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Integrated design study for DEMO concept defini7on
Y. Sakamoto, K. Tobita, H. Utoh, N. Asakura, Y. Someya, K. Hoshino, M. Nakamura, S. Tokunaga and the DEMO Design Team
Japan Atomic Energy Agency
3rd IAEA DEMO Programme Workshop InsGtute of Plasma Physics, Chinese Academy of Sciences (ASIPP)
11-‐15, May 2015
1. Recent situa7on on DEMO development ü Broader Approach Ac7vity ü Joint Core Team Ac7vity
2. DEMO concept development ü Basic outline of DEMO concept ü Assessment of relevant technologies
3. Summary
Contents
Broader Approach (BA) Ac7vity (2007.6 – 2017.5)
In parallel to the ITER project, BA acGviGes are being implemented by EU and JA.
l IFERC project (DEMO design and R&D, CSC, REC) l IFMIF/EVEDA project l STP project (JT-‐60SA)
“Joint Core Team” organized by Fusion Research WG under MEXT (2013.7 – 2015.1 )
l The team is composed of 8 members from JAEA, NIFS, Univ., Industry. l Mission is to develop strategy for establishment of technology bases
required for DEMO by considering the status of ongoing projects (incl. ITER)
l “Report of Joint Core Team (July, 2014) defines requirements for DEMO
ü Steady and stable power generaGon with several 100s of MWe ß reduced from 1GWe in AEC report
ü Plant availability leading to commercializaGon ü TriGum breeding raGo > 1
1. Recent situa7on on DEMO development in JA
l Previous DEMO reactor study on SlimCS focused on a steady state and relaGvely compact reactor (Rp=5.5m) that is capable of producing a Pfus=3GW and Pnet=1GWe.
Ø To respond the requirement, JAEA DEMO design team has begun to look into the feasibility of ü a medium size DEMO with full size CS coil, ü lower fusion power for miGgaGng heat load,
by assessing the relevant technologies.
l However, the design study in recent years suggests that such a compact and high power reactor has intractable problems in ü Huge power exhaust in the divertor ü Capability of CS flux (ΔIpCS / Ip =0.23 in SlimCS)
l For commissioning operaGon and early demonstraGon of electric generaGon, full size CS coil is favarable.
2. DEMO concept development – Introduc7on –
l To minimize the development subjects by uGlizing exisGng technologies
Tokamak (Medium size & low power) l Reactor size: Rp > 8.0m l Fusion output: ~1.5GW l Steady-‐state operaGon l TriGum self-‐sufficiency (TBR>1.05) l Water-‐cooled solid breeder blanket
l Cooling water: PWR condiGon 15.5 MPa、290-‐325℃ l Thermal output: ~1.7GW
(fBLK=1.45, SBLK=0.8) l Net electricity: 0.2-‐0.3 GWe (ηth 〜30%)
BoP (Balance of plant)
EffecGve uGlizaGon of nuclear reactor technologies
Based on ITER technologies as much as possible (conv. Div, TF, TBM,,,)
Basic outline of DEMO design concept
DEMO design
l In Tokamak design, ITER technologies will be uGlized as much as possible.
l However, principal differences from ITER have a large impact on DEMO design, which are related to each other.
Large neutron fluence
• Several Gmes larger than ITER Ø Different maintenance scenario Ø RadioacGve waste management
Large power handling
• Several Gmes larger than ITER Ø Severe condiGon for divertor
ConducGng shell for VS
• ITER decided to install in-‐vessel coils for verGcal stability.
Ø No in-‐vessel coils in DEMO due to neutron irradiaGon and maintainability.
Ø The shell posiGon is far from plasma due to existence of thick breeding blanket
Breeding blanket
• No breeding BLK in ITER Ø Roles of BLK are triGum breading and
heat extracGon for electric generaGon
Design issues raised by gaps between ITER and DEMO
l Size of CS coil required for several hours-‐long operaGon
l Thickness of breeding blanket required for overall TBR>1.05 l Capability of heat removal in divertor
l Maximum toroidal field generated in the medium size DEMO
Possible DEMO design parameter has been developed through the assessment of technologies.
l Amount of radioacGve waste and waste management
l Maintenance scheme suitable for the medium size DEMO
l Impact of conducGng shell on device configuraGon
Mainly related to fusion power
Mainly Related to reactor size
Viewpoints of technology assessment
Basic concept of divertor l Water-‐cooling and W mono-‐block l ConvenGonal divertor configuraGon
l Heat removal capability l ReducGon of heat load ü Assessment of
allowable heat flux ü Div. simulaGon study
q div
Technology
Plasma physics (detachment & high frad)
Design point
Approaches for divertor design
similar to ITER design
! Large reducGon of heat load on divertor target is required for DEMO than ITER.
