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  • Nuclear Energy Southern African Institute of Mining and Metallurgy (SAIMM)

    UJ-NECSA-NIASA Public Debate : Nuclear Energy 31 March 2011

    1

    The energy debate

    Nuclear energy primer

    Radiation primer

    Oklo the natural reactor

    Forensic analysis of Fukushima

    Thorium reactors

    The future

  • Current policy unsustainable

    Dominated by accessibility rather than exhaustion of supply

    Security of supply (fossil reserves localised in unstable regions)

    Climate change mitigation policies

    Long term perspective (several decades)

    Energy infrastructure takes a long time to build and has a long lifetime

    Climate change mitigation has a long response time

    Cost of

    energy

  • What is the Nucleus ?

    SAIMM 18 Aug 2011

    5

  • Nuclear Fission, Fission Fragments, the

    Chain Reaction

    6 SAIMM 18 Aug 2011

  • Energy Comparison Fossil - Nuclear

    7

    During one fission process energy is

    produced of about 200 MeV = 3.2 x 10-11 J

    During coal burning one molecule of CO2

    liberates 4.2 eV = 6.7 x 10-19 J

    i.e. Nuclear about 50 million times higher

    High power density, less fuel,

    flexible siting, small waste volumes

    SAIMM 18 Aug 2011

  • Energy comparison - again

    8

    (10g of 10%

    enriched uranium)

    1.5 to 2.5 tons of ash

    5.76 tons of

    coal

    21 tons of CO2

    SAIMM 18 Aug 2011

  • Fukushima type BWR Reactor

    9 SAIMM 18 Aug 2011

  • Radiation also from Coal Fired Power

    Stations

    11

    Coal has ~ 1 ppm U and

    ~3 ppm Th.

    Uranium released into the

    atmosphere from coal

    fired power stations, 25

    000 tons / year.

    1GW power station 100 times more activity release.

    Oak Ridge Nat Lab Review Vol. 26, No. 3&4, 1993

    SAIMM 18 Aug 2011

  • UJ NECSA NIASA Public Debate

    Nuclear Energy

    UJUJ-NECSA-NIASA Public Debate : Nuclear Energy 31 March 2011

    13

    Nuclear

    fuel

    cycle

    1 power

    station for one

    year is 1 ton

    of waste

  • Nuclear Fuel Cycle . again

    Origins Centre Public Lecture Series with GSSA 14 June 2011

    14

  • 0.5

    0.3

    0.3

    1.3

    0.04

    1.5

    environment

    cosmic

    medical

    body

    radon

    nuclear

    Exposure to background radiation (mSv/a)

    Jet travel (3 mSv/hr)

    Skiing holiday (8mSv/week)

    MPD for public (natural background + 1mSv/a)

    The earth is a piece of radioactive waste left over from the supernova that

    spawned the solar-system)

  • 16 SAIMM 18 Aug 2011

  • The hottest spot on earths surface - Morro de Ferro, Brazil.

    measures 250 mSv/a

    (World surface average 2.4 mSv/a)

    MPD(public) = 1 mSv/a

  • t1/2(235U) ~ 713 million years

    t1/2(238U) ~ 4150 million years

    2 billion years ago,

    intermittent fission for

    500 000 years.

    Large ore body (50-70% U-

    oxide, 3% enrichment)

    An opportunity to study

    radio-nuclide transport.

    A Natural Nuclear Reactor

    (Oklo, Gabon)

  • The Fukushima Nuclear Accident

    20 SAIMM 18 Aug 2011

  • Japans largest ever quake

    11 March 2011 magnitude 9.0

    21 SAIMM 18 Aug 2011

  • NATURE : The Meltdown that wasnt .

    22 SAIMM 18 Aug 2011

  • Fukushima

    23 SAIMM 18 Aug 2011

  • The Fukushima Daiichi Incident Dr. Matthias Braun - 05 September 2011 -

    p.25

    The Fukushima Daiichi Incident

    1. Plant Design

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    Building structure

    Concrete Building

    Steel-framed Service Floor

    Containment

    Pear-shaped Dry-Well

    Torus-shaped Wet-Well

  • The Fukushima Daiichi Incident Dr. Matthias Braun - 05 September 2011 -

    p.26

    The Fukushima Daiichi Incident 1. Plant Design

    Service Floor

  • The Fukushima Daiichi Incident Dr. Matthias Braun - 05 September 2011 -

    p.27

    The Fukushima Daiichi Incident 1. Plant Design

    Reactor Service Floor

    (Steel Construction)

    Concrete Reactor Building

    (secondary Containment)

    Reactor Core

    Reactor Pressure Vessel

    Containment (Dry well)

