# Presentation: 649845

## Concept development of compact DEMO reactor

**Kenji Tobita**
**for DEMO Plant Design Team**
***Japan Atomic Energy Research Institute***

**Special thanks:  F. Najmabadi (UCSD), C.P.C. Wong (GA),**
** ****	****	****  ****K. Okano(CRIEPI)**

- IEA/LT Workshop (W59) combined with DOE/JAERI Technical Planning of Tokamak Experiments (FP1-2)
- 'Shape and Aspect Ratio Optimization for High Beta Steady-State Tokamak'

## OUTLINE

**1.  ABC of Fusion Reactor Study**
**2. Compact reactor study at JAERI**
**3. DEMO design study at JAERI**

***Started in 2003***

***Focus on the possibility of an economically attractive reactor ***
***in low-A (= 2-2.9), left behind in fusion reactor study previously***

***- 2 -***

## 1. ABC of Fusion Reactor Study

**Direction of fusion reactor studies**
**Necessity to pursue economic fusion energy**

***- 3 -***

## (A) Reactor study seeks for an economic reactor concept

**Design Year**

**COE (¢/kWh)**

**SSTR**** ****(16 ¥/kWh)**

**ARIES-I**

**ARIES-RS**

**ARIES-AT**

**CREST**** ****(12.5 ¥/kWh)**

**Cost-of-Electricity of Fusion **

**COE of other sources **

| fission | ~5¢/kWh |
| --- | --- |
| coal-fired | ~6¢/kWh |

***[1992 JA price basis]***

***- 4 -***

##  (B) In fusion energy,        60~70% of COE is capital cost

** ****(B) In fusion energy, ****       60~70% of COE is capital cost**

**COE (¢/kWh) = **

**C****c**** + C****F**** + C****OM**

**P****e**** • 8760 (h/yr) • f****av****  **

**Capital**

**Fuel**

**Operation & maintenance**

| Capital  | 53.87 B¥/yr |
| --- | --- |
| Fuel | 0.04 B¥/yr |
| Operation | 19.77 B¥/yr |
| Maintenance | 17.95 B¥/yr |

**Costs of CREST**** (discount rate 2%)**

**Availability**

**output**

_**To  reduce  COE**_
** ****1) Capital cost**
** ****2) Thermal efficiency**
** ****3) Availability**

***- 5 -***

## (C) Much lower construction cost required for commercialization of FE

|  | Const. Cost | Electricity Share |
| --- | --- | --- |
| SSTR | ~4,500 $/kW |  |
| ARIES-RS | 3,770 $/kW |  |
| Default | 3,440 $/kW | 0 ~ 6% |
| Low Cost | 2,400 $/kW | 4~11% |

***- 6 -***

**Fusion share assessment in 2100**

**4% ~ 1,500 plants**

**Share depends on **

**• ****COE of other sources**
**• ****CO****2****-emission standards, etc.**

**The estimated fusion cost may not be competitive in market**

***Tokimatsu (2003)***

## Exploration of compact reactor 

**USA**

***Najmabadi (2000)***

**JAERI**

**SSTR**** (1990)**

**A-SSTR2**** (1999)**

**R****p**** = 7 m**

**R****p**** = 6.2 m**

***- 7 -***

## How to compensate for reduced Vp in compact reactor

** ****low recirculating power by high bootstrap**
** ****higher thermal efficiency**
** ****higher ********N**
** ****higher B****max**** **

**ARIES**

**JAERI**

***High ************ to reduce B******max***

***Moderate ************ at high B******max***

***- 8 -***

## 2. Compact reactor study at JAERI

***   ******What led us to low-A compact reactor concept?****** ***

***- 9 -***

## JAERI’s approach toward compact reactor

**R****p**** = 7 m**
**B****max**** = 16.5 T**
******N**** = 3.5**

**R****p**** = 6.2 m**
**B****max**** = 23 T**
******N**** = 4**

**A-SSTR2**

**VECTOR**

**SSTR**

**Higher B****max**** and ********N**** **

***- 10 -***

## High BT can make it heavy

**High B****T**** can make it heavy**

**SSTR**

**A-SSTR2**

| 7.0 m | Rp | 6.2 m |
| --- | --- | --- |
| 16.5 T | Bmax | 23 T |
| 136 GJ | WTFC  | 181 GJ |
| 11,200 tons | TFC Weight  | 14,640 tons |

