# Presentation: 919876

## 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.**
_**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. **

***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 

-       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
- 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.

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

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

**Theory/Modeling**

**Basic**

**Separate**
**Effects**

**Multiple**
**Interactions**

**Partially**
**Integrated**

**Integrated**

**Property Measurement**

**Phenomena Exploration**

**Non-Fusion Facilities**

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

**Design Codes**

**Component**

**Fusion Env. Exploration**

**Concept Screening**

**Performance Verification**

**Testing in Fusion Facilities**

**(various non neutron test stands, ****fission reactors and accelerator-based neutron sources)**

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

-  Thermo-mechanical	 Tritium
- High Heat Flux	 Magnetic
- Plasma/Tokamak	 ...

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

- ITER has allocated **3 ITER equatorial ports** (1.75 x 2.2 m2) for TBM testing, and space in the reactor hall and TCWS building for support systems

- 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.
- ITER-TBM can be used tostudy synergistic effects among FW/blanket phenomena and provide data to improve models and benchmark simulation codes.
- TBM experiments in ITER can provide a bridge between laboratory and NCT experiments.
- There is currently no ITER program for testing advanced divertor designs

## 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**

**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...

## D E M O

- 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/m2)
- 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

**Sub-Modules/Modules**

** **

**Stage I**

**Fusion “Break-in” & Scientific Exploration**

**Stage II**

**Stage III**

** ****Engineering Feasibility & Performance Verification**

**Component Engineering Development & Reliability Growth**

**Modules**

**Modules/Sectors**

**D E M O**

**1 - 3 MW-y/m****2**

**> 4 - 6 *****MW-y/m******2***

**   ****0.5 MW/m****2****, burn > 200 s**

**1-2 MW/m****2****,**
**steady state or long pulse**
**COT ~ 1-2 weeks**

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

**0.1 – 0.3 MW-y/m****2**

**Role of ITER TBM**

**Gap?**

** ****Stages of FW/Blanket/Divertor Testing in Fusion Facilities**

**Fluence**

**NWL**

**Exp type**

## Blanket Functions (including first wall)

**Blanket Functions (including first wall)**

- 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*_
- 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

## 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***

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

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

| Material or Configuration | Options |
| --- | --- |
| Structural Materials | Reduced Activation Ferritic Steel Alloys (including ODS), Vanadium Alloys, SiC Composites |
| Coolant Media | Helium, Water, Liquid Metals, Molten Salts |
| Breeder Media | Lithium-Bearing: Ceramic Breeders (Li4SiO4, Li2TiO3, Li2O); Liquid Metals (Li, PbLi, SnLi); Molten Salts (FLiBe, FLiNaBe); Varying enrichments in Li-6 |
| Neutron Multiplier Materials | Beryllium, Be12Ti, Lead |
| MHD/Thermal Insulator Materials | SiC composites and foams, Al2O3, CaO, AlN, Er2O3, Y2O3 |
| Corrosion and Permeation Barriers | SiC, Al2O3, others |
| Plasma Facing Material | Beryllium, Carbon, Tungsten alloys, others |
| HX or TX Materials | Ferritic Steels, Refractory Alloys, SiC, Direct Gas Contact |
| Blanket Configurations | He or Water Cooled Ceramic Breeder/Be; Separately Cooled, Self-Cooled, Dual-Coolant LM or MS |
| Ceramic Breeder Configurations | Layered, Mixed, Parallel, Edge-On (referenced to FW) |
| Liquid Breeder Configurations | Radial-Poloidal Flow, Radial-Toroidal Flow, others |
| MHD/Thermal Insulator Config. | Flow Channel Inserts, Self-Healing Coatings, Multi-Layer Coatings |
| Structure Fabrication Routes | 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

**He-cooled RAFS FW**

**Poloidal flow**
**PbLi channel**

**Dual-Coolant PbLi Liquid Breeder Module **

**He-cooled RAFS FW**

**Be Pebbles**

**Purge gas pipe**

**Helium-Cooled Li****2****TiO****3**** Ceramic Breeder Module**

**SiC FCIs**

- The Blanket provides the mechanisms by which:
***tritium is generated for ***
***	******fuel self-sufficiency ***
***high grade heat is extracted for ******efficient energy production***
- 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** *

- Yet, *no fusion blanket has ever been built or tested. * **ITER has always been planned as the facility to begin blanket testing.**

**Ceramic breeder pebbles**

- All blanket concepts have feasibility issues!

## 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)**

**Ha = 929, Re = 1500, N = 575**** **
***(based on Parallel Channel Half-Width)***

***Electric current***

***Stream lines***

***Velocity profiles***

## DEMO Availability of 50% Requires Blanket Availability >85%

**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)***

**DEMO Availability of 50% Requires Blanket Availability >85%**

- (Table based on information from J. Sheffield’s memo to the Dev Path Panel)