Fig. 6-3 Large Marine Reactor MRX (100 MWt)

MRX Main Specifications

item	description
reactor output (MWt)	100
reactor type	integrated PWR
primary coolant	water
operating pressure (MPa)	12
core output temperature (degrees cent.)	297.5
reactor core
equivalent diameter (m)	1.49
effective height (m)	1.40
number of fuel assemblies	19
fuel loaded (t)	6.3
fuel enrichment (%)	4.3/2.5 (w/wo Gd)
control rod drive mechanism
type	built-in within reactor vessel
number of drives	13
steam generator
type	once-through helical coil type
steam temperature (degrees cent.)	289
steam pressure (Mpa)	4
container
type	submerging reactor vessel
maximum
permissible pressure (MPa)	4.0

Fig. 6-4 DRX-Installed scientific deep-sea survey submarine (for 6,500 m)

Fig. 6-5 In-deep-sea used reactor DRX

In preparation for commercial use of nuclear ships, the research and development of the next-generation improved-type ship reactor is under way. This effort is based on results from the "MUTSU" project. For a nuclear ship to be commercially viable, improved economy and reliability is needed. Hence, a light, compact, reliable, and safe ship reactor is being developed. It must require only a small crew for operation and maintenance. To date, design studies have been made that address a loop-type PWR, similar to that in "MUTSU," and an integrated-type PWR with steam-generators built into the reactor vessel. Through the studies, the design of an integrated PWR has been selected.It is named MRX (Marine Reactor X). Presently, the conceptual design and R&D for the main equipment (like the control rod drive mechanism) and the safety system of MRX are ongoing. This reactor is designed to have a thermal output of 100 MWt. This would be suitable for a near-future fast cargo ship (like a container ship) or an ice-breaker. It can be much smaller in comparison with a conventional reactor having the same power. Furthermore, the design is expected to be applicable for a reactor for future ultra-high speed cargo vessels crossing the Pacific Ocean with speeds as fast as 50 knots. Another conceptual design is also progressing. This is for a deep-sea marine reactor DRX (Deep-Sea Reactor X). This reactor would have a small thermal output of 750 kW (electric output of 150 kW) and would be similar to but simpler than the MRX.

Reference A. Yamaji et al., Core Design and Safety System of Advenced Marine Reactor MRX, ICONE-3. The Third International Conference on Nuclear Engineering, Apr. 23-27, 1995, Kyoto, Japan. T. Ishida et al. DRX (Deep-Sea Reactor X) Design Study, ICENES '93 Seventh International Conference on Emerging Nuclear Energy Systems, Sep. 20-24, 1993, Makuhari, Japan, 339.

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