coolant conditions.

Box structure of RAFM steel as container

Pebbles of breeder and multiplier materials are packed in layered-configuration

5/18

WCCB TBM demonstrates functions required for DEMO blanket in ITER condition

Power generator

ITER Cross Section

With TBM corresponding to DEMO blanket configuration,demonstration of tritium production and electric power extraction

TCWS Vault

V.V.

Water loop

Tritium building

Purge gas loopTES

WCCB TBM

Plasma side

RAFM(F82H)

Pebble bed(Be)

Pebble bed(Li2TiO3)

Japan is in a position to- act as a Port Master and a TBM Leader to test the WCCB TBM,- participate as a Partner in HCPB/HCCB and LiPb-based TBMs. 6/18

Issues for blanket development and relationship with TBM testing

Issue Purpose Outcomes from TBM (inc. ITER)

TBR evaluation with high accuracy

To show ensuring TBR in DEMO

A unique environment for integrated demonstration

EM loads To show structural soundness in DEMO

Demonstration + practical plasma conditions

Irradiation effects in materials

To show structural/functional soundness in DEMO

Very limited demonstration(low fluence)

In-box LOCA To show structural soundness in DEMO

Direct demonstration will be difficult

Remote handling To show compatibilityin DEMO

Partial demonstration (different requirements are expected in DEMO)

Decay heat (LOCA)

To show structural/functional soundness in DEMO

Direct demonstration will be difficult

7/18

Issue Purpose Outcomes from TBM (inc. ITER)

TBR evaluation with high accuracy

To show ensuring TBR in DEMO

A unique environment for integrated demonstration

EM loads To show structural soundness in DEMO

Demonstration + practical plasma conditions

Irradiation effects in materials

To show structural/functional soundness in DEMO

Very limited demonstration(low fluence)

In-box LOCA To show structural soundness in DEMO

Direct demonstration will be difficult

Remote handling To show compatibilityin DEMO

Partial demonstration (different requirements are expected in DEMO)

Decay heat (LOCA)

To show structural/functional soundness in DEMO

Direct demonstration will be difficult

Issues for blanket development and relationship with TBM testing

New knowledge through TBM testing is only achievement of practical DT plasma conditions (loads on TBM).

DEMO blanket concept has to be well developed before TBM testing.

For demonstrations to show DEMO relevancy, developments of models and design schemes before or in parallel to TBM testing are important.

Following to the limitation of TBM testing, additional tests to TBM are also necessary.

8/18

Actions to irradiation effect in materials In ITER, total fluence is 0.3 MWa/m2 for 20 years. In DEMO, expected neutron wall loads range 1 – 3 MW/m2.

For 3 years operation fluence will be 3 – 9 MWa/m2, 15 – 30 times higher than all period of ITER operation.

Actions before TBM testing Elemental understandings of material properties based on

irradiation data Development of design scheme treating irradiation effects

Actions in parallel to TBM testing Irradiation data using fusion nuclear source (He effect) Sophistication of irradiation data, understandings of

material properties (including simulation techniques) and design schemes. 9/18

Actions to irradiation effect in materials In ITER, total fluence is 0.3 MWa/m2 for 20 years. In DEMO, expected neutron wall loads range 1 – 3 MW/m2.

For 3 years operation fluence will be 3 – 9 MWa/m2, 15 – 30 times higher than all period of ITER operation.

Actions before TBM testing Elemental understandings of material properties based on

irradiation data Development of design scheme treating irradiation effects

Actions in parallel to TBM testing Irradiation data using fusion nuclear source (He effect) Sophistication of irradiation data, understandings of

material properties (including simulation techniques) and design schemes.

There is no real-scale experimental fusion environments before DEMO.

Developments and sophistications of modeling and design scheme are important.

10/18

In-box LOCA leading to inner pressure loading to container structure

Break of the coolant pipe in blanket leads to ingress of high temperature and pressure water/vapor into the container and increase of inner pressure to the container.

SRD for TBMEvent title: In-TBM LOCAMain requirements: TBMs structure able to withstand the coolant pressure

Decrease in TBR

Increase thickness of container structure

For TBM testing, demonstration of accurate prediction capability in TBR is important to extrapolate the design schemes to DEMO.

Modification of container configuration might be necessary for DEMO.

WCCB TBM

11/18

Consideration of pressure relief equipment

15.5 MPa

1

2

Partial water pressure will load to the container due to flow resistance of water/vapor through pebble beds.

Two aspects are being studied to find compatible conditions; decrease pressure load to container by pressure relief, improve pressure resistance of container by configuration

change.

1. Coolant pipe break2. Container break3. Ingress of water/vapor

and pebbles into VV

3

Blanket

VV

Pressure relief

Water

If it is acceptable in view of plant safety, container break has to be avoided for investment protection.

12/18

Actions to in-box LOCA

Actions before TBM testing Development of guideline to secure plant safety defining

safety requirement of blanket Development of DEMO blanket design treating in-box LOCA

Design of pressure relief systemThermal-hydraulic studies of water/vapor in pebble beds (analyses

and experiments)Development of thermal-hydraulic analysis code

Actions in parallel to TBM testing Functional demonstration of pressure relief system Development of cooling system compatible with the

pressure relief system

13/18

Actions to Be/water chemical reactionReduction of chemical potential Developments of new neutron multiplier materials such as

Be12Ti (chemical reaction rate is lower than Be).

Improvement of accuracy in numerical analysis Modified thermal-hydraulic calculation code that can treat

the chemical reaction in pebble bed are being developed. Safety analysis for WCCB-TBM shows in-box LOCA will not

lead to a runaway reaction. Water/vapor ingress has two aspects; production of

hydrogen and reaction heat, and increase of heat transfer capability (with expansion of heat transfer area).

In DEMO expected situation might be different from TBM, and balance of two effects has to be evaluated under reasonable initiating events in view of safety. 14/18

Actions to TBR prediction with high accuracy

TBR prediction requires integrated understandings of nuclear, thermal and chemical behaviour for tritium in blanket system.

No margin in TBR design results in necessity of demonstration in TBM with high accuracy.

In addition, to understand tritium behaviour in TBM is more difficult than in DEMO.TBM is located in limited area of vessel (equatorial port) Information of irradiated neutron into TBM will be limited.Transient behaviour of tritium has to be evaluated due to pulsed

operation of ITER.

Actions before TBM testing Establishment of modeling and analysis methods related to

TBR prediction 15/18

Tritium Extraction

In-situ measurement for TBM testing and corresponding modeling & analyses

TBM

TBM shield Bio shield

Neutron spectra

Temperature

Thermo-mechanical & Thermo-hydraulic analyses Concentration

Chemical statePermeation to water or atmosphere

Tritium analysesNuclear analyses

Tritium in water

Tritium buildingTCWS vault

Port cellTritium concentration

Tritium concentration and chemical state

Cooling & power generation

Agreement between measurements and analyses results shows feasibility of design scheme.

Water temp.

16/18

Tritium productionNuclear heating Temperature in

pebble bed

Difficulty related transient response in TBM

Temperature distribution in TBM after 400sTransient response of temperatures in TBM

After 1000s temperatures reach stable. For 400s pulsed operation, temperatures of breeding

materials are transient. Tritium behaviour is also transient. Later period in ITER, pseudo stable experiments are

planned by repeatable pulsed operation.17/18

Summary

18/18

Japan is in a position to develop DEMO reactor with water-cooled blanket as a first option, and to act as a Port Master and a TBM Leader to test the WCCB TBM.

For TBM testing, demonstration of accurate prediction in TBR is important to extrapolate the design schemes to DEMO.

Evaluation of tritium behaviour in TBM system is difficult due to ITER environment (for example, pulsed operation).

With consideration of circumstances,TBM testing has limitation due to ITER environment,There is no real-scale experimental fusion environments before

DEMO,developments and sophistications of modeling and design scheme are important.