Wednesday, July 21, 2010

More on Small Modular Nuclear Reactors from Rod Adams

A growing body of plant designers, utility companies, government agencies and financial players are recognizing that smaller plants can take advantage of greater opportunities to apply lessons learned, take advantage of the engineering and tooling savings possible with higher numbers of units and better meet customer needs in terms of capacity additions and financing. The resulting systems are a welcome addition to the nuclear power plant menu, which has previously been limited to one size - extra large. Developing a broader range of system choices using nuclear fission energy could have a measurable impact on segments of the energy market that have been most often served by burning distillate fuel or natural gas. Small modular reactors offer a reason to be optimistic that human society will have access to all of the energy that it needs for increased prosperity for larger portion of the population. _RodAdams
Small, factory-built, modular nuclear reactors have the potential to solve a lot of the problems with nuclear power development in both the advanced and the undeveloped world. Rod Adams recently published an article in The Oil Drum, providing more specifics:
... The complexities of putting together the very large systems and projects kept adding to the risk, which added to the cost and complexity of financing which added to the project complexity by requiring additional partners - including government agencies and public subsidies.

Some frustrated nuclear plant designers, inspired by talking with customers about their needs and remembering what was technically possible in terms of nuclear reactor sizing determined that they might be able to solve some of the cost and schedule complaints by a complete rethinking of the old economy of scale paradigm. For anyone who has been paying attention during the past five years or so, the names of Hyperion, NuScale and Toshiba 4S have been increasingly frequent terms of discussion as start-ups and some established vendors began designing nuclear fission based systems sized at 10, 25, or 45 MWe, which is a radical departure from the 1000 MWe (plus) sizes of the AP1000 (Westinghouse), ESBWR (GE-Hitachi), or EPR (Areva).

Initially, the project leaders for these new designs thought about using them in distributed remote locations where power is either not available or is being supplied by expensively delivered diesel fuel. John (Grizz) Deal and his sister, Deborah Deal Blackwell, the Hyperion Power Generation founders thought about the how a simple, infrequently fueled nuclear plant could supply power to a remote area for up to a decade without refueling. They recognized the value that such a system could provide to the previously powerless people living in that remote area.

The system could provide power for refrigeration, water treatment and distribution systems, communications systems, and reliable, flicker free lighting. Unfortