Experimental Demonstration of Flow Diodes Applicable to a Passive Decay Heat Removal System for Sodium-Cooled Reactors

Abstract

In remote areas, a small power source with a capacity less than 50 MW electricity without refueling is attractive since fuel transfer cost is high. In a previous 50 MW sodium-cooled reactor study, a concept with a long-life core and a simple plant system without refueling was proposed. The 50 MW plant decay heat removal system adopts direct reactor auxiliary cooling systems (DRACSs). To enhance passive safety features, the 50 MW plant DRACSs adopt flow diodes instead of valves which need active signals to become activated. In this study, two full-scale flow diode models, Types A and B, were manufactured and water tests were conducted. The Type A flow diode is a conventional vortex flow diode and Type B is a modified vortex flow diode which provides easy maintenance. Under the test condition, the former showed good performance while the latter lacked sufficient performance. Then, flow diodes for the 50 MW plant DRACSs were designed according to the experimental results. An optimized Type A flow diode and a modified Type B flow diode were evaluated and found to meet requirements of natural convection decay heat removal operation while maintaining a sufficient lowbypass flow during normal power operation.

On the Use of Selected 4th Generation Nuclear Reactors in Marine Power Plants

“…Th e small reactor with a sodium-based Direct Reactor Auxiliary Cooling System (DRACS) (Fig. 2) [16] has apower of 50 MWe, and the device can be used on land. Th e advantages of this reactor are the lack of the requirement for continuous fuel supply and the service life of its core without refuelling, assumed to be 30 years.…”

“…2. Th e DRACS system based on [16] Th e NEREUS project acronym stands for: "A Naturally safe, Effi cient, pebble-bed Reactor graphite moderated easy to operate, Ultimately Simple and small" [17]. Th e project includes ideas on the possibilities of nuclear energy and aims to implement modular HTR installations cooled by helium with a moderator in the form of graphite.…”