Divertor design
Assessment of reduc7on of heat load
Assessment of heat removal capability
ü Neutronics analysis: Pfus < ~1.5 GW allows the parGal use of Cu alloy near high heat flux region with dpa/FPY < ~1.5. (EU proposal, originally)
l To reduce qdiv<10MW, simulaGon study of the convenGonal divertor for Rp=5.5 m indicates frad>0.8 is required for Pfus=1.5 – 2.0GW.
Ø frad=0.7 could be consistent with Pfus=1.5 GW and larger Rp~8m (qtarget∝Pout/Rp).
l F82H cooling pipe: qtarget ~ 5 MW/m2 l Cu alloy cooling pipe: qtarget ~ 10 MW/m2
Cu alloy
F82H
q div (MW/m2)
Cooling pipe
Possible design point for Pfus=1.5GW & Rp=8m
5 10
F82H Cu alloy
70% 80%
Radiation fraction
SONIC simulaGon
Divertor heat load and compa7ble heat removal technology are important key reactor design
Basic concept of blanket
ü Cooling water: PWR condiGon (290-‐325 ℃, 15.5 MPa) ü Breeding materials: neutron mulGplier (Be12Ti pebbles)
and solid breeder (Li2TiO3 pebbles)
Water cooled solid breeder based on ITER-‐TBM strategy
Assessment of blanket thickness for overall TBR~1.05 l Layout of cooling pipe should be opGmized along with
profile of neutron wall load (NWL), because local TBR decreases with increasing the cooling pipe area.
l Overall TBR >1.05 is evaluated for blanket thickness of 0.6m and Pfus < 2.0 GW.
Op7miza7on of blanket cooling pipe and determina7on of its thickness for overall TBR~1.05
Waste by periodic replacements The amount of radioacGve wastes generated in every replacement (4 years) is esGmated to over 9,000 tons (BLK: 5723 ton, DIV: 924 x 4 = 3696 ton).
Assessment of waste management strategy
The amount of wastes can be reduced to 1879 ton (20%) by ü reusing back plate (F82H: 3776.6 ton), conducGng shell (CuCrZr: 372.4 ton) and
divertor cassese body (F82H: 627.8 ton), ü recycling mixed breeder (Li2TiO3 & Be12Ti: 881 ton)
Component DPA/FPY Limit value
Blanket (FW) 9.0 < 20 dpa
ConducGng shell 0.2 < 2 dpa
Back plate 0.2 < 3 dpa
Divertor (CuCrZr pipe) 1.5 < 1 dpa
Divertor (cassese body) 0.6 < 20 dpa
Pfus = 1.35 GW
Reuse & recycle of components are a key strategy to reduce radioac7ve wastes
Maintenance scheme
Various maintenance options
Sector m
ainten
ance
port
BLK port
DIV po
rt
l Maintenance scheme should be different from ITER and significantly impacts on torus configuraGon. ü In-‐vessel components, PF and TF coils,,, ü Reactor buildings incl. hot cell and waste
management scenario. l Various concepts have been assessed to
narrow down the concept.
Blanket maintenance
ü Ease of handling due to lightweight ü Smaller size of TF coil ü Support of TFC turnover force by wide area intercoil structure ü MagneGc energy of PF coils (68GJ à 27GJ) ü Separately-‐maintenance of blanket and divetor
At present, it is considered that the segmented maintenance scheme provides a lot of advantages for medium size DEMO
Divertor maintenance
• 3 DIV casseses /sector • 2 modules / inboard sector • 3 modules / outboard sector
Segmented maintenance scheme provides advantage for medium size DEMO
Inboa
rd se
gmen
t
Outbo
ard
segm
ent
Divertor cassette
Similar to ITER technologies: ü Radial plate, and wedge support structure ü Cable-‐in-‐conduit type conductor (68kA) ü Withstand voltage of 20kV and operaGon
temperature of 5K
The choice of SC strand material should be considered by: ü Strain property of Jc ü Manufacturability (R&W or W&R)
Conductor Design stress BTmax
Nb3Sn 667 MPa 11.5 T
800 MPa 12.1 T
Nb3Al 667 MPa 11.7 T
800 MPa 12.4 T
Basic concept of TF coil design
14.1m
20.1m
9m
13.5m
BTmax is evaluated for Nb3Sn and Nb3Al at design stress of 667 and 800 MPa by SCONE code.
Assessment of maximum BT (BTmax)
ü Difference in BTmax between Nb3Al and Nb3Sn decreases with increasing Rp.
