The sodium is now in liquid form and hence can easily be charged.
The canister valve and the heat pipe valve are opened and the valve
connected to vacuum line is closed. The sodium is pressurized slightly
by argon from the top of the canister for easy flow of the liquid sodium
in to the heat pipe. Heaters are switched off after charging and the heat
pipe is allowed to cool down gradually. The heat pipe valve and the
canister valve are closed and heat pipe is removed from the canister.
Heat pipe is weighed to know the exact amount of sodium charged.
Then the entire heat pipe is heated up to 600ºC using ceramic
heater. The heat pipe is kept vertical and this process is continued for
48 hours. Then the heater is switched off and the heat pipe is allowed to
cool down gradually. Again the heat pipe is evacuated to 10-6 mbar to
remove any non-condensable gases like argon which was present during
charging.