Coupling a Hydrogen Production Process to a Nuclear Reactor

COUPLING A HYDROGEN PRODUCTION PROCESS TO A NUCLEAR REACTOR

P. Anzieu, P. Aujollet, D. Barbier, A. Bassi, F. Bertrand, A. Le Duigou, J. Leybros, G. Rodriguez CEA, France

NEA 3rd Meeting on Nuclear Production of Hydrogen, OARAI, Japan, 5-7 Oct. 2005

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Basic Options (1/2) •

Co-generation is often proposed, but: – Operation of a co-generation plant seems to be difficult – Relative power of H2 and electricity production is an open parameter – Detailed coupling circuit is complicated

•

A dedicated VHTR is studied to deliver heat to a Sulfur/Iodine chemical process – It reduces the number of difficulties – Outlet temperature of the VHTR is adapted to the needed temperature of the process – Electricity comes from the grid – A detailed scheme for the coupled plant should be obtained – Optimization can be done


2

Basic Options (2/2) • • •

A dedicated 600 MWth VHTR Temperature is above 900°C H2 production is around 1 kmol/s H2 storage

Reactor building

Heat exchange

Thermo-chemical Water splitting process


3

Towards a Hydrogen Production Plant •

A reference flow-sheet – With present thermodynamic data – Using chemical engineering techniques – Assessed by expert judgment

• • •

Very detailed flow-sheet based on a conceptual design for an experiment Thermo-chemical analysis of each component Design of each main component – Heat exchangers – Reactive columns

•

Finally a plant layout is drawn


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A reference flow-sheet • •

Each section is clearly defined in detail Example : Section I (Bunsen) – Excess of water and Iodine (to be optimized in the future) – Elimination of outlet Sulfur dioxide 20bars

C101

3bars

128

133

123

H2O de section II

T101

125

2bars 15bars

124

H2O de section III

O2

1bar

C102

T102 E104

116

D103

115

E103

129

15bars

15bars

117

127

105

121a D101

106

126

122b

E103

121b E104

15bars

F101

E102

E105

111

110

103

F102

131

113 H2SO4 vers section II

3bars

119

SO2

H2O

120

112

107

E101

121d

122a

O2 102

121c

P103

130

114

D102

101 104

108

R101 132

7bars

118

P101 SO2 + O2 + H2O De section II

109 P102

I2 de section III HIx + H2O Vers section III


5

Component design : Bunsen reactor Scaling for a 1 mol/s unit • • • • • •

6200 8100

• • •

900

Entrée SO2 Zone séparation DN 4500

•

1900

Corps réacteur DN 2200 Serpentins 3 nappes Agitateur Rushton 6 pales

2600

Entrée eau

Entrée iode

1300

Sortie H2SO4

1300

1000

REACTEUR DE BUNSEN R101

• • •

Diameter : 300 mm Total Height : 2,100 mm Reactive zone : 1,350 mm Thermal Power : 95 kW Liquid-liquid heat exchange Degraded heat transfer coef. : 540 W.m-2.K-1 Water Coolant : 15 °C – 0.2 MPa (E = 140 °C) Log Pinch Temp. : 98 °C, S = 2.1 m2 Serpentin : 38 spires - DN 25 – D = 0,25m – Pinch 30mm 9 compartments of 150 mm in the reactor Residence time : 180 s. Enlarged reactor bottom diameter : 450 mm DI-Iodine loading : ~ 550 kg

Sortie HIx


6

Component design : H2SO4 / SO3 convertor Scaling 1 mol/s 2 Evaporators (KESTNER type )

SO2 + SO3 + H2O

E207 - Bundle : 9 tubes DN38/34 mm - Height 7,000 mm - Thermal Power 105 kW - Operating temperature : 250 to 370 °C -Operating pressure : 0.4 MPa

E208 - Bundle : 18 tubes DN38/34 mm Height 7,000 mm - Thermal Power : 270 kW - Operating temperature : 370 to 800 °C - Operating pressure : 0.4 MPa

Coupe réacteur H2SO4 87,7%

Hélium

E207

E208

E209


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Hydrogen Production Plant layout • • •

1 kmol/s = 80 000 m3/h 599 MWth + 100 MWe from the grid 10 shops


8

Coupling the HYPP with a VHTR • • • •

Heat is delivered to High Temperature stage Then to Medium Temperature stage The intermediate circuit includes 1 IHX and 1 Process HX Heat Exchanger temperature pinch must be at least 30°C


