Why is the study of FW/Blanket/Divertor Components

Reliability and Lifetime

a DEMO R&D Gap?

NCT Discussion Group, FNT-7: Alice Ying, Neil Morley (UCLA)

What is the Broad Issue?



FW/blanket/divertor components performance, reliability, and lifetime must lead to DEMO availability goal ~50-70%, tritium self-sufficiency, high grade heat generation for electricity production, and sufficient radiation shielding for components and personnel.

Tritium Breeder Li 2 TiO 3 (<2mm ) Neutron Multiplier Be, Be 12 Ti (<2mm ) What Is the R&D gap?



No FW/blanket module or system has ever been built or tested – potential interdependent and synergistic phenomena and failure mechanisms have not necessarily been identified or understood.



Plasma facing components that are capable of withstanding continuous high surface heat load of ~10 MW/m 2 are yet to be tested at the Demo-level materials, high temperature, transients, and irradiation.

Surface Heat Flux Neutron Wall Load

High-P, High-T He coolant First Wall (RAFS)



Blanket example: Typical vision of a ceramic breeder –based blanket module.

FW/Blanket systems are complex and have many integrated functions, materials, and interfaces

Summary of R&D Issues for FW/Blanket/Divertor

1. D-T fuel cycle

tritium self-sufficiency

in a practical system (from El-Guebaly and Sawan, UW) depends on many physics and engineering parameters / details: e.g. fractional burn-up in plasma, tritium inventories, FW thickness, penetrations, passive coils, doubling time • Tritium production, extraction and inventory in the solid/liquid breeders under actual operating conditions • Tritium permeation, control and inventory in blanket and PFC 2. Identification and characterization of

performance, failure modes, effects, and rates

in blankets and PFC’s • • • Thermo-magnetic-mechanical-vibration loadings and response of blanket and PFC components under normal and off-normal operation Materials interactions, compatibility, and chemistry Radiation damage and Plasma driven synergistic effects • Lifetime of blanket, PFC, and other fusion nuclear components 3.

Remote maintenance

with acceptable machine shutdown time .

077-05/rs

Experiments in non-fusion simulation facilities are essential to establishing FW/Blanket/Divertor scientific foundations …

Theory/Modeling Design Codes Basic Separate Effects Property Measurement Multiple Interactions Phenomena Exploration Non-Fusion Facilities (various non neutron test stands, fission reactors and accelerator-based neutron sources) Partially Integrated Integrated Component

•

Fusion Env. Exploration

•

Concept Screening

•

Performance Verification

 Thermo-mechanical  High Heat Flux  Plasma/Tokamak    …

Design Verification & Reliability Data

Tritium Magnetic

Testing in Fusion Facilities

… and critical to understand & interpret complex, synergistic experiments in the integrated fusion environment

ITER will provide the first opportunity, through the test blanket module (TBM) program, to perform low fluence integrated environment and phenomena experiments

He pipes to TCWS

 ITER will test and develop the knowledge base for low temperature, water-cooled copper FW and divertor designs. However, DEMO will require different materials, designs, and temperatures.

Vision of TBM System

 ITER-TBM can be used to study synergistic effects among FW/blanket phenomena and provide data to improve models and benchmark simulation codes.

2.2 m Vacuum Vessel

 TBM experiments in ITER can provide a bridge between laboratory and NCT experiments.

 There is currently no ITER program for testing advanced divertor designs

Bio-shield A PbLi loop Transporter located in the Port Cell Area

ITER has allocated

3 ITER equatorial ports

(1.75 x 2.2 m 2 ) for TBM testing, and space in the reactor hall and TCWS building for support systems

A NCT Facility Is Unique in Filling the FW/Blanket/Divertor Reliability and Lifetime Gap in the Following Ways



Provide a true fusion environment ESSENTIAL to activate mechanisms that drive coupled phenomena, integrated behavior, and prototypical failure modes; and thus allow development of engineering performance and growth of reliability. The requirements for testing nuclear components are estimated as:



NWL 1-2 MW/m 2 , ~ 6 MW.y/m 2 , ~ 10 m 2 test area, and high surface heat load (SHF ~0.5 / 10 MW/m 2 for FW / divertor).

