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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