# Presentation: 106736

## Design Study of Fusion DEMO Plant at JAERI

***Japan Atomic Energy Research Institute***

***K. Tobita****, S. Nishio, M. Enoeda, M. Sato, T. Isono, S. Sakurai, *
*H. Nakamura,S. Sato, S. Suzuki, M. Ando, K. Ezato, T. Hayashi,*
*T. Hayashi, T. Hirose, T. Inoue, Y. Kawamura, N. Koizumi, Y. Kudo, R. Kurihara, T. Kuroda*, K. Mouri, Y. Nakamura, M. Nishi, Y. Nomoto, J. Ohmori, N. Oyama, K. Sakamoto, T. Suzuki,** **M. Takechi, *
*H. Tanigawa, K. Tsuchiya, D. Tsuru*
*  **( * Kawasaki Heavy Industries) *

*ISFNT7, Tokyo, May 23-27, 2005*

***S6-14-O-02***

## OUTLINE

**Background**
**Concept of DEMO**
**Features of DEMO plant**
**Next steps in design study**

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## 1. Background

**IFMIF**

**Commercial.**

**Economy**

**Tech.R&D**

**Satellite**
** ****tokamaks**

**ITER**

**Situation of JA strategy for FE commercialization**

***Middle of ***
***this century***

**Technology**

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**• ****JA strategy still argued in AEC, not settled**
**• ****Point of argument: ****ONE or TWO steps to commercialization?**

**Technology**
**Economy**

**2 steps?**

**1 step?**

**DEMO stage**

**Notes:**
Let me tell you the situation of JA strategy for FE commerc...
They have been still arguing in the AEC

We can’t wait for the conclusion. So we got started with our design study, assuming this challenging strategy.

## Place of DEMO

***competitive***

**Technology**

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***advanced***

***conservative***

***expensive***

**Economy**

**Notes:**
the place of DEMO. 
First, let me try to explain previous reactor designs at  JAERI 

## Philosophy for DEMO design

**SSTR (1991)**

**VECTOR (2001)**

***Low-A***
**DEMO**

**Modify “VECTOR concept” **
**to reduce tech. requirements**
**without losing compactness**

**Comparable in **
**tech. level**

***Design compromise of VECTOR, ***
***              ******based on foreseeable technologies***

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**Technology**

***advanced***

***conservative***

***expensive***

**Economy**

***(Exp. in low-A scarce. Needs***
***support by satellite tokamak)***

***competitive***

***ex. NCT***

**Notes:**
It may sound too good to be true, but I believe we can envision 

## VECTOR concept:           superconducting low-A w/o CS coils

**VECTOR concept: ****          superconducting low-A w/o CS coils**

**Aspect ratio**

**Remove CS**

**R****TFC**** giving B****max**

**( magnetic energy         ) **

**Slender TFC system**

**(elongation         )**

**High ******

**Compact, low-A & high ********with slender TFC**

**A ~ 2-2.5**

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## 2. Concept of DEMO

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**VECTOR**

**Difficulties**

**plasma shape control **

**• ****triangularity ****(HH, ELM contr)**
**• ****positions**

**plasma current ramp-up **

**Advantage**

**very compact (light) **

**(null point, div. hit point)**

**CS-less**

## 2. Concept of DEMO

**VECTOR**

**Difficulties**

**plasma shape control **

**• ****triangularity ****(HH, ELM contr)**
**• ****positions**

**plasma current ramp-up **

**Advantage**

**very compact (light) **

**(null point, div. hit point)**

**CS-less**

**DEMO(J05)**

**Slim CS**

**reduced but still compact **

**improved but still limited**

**R****cs**** = 0.7m, ********cs**** = 38 Vsec**

**resolved **

***compromise***

***induce 3.8 MA***

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***I******cs****** 10 MA/m***

## Impact of CS on reactor weight

|  | Rcs | shaping | Ip-ramp |
| --- | --- | --- | --- |
| CS-less | - | limited | - |
| Slim CS | 0.7m | good | ~ 3.8 MA |
| Full CS | 1.5m | good | flattop |

**Impact of CS on reactor weight**

**~40Wb**

**170Wb**

- Systems code analysis

_**Conditions**_**:**

**• ****TFC stress 800 MPa**
**• ****same ********, ********N**** margins,  **
**• ****fusion output 3 GW, etc.**

** ****to find the *****minimum reactor ***
***  ******weight***** of the following cases**

**DEMO**

***weight  ==> constr. cost***

***DEMO(J05)***

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***Considering tech. feasibility and weight,***
***“******Slim CS” is a good compromise.***

**Notes:**
Notice that the introduction of such a slim CS leads to only 2000 ton increase in reactor weight. 
Considering the significant  roles of CS and the reactor weight , slim CS seems to be  a good design compromise. 
That’s why we chose the slim CS  as the prime option.

