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Lectures on Fusion Energy TechnologyKyoto University, Fall 2007

• Requirements and goals for an attractive power plant

• Magnetic fusion power plant systems and components

• Blanket functions, elements and designs

• DCLL blanket features and concerns

2 of 13Top Requirements for Fusion Energy

(provided by ARIES utility advisory committee)http://aries.ucsd.edu/ARIES

• No public evacuation plan is required: total dose < 1 rem at site boundary;

• Generated waste can be returned to environment or recycled in less than afew hundred years (not geological time-scale);

• Closed tritium fuel cycle on site;

• Ability to maintain the power core;

• Ability to operate reliably with <0.1/yr major unscheduled shut-downs;

• Ability to operate at partial load conditions (50% of full power);

• No disturbance of public’s day-to-day activities;

• No exposure of workers to a higher risk than other power plants.

Above requirements must be achieved consistentwith a competitive life-cycle cost of electricity goal.

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No evacuation plan: worst possibleaccident dose at site boundary < 1 rem

http://www.nucleartourist.com/systems/rad.htm

Workers: 5 rem/yrUnrestricted area: 0.5 rem/yr“High” dose rate: 100 mrem/hrDangerous level: 25 rem “over a short period of time”Normal public: 100 mrem/yrJapan (?): 10 µSv/yr = 1 mrem/yr

Passive safetyMaterials choices

Designstrategy

rad = Roentgen Absorbed Dose = 100 erg/g = 0.01 Gy

rem = Roentgen Equivalent Man = rads x Quality Factor (QF)• heavy particles such as alphas have a QF of 20.• neutrons have a QF of 3-10 depending on energy. • betas and gammas have a QF of 1.

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Low level waste:US “Class C” shallow land burial

Piet et al., “Initial Integration of Accident Safety, Waste Management, Recycling, Effluent, and MaintenanceConsiderations for Low-Activation Materials,” Fusion Technology 19, Jan. 1991, pp. 146-161.

10 CFR part 61 – materials are safe after 100 yrs (A), 300 yrs (B) or 500 yrs (C)Compare with “high level waste” that requires federal government management

Materials,Recycling

Designstrategy

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Closed fuel cycle

L. A. El-Guebaly and the ARIES Team,“Breeding potential of Candidate Breedersfor the U.S. Demo Plant,” 16th IEEE/NPSSSymposium on Fusion Engineering (1997).

High TBR breeder TBR flexibility

Designstrategy

Consumption rate:1000 Mwe ~ 2500 MWf17.6 MeV/fusion → 1018/s D(T,n)4He→ 382 g/day tritium consumption

Inventory:~10 days supply, or 3.8 kg

ITER release limit:~0.1 g/yr (10 ppm)

Decay rate (τ1/2=12.3 yr):~0.5 g/day

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Plant capacity factor depends onscheduled and unscheduled outages

A2 = ––––––––––––––MTBFMTBF + MTTR

Planned outages:

Plant capacity factor: C = ––––––––––––––––MW-hr generated

Plant size x hours

Unplanned outages:

(for fission:~90% US, ~80% Japan)

A1 = ––––––––––––––lifetimelifetime + MTTR

A = A1 x A2

(goal ~ 24/25 = 96% for fusion)

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Easy, rapid maintenance is essential(lost revenue ~$1.5M/day)

The ARIES Team strategy is to remove itemsquickly and service externally.Large sectors move on rails.Goal down time ~4 weeks for core replacement.

Simple plumbingSimple attachments

Designstrategy

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Reliability

1/MTBF = Failure rate F ~ ∏ Fi

Failure rate data requires extensive testing

Small number of partsDesign marginsEasy to test*

Designstrategy

*e.g., issues don’t depend on neutrons

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Cost of Electricity(estimates from ARIES studies)

1980s physics

1990s

physics

Pulsar ARIES-I ARIES-RS ARIES-AT

Major radius (m) 9 7 5.5 5.2

2.3% 1.9% 5% 9.2%

N 3 3.2 4.8 5.4

Plasma current (MA)

10 10 (68% bs)

11 (88% bs)

13 (91% bs)

COE (¢/kWh) 13 9.5 7.5 5

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Economic factors

To have an economically competitive life-cycle cost of electricity:1. Low fabrication costs2. Low cost of replacement parts (e.g., blankets)3. High thermal conversion efficiency, Low recirculating power4. Component lifetime and reliability

COE = (1) Annualized Capital Cost + (2) Yearly Operating Cost

(3)(3) Net Power Net Power ×× (4)(4) Plant Availability Plant Availability

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A pathway to improved economics

ARIES-RS

CO

E, m

ill/

kW

e-h

Improvements

50

60

70

80

ARIES-AT

AT physics,

PbLi/SiC

!"59%

LSA=1

HTSC

A=80%