Sodium boiling

It should be mentioned that boiling within a liquid metal-cooled reactor (such as a sodium-cooled reactor) is an accident condition and may give rise to rapid fuel failure. In designing a reactor core, on the other hand, sodium boiling should... 

Granziera, R., and M. S. Kazimi, 1980, A Two-Dimensional Two-Fluid Model for Sodium Boiling in LMFBR Fuel Assemblies, Energy Laboratory Rep. No. MIT-EL-80-011, Massachusetts Institute of Technology, Cambridge, MA. (4)... 

Holland, P. K., and R. H. S. Winterton, 1973, The Radii of Surface Nucleation Sites Which Initiate Sodium Boiling, Nuclear Eng. Design 24 388. (3)... 

Lewis, J. P, and D. E. Graesbeck, 1969, Tests of Sodium Boiling in a Single Tube-in-Shell Heat Exchanger over the Range 1720° to 1980°F, NASA TN D-5323, Lewis Res. Ctr., Cleveland, OH. (3) Liaw, S. P., and V. K. Dhir, 1986, Effect of Surface Wettability on Transition Boiling Heat Transfer from a Vertical Surface, Int. Heat Transfer Conf, San Francisco, CA, voL 4. (2)... 

Lurie, H., 1966, Steady State Sodium Boiling and Hydrodynamics, NAA-SR-11586, North American Aviation, Inc., Atomic Int. Div., Canoga Park, CA. (5)... 

Schlechtendahl, E. G., 1970, Theoretical Investigation on Sodium Boiling in Fast Reactors, Nuclear Sci. Eng. 41 99. (6)... 

Acetic anhydride can be purified by fractional distillation through an efficient column. To remove acid, 97% anhydride is allowed to stand for several days over thin slices of sodium, boiled in vacuum under reflux for several hours, and finally distilled over a mixture of sodium and sodium acetate. It is further purified by fractional distillation. 

Potassium antimonate (reagent for sodium). Boil 22 g of potassium ant imonate with 1 L of water until nearly all ofthe salt has dissolved, cool quickly, and add 35 mL of 10% potassium hydroxide. Filter after standing overnight. 

OEMs m the core, there occurred a sodium boiling since the reactor power decreases rather slowly and power-to-flow ratio increases As shown in the Figure 6, the net reactivity is always negative dunng the course of the transient due mainly to the largest contnbution from GEMs[4]... 

The results obtained are not sufficient for giving recommendations on the stable sodium boiling modes in the core of fast reactor. In order to specify the area of stable boiling depending on various parameters and factors and to generalize and justify data for their application in fast reactors, fine experimental studies are to be performed. 

There was carried out a work on mounting a new sodium loop for a study of sodium boiling at a 19 pins bundle (Fig. 5). Trial circulation of coolant in the circuit was carried out. 

The calculational models should allow calculation of the fuel pin characterisation for the End of Equilibrium Cycle Core Loading Scheme and during the transient as well as the transient thermal and hydraulics processes in the reactor and in the primary circuit taking into account the sodium boiling. The models should include multichannel representations of the core (12-30 channels), with appropriate models of the out- and inlet plenum and the IHX, or prespecified in-/outlet boundary conditions (pressure and temperature). 

The RAPID system has a central 300 mm diameter channel which is normally filled by a small sodium flow. In the event of sodium boiling in the core, the channel fills with sodium vapour providing a neutron streaming path to offset the positive sodium void effect. Positive sodium void reactivity effects present one of the major safety issues in LMRs since they could cause an overheating event to escalate. There has been much attention to ways of reducing the effect, such as the RAPID proposal. 

For the transient overpower event without scram, it is assumed that all nine rods would be withdrawn from fheir normal full power posihon at the maximum withdrawal rate. Initially, there would be a rapid rise in power, which is halted by negative reachvity feedbacks from radial core expansion, fuel assembly bowing, and Doppler feedback associated with rise in sodium and fuel temperatures. The PRISM core and fuel can safely accommodate this transient without melhng of fuel or sodium boiling and void formahon in the cooling channels that is, the consequences are benign. 

Figure XV-7 shows the predicted temperature changes of the fuel and the coolant at the nominal hottest pin, which has the highest temperature of all the pins. The maximum temperatures are lower than the fuel melting point of 1180°C and the sodium boiling point of 960°C, respectively.

Residual heat is removed only through the reactor vessel surface to the atmospheric air. In this, the reactor is cooled down without sodium boiling and the temperature of the main reactor vessel does not exceed 700°C. 

The boiling temperature of sodium is 1156 K and it is not easy to prevent boiling in severe accidents. If the void coefficient is positive, sodium boiling may lead to a core destmction accident. By contrast, the boiling temperature of LBE is 1943 K with which the possibility of boiling is negligible. Furthermore, as mentioned before, the void coefficient for LBE is more negative than for sodium. 

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