    Containment (Wet Well) /

    Condensation Chamber

    Spent Fuel Pool

    Fresh Steam line

    Main Feedwater

  • The Fukushima Daiichi Incident Dr. Matthias Braun - 05 September 2011 -

    p.28

    The Fukushima Daiichi Incident 2. Accident progression

    11.3.2011 14:46 - Earthquake

    Magnitude 9

    Power grid in northern Japan fails

    Reactors itself are mainly

    undamaged

    SCRAM

    Power generation due to Fission

    of Uranium stops

    Heat generation due to radioactive

    Decay of Fission Products

    After Scram ~6%

    After 1 Day ~1%

    After 5 Days ~0.5%

  • Decay Heat

    29 SAIMM 18 Aug 2011

  • The Fukushima Daiichi Incident Dr. Matthias Braun - 05 September 2011 -

    p.30

    The Fukushima Daiichi Incident 2. Accident progression

    Containment Isolation

    Closing of all non-safety related

    Penetrations of the containment

    Cuts off Machine hall

    If containment isolation succeeds,

    a large early release of fission

    products is highly unlikely

    Diesel generators start

    Emergency Core cooling systems

    are supplied

    Plant is in a stable save state

  • The Fukushima Daiichi Incident Dr. Matthias Braun - 05 September 2011 -

    p.31

    The Fukushima Daiichi Incident 2. Accident progression

    11.3. 15:41 Tsunami hits the plant

    Plant Design for Tsunami height

    of up to 6.5m

    Actual Tsunami height >7m

    Flooding of

    Diesel Generators and/or

    Essential service water

    building cooling the

    generators

    Station Blackout

    Common cause failure of the

    power supply

    Only Batteries are still available

    Failure of all but one Emergency

    core cooling systems

  • The Fukushima Daiichi Incident Dr. Matthias Braun - 05 September 2011 -

    p.32

    The Fukushima Daiichi Incident 2. Accident progression

    Reactor Core Isolation Pump still available

    Steam from the Reactor drives a

    Turbine

    Steam gets condensed in the

    Wet-Well

    Turbine drives a Pump

    Water from the Wet-Well gets pumped

    in Reactor

    Necessary:

    Battery power

    Temperature in the wet-well

    must be below 100C

    As there is no heat removal from the

    building, the Core isolation pump cant work

    infinitely

  • The Fukushima Daiichi Incident Dr. Matthias Braun - 05 September 2011 -

    p.33

    The Fukushima Daiichi Incident 2. Accident progression

    Reactor Isolation pump stops

    11.3. 16:36 in Unit 1

    (Batteries empty)

    14.3. 13:25 in Unit 2

    (Pump failure)

    13.3. 2:44 in Unit 3

    (Batteries empty)

    Decay Heat produces still steam in Reactor

    pressure Vessel

    Pressure rising

    Opening the steam relieve valves

    Discharge Steam into the Wet-Well

    Descending of the Liquid Level in the

    Reactor pressure vessel

  • The Fukushima Daiichi Incident Dr. Matthias Braun - 05 September 2011 -

    p.34

    The Fukushima Daiichi Incident 2. Accident progression

    Reactor Isolation pump stops

    11.3. 16:36 in Unit 1

    (Batteries empty)

    14.3. 13:25 in Unit 2

    (Pump failure)

    13.3. 2:44 in Unit 3

    (Batteries empty)

    Decay Heat produces still steam in

    Reactor pressure Vessel

    Pressure rising

    Opening the steam relieve valves

    Discharge Steam into the Wet-Well

    Descending of the Liquid Level in the

    Reactor pressure vessel

  • The Fukushima Daiichi Incident Dr. Matthias Braun - 05 September 2011 -

    p.35

    The Fukushima Daiichi Incident 2. Accident progression

    Reactor Isolation pump stops

    11.3. 16:36 in Unit 1

    (Batteries empty)

    14.3. 13:25 in Unit 2

    (Pump failure)

    13.3. 2:44 in Unit 3

    (Batteries empty)

    Decay Heat produces still steam in

    Reactor pressure Vessel

    Pressure rising

    Opening the steam relieve valves

    Discharge Steam into the Wet-Well

    Descending of the Liquid Level in the

    Reactor pressure vessel

  • The Fukushima Daiichi Incident Dr. Matthias Braun - 05 September 2011 -

    p.36

    The Fukushima Daiichi Incident 2. Accident progression

    Reactor Isolation pump stops

    11.3. 16:36 in Unit 1

    (Batteries empty)

    14.3. 13:25 in Unit 2

    (Pump failure)

    13.3. 2:44 in Unit 3

    (Batteries empty)

    Decay Heat produces still steam in

    Reactor pressure Vessel

    Pressure rising

    Opening the steam relieve valves

    Discharge Steam into the Wet-Well

    Descending of the Liquid Level in the

    Reactor pressure vessel

  • The Fukushima Daiichi Incident Dr. Matthias Braun - 05 September 2011 -

    p.37

    The Fukushima Daiichi Incident 2

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