## 3. Features of DEMO plant 

** ****Nb****3****Al S.C. **
**    • ****12 TF coils, B****max**** = 16.4 T**

** ****Blanket**
**    • ****Li****2****TiO****3**** / Be****12****Ti (pebble)**
**    • ****F82H / pressurized water**

** ****Current drive**
**    • ****NBI  : 1.5 MeV**
**    • ****ECRF :  170-190 GHz**

**R****p**** = 5.5m, a = 2.1m, A = 2.6**
**B****T**** = 6T, I****p**** = 16.7MA,**
******N**** = 4.3, P****fus**** = 3 GW**

** ****Divertor**
**   • ****W monoblock / F82H cooling tube**

** ****Maintenance**
**    ****Sector maintenance**

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***Extrapolation of TBM(JA)***

***Firm support of BLK / high availability***

## (1) Light reactor weight,    leading to a reduction of construction cost

**Reactor weight :**

| DEMO(J05) |  ~17,500 tons |
| --- | --- |
| ARIES-RS, ARIES-ST
SSTR,A-SSTR2, ITER |   > 22,000 tons |

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**Notes:**
Notice that the reactor weight of DEMO is more than 5000 tons lighter than those of other tokamaks.

## (2) Seemingly N (=4.3) is high,                but likely to have a large N margin

**Theoretically, higher ********N**** expected in lower A**

**Margin to LL-S ********N**

| Margin | designs |
| --- | --- |
| ~0% | A-SSTR2 |
| ~10% | SSTR, PPCS(D) |
| ~20% | DEMO(J05), PPCS(C) |

*********N****** limit for 100% ***_***BS-driven plasma***_

** ****ex., Lin-Liu / Stambaugh formulation**

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***Tough constraint***

## (3) DEMO requires technologies comparable to SSTR

**(3) DEMO requires technologies comparable to SSTR**

**Magnet**

**Plasma**

**Vertical stability**

**ballooning stability**

**Confinement**

**Density**

**Maximum field**

**TFC magnetic energy**

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## 4. Next steps in design study

**Refine divertor concept**
**     – ****consistent solution of shape control (********), radial build and **
**        ****heat/particle control**
**• ****study startup and shutdown scenarios**
**     – ****overdrive in startup / shutdown by impurity gas puff**
- • **Provide feasible maintenance scheme**
-     **– ****sector transport / hot cell maintenance**
**• ****Assess supercritical CO****2 ****as alternative coolant**
**  – ****Advantages : Compact turbines, compatible with Be, **
**                                ****easy separation of T, etc. **
**  – ****Disadvantage : organic compounds by CO+T****2**** reaction**

***Major change from the ITER scheme***

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**Notes:**
Flammable organic compaunds

## Presentations on DEMO

| MAY 23 (MON) | M. Nishi
S1-01-0-01 |   Tritium accountancy |
| --- | --- | --- |
| MAY 24
(TUE)  | H. Nakamura
P2-20 |   Tritium penetration |
| MAY 26
(THU) | T. Isono
P5-27 |   Magnet design |
|  | M. Sato
P5-30 |   Core and divertor concept |
|  | S. Nishio
P5-29 |   Reactor structure |
|  | T. Inoue
P5-32 |   NBI system |
|  | K. Sakamoto
P5-28 |   ECRF system |

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## Summary

**A ****compact low-A (A ~ 2.6)**** ****reactor is under consideration at JAERI as a ****DEMO**** concept.**
**DEMO ****has a**** ****slim CS**** for plasma shape control as a compromise of the *****CS-less***** VECTOR concept. Yet, the reactor ****weight is still light compared with other tokamak designs****.**
**Required ****technologies seem comparable**** in difficulty level to those for ****SSTR****.**

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