***TFC weight is significant part of reactor: ~ 45% in SSTR***

***- 11 -***

## JAERI’s approach toward compact reactor

**R****p**** = 7 m**
**B****max**** = 16.5 T**
******N**** = 3.5**

**R****p**** = 6.2 m**
**B****max**** = 23 T**
******N**** = 4**

**R****p**** = 3.5 m**
**B****max**** = 20 T**
******N**** = 5.5**

**A-SSTR2**

**VECTOR**

**SSTR**

**High B****max**** with slim TFC **

***- 10 -***

## _x0012_Reduce WTFC by small RTF 

**_x0012_****Reduce W****TFC**** by small R****TF**** **

**ITER**
**B****max****= 13T**
**W****TFC**** = 41 GJ**

**SSTR**
**B****max****= 16.5T**
**W****TFC**** = 140 GJ**

**VECT****_x000f_****OR**
**B****max****= 19T**
**W****TFC**** = 10 GJ**

**High W****TFC**

**Low W****TFC**

**Massive TFC**

**Slender TFC**

**R****TF**

***- 12 -***

**Notes:**
核融合炉、

## VECTOR

- 18.2m

| Rp | 3.2 m | Ip | 14 MA |
| --- | --- | --- | --- |
| a | 1.4 m | N | 5.5 |
| A | 2.3 | HH | 1.3 |
|  | 2.35 | n/nGW | 0.9 |
| Bmax | 19 T | qMHD | 6.5 |
| BT | 5 T | Pfus | 2.5 GW |