9

Transferring heat •

Optimization of the heat transfer piping – Heat loss less than 0.001°C/m (1kW/m) – Pressure drop = 400 Pa /m – Steel tube no more than 400°C

•

Allows several 100 m length of circuit Air e=0.1 m

•

Low temperature Thermal screen

D=0.51m

D=0.2 D=1.2 m

• Inside Ceramic isolation • Ash60 E < 0.5 m

• Hot Helium

Outer Ceramic isolation Ash60 E = ±0.5 m

Finally the needed minimum temperature from the VHTR is calculated 870°C in the process 2 X 30°C temperature drop in IHX > 930°C at the outlet of the core

Liner

Steel Tube 9Cr T= 420°C e= 16 mm


10

Safety Rules for Coupling •

Plants Safety Classing VHTR = Regulated Nuclear Plant Regulations Safety Approach

HYPP = Seveso II Regulations …

Safety of the Coupling = Regulated NP Rules

•

4 levels of sates are studied 1. Normal operation • Respect operating constraints, Master dangerous materials ¾ Heat transfer stability, Hydrogen transfer limitation (T, H2)

2. Abnormal operation • Control, to limit deviations, Protection, to come back to a safe state ¾ Rapid decrease of thermal exchanges,Chemical burst, Abnormal Tritium concentrate, IHX leakage,Isolation valve default

3. Accidents • Uncoupled the facilities, Emergency shutdown systems, Heat removal systems ¾ Loss of elec. Supply, coupling failure, limited HYPP leakages

4. Severe accidents • Impact from one plant on the other, Safety arrangements ¾ Hydrogen risk NEA 3rd Meeting on Nuclear Production of Hydrogen, OARAI, Japan, 5-7 Oct. 2005

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VHTR-HYPP Coupling : Operation Verify compatibility of VHTR and HYPP states –

•

During normal operation, start up, shut down

Heat transfer stability 1. Hot towards HYPP 2. Cold back to VHTR

•

Hydrogen transfer limitation 3. Respect Tritium regulations - Limit H2 permeation

•

1 et 2 : Procedure & system for coupling/decoupling when nominal T° is achieved : – – –

•

Isolation valves VHTR heat removal systems : Self Operating System Possibly, auxiliary heating system on HYPP

3 : Tritium/H2 management – Purification of primary and intermediate circuits – Low IHX permeation Achievable 0,05% transferred = respect 10 pCi/g H2 produced


12

VHTR-HYPP Coupling - Incidents Objectives : • Avoid significant impact from one on the other • Maintain each plant under safe state Incidents to be studied – – – – – –

•

Rapid decrease of thermal exchanges Chemical burst (Bunsen) Abnormal Tritium concentrate IHX leakage Intermediate circuit leakage Isolation valve default : shut-off - rejection

Introduce a tank for heat transfer inertia – Stabilizing SG on intermediate circuit, coupled to HYPP through steam pre-heating


13

VHTR-HYPP Coupling - Accidents • •

Analysis of each plant : internal hazard + coupling Probability/consequences approach : scenario evaluation, acceptance

•

Only concern in a first step : HYPP Accident Products release Explosion - Fire cumulative with VHTR Fission Products release

Provisions • Reduce H2 risk on HYPP + Protect VHTR • Prevention – Detection on production column – Cut off incoming flow in various sections • Back stream on HI distillation column - Stop electrolysis

– Continuous evacuation of H2 production – Non explosive production of H2+H2O – Leakage dilution : HYPP at open air

•

Protection – Separating hill – VHTR underground – Distance • Distant H2 production zone, located in the HI section. Far from the high temperature zone.


14

Hydrogen Risk Mitigation Separating hill

Flow regulation

Distant storage

Reactor building underground

Safe Distance

Leak detection on producing tank


15

Coupling a HYPP to a VHTR : Conclusion • • •

Work is underway to determine the layout of a first S/I chemical facility coupled to a VHTR Using a dedicated plant simplifies the study One needs to iterate between – – – –

• •

Basic data Detailed Flow-sheet Component design Safety needs

For the chemical facility For the coupling circuit – That are new complex systems

• •

Key points are progressively identified Economic evaluation will end the study

Comparative work on other processes is scheduled NEA 3rd Meeting on Nuclear Production of Hydrogen, OARAI, Japan, 5-7 Oct. 2005

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