French term (edited): fond

As the given context does not specify the type of steam generator and the exact location of the "bottom" I propose to translate more or less literally in order not to over-translate and to focus on certain executions not subject to the dispute.

b. Typical Horizontal Steam Generator of the VVER-1000 Plant (Sánchez-Espinoza 2009) In a once through design, the primary-side water enters at the steam generator at the top, flow through the generator in unbent tubes end exits at the bottom (fig. 3c). According to the Power Reactor Information System (PRIS) of International Atomic Energy Agency (IAEA 2005) the steam generators of a power plant are described by the following data: type of SG (vertical, horizontal), steam output (saturated or superheated steam), number of steam generators (from two to six), number of drum separator (if present), tub shape (U tube or straight), ,tube material , SG shell material, drum separator shell material, design thermal capacity for single SG, design heat transfer surface.
https://www.researchgate.net/figure/b-Typical-Horizontal-Ste...
Note: As shown in the illustration, the "steam header" (steam collector) is located above the vessel as hot vapour is lighter than air.
https://www.researchgate.net/profile/De-Salve-Mario/publicat...

Most of NSGs are of the recirculating vertical type (Figure 1). They carry the primary system coolant through U tubes with a tubesheet at the bottom of the steam generator and inverted U bends at the top of the tube bundle. The secondary system coolant is fed through a feedwater nozzle into the downcomer, where it mixes with recirculating water draining from the moisture separators. Secondary water partially converts into steam as it passes through the tube bundle upwards while the remaining water (∼75%) is recirculated into the downcomer.
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Once-through superheated steam generators have straight tubes which carry the primary water from top to bottom (Figure 2).
https://www.degruyter.com/document/doi/10.1515/corrrev-2020-...

Cold feedwater at a lower pressure enters into tubes at the bottom of the SG. Steam is produced inside the tube as a result of boiling. On further moving along the length of the tube, steam gets superheated and is finally collected at the top.
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Fig. 12. Internals of IRIS integral. IRIS, International Reactor Innovative and Secure. Note. From “The design and safety features of the IRIS reactor,”
https://www.sciencedirect.com/science/article/pii/S173857331...

Vertical type steam generator manufactured by Westinghouse Electric Corporation (USA): 1 – inlet of coolant of the primary cooling circuit; 2 – bottom part of the vessel ; 3 – feed water inlet; 4 – upper part of the vessel; …
https://nucet.pensoft.net/article/33980/zoom/fig/13/

On the right side of this illustration we see the feedwater inlet; this supplies a ring that runs around the steam generator, spraying the water downward into the downcomer region that is outside of the tube bundle, but surrounds it completely. As the feedwater goes down, it both mixes with the water raining from the steam separators (more on those in a moment) and heats up. At the bottom, it makes the turn and moves up into the tube bundle area where it is heated to the boiling point; it blasts upward toward the top of the tube bundle.
http://atomicpowerreview.blogspot.com/2012/03/steam-generato...

The heating element is a single tube, arranged into a number of helical cylinders. The first helices (in the flow direction) are small-diameter tubes, wrapped in large diameter turns. Succeeding turns are coiled inside this and the tube is of progressively increasing diameter, to allow for a constant flow rate as the water evaporates into steam and forms bubbles. The steam outlet is from the final turn at the bottom of the inner helix.
https://en.wikipedia.org/wiki/Steam_generator_(boiler)

Steam Generator Test Facility (SGTF) is set up in IGCAR to optimize the design of Steam Generators (SG) for Fast Breeder Reactors.
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A three dimensional static thermo-mechanical analysis was done for the bottom tube sheet with with and without thermal baffle assembly
https://www.comsol.fr/paper/thermo-mechanical-analysis-of-st...

Failure analysis of the leakage at boiler bottom wall tube of steam power plant
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In this paper, the mechanism of the leakages that occurred at boiler bottom wall tubes of the steam power plant was investigated. Quality of (feed) water and several factors associated with the leakages such as temperature, pressure, and fluid characteristic are mainly considered the suspect contributing to the damage.
https://aip.scitation.org/doi/abs/10.1063/5.0071495

The branch sodium inlet and outlet chamber is limited by the tube plate and a flat bottom with an inlet and outlet sodium nozzle of 108 x 8 mm.
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A difference in the sodium temperature in tubes across the tube bundle was registered. The sodium temperature in tubes positioned at the top have been higher by 15 to 20°C than that at the bottom [18].
https://inis.iaea.org/collection/NCLCollectionStore/_Public/...