Valves Wide Open: Eyes Wide Shut

An open letter to the people of Wyoming

Natrium is a New Kid on the Nuclear Block and plans its first reactor in Wyoming. Natrium has never designed, constructed, or operated any operating nuclear power plant. Its claim to fame is that it has some financial backing from Bill Gates, the former founder of Microsoft. It also claims to be building its unique SMR design in Wyoming on the site of an abandoned coal plant. The choice of Wyoming appears to be driven by the fact that the Chair of the Senate Energy Committee hails from Wyoming and controls funding. Mr. Gates has secured financing for his design through influential connections.

Previously, I published an extensive analysis of my technical concerns for the Natrium design in CounterPunch entitled An Open Letter to Bill Gates About His Atomic Reactor. It is available here.

In addition to the technical concerns I already identified in CounterPunch, I also developed significant financial concerns about the project after the first CounterPunch article was published. Simply put, electricity from the Natrium design makes no economic sense to the people of Wyoming.

The Natrium reactor is cooled with liquid sodium, and excess heated sodium is stored in a secondary insulated thermal storage system and released when necessary. Natrium claims this thermal storage allows it to ramp up its power for six hours each day if the sun isn’t shining and the wind isn’t blowing. Regardless, this feature is an expensive marketing ploy to differentiate the Natrium reactor from its competition. Here is what is going on at Natrium.

Natrium is not a Small Modular Reactor (SMR) in view of the fact that its claimed electrical output exceeds the 300 MWe threshold, which is the line of demarcation between SMRs and traditional reactors. Natrium’s electrical output for 18 hours a day is 345 MWe, and then it ramps up its power for six hours daily to 500 MWe.

The continuous output from the Natrium reactor is not 345 MWe but it is 385 MWe. During the initial 18-hour run, the Natrium reactor sends its excess thermal power to a “thermal battery” for storage. Then, for the final 6 hours, Natrium creates the same reactor heat and adds thermally stored excess heat from the “battery” to produce 500 MWe for six hours. That means that the actual continuous power from the Natrium reactor core is around 385 MWE, of which 345

MWe is available electricity for the initial 18 hours. [(500×6 + 345×18) /24 = 385 MWe]

So, the Natrium Balance of Plant (BOP), i.e., the turbine and rest of the electrical components, must be built 45% bigger (500/345) to achieve 500 MWe than required if the electric output was continuously 345 MWe.

Power plants are designed to operate in a condition called Valves Wide Open (VWO) at all times. But Natrium runs in the desirable Valves Wide Open mode (VWO) for only six hours. More importantly, when the electric power output is throttled back for the remainder of the day, the control valves wear out much faster. There is a substantial throttling loss (inherent lower thermodynamic efficiency) and extra control problems, with additional wear on valve faces that are only partially open and subject to turbulent flow degradation.

Why would Natrium do this? I believe that Natrium has a “thermal storage” marketing gimmick. It sends hot sodium to a separate tank to be released into the steam cycle when the sun isn’t shining and the wind is not blowing. Thus, it appears that the thermal storage marketing gimmick is an attack on the intermittency of renewables.

Natrium could reduce the Balance Of Plant (BOP) costs and increase thermodynamic efficiency and valve reliability if the reactor ran at 385 MWe full-time AND CHARGED a Battery!! However, if Natrium acknowledges that battery storage is indeed a lower-cost, more straightforward alternative, Natrium loses its marketing gimmick that its unique reactor design is the solution to intermittency. After all, wind turbines can charge batteries, too!

Natrium’s steam cycle (called Balance of Plant, BOP) is about 30% bigger (500/385) than it would be if it simply ran at 385 VWO all the time and sent 40 MWe to a battery for 18 hours! Instead, Natrium uses an oversized BOP, a secondary heat storage system, and complicated BOP controls as a marketing gimmick. How can this be an inexpensive alternative to renewables with battery backup?

When the Chair of the Senate Energy Committee is from Wyoming, there is no need to ask this question! And, when there is so much government money invested and embedded in keeping atomic power active and viable, no matter what the cost ––you know there is a lot of money in ‘them thar hills’.

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