Qark One 001

Thorium power,
refuelled while running

Qark One is a thorium-fuelled reactor of about 300 MWe, designed from published data for India’s AHWR-300 LEU. Its coolant circulates without pumps, its fuel is changed while it runs, and it can cool itself for 72 hours with no power or operators.

Principal data View the drawing
Concept render of a Qark One plant in cutaway: turbine hall on the left, reactor building in the centre, control building on the right
Concept render

  • Turbine hall

    Steam from the reactor drives a turbine-generator.

  • Reactor building

    The reactor, with a large pool of water held above it.

  • Control building

    The control room, electrical and instrumentation systems.

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How Qark One works

Qark One is a pressure-tube reactor. Its fuel sits in 452 vertical tubes that pass through a tank of heavy water, the calandria. The heavy water slows neutrons so the thorium fuel can sustain its chain reaction, and it stays at low pressure and temperature.

Ordinary water flows up through each tube and boils as it passes the fuel. The mix of steam and water rises about 39 metres to four steam drums, where the steam is separated and sent to the turbine, while the water falls back to the bottom of the core. Gravity and the difference in density keep this loop moving, so the main circuit has no pumps.

Fuel is changed from above while the reactor keeps running, so Qark One does not need to shut down to refuel.

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Three ideas at the core

  • Thorium fuel

    (Th–HALEU)O₂ clusters in 452 vertical channels, with heavy water as the moderator.

  • Natural circulation

    Boiling water rises through the core to the steam drums and falls back through downcomers. No primary pumps.

  • On-power refuelling

    A fuelling machine on the reactor deck changes fuel from the top while the reactor keeps running.

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Safe by design

Qark One is designed so that gravity and natural circulation, not pumps and operators, keep it safe when something goes wrong.

Concept render of an underground reactor building with deep pools of water
Concept render

  1. Two ways to shut down

    SDS-1 drops shut-off rods into the core. SDS-2 injects a liquid neutron poison into the moderator. Either one can shut the reactor down on its own.

  2. Cooling without power

    Isolation condensers sit in a gravity-driven water pool of about 8,000 m³ high in the reactor building. They carry decay heat away with no pumps and no electricity.

  3. 72 hours of grace

    If everything else fails, the plant needs no operator action and no outside power for 72 hours.

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The drawing

General arrangement QE-GA-001, rev A. Concept status, not for construction.

General arrangement drawing QE-GA-001 for Qark One: reactor block section, core lattice plan, coolant channel detail, parts list and principal data Open full size
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Principal data

Reference values from drawing QE-GA-001, indicative of published AHWR-300 LEU data. Dimensions are approximate and will change as the design develops.

Reference design

AHWR-300 LEU (BARC, published data)

Thermal / electric

920 MWth / ≈300 MWe

Coolant

Boiling light water, natural circulation

Moderator

Heavy water (D₂O), low pressure and temperature

Fuel

(Th–HALEU)O₂, 54-pin clusters

Fuel channels

452 vertical, 225 mm square pitch

Main heat transport

7 MPa, 285 °C coolant outlet

Refuelling

On power, top entry

Shutdown

SDS-1 shut-off rods, SDS-2 liquid poison

Passive cooling

72 h grace period, ≈8,000 m³ gravity-driven water pool

Lattice

513 positions: 452 fuel channels, 61 reactivity and shutdown devices

Active core length

3.5 m

Pressure tubes

120 mm inside diameter

Steam drums

Four

Natural-circulation loop height

≈39 m

Decay-heat removal

Isolation condensers in the gravity-driven water pool

Status

Concept design; not for construction

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