Assessment of Screen-Covered Grooved Sodium Heat Pipes for Microreactor Applications

Abstract

New nuclear reactor designs that incorporate heat pipes are being investigated for possible near-term deployment in terrestrial applications. This study explores the use of screen-covered axially grooved sodium heat pipes and their applicability for providing heat removal for microreactors. A sodium working fluid is appropriate for microreactors operating in the 5 to 20 MWt range at approximately 650ºC. HTPIPE, a legacy software code, was validated for the case of screen-covered grooves and used to perform steady-state analyses to determine the performance limits of a proposed heat pipe design. The performance limits of a sodium heat pipe with a screen-covered square grooved wick structure is compared to that of an equivalent heat pipe with an annular wick. In a horizontal orientation at an operating temperature of 650ºC, the performance limits for the heat pipe with an annular wick configuration are 15% higher than for the screen-covered groove wick. At operating temperatures below 777ºC the annular wick outperforms the screen-covered groove wick and at temperatures above 777ºC the screen-covered grooved wick outperforms the annular wick. However, the marginal performance gain at higher temperatures may not justify the use of heat pipes with a screen-covered groove wick structure due to increased manufacturing costs.

Heat Pipe Cooled Microreactors

“…Tillman et al recently demonstrated their x-ray tomography/fluoroscopy system with a sodium heat pipe and reported their procedures for heat pipe fabrication [97]. The manufacturing processes described by Edelstein and Haslett [117] were employed to fabricate, clean, fill, seal, and inspect a heat pipe with the design parameters shown in Table 9.…”

“…35. A schematic design of the heat pipe filling system utilizing a sodium loop with a cold trap [97].…”

“…A diverse group of U.S. institutions are involved in recent experimental work related to heat pipes. These include Idaho National Laboratory (INL) [1, 19-21, 75, 85], LANL, the National Aeronautics and Space Administration (NASA) [8,[86][87][88][89][90][91][92][93], Rensselaer Polytechnic Institute (RPI) [16,47,54,79,80,94], Texas A&M University (TAMU) [33,43,52,53,75], University of Michigan (UM) [64,95,96], and University of Wisconsin-Madison (UW) [97,98]. These institutions have taken a variety of different approaches in their respective experiments.…”

Analyses Supporting Heat Pipe Experiments

“…The annulus-screen wick is commonly used for such applications as it provides a low resistance flow path to the liquid [51]. In addition, efforts exist on the utilization of additive manufacturing technologies for heat pipe and wick fabrication [52,53]. This technology enables the free-form production of heat pipe wick structures and the tailoring of wick properties such as pore size and permeability [54].…”

Review of reactor conceptual design and thermal hydraulic characteristics for heat pipe in nuclear systems

“…This research further confirmed that these HPs could meet the performance requirements for radiator systems. The steady-state performance of sodium HP was investigated by Guillen and Turner (2022). They found the sodium HP with screen-covered grooves was generally superior to that of open grooves in a vertical gravityassisted orientation.…”