Flibe Inventory

Flibe inventory will be calculated based on volumes of the FHR sub-systems and components containing the primary salt. A list of these sub-systems and components is provided here. Some volumes can be directly computed from the current FHR CAD model. When geometry/volumes are unknown, the sub-system or component has been italicized and sources for future calculations are provided where possible.


  • Active core region
  • Defueling chute

Reactor internals

  • Coolant injection channels
  • Control rod channels
  • Inner reflector bypass paths (estimate from graphite blocks geometry, thermal expansion and resulting gap size)
  • Pebble injection lines
  • Free space below pebble bed (will depend on pebble injection method as well as divider plate geometry)
  • Outer reflector¬†bypass paths (estimate from graphite blocks geometry, thermal expansion and resulting gap size)

Cold leg

  • 2 x CTAH to drain tank (need to locate drain tank)
  • 2 x stand pipe (need to estimate level swell based on flow velocity and properly size the stand pipes)
  • 2 x drain tank to reactor cavity wall (need to locate drain tank)
  • 2 x reactor cavity wall to reactor vessel wall
  • 2 x reactor vessel to downcomer coolant distribution system
  • downcomer

Hot leg

  • Hot salt collector ring
  • Hot salt extraction (collector ring to reactor vessel wall)
  • Hot salt extraction (reactor vessel wall to reactor cavity wall)
  • Hot salt extraction (reactor cavity wall to hot salt well) (need to locate hot salt well)
  • Hot salt well (need to estimate volume; based on level swell, what else?)
  • 2 x hot salt well to CTAH (need to know relative locations of hot salt well and CTAHs)

CTAH (need to estimate CTAH tube bundle total volume)

DHX (primary side)

  • Hot leg to DHX (need to figure out pathway)
  • DHX (shell side) (need to adapt numbers from MSBR heat exchangers; look at Cristhian’s RELAP model; implement heat transfer coefficient multiplicator based on twisted tube HX performance)
  • Check valve
  • Valve to downcomer (need to figure out pathway; this will be a bypass path under normal operation)

DRACS loop

  • DHX (tube side)¬†(need to adapt numbers from MSBR heat exchangers; look at Cristhian’s RELAP model; implement heat transfer coefficient multiplicator based on twisted tube HX performance)
  • NDHX (tube side) (need to adapt numbers from European Breeder Reactor and other metal-cooled reactors designs; look at Cristhian’s RELAP model)
  • DRACS piping (total inventory will be based on required elevation difference between the DHX and NDHX centerline and pipe size to drive natural circulation; performance will be based on a 2/3 rule and 2% nominal power extraction [or should this be 6%?], hence 1% nominal power [or 3%?] per DHX; need to determine design average and delta T between hot and cold leg of the DRACS loop, based on DHX LMTD)

Fuel handling system

  • Defueling mechanism
  • Storage space (use wet canisters? room filled with flibe? should we use some multiplication factor of the core salt inventory? Mike is working on this)

Revisiting Option 2 for Coolant Flow Routing

I hand-sketched some thoughts on routing the hot salt through the central reflector. The motivations were:

  1. to keep the outer lid uniformly at 600 C, and the inner lid at 700 C.
  2. in option 1, the hot salt torus has a large volume and the hot leg are very close to the downcomer, likely leading to leakage and heat losses, hence inefficiencies
  3. it simplifies design of cold and hot plena.
  4. to keep the geometry of the outer reflector simpler
  5. this also makes hot salt routing to DHX simpler



Outer Reflector and Upper core structures

Coolant flow path design

  • move dhx down, and integrate into lid
  • what is the stand-off, for neutron irradiation? – ask Tommy/Madicken
  • bring outlet plenum down, and run hot duct up through the outer reflector
  • downwards flow through the defueling chute?
  • dead space in the top metalk structure is to be filled with graphite
  • beyond design basis – if the lid looses structure, we want to be able to carry loads through the graphite
  • outlet can be channels, rather than slots, because outer reflector is shielded by graphite pebbles
  • talk to Madicken/Tommy to estimate doses on outer reflector surface, and consider issue of cracking due to differential shrinking

Rationale for the elevation of the skirt

  • at faulted salt level
  • additional salt faulting: 50-60 cm, in the event of vessel faulting, and leaking into the reactor cavity (need to know residual porosity of cavity insulation)
  • need room for the vessel to expand downwards when heating up
  • if the metal structure fails, everywhere, there needs to be structure from the ceramics
  • cavity wall, frozen interface – water boiling, or let the concrete heat up
  • use concrete with modest off-gassing
  • cavity wall: metal composite, tie rods etc, so good conduction path

100 DT:

  • pressure drop vs. materials
  • below 600: changes average temperature on power conversion system
  • above 700: limited by metallics
  • less than 100 DT, high pressure drop, but also higher temp to power conversion system

To Discuss Further:

  1. Stacking problem, elevation for (a) DHX, (b) start point for metallic upper structures
  2. Design of outlet plenum torrous, to ensure uniform azymuthal flow distribution.
  3. Outlet and inlet lines: channels vs. slots
  4. Consider again Option 2 for coolant routing, with hot leg extending down into the central reflector

(notes taken by Raluca, design meeting on 25 Jun 2013)


(design meeting notes)

First Stage

first nozzle stage: should be an impulse stage. flow goes to sonic velocity, choke flow regime, pressure drop is significant. The blades are impulse blades, and pressure drop will be very low. The air will cool, across the nozzle.

gives you a way to control mass flow

the air that strikes the blades will be much cooler because of expansion to high velocity (20% temp drop)

How many rows of blades do we need, to get expansion ratio of about 4?

Second Stage

may be difficult to also get it in choked flow. so we have to choose between first or second stage being in chocked flow.

inlet manifold and nozzle must have about double the flow area, compared to those of the first stage

challenge: peak temperature is on the second stage, rather than the first stage. does this mean that impulse blades should be used here, rather than reactive blades?

Constant air mass flow

power varies by varying turbine inlet temperature. so when running at part load, these types of turbines will be inefficient.

Turbine casing width must stay below 3.5 m, to remain rail-transportable, excluding the external combustor, which connects via a flange

Combutor cooling flow:

420+1300 -> 670


torrous: you want to keep the velocity constant, so that you don’t have to accelerate and decelerate, and you get constant pressure

applies to inlet plenum upstream of each of the two turbine nozzles. also applies to the outlet plenum on the reactor vessel.

Cold Air Line

what is the design assumption on the diameter of the cold air pipe? also, need to transition to higher diameter, because we shift to insulated piping

need to rotate around so it comes off the bottom

Hot Air Line

add the extension

to mention:

  1. adding notes in wordpress
  2. design of torrous
  3. posting edrawing of latest design