Early Realization of Fusion Electricity Target and Path by Kunihiko OKANO Central Research Institute of Electric Power Industry (CRIEPI) Based on the contributions by K. Tokimatsu (RITE) S. Konishi (JAERI), Y. Asaoka, R. Hiwatari and K. Tomabechi (CRIEPI) Presented at FESAC Development Path Panel Laurence Livermore National Laboratory, USA on 28 October 2002

Our target to keep the concentration of CO 2 less than 550ppm after 2100 What we have to do? 1) Immediately Reduce the gradient of CO 2 production by using all the available technologies 2)After the middle of this century Reduce further by Introducing new technologies There are a lot of competitors. If fusion is not ready in time as one of these new technologies, the motives (and budget) for fusion study might be diminished. By what time the fusion should be ready?(1) From an environmental point of view

IIC case ( Initial Intro. Constraint) Initially, TBR is a major constraint. To achieve a similar pace to the history of fission plants, TBR=1.08 is required (with 75% plant availability). After 100 plants constructed, the manufacturing capacity may become the major constraint; we assume 100GW/y as an upper limit. How high pace is possible? Fusion plants (estimated) History of Fission plants Time (years) Capacity (GW) Asaoka et.al, Fusion Technol. 39(2001)518 Tokimatsu et al., Fus. Science & Technol. 41(2002)831 Pace of fusion energy deployment is restricted by TBR and plant manufacturing capacity By what time the fusion should be ready?(2) Technological maximum of deployment pace This curve gives a possible maximum pace. The actual pace and the share should be determined by competition with the other energy sources and such an analysis requires a sophisticated model for the global energy assessment.

K. Tokimatsu used a world energy and environment analysis model code LDNE21 to assess a possible contribution of fusion energy in the world energy supply. By what time the fusion should be ready?(3) Break even cost for fusion plants In the BAU (Business as Usual) case, break even cost for fusion is less than 50 mil/kWh in 2050, which may be difficult to achieve by fusion plants: No contribution by fusion will be expected. In the 550ppm case, the break even cost in 2050 is mil/kWh, which may be attainable. ARIES-RS (  N =5.0): COE=64-86mil/kWh COEn=COE/COEcoal = (in USA) R. Miller, Fus. Eng. Des (2000)33 CREST (  N =5.5): COE=12yen/kWh COEn=1.2 (in Japan) K. Okano et al. Nucl. Fus., 40(2000)635. Our possible target for 1st commercial plant: COEn<1.5

In the LDNE21 model, the break even COE at the introduction year is assumed and the COE will be reduced by a rate of 2.3%/y for the initial 25 years. The maximum pace is limited by the above IIC case. The calculation gives the shares of various energies so that the global energy cost is minimized. By what time the fusion should be ready?(4) Possible contribution of fusion energy Early introduction of fusion is critical in order to provide a significant contribution of the fusion energy. "Introduction in 2070" seems too late in order to meet people's expectation as a New Technology. A fusion plant of COEn<1.5 by the middle of this century. How?

How to achieve COEn<1.5 (in the case of Japan) Examples for COEn=1.5: Bmax=20T(on coil),  N =3.4 thermal efficiency  th =40% Bmax=16T(on coil),  N =3.9 thermal efficiency  th =40% The early DEMO on the fast- track must be designed sufficiently conservatively, but also the operative range must cover the above parameter ranges. A simple scaling proposed by CRIEPI based on COE analysis in Japan, where a plant availability =0.75 has been assumed. For 3GWth output:

Request for commercial use Reference dataTarget of 1st generation of commercial plants (decided by Committee*) Economicsless than the present COE (10 yen/kWh) by 30% or more COE of early LWR plants yen/kWh CO2 cont. coal: less than 15 yen/Kwh design value less than 10 yen/kWh is desirable. If impossible, 15 yen/kWh is upper limit. Operation features output stability unscheduled interruption Load following capacity +/-0% ~0% ~17%/h, 100%-50% range perturbation in daily load curve: ~1% LWR:1.5%, 0.2 event/y 0.5 event/y ( ) LWR:baseload only in JP. < 1% 0.5 event/y (incl. disruption) Partial load in emergency Output rangedesign from 1GWe max GWe (but the demand will be limited) ABWR: 1.35GWe 1.7GWe in French LWR FBR target 1-1.5GWe Less than 2 GWe, as small as possible Availabilityhigher than 80%history of LWR : 1975:40 %, 1985:75%, 1995:80% 85% or higher in design value (w/o trouble repair) initial availability >70% Possible introduction pace similar to LWR15GWe/y in average throughout the history TBR>1.1 is desirable for 1st generation. Requirements from a view point of utility and targets *Subcommittee of the Fusion Council for Fusion Development Strategy held by the Atomic Energy Commission.