ü Design stress (Sm) has a large impact on BTmax.
Sm=800MPa could be foreseeable by raising the raGo of high quality material.
BTmax decreases with Rp, but >12T can be generated at
Rp~8.5m by both Nb3Sn and Nb3Al with Sm=800MPa
Elonga7on (κ)
l ConducGng shell has essenGal role in verGcal and high beta stabiliGes, especially in DEMO due to no in-‐vessel coils.
l The posiGon is far from plasma, typically rW/ap~1.35 due to thick BLK of 0.6 m
" large impact on device configuraGon (κ, A).
ΔBLK ΔSOL Δgap
l Plasma elongaGon is one of the key factors in determining absolute plasma performance, while highly elongated plasma is verGcally unstable.
l VerGcal stability analysis indicates design elongaGon of κ95 ~ 1.65.
Requirement of conduc7ng shell posi7on has a large impact on device configura7on (κ, A)
Back plate
ConducGng shell
Blanket
Aspect raGo (A)
l The shell posiGon determines the max A. e.g.) rw/ap<1.35, rw =a+ΔSOL+ΔBLK+Δgap = a+0.2+0.6+0.05
A≦0.35Rp/(ΔSOL + ΔBLK + Δgap ) à A≦3.5 at Rp~8.5m. v The required CS size determines the min A, typically A>3.1
at Rp~8.5m and q95~4.1.
Parameter Pulse 2 hrs S.S. Ref.
ITER
Size & Con
figuraG
on Rp (m) 8.5 ß 6.35
ap (m) 2.42 ß 1.85 A 3.5 ß 3.43 κ95 1.65 ß 1.85 q95 4.1 ß 5.3 Ip (MA) 12.3 ß 9.0 BT (T) 5.94 ß 5.18 BTmax (T) 12.1 ß 11.8
Absolute
Performance
Pfus (MW) 1085 1462 356 Pnet (MWe) 185 303 -‐ Q 13 17.5 6 PADD (MW) 83.5 83.7 59 ne (1019m-‐3) 6.5 6.6 6.7
Normalize
d Pe
rformance
HH98y2 1.13 1.31 1.57 βN 2.6 3.4 2.95 fBS 0.46 0.61 0.48 fCD 0.32 0.39 0.52 ne/nGW 1.2 1.2 0.82 fHe 0.07 0.07 0.04
Based on the assessment of technologies, possible design parameter set are analyzed by systems code.
l BTmax>12T based on Nb3Sn or Nb3Al, Sm=800MPa
l BLK thickness of ~0.6m for net TBR>1.05 l Considering the conducGng shell (rW/ap~1.35), ü κ95=1.65 for verGcal stability ü A=3.5 to increase nGW for DIV detachment
l Steady-‐state and pulse operaGon in the same device design including CD power.
ü Rp=8.5m for full inducGve Ip ramp up and 2hrs pulse by expanding CS size
Ø OperaGonal flexibility for commissioning/ early demonstraGon of electric power.
Key concept /consideraGon
l Pfus<1.5GW and Pnet~0.2-‐0.3GWe to demonstrate electric generaGon and to be compaGble with
ü Divertor heat removal capability ü neutron flux on BLK for enhancement of TBR
Design parameters for steady-‐state and 2 hours pulse opera7on in the same device design
l Segmented maintenance scheme
The DEMO concept has been developed through the assessment of relevant technologies from the viewpoints of the fusion power and the reactor size, to minimize the development subjects by extending the present technologies.
l Rp > 8.0 m for full inducGve Ip ramp up by CS coil ü OperaGonal flexibility from pulse to steady-‐state
l Pfus = 1.5 GW and Pgross ~ 0.5 GW is foreseeable from the viewpoints of ü Divertor heat removal capability and triGum self-‐sufficiency in blanket.
By considering above and other assessments, DEMO concept design study shows, ü Pfus~1.5 GW & Rp ~ 8.5 m could demonstrate Pnet ~ 0.3 GWe. ü frad = 70% will be compaGble with Pfus=1.5 GW, Rp > 8.0 m and parGal use of Cu alloy
as cooling pope near high qtarget and low dpa/year region ü Water cooled solid breeder blanket with its thickness of 0.6 m for TBR >1.05 ü Segmented maintenance scheme ü Reuse & recycle of components are a key strategy to reduce radioacGve wastes. ü BTmax > 12T based on Nb3Sn or Nb3Al, Sm=800MPa ü ConducGng shell posiGon and CS size constrains 3.1<A<3.5, and A=3.5 for high nGW ü κ~1.65 for verGcal stability
3. Summary