:This paper describes the results of an experimental investigation of the response of liquid metal heat pipe to pulse heat load at the condenser section. A 0.457 m (18″) long, screen wick, sodium heat pipe with 0.0127 m (0.5″) outer diameter was tested in the sodium loop facility. Both forward and reverse mode were studied; each with different heat loading conditions. Major finding was that the heat pipe did indeed reverse under a pulsed heat load applied at the condenser. The time of reversal was approximately 15 to 25 seconds. The startup of heat pipe from frozen state was also studied using sodium loop facility. It was found that during startup process, at least part of the heat pipe was active. The active region extended gradually down to the end of the condenser until all working fluid in the heat pipe was molten.