XYLENE POWER LTD.

FNR GANTRY CRANE

By Charles Rhodes, P.Eng., Ph.D.

INTRODUCTION:
The FNR Polar Gantry Crane is located above the sodium pool, just below the hot ceiling, as shown in the FNR Side Elevation.

The FNR Polar Gantry Crane is used for manipulating and lifting heavy objects within the sodium pool space. The tasks of the FNR Gantry Crane include but are not limited to:
a) Assisting with assembly of the sodium pool;
b) Assisting with assembly of the sodium pool deck;
d) Assisting with installation of the open steel lattice;
e) Assisting with installation of the NaK piping;
f) Assisting with installation of the intermediate heat exchange bundles;
g) Assisting with installation of liquid sodium;
h) Assisting with sodium filtering;
i) Initial installation of fuel bundles;
j) Repositioning of fuel bundles;
k) Extraction of used fuel bundles;
l) Installation of replacement fuel bundles;
m) Enabling replacement of intermediate heat exchange bundles.

The polar gantry crane has a circular track located at the transverse cross beam ends for optimum support. The 2 m X 25.8 m cross beam has a central pin for pivot point and vertical axis stabilization. Each track contains 4 wheels with worm gear drives for cross beam rotation about its vertical axis. The cross beam supports a 1 m long X 1 m high dolly. Below the dolly is a 1 m long X 1 m high hook assembly.

The worm gear drives and dolly are removed prior to reactor operation at high temperatures.

The transverse cross beam supports one motorized 8 wheel trolley for transverse load positioning. This 8 wheel trolley has a variable height lifting hook and vertical axis rotation. The resulting gantry crane lifting point has a horizontal travel of:
25.8 m - 2 (1.0 m) = 23.8 m .

The central pin also provides cross beam safety support. This safety support exists in order to ensure against an accident in which a cross beam track fails. It is essential to have sufficient redundant gantry crane cross beam support that a cross beam collapse accident is not credible.

The circular track is supported at 56 places along its length by reinforced angle brackets that are welded to the vertical hot bird cage I beams.

Thus if the trnsverse beam flange is 0.5 m wide it must be more than 2 cm thick.

Preliminary calculations indicate that the transverse beam will weigh about 20 tons. Hence the total gantry weight will likely exceed 100 tons.

Each transverse beam support dolly normally has a load of 10 tons related to the transverse beam dead weight and up to 10 tons for the live load. However, if the end dolly fails while the load is at the end of the cross beam near the failed dolly the load on the adjacent dolly can jump up to 20 tons_____.

Thus each transverse beam support dolly must be rated at 20 tons._______ Suitable transverse I beam material is 2 m high with flanges 17.1 inch wide X 2.68 inch thick._______

The transverse beam supports an eight wheel load trolley, where each wheel is about 0.6 m diameter and is rated to continuously support 2.5 tons. Thus the load trolley length will be about 2.7 m which will reduce the lifting point travel to 25.0 - 2.8 m = 22.2 m.

Suitable transverse beam material seems to be:
WF36487,Section W36, 487 lb / ft, 39.33 inch (1 m) high, 17.105 inch wide flanges, 2.680 inch flange thickness.________

Check that the track flanges can safely withstand the flange torque caused by the loaded dollies.

The gantry lifting mechanism must be able to lift the intermediate heat exchange bundles over the pool deck for extraction from or insertion into the equipment transfer airlocks.

Allowing for a lifting band, the top hook path must be ~ 5.0 m above the pool deck.

When the gantry crane is not in use its electric/electronic components are stored in cool regions near the transverse beam rest ends. This space is kept cool by:
a) Thermal breaks in the gantry crane rail supports;
b) A removable hinged insulation barrier;
c) Top and end access for service, including the trolley motors and related positioning electronics;
d) Note that the remote manipulator which reaches down into the liquid sodium enters and leaves the primary pool space via an Equipment Transfer Airlock.

Another key issue is the height of the I beam like material used to make the gantry. If each I beam is 1.0 m high and the two I beam clearances are 0.1 m, and the load trolley is also 1.1 m thick the top hook path is 3.3 m below the ceiling. If the ceiling is 14.5 m above the pool deck then the top hook path is 11.2 m above the pool deck. That allows for a 1.0 m high lifting band. That band will have a 2 m perimeter which should fit over the ~ 2 foot diameter flange on the NaK pipe of an intermediate heat exchange bundle.

Note that the bottom of the load trolley must be higher than the hotter NaK pipes.

The gantry has a laser positioning system with a horizontal positioning error of less than ___ mm and a vertical positioning error of less than ___mm.

The gantry crane normally lifts individual loads of less than 5 tonnes but occasionally, if a load sticks, might have to apply a lifting force of up to 10 tonnes.

Each gantry track is firmly supported by angle track that is welded to the hot bird cage.

The lifting mechanism together with its laser positioning system must be easily removable and should fit through the equipment transfer airlock. The trolleys must all be rated for continuous long term exposure to 500 degree C. This issue has trolley wheel bearing implications.
 

GANTRY CRANE SERVICE:
The gantry crane electronic positioning system cannot survive at the normal sustained 500 degree C temperature of the argon and sodium vapor above the sodium pool. Prior to use of the gantry crane the space temperature must be lowered to about 120 degrees C. Then the gantry crane electronic positioning system can be temporarily installed.

When planned fuel bundle shuffling work with the gantry crane is complete the gantry crane motors and electronic positioning system are removed before the reactor is restarted. The motors that move the gantry must be accessible via service ports in the walls.
 

GEOMETRY:
Note that the gantry crane transverse cross beam will always cross over the midpoint of the sodium pool.
 

This web page last updated December 10, 2025