Fusion Energy Development Strategy of Japan Issues FacilityTarget Long time burn at Q>10 with technology integration (except for blanket) ITER Burn control for Q>10,  N <3, steady state Advanced plasma high  p for steady state high  N for low cost (compact) high Q burning control ITER + supporting machine like JT60SC Fully steady state burn with  N >3.5 with suitable HH & f GW Advanced materials long life high temp. ITER IFMIF Reactor scale>3dpa Small specimen>100dpa Blanket development TBR >1 high efficiency easy maintenance ITER test module 1MW demo Burn up ~20% High efficiency Advanced Technology for non-replaceable compo. ex. Super conductor developed in parallel High magnetic field High current density based on the presentation by Prof. Inoue at Int. Sym. for ITER, Jan 24, 2002 GWe level based on Ferritic steel and water cooling but complete replacement by advanced blankets will be possible developed in parallel 13T 16T 20T SC water Gas Liq.metal Selection 2035~40 DEMO

Design policy for DEMO plant by CRIEPI 1) Net TBR>1 must be achieved (with P w ~1MW/m 2 at initial phase, ~3MW/m 2 at final phase) 2) At least, stable net electric power generation must be demonstrated: Pnet = (gross power) - (circulating power) Pnet >0 must be guaranteed with minimum extrapolation from ITER ignition plasma parameters (for example  N <2.0, HH<1, f GW <0.9). This is because that we have to start the DEMO design within 5 to 8 years after ITER first plasma (2014?), in order to complete the construction of DEMO plant and to demonstrate Pnet>0 before It is mandatory to demonstrate net electric power > 0MW in the initial phase of DEMO operation. The design must be sufficiently conservative, like ITER. Major parameters and basic components must be tested by ITER. We assume a minimum extrapolation from the high Q operation of ITER (not advanced operational mode).

3) The plant must have a capacity to test advanced plasma up to  N >3.5 (and P f up to 3GW th), which may be attained during the ITER operation after the initial phase of BPP. It will allow to achieve MWe in the net electric power and a next path toward COEn<1.5. Note:  N >3.5 will require "MHD stabilizing shell" in the breeding blanket (like CREST), which will reduce the TBR by several percents. 4) Practicability of maintenance scenario must be demonstrated by DEMO. In the final stage of operation, a high plant availability must be demonstrated by achieving a continuous operation for about one year and the necessary maintenance period less than about 60 days. (The life- averaged availability of DEMO is inessential.) 5) The initial (conservative design) blanket may be replaced by an advanced one, for example,  th >40% by ODS steel and super-critical water, which allows Pnet~1GWe. This is the final target of the DEMO plant. Note: Fully replaceable blanket widens the development path of fusion reactor. The maximum use of this feature is a key for early realization of fusion energy.

Parameter Scan for DEMO by System Code FUSAC (fusion power plant system analysis code) With an extensive analysis by FUSAC, covering the plasma parameter ranges listed in the table, the database for about hundred thousand (100,000) operational points has been constructed. Major radius R m Aspect ratio A Elongation  Triangularity  Operational temp keV Safety factor q  Max toroidal field on coil16T *(13T for ITER) NBI sys. efficiency  NBI 50% *(35% for ITER) NBI power limitless than 200 MW# Thermal efficiency  th 30% Thickness of blanket + shields1.4 m Volt sec of central solenoidenough for Ip ramp-up * Based on the communication with the ITER team, we convinced for the feasibility of the quoted values. # The 200MW limit comes also from a possible number of ports available in the Tokamak machine.

With  N =3.5, HH=1.2, f GW <1.0 (possible by ITER ） P net =600MWe is achievable. With  N =1.8, HH=1.0, f GW = 0.85 (ITER ref. design ）, Pnet=0 is achievable. Pnet=900MWe with  th =40%, P w =1 MW/m 2 P w =3MW/m 2 R. Hiwatari et al, J. Plas. Fus. Res., Vol.78, No.10 (2002)  th =30% Boundary lines of  N, HH and f GW show the design points where the maximum P f has been obtained with the corresponding  N, HH and f GW, respectively.

R=6.5m with  N =2.5, Pnet=0 with  N =4.0, P net =600MWe This is desirable, but may be too optimistic. We may fail for Pnet=0. with  N =1.5, Pnet=0 with  N =3.0, P net =600MWe This is too pessimistic and too expensive. No next path toward COEn<1.5 will be expected with  N <3. R=8.5m  th =30%

Summary 1. An earlier introduction of fusion results in a larger impact in the world energy supply. Introduction in 2070 seems too late, to satisfy people's (tax payer's) expectation. Possible maximum share of fusion energy in 2100 is ~20% for 2050y introduction and nearly zero for 2070y introduction. 2. Break even cost for fusion in 2050 is estimated as mil/kWh for the 550ppm restriction case. Based on the previous reactor design studies, COE less than 50 mil/kWh seems difficult to achieve, but mil/kWh might be possible.

3. If we seriously consider to construct and operate a DEMO plant by , the design must be sufficiently conservative and practical, because the failure of initial operation for Pnet>0 is intolerable. Such a plan should be a practical one rather than an overly optimistic. 4. Based on the conservative design policy described above, a design with R~7.5m can be a candidate for Demo, because a) With ITER reference parameters (  n =1.8, HH=1.0, f GW =0.85), Pnet = 0 with P w ~1.0MW/m 2 b) With parameters of advanced plasma (possible by ITER) (  n =3.5, HH=1.2, f GW =1.0), Pnet= MW with P w =3~4MW/m 2 is attainable. Then the path toward the break even cost may be in sight. A design of DEMO with R=7.25m is in progress in the CRIEPI, although another optimization may be found with different design policies.