**Physical features**

** ****CS-less**
** ****Low A (~2.3)**
**          *****high ************, high n******GW******, high q***

***- 13 -***

**Remove CS to shorten R****TF**** and reduce W****TFC**

**Concept of VECTOR**

**Slender CS**

**Low-A**

## Difference between VECTOR and ST

**Difference between VECTOR and ST**

**conventional**

**VECTOR**

**ST**

**CS  removed**

**Cu coil**

**SC coil**

**A ~ 2.5**

**A ~ 1.5**

**Power reactor**

**VNS**

***w. n-shield***

***w/o. n-shield***

**A = 3-4**

***- 14 -***

## VECTOR, likely to have economical and environmental advantages

**Reactor weight (t)**

**Power / Weight (kW****th****/t)**

**Low const. cost**
**Resource-saving**

**Economical**

***- 15 -***

## Radwaste of VECTOR, ~4,000 t

**•  ****LLW, vulnerable point of fusion**
**       ****(usually, ≥ 10,000 t)**
**• ****PWR ~ 4,000 t**

**Clearance**

**Clearance**

**Clearance**

**Reinforced shield**

**Reinforced shield**

**Recycle**

**Reuse**

**Compactness**

**Resources (t)**

***- 16 -***

## Remarks on VECTOR

**    ****VECTOR concept on TFC system breaks new ground of power reactor design  in low-A**

_**What is sure**_

_**Open question**_

**    ****Is the optimal design point for cost-minimum really A ~ 2.3 for the VECTOR concept?**

**Assumed parametric dependence of ********N****(A) is uncertain.**

***- 17 -***

## 3. DEMO design study at JAERI

**How to fit VECTOR concept to DEMO**
**Three DEMO options **

***- 18 -***

## JA Strategy for FE commercialization

** ****IFMIF**

**Commercial.**

**DEMO**

**ITER**

**Tech.R&D**

**NCT**

***- 19 -***

## Tradeoff between size and feasibility

**small as possible to reduce W****TFC**

**CS**

**Remove**

**Install**

**Compact**

**Large R****p**

**More feasible**

**+**

**difficult**

**+**

**Size**

**plasma**

**Based on roles of CS, three DEMO options are under consideration**

**VECTOR concept**

***- 20 -***

## Difficulties caused by CS-less

**I****p**** rise/control**

**Ex) CS-less Ip ramp-up Exp. **
**                   ****(JT-60U, etc)**

***will be resolved***

***- 21 -***

## Best effort to raise  w/o CS

| Rp | 5.1 m |
| --- | --- |
| a | 2.1 m |
| Ip | 17.5 MA |
| p | 2.5 |
| li | 0.8 |
| up | 2.0 |
| up | 0.3 |

**A far distance between plasma and PF coils makes the shaping difficult. **

***- 22 -***

## Three DEMO options

**Three DEMO options**

**challenging**

**conservative**

***- 23 -***

## Preliminary design parameters

|  | CS-less | Slim CS | Full CS |
| --- | --- | --- | --- |
| Rp (m) | 5.1 | 5.5 | 6.5 |
| a (m) | 2.15 | 2.1 | 2.1 |
| A | 2.4 | 2.6 | 3.1 |
|  | 2.08 | 2.0 | 1.9 |
|  | ~0.3 | 0.4 | 0.45 |
| BT /Bmax (T) | 5.4 / 18.2 | 6.0 / 16.4 | 6.8 / 14.6 |
| Ip (MA) | 18.1 | 16.7 | 15.0 |
| q95 | 5.7 | 5.4 | 5.3 |
| N | 4.6 | 4.3 | 4.1 |
| HH | 1.3 | 1.3 | 1.3 |
| fBS | 0.76 | 0.77 | 0.79 |
| n/nGW | 0.95 | 0.98 | 1.0 |
| Pfus (GW) | 3.1 | 3.0 | 3.0 |
| Pn (MW/m2) | 3.6 | 3.5 | 3.0 |
| Q | 49 | 52 | 54 |
| Weight (tons) | 15,700 | 17,500 | 23,900 |

***- 24 -***

## Comparison of Options

**0**

**100**

**200**

**300**

**0**

**10,000**

**20,000**

**30,000**

**ITER**

**ARIES-RS**

**ARIES-ST**

**SSTR**

**A-SSTR2**

**DREAM**

**VECTOR**

**Economical**

**Low const. cost**

**P****fus****  / weight (kW/t)**

**Reactor weight (t)**

**Option A**

**CS-less**

**R****p****~5.1m**

**Full CS**

**R****p****~6.4m**

**Option C**

*** ******shaping, I******p****** ramp ***

**Slim CS**

**R****p****~ 5.5m**

**Option B**

***shaping***

***- 25 -***

## Key parameters in reactor design

**inboard SOL**
**Gap**
**BLK**
**n-shield**
**VV**
**th-insulator**

**R****p**

**R****TF**

**B****max**

******TF**

******TF**

**1.3 m **

***Rule of thumb ***

**TFC**

**CS**

**Minimum shield thickness enough to protect TFC from neutron damage**

**Four key parameters : R****p****, B****max****, R****TF****, ********TF**

**_x0014_****To use B****T**** effectively, the inboard SOL width should be small**

***- 27 -***

## SOLin, expected to increase with A 

******SOL****in****  ****usually assumed to be 10 cm**
**             ****but expected to decrease with A.**

******SOL****out  ****~**

**Roughly,**

**defined by the width of heat flux in SOL (****assumed to be 3 cm)**

***- 28 -***

## Low-A requires a wide inboard clearance, especially for “CS-less”

** ****For A~3**
**   ********SOL****in** **~ 10 cm, good approx.**
** ****For A < 2.5**
**   ****must be careful about ********SOL****in**

