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The Safe Production of H d b N l PHydrogen by Nuclear Power
Karl Verfondern
Research Center Jülich, Germany
3rd N l H d W k h "N l H d f G H i "3rd Nuclear Hydrogen Workshop "Nuclear Hydrogen for Green Horizon"May 20, 2009, Jeju, Republic of Korea
Forms of energy utilisation Other
Forms of Energy UtilizationFinal Energy Consumption
(10 224 MTOE in 2004)Coal7%
renewables4%
Combustible
• Final Energy Marketdominated by fossil fuels
• Electricity is 16 % of final
(10,224 MTOE in 2004)
Oil
renewables14%
Electricity is 16 % of finalenergy (25 % for OECD)
• Nuclear only for electricity43%• Penetration of nuclear into
two directions or combined
• Nuclear process heat has aElectricity
16%
• Nuclear process heat has ahuge potential in the energy sector !!!
Gas16%
• Combined Heat & Power saves resources & reducesGHG emissions Nuclear Energy
3Heat Market
gytoday
Driving Forces for Nuclear Hydrogen
• Nuclear energy can be takento produce hydrogen at alarge scale to replaceGHG emitting fossil fuels;
• Thus fossil reserves will besaved for later use insaved for later use inenvironmentally friendlyapplications;
E it f• Energy security fromextended fuel reserves andindependence of foreign oiluncertaintiesuncertainties.
EC High Level Group 2003
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Advanced R t Future
Nuclear Power Plant Generations
CommercialPower
Reactors:
e.g., EPR, SWR-1000 Fusion
FutureReactorConcepts:e g HTR
ReactorsPWR, BWR, CANDU,WWER, RBMK, ...
1000,CANDU 6, ABWR, ...
FusionGeneration IV
Generation III, Generation III+Generation II
e.g., HTR
Gen II
Early Prototype-Reactors
Generation II
Generation IConcepts
FusionEPR / SWR 1000 HTR
1950 201019901970 2030 2050
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Requirements for a Gen-IV Nuclear Reactor
• Safety improvements by innovative technologies• Competitive cost• New approaches for waste minimization & disposal• Reduction of proliferation risk• Improvement of public acceptancep p p• Extension of applications (electricity, heat, hydrogen)• Conservation and extension of expertise & competenceConservation and extension of expertise & competence
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Very High Temperature Reactor (VHTR)
• 400-600 MW(th) for electricity and process heatproduction;
• Helium-cooled, graphite-moderated, g pthermal spectrum;
• Gas outlet temperatureGas outlet temperature of 900-1000 °C;
• IHX for heat transfer toIHX for heat transfer to H2 production plantor gas turbine.
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Short-Term Option: Steam Methane Reforming
appears to be a reasonable first step
Steamreformer
Steamgenerator
• most widely appliedconventional productionmethodreformer g
• savings of ~ 35% of NG,if process heat is fromnuclear
He circulator
Electricheater
nuclear
• tested under nuclearconditions in pilot plantsi b th G dHe circulator
Oarai, Japanin both Germany andJapan
10Jülich, Germany
Combined HTTR/SMR Complex
Reactor System Hydrogen Production System
Control centercenter
Containment vessel
Hot gas duct
Steam reformingIHXReactorvessel
CH4 + H2O → 3H2 + CO
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4 2 2
Potential Ha ards in aPotential Hazards in a Combined Nuclear/Chemical Complex
• Thermal turbulences induced by problems iny psteam reforming system;
• Tritium transportation from core to product gases;Tritium transportation from core to product gases;
• Fire and explosion of flammable mixtures withprocess gasesprocess gases.
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Tritium and Hydrogen Flow Paths in the HTTR
Sources:- fission (51%)- lithium (34%)- helium (15%)
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( )
Problem Tritium
• High mobility of both HT and H2 at high temperatures- radiation problem to consumer
i bl i hiti t t- corrosion problem in graphitic core structures
•Measures of reducing HT and H2 transport- oxide layers (doping with O2)- gas purification system
intermediate circuit (doping with H O)- intermediate circuit (doping with H2O)
•Results from German and Japanese studiesHT l l i d t d d ffi i tl l- HT level in product gas deemed sufficiently low
- permeability of oxide layer reduced by factor 100-1000
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Tritium in German Legislation
• According to German Preventive Radiation Protection• According to German Preventive Radiation ProtectionOrdinance, specific radioactivity limit for any fabricatedproduct is 0.5 Bq/g.p q g
• Exception from the rule:No licensing required for fossil products to be refined byNo licensing required for fossil products to be refined bynuclear process heat with tritium content < 5 Bq/g.
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Safety Design against Fire and Explosion
Reactor System Hydrogen Production System
Take safe Take safe distanceTake safe distance
Take safe distance to storage tank
- Prevent leakage and ignition
- Prevent inflow into nuclear building
- Detect leakage and
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gshut off natural gas line
JAEA A l ti l St d fJAEA Analytical Study of Explosion/Fire Scenarios
Accident scenarios considered
Inaba 2004
• Pipe rupture with NG release175 m distance, 35 kg/s NGignition at 140 mresult: 6.3 kPa at reactor building
• LNG pool fire• LNG pool fire6 m dia pool
• Detonation inside containment
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Detonation inside containment16.2 kg methane leaks within 0.1 s
Flame Velocities of H2-CO-Air Mixtures
PNP Vapor Cloud Explosion Program
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Breitung 2000
Fraunhofer Institute of Chemical Technology (ICT)
Hydrogen Storage Option as Liquid
• Option: stored as LH2 in underground tank;
• IAEA recommended assumptionpof cryogen vaporization rate(too low for LH2)
Ob i 30 66 / i O erpress res• Observation: 30-66 mm/min(can be up to 1000 mm/min)
• Assuming tank of
Overpressures
• Assuming tank of dia. 15 m, height 10 m,vaporization takes2 5 h2-5 hours
20Zabetakis 1960
German BMI Guideline (1974)for the Protection of NPP against External Explosionsfor the Protection of NPP against External Explosions
R = 8 * M 1/3
Protection by means of safety distance
R = 8 M 1/3
100% for unsaturated HC and non-liquefied gases50% f li fi d d50% for gases liquefied under pressure10% for gases liquefied at low temperatures0 3% for combustible liquids0.3% for combustible liquidsTNT equivalent for explosives
21Minimum Distance: R ≥ 100 m
German BMI Guideline (1974)
• Guideline was the result of experts‘ opinion.
• It was confirmed by PNP gas cloud program that gas mixtures typical for PNP cannot generatepressures beyond the design curve.
•Guideline, however, must not be applied to nuclear process heat plants.
If applied to HTTR/SR:ppk = 3.7 R = 205 m for LNG storage tank(not considered: inventory in steam reformer)
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US Regulatory Guide 1.91 (1975)
LNG: 400 m3 169 t 1859 t TNTR = 2.2 km
( h th t tt d t i k b ffi i tl l )24
(or show that attendant risk be sufficiently low)
H
Safe Design of Gen-IV Concepts
H2storage
Reactor building
Thermo-chemical
Example:Heat exchange Water splitting
process
France
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Further Safety Research Needed
• Safety aspects in nuclear hydrogen production systemsbased on I-S process, HT electrolysis
• Sufficient cleanliness of nuclear hydrogen (tritium)y g ( )
• Effect of thermal turbulences on systems others thanHTTR/SR (design of components).( g p )
• Protection of chemical plant against nuclear accidents(confinement vs containment)(confinement vs. containment)
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