2013-12-04 Design Meeting Notes

Upper core internals

  • With the 3 DHXs in the space between the inner and outer lids, there is significant room for pebble handling containers.
  • Refueling deck could be thinner (1 m rather than 2 m; higher at the bottom, same at the top) and add steel or lead locally where additional shielding is needed.


  • Fill tank: needs to be big enough to hold whole DRACS salt inventory. Locate it inward compared to TCHX (needs to fit in footprint of DRACS hatch).
  • Hot and cold leg should not penetrate the RV wall if we want to mount the DRACS modules on frames. Extend upward (above cap).
  • Hot and cold leg elbows should be bends.
  • Space out the TCHXs 120° rather than 90° (Aligned with DHXs).
  • Frame should be key shaped structure going through cavity cap. Reactor will have to be defueled when pulling out the DRACS (breach in containment).
  • Condenser can be on the outside, at the base of the chimney structure, at grade level.
  • Water tanks for makeup water: look at ESBWR design. Bottom can be aligned with bottom of TCHX. Shape doesn’t matter. Locate inside key shape, inside containment, against wall.s
  • Partition the water tanks with independent valve systems so that if a line breaks, they don’t drain completely.

Reactor cavity

  • May want to change the shape of the reactor cavity wall to key shape (not flat walls everywhere but rather circular walls where not interfering with hot/cold leg of primary system.
  • Having flat outer walls of the cavity would help for manufacturing (cf AP1000). Could be done by having 12 flat sections (spaced by 30°).
  • Outer reactor building wall below grade could be thinner (~ 50 cm). Look at IAEA report for water proofing.

2013-10-25 Design Meeting Notes

Design report

  • Include section on rationale for important decisions that were made in the past (coolant, NACC, etc.).

CAD model

  • CAD model is broken right now (some pipes were not built to be moved).
  • Need rupture disk on low pressure end of air duct.
  • CTAHs could be open-pressurized.

Startup/Shutdown cooling

  • When in shutdown cooling mode, air at outlet of compressor is at ~400°C, by-passes heat exchanger, goes through 2 stages of expansion, therefore ends up at significantly colder temperatures.
  • May want to by-pass some flow from compressor outlet through CTAHs to heat air up and mix with cold air.
  • For startup, need to integrate with neutronics model. 2 startup conditions:
    • From fresh fuel
    • From equilibrium fuel
    • Because the 2 CTAH loops are independent, need to design pump control strategy (2 pumps) to keep salt temperatures coming from 2 CTAHs into cold leg at same temperature (in order to avoid large delta T across reactor vessel). Other adjustable inputs to achieve this are control rod positions.
    • Need to validate some control strategies with CIET (distortion from having only one pump and one heat exchanger).
    • Also need to assess risk of freezing from cold air exchanging heat with salt.

Plant arrangement (see pictures)

  • Switch to cylindrical building, ~ 24 m diameter, ~ 35 m high
  • Need some kind of holes over CTAH vessels
  • Minimum distance between inner wall and center of any element that will need to be pulled out is determined by crane capacity (investigate and select crane) (see picture)
  • Space between refueling deck and roof of building must be tall enough to accommodate reactor vessel
  • Use AP1000 and NGNP (pre-conceptual design) for overall dimensions

2013-10-25 Crane 2013-10-25 Elevation view 2013-10-25 Plant arrangement

Ballpark sizing of water pools for TCHX

  • 1% total power for 72 hours (1% is a good average over 72 hours)
  • (2.4 MWt * 72 hrs * 3600 s/hr) / (2.4 m^3/kg * 1000 kg/m^3) = 260 m^3
  • 4 m high vessels (3 pools), meaning 8 m^2 area total: too big
    • Hence need for recondensation, using 3 air stacks, spaced 120°, in boxes against outer wall of the building


  • Look at ESBWR emergency core cooling condenser
  • Horizontal tubes for water, square lattice
  • Variables:
    • Tube diameters
    • Pitch to diameter for lattice

2013-08-28 Design Meeting Notes

Design Report

  • Need to have a design report done in time to generate a summary for ICAPP (final papers due January 2014).
    • Need to have a draft design report for December.
    • Also need to have a draft white paper for the January workshop by December.
    • Regis Matzie (and Jim Rushton?) to review preliminary design. October 7-8 (preferred). Need to send draft design report in advance (mid-september) and have plant layout figured out.
    • Outcome of the meeting: 1/ take action for Mark-1 design, or 2/ implement changes for Mark-2 design.

Plant Layout

  • Low pressure air duct diameter might have to bump up to 2 m to stay at reasonable circulating power (high pressure air duct is ~ 1.5 m).
  • Most compact configuration could be ~11.5 m from center of RV to center of CTAHs. Resulting thermal expansion could be up to 12 cm.
  • Shutdown conditions:
    • All plant is stopped and put in hot standby
    • One CTAH is drained, the other is used for normal shutdown cooling
    • Elevation of crane above grade must accommodate pulling out the longest object from below grade (probably RV).

2013-08-29 - Plant layout top and side view

CTAH Design

  • CTAH head and bottom: ASME standard dished head (flanged and dished)
  • CAD model should start with external vessel of the CTAH

2013-08-29 - CTAH