**Determined from the flux surface corresponding to********SOL****out**** = 3cm **

***- 29 -***

## Selection of   design parameters 

**R****CS**

**R****TF**

******TF**

**a**

**R****P**

**B****max**

**CS**

**TFC**

**Selection of ****  ****design parameter****s **

***- 30 -***

## Selection of   design parameters

******N****, B****T**

**Selection of ****  ****design parameter****s**

**R****CS**

**R****TF**

******TF**

**a**

**R****P**

**B****max**

**CS**

**TFC**

***- 30 -***

## Selection of   design parameters

******N****, B****T**

**R****CS**

**R****TF**

******TF**

**a**

**R****P**

**B****max**

**CS**

**TFC**

**75% of ******

**78% of ********N**

**Wong’s formula **
** ****(********, ********N****)**

**HH (=1.3)**

**I****P****, q************V****P****, P****fus****, P****CD****, f****GW****, ....**

**Check consistency **

***- 30 -***

## Optimal design point (“Slim CS”)

**Optimal design point (“Slim CS”)**

** ****P****fus ****=  3GW**
**    ←****P****e****net****  = 1 GWe**
** ****Weight minimum**

** ****Optimal range, rather wide**

**optimal**

**–– ****less dependent on A (or R****TF****)**

**fat TFC &  high-A**

**slender TFC &  low-A**

***- 31 -***

## Breakdown of weight

**A= 2.2**

**A= 2.8**

**Weight (t)**

|  | light | heavy |
| --- | --- | --- |
| Higher A | Torus comp.
PFC | TFC |
| Lower A | TFC | Torus comp.
PFC |

***- 32 -***

## Problem in parameter selection:  N (A) is not sure

**Kessel ****(ARIES-AT, -RS)**

**Wong ****(based on Miller’s stab.DB)**

**A**

******(A)**

******N****(A,********)**

******-dependence hidden**

******N**** vs ******** curve, depends on ******
******N****, less dependent on ******** in our conditions**

**Our conditions**

***100% BS-driven plasma***

**Our systems code uses this**

***- 33 -***

## How does the optimal design point change when N is independent on ?

**How does the optimal design point change when ********N ****is independent on ********?**

**Original assumption**

**Alternative assumption**
**     ****to check an impact of ********N****(********)**

***Based on Wong’s formula***

***Kessel-like ***
*** ******(but not incl. dependence of ************N****** on A)***

***- 34 -***

## A ~ 3 optimum when N(A,) = const 

**A ~ 3 optimum when ********N****(A,********) = const **

**Original design**

**Constant  ********N**

******N**** = 4**

**optimal**

**Optimal**
**Slight increase in R****p**

***- 35 -***

## Present understanding on DEMO

**Present understanding on DEMO**

**With slim CS, DEMO seems to succeed in  adopting the VECTOR concept with plasma shaping capability. **
**At the optimum design point, DEMO can have low-A (= 2.5-3) which is unexplored A in previous power reactor study before VECTOR.**

**ST**

- 1

- 2

- 3

- 4

- 5

- 2

- 4

- 6

- 8

**ARIES-ST**

**ARIES-AT**

**ARIES-RS**

**ARIES-I**

**A-SSTR2**

**SSTR**

**PPCS(B)**

**PPCS(A)**

**PPCS(C)**

**PPCS(D)**

**CREST**

**VECTOR**

**VECTOR-opt**

**conventional**

**A**

******N**

**DEMO**

***- 36 -***

## Summary

**VECTOR concept**
**  ****Removes CS to shorten R****TF**** and reduce W****TFC ****, **
**        ****leading to slim TFC system compatible with high B****max**** **
**           ****Suggests a possibility of power reactor with A = 2-3**
**DEMO**
**   • ****CS will be necessary for shaping.**
**   • “****Slim CS”, i.e., modified VECTOR concept, enables us to envision DEMO with A = 2.5-3**
**       **

**To make the proper footing of DEMO, dependence of ********N**** on A and ******** should be investigated in the range of A = 2.5-4, hopefully through international cooperation**

***- 37 -***