SMR are less vulnerable to some types of accidents, including those like the accident at Japan’s Fukushima 1 nuclear power plant that were caused by the complete loss of power.

  • Looks to me, we are compare here 40 years old reactor and some modern reactor which do not exist yet? Of cause, interesting to compare jet and car, but what for?

NuScale Power’s 45-MWe modular unit/reactor have no reactor coolant pumps because they rely on natural circulation for emergency cooling… Analysis by NuScale shows it does not need an external supply of water or any power to maintain cooling. The NuScale units sit inside an area flooded with 4 million gallons of water that can be used for cooling…

  • Interesting point. I was sure, NC for core cooling in all power diapason, not only in emergency cooling. Looks to me, something wrong here with technical level of presentation.
  •  And if Fukishima’s reactors will put in huge-huge pool, it will be more safe reactor? Not true.

The NuScale accident analysis showed that if offsite power were lost for 30 days, the cooling water supply onsite would boil off, but by that time the temperature of the reactor core would be low enough to be cooled by air, he said. The system relies on automatic valves to operate.

  • How about this: NO WATER on site? Like Fukushima… Just same condition?
  • NuScale analysis related some calculations, which depend from (I am pretty sure) not exact initial conditions.

Once shut down, air cooling would work indefinitely, according to a slide in Landrey’s presentation.

  • Not exactly. According presentations NuScale has a lot of problems in safety systems design and conceptual philosophy.

The NuScale reactor does not require backup power because of its passive cooling design.

  • Oh, really? How about operating and control? Data aquisitions? Valves operating?

The NuScale containment vessel, which encloses the reactor, is made of stainless steel 10 times stronger than that of a large pressurized water reactor, NuScale said in a presentation on safety on its website.

  • 10 times, is really funny number. Why not in 1,000 or not in 10,000? Interesting “engineering” calculations.

Even without power, SMRs, like the NuScale design, are also more resistant to earthquakes because the reactor and containment vessels are located below ground. The NuScale design can resist earthquakes that result in ground motion equal to 0.5 times the acceleration of gravity, whereas many larger reactors are proven to safely resist only an earthquake with half that ground motion…

  • Looks like extremely “simple” solution. And different planet for NuScale. Actually if all future NPP will put under ground, no problems in future?

Howver, that “may prove to be a challenge” because of a slowdown related to financing problems encountered recently by the company.

  • Of cause, 350,000,000 USD per NPP not a lot. Interesting, how much price in Westinghouse. I see here, this guy (Landrey) just asking more money?



William Freebairn (

Yanmei Xie (

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