Since I was talking about small nuclear reactors in my previous post I thought I might comment on their announcement of the mPower system. The newspaper stories about the announcement made it difficult to heads or tails of what features the mPower reactors had.
The mPower is a light water reactor with a projected output of 125 Megawatts of electricity. This is abbreviated as MWe as opposed to MWt which stands for thermal or the amount of heat the reactor can produce. The MWe number is usually 1/3 to 1/2 the MWt number. This is less than 1/9th what a large reactor like the AP1000 can produce.
Buying a series of small reactors instead of of one large one can have advantages for a utility company. They don't have to make a huge financial commitment upfront and the interest charges that entails and often ending up with more capacity than they require for current demand. Units can be added as needed, while the earlier units are paying down the debt for their construction. This can save years of interest charges.
There is also the advantage that with several mPower units installed, you don't have to take them all offline at the same time for maintenance and refueling, which means much better availability numbers. This can be critical in third world countries where there isn't a large national grid to take up the slack when you have a large reactor offline.
This approach also can have big advantages for B&W. The reactor is small enough that is can assembled in a few major modules which can be transported to the construction site and only the final assembly is done on-site. Not only do you achieve much lower component costs when purchased in quantity, but the quality control can be much more through in a factory setting, which will improve safety and reliability.
The mPower represents an intermediate step between the AP1000, which has modular subunits and the SSTAR that Lawerence Livermore is designing which is assembled prefueled at the factory and only needs to hooked up to the turbines and generators at the site.
This brings me to the most interesting feature of the mPower: All the components will be made in North America. During the long dark night for nuclear power in the United States following Three Mile Island, we lost almost all domestic capacity for making the components for nuclear reactors. The Republican energy bill has a provision to waive tariffs for nuclear reactor components, where there is no domestic manufacturer. B&W just went back into the business of building heavy reactor components a couple of years ago after leaving the business 20 years ago.
Rebuilding our nuclear infrastructure is important not just from a buy American point of view. There is a lot of demand worldwide for reactor components. The last time I looked the lead time for a reactor pressure vessel was three years. Being able to supply their own heavy components gives B&W a big leg up.
The next feature of note is that reactor is designed to be built underground. The picture at the top is a 500MW underground facility with 4 mPower reactors. It looks like the generators and maybe the turbines are above ground. I suspect that the underground design is a reaction to the new rule that the Nuclear Regulatory Commission (NRC) announced in February 2009, that new reactors designs must be able to withstand the crash of a commercial jetliner. B&W probably decided it was prohibitively expensive to build an above ground containment for a low cost reactor to meet that specification and that building below ground was cheaper. I have reservations about this requirement. It isn't obvious to me that crashing a jetliner into a nuclear reactor would actually cause more loss of life than doing it to a natural gas storage facility.
I live in Orlando, Florida and I wonder how practical this is for this area. I'm not a civil engineer, but anytime someone digs a hole around here, it fills up with groundwater. It would be a pain to shut down the reactor because the sump pump failed. It also looks like the spent fuel storage is underground. I don't know if this creates a risk of groundwater contamination if there is a leak.
I often find it useful to look at vendor literature and note what they don't say. Since it against human nature to emphasize the weaknesses in your product, silence often speaks louder than words. The thing I notice is not mentioned is the size of the mPower. There aren't any people in the renderings to give a sense of scale. This combined with the vagueness on the construction costs and the fact the they said that they would be submitting their application to the NRC in 2011 indicate that the mPower design is in the early stages.
Overall I think the mPower is a good thing and hope it moves along smoothly.
References:
B&W Modular Nuclear Reactors
http://www.babcock.com/products/modular_nuclear/
Company Calls New Small Nuclear Reactor a 'Game Changer'
http://www.nytimes.com/gwire/2009/06/10/10greenwire-company-calls-new-small-nuclear-reactor-a-game-45123.html
New Reactors Must Handle Plane Strike
http://www.nytimes.com/2009/02/18/us/18nuke.html
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