Introduction to Desalination Challenge

• Earth covered in water, over half planet is ocean
• Cannot drink seawater due to salt content
• Desalination removes salts from sea/brackish water to produce fresh water
• Current processes energy intensive, often powered by oil
• Nuclear energy proposed as fossil fuel alternative

Three Main Desalination Technologies

Multi-Stage Flash (MSF)

• Invented early 1950s
• Brine heater heats seawater to vapor
• Vapor fed through 10-30 chambers with rapidly reduced pressures
• Causes rapid evaporation/flashing
• Reliable, easy to operate, scales well
• Most widely used industrial desalination technology
• Common in Middle East coastal deserts
• World's biggest: Ras Al-Khair plant, Saudi Arabia
  • Generates 1 million cubic meters/day
  • Equivalent to 415 Olympic pools/day

Multi-Effect Distillation (MED)

• Multiple stages called "effects"
• Spray salt water onto steam-filled hot tubes
• Heat causes evaporation, steam feeds next stage
• Heat reuse cycle makes MED very efficient

Reverse Osmosis (RO)

• Membrane-based methodology
• Uses electricity to push salt water through semi-permeable membrane
• Made of cellulose or nylon
• High pressures applied, salts caught in membrane
• Other membrane tech: electrodialysis (brackish water only)

Energy Efficiency Comparison

• Thermal processes: 10-15 kWh per cubic meter
• RO: ~5 kWh per cubic meter (excluding pre-processing)
• Thermal processes more scalable, reliable operations
• No pre-treatment required for thermal vs RO
• Middle East prioritizes scalability over efficiency due to abundant energy

Historical Nuclear Desalination Projects

Kazakhstan (1973)

• First legitimate nuclear desalination plant
• BN-350 sodium-cooled reactor, Caspian Sea east coast
• Provided electricity and nuclear heat
• Located 12km from host city
• Complemented coal-fired power plant
• Heat powered first stage of MED system
• 85% availability, 40,000 cubic meters/day
• No sodium leakages or abnormal operations
• Shut down twice yearly for maintenance
• Closed/decommissioned late 1990s

Japan (1978)

• Ohi nuclear power station
• Multi-stage flash system
• 1,300 cubic meters potable water/day
• Added 9 additional plants since then
• Many still operational despite safety disputes
• No issues or anomalies reported

Other Countries

• Pakistan, India, China have nuclear desalination plants

Cost Analysis

Cost Variability

• Highly dependent on plant design, type, location
• Costs vary wildly plant to plant

Reverse Osmosis Costs

• Brackish water, low capacity (<1,000 cubic meters/day): $3-5 per cubic meter
• Modern industrial RO (Florida): up to 100,000 cubic meters/day
• Cost: little over $0.50 per cubic meter
• Pathway to 200,000 daily cubic meters at same cost

Thermal Desalination

• Gulf countries use thermal due to energy abundance
• Capacities regularly exceed 100,000 cubic meters/day
• Saudi plant: 1 million cubic meters/day

Cost Structure

• Biggest cost: capital investment (millions spent)
• Biggest operating cost: energy
• Doubling oil cost raises water cost 70%
• Oil volatility creates pricing issues
• Nuclear operating costs very stable
• Uranium fuel costs have little impact on water costs

Nuclear Integration Systems

Cogeneration Approach

• Most systems cogenerate power and water
• Integration depends on methodology

Reverse Osmosis Integration

• Use generated electricity to power desalination
• Relatively straightforward
• Most energy efficient process
• Power to spare available

Thermal Process Integration

• More involved integration
• Reactor generates steam → turbine → electricity
• Steam routed from turbine to heat exchanger
• Heat exchanger heats salt water
• Most existing reactors: large PWR >1,000 MW capacity
• Smaller reactors possible, several countries investigating

Plant Lifespans and Maintenance

• Nuclear plant: ~40 years
• Desalination plant: 25-30 years
• Thermal processing tubes: re-tubed every 10-20 years
• RO filters/systems: regular replacement intervals
• Integration design must consider maintenance costs

Safety Considerations

Public Perception Issues

• Chernobyl and Fukushima impact public perceptions
• Nuclear plants expensive, shutdowns due to safety concerns problematic

Radioactive Contamination Risk

• Biggest risk: radioactive contamination of water
• Especially for thermal desalination technologies

Tritium Concerns

• Radioactive hydrogen isotope
• Produced naturally in all reactors
• Highly permeable, diffuses through barriers
• Cannot be filtered out
• Reacts with water forming tritiated water
• Primary health concern: cancer
• Drinking 25,000x more hazardous than breathing

Regulatory Limits

• Vary widely: 100 becquerel/liter (EU) to 30,000 (Finland)
• Limits controversial, subject to politics

Safety Engineering Solutions

• Barriers between primary reactor coolant and seawater brine
• At least two loops and barriers (steam generator, heat exchanger)
• Pressure differentials monitored in circuits
• Unusual discrepancies flag potential leakage

Safety Performance Record

• Nuclear desalination consistently generates water below regulatory limits
• BN-350 Kazakhstan: maximum 6 becquerel/liter
• Japanese systems: 0.5 becquerel/liter in secondary loops
• Both below natural tritium in Seattle rainwater (11.1 becquerel/liter)

Environmental Impacts

Marine Life Concerns

• Ocean water intake threatens marine/sea life
• Fish larvae, eggs, plankton swept up
• 10-30% fish embryos affected
• Has caused desalination plant shutdowns
• Mitigation: slower intake rates, nets, barriers
• Not specific to nuclear desalination

Atmospheric Impact

• Nuclear desalination environmentally benign
• Secondary benefits: no fossil fuel burning for drinking water

Current Global Projects

Countries Trialing Technology

• Argentina, Egypt exploring feasibility
• Russia: adding desalination to floating nuclear power plants (repurposed boats)
• South Korea: integrated desalination with SMART reactor
  • Smaller, safer experimental reactor
  • Produces 40,000 cubic meters/day
  • Not currently rolling out

China's Nuclear Desalination Program

• Significant water scarcity concerns
• Building massive billion-dollar water transfer project
• As of 2020: ~115 desalination facilities (mostly industrial)
• Currently all powered by coal
• First commercial nuclear desalination: Hongyanhe nuclear power plant
  • Generates 10,000 cubic meters/day
• Proposed projects: Ningde, Haiyang

Economic and Strategic Benefits

• Many countries have nuclear plants near salt water (for cooling)
• Makes cogeneration attractive economically
• Solar/wind desalination projects moving forward
• Nuclear offers reliably high potable water amounts at low operating cost
• Enables water-led growth for societies/economies
• Allows water-intensive agriculture
• Reduces tension/conflicts over limited surface waters
• Prevents fossil fuel burning
• Cost-benefit calculations hard to ignore