 

Long pulse / continuous plasma operation Large module to sector size tests for prototypic geometry



Meet testing needs with practical machine and cost:



reasonable fusion power / tritium consumption



high base availability and capacity for fast replacement of failed test components 30 25 20 15 10 5 1000 MW Fusion 10% Avail, TBR 0.0

CANDU Supply w/o Fusion ITER-FEAT (2004 start) 0 1995 2000 2005 2010 2015 2020 2025 2030 2035 2040 2045

Year

Performing these tests in large fusion device (e.g. ITER, early DEMO) leads to large tritium consumption and cost



e.g., A 1000 MW fusion power facility, even at a low availability will consume the projected CANDU tritium supply in just a few years THEREFORE, NCT should be done at low power, <150MW (hence driven plasma), or breed/recover much of its own T

Backups…

Stages of FW/Blanket/Divertor Testing in Fusion Facilities Role of ITER TBM Fusion “Break-in” & Scientific Exploration Engineering Feasibility & Performance Verification Gap?

Component Engineering Development & Reliability Growth D E M O Stage I Stage II Stage III 0.1 – 0.3 MW-y/m 2



0.5 MW/m 2 , burn > 200 s Sub-Modules/Modules 1 - 3 MW-y/m 2 1-2 MW/m 2 , steady state or long pulse COT ~ 1-2 weeks Modules > 4 - 6 MW-y/m

2

1-2 MW/m 2 , steady state or long burn COT ~ 1-2 weeks Modules/Sectors

• Initial exploration of

coupled, prompt phenomena

in a fusion environment • Uncover unexpected synergistic effects, Calibrate non-fusion tests • Impact of rapid property changes in early life • Integrated environmental data for model improvement and simulation benchmarking • Develop experimental techniques and test instrumentation • Screen and narrow the many material combinations, design choices, and blanket design concepts • Uncover unexpected synergistic effects coupled to radiation interactions in materials, interfaces, and configurations • Verify performance beyond beginning of life and until changes in properties become small (changes are substantial up to ~ 1-2 MW · y/m 2 ) • Initial data on failure modes & effects • Establish

engineering feasibility

of blankets (satisfy basic functions & performance, up to 10 to 20 % of lifetime) • Select 2 or 3 concepts for further development • Identify lifetime limiting failure modes and effects based on full environment coupled interactions • Failure rate data: Develop a data base sufficient to predict mean-time between-failure with confidence • Iterative design / test / fail / analyze / improve programs aimed at

reliability growth

and safety • Obtain data to predict mean-time-to replace (MTTR) for both planned outage and random failure • Develop a database to predict overall availability of FNT components in DEMO

Fluence NWL Exp type

Blanket Functions (including first wall)

A.

B.

– – –

Power Extraction

Convert energy of neutrons and secondary gamma rays into heat Absorb plasma radiation on the first wall Systems to Extract the heat (at high temperature, for energy conversion) – –

Tritium Fuel Replacement

Tritium breeding, must have lithium in some form Tritium extraction and control systems C.

D.

Radiation Shielding of the Vacuum Vessel

– – –

Physical Boundary for the Plasma

Physical boundary surrounding (surface facing) the plasma, inside the vacuum vessel Share space with / Provide access for plasma heating, fueling Part of greater electomagnetic environment – conducting materials, ferromagnetic materials, induced currents 10 077-05/rs

Fusion environment is unique and complex: multiple fields and varied environments

  

Neutrons

•

(fluence, spectrum, temporal and spatial gradients)

Radiation Effects (at relevant temperatures, stresses, loading conditions)

• • •

Bulk Heating Tritium Production Activation

Heat Sources (magnitude, gradient)

•

Bulk (from neutrons and gammas)

•

Surface Heat Flux (steady, MARF, Disruption)

Particle Flux (energy and density, gradients)



Steady/Blobs



Unsteady

  

Magnetic Field (3-component with gradients)

•

MHD from Steady Fields with and without Plasma Current

•

Currents from unsteady fields/disruptions

Mechanical Forces

•

Pressurization

• • • •

Thermal stresses EM forces Weight Vibrations

Chemical Environment

•

Hydrogen, Transmutation, Corrosion

Multi-function, multi-material, multi-interface blanket in multi-component field environment leads to:

- Multi-Physics, Multi-Scale Phenomena - Synergistic effects 077-05/rs

[18-54] mm/s

Blanket systems are complex and have many integrated functions, materials, and interfaces

[0.5-1.5] mm/s Neutron Multiplier Be, Be 12 Ti (<2mm ) Tritium Breeder Li 2 TiO 3 (<2mm ) PbLi flow scheme

Surface Heat Flux Neutron Wall Load First Wall (RAFS, F82H)

There are Many Blanket Concepts Proposed Worldwide They all have feasibility issues and attractive features

Material or Configuration

Structural Materials Coolant Media Breeder Media Neutron Multiplier Materials MHD/Thermal Insulator Materials Corrosion and Permeation Barriers Plasma Facing Material HX or TX Materials Blanket Configurations Ceramic Breeder Configurations Liquid Breeder Configurations MHD/Thermal Insulator Config.

Structure Fabrication Routes

Options

Reduced Activation Ferritic Steel Alloys (including ODS), Vanadium Alloys, SiC Composites Helium, Water, Liquid Metals, Molten Salts Lithium-Bearing: Ceramic Breeders (Li 4 SiO 4 , Li 2 TiO 3 , Li 2 O); Liquid Metals (Li, PbLi, SnLi); Molten Salts (FLiBe, FLiNaBe); Varying enrichments in Li-6 Beryllium, Be 12 Ti, Lead SiC composites and foams, Al 2 O 3 , CaO, AlN, Er 2 O 3 , Y 2 O 3 SiC, Al 2 O 3 , others Beryllium, Carbon, Tungsten alloys, others Ferritic Steels, Refractory Alloys, SiC, Direct Gas Contact He or Water Cooled Ceramic Breeder/Be; Separately Cooled, Self-Cooled, Dual Coolant LM or MS Layered, Mixed, Parallel, Edge-On (referenced to FW) Radial-Poloidal Flow, Radial-Toroidal Flow, others Flow Channel Inserts, Self-Healing Coatings, Multi-Layer Coatings HIP; TIG, Laser and E-beam Welding; Explosive Bonding; Friction Bonding; Investment Casting; and others

Tritium breeding blankets are complex, integrated systems critical to the feasibility of D-T fusion energy

   The Blanket provides the mechanisms by which: –

tritium is generated for

–

fuel self-sufficiency high grade heat is extracted for efficient energy production

Poloidal flow PbLi channel Dual-Coolant PbLi Liquid Breeder Module

Breeding blankets are complex, heterogeneous, highly integrated systems, with: – Multiple functions, materials and material interfaces – Integrated

Plasma facing FW, tritium breeder, neutron multiplier, specialized insulators and permeation barriers, structure, and high temperature coolant

He-cooled RAFS FW

All blanket concepts have feasibility issues!

SiC FCIs Ceramic breeder pebbles Helium-Cooled Li 2 TiO 3 Ceramic Breeder Module

Yet,

no fusion blanket has ever been built or tested.

ITER has always been planned as the facility to begin blanket testing.

He-cooled RAFS FW Purge gas pipe Be Pebbles

Simulation capabilities continue to advance and can play a larger role

 

Example – 3D MHD PbLi flow through and expansion maniflold 17-44% flow mismatch between center and side channels (controlled by MHD)

Electric current

Ha = 929, Re = 1500, N = 575

(based on Parallel Channel Half-Width) Velocity profiles Stream lines

DEMO Availability of 50% Requires Blanket Availability >85%

(Table based on information from J. Sheffield’s memo to the Dev Path Panel) Component Toroidal Coils Poloidal Coils Magnet supplies Cryogenics Blanket Divertor Htg/CD Fueling

Num ber 16 8 4 2 100 32 4 1 Failure rate in hr -1 5 x10 -6 5 x10 -6 1 x10 -4 2 x10 -4 1 x10 -5 2 x10 -5 2 x10 -4 3 x10 -5 1 x10 -4

MTBF in years 23 23 1.14 0.57 11.4 5.7 0.57 3.8

MTTR for Major failure, hr 10 4 5x10 3 72 300 800 500 500 72 MTTR for Minor failure, hr 240 240 10 24 100 200 20 -- Fraction of failures that are Major 0.1 0.1 0.1 0.1 0.05 0.1 0.3 1.0

Tritium System

1

1.14

180 24 0.1

Vacuum

3 5 x10 -5

2.28

72 6 0.1 Conventional equipment- instrumentation, cooling, turbines, electrical plant ---

Outage Risk 0.098 0.025 0.007 0.022 0.135 0.147 0.131 0.002 0.005 0.002

Component Availability 0.91 0.97 0.99 0.978 0.881 0.871 0.884 0.998 0.995 0.998

TOTAL SYSTEM 0.05 0.624

0.952 0.615

Assuming 0.2 as a fraction of year scheduled for regular maintenance. Demo Availability = 0.8* [1/(1+0.624)] = 0.49 (Blanket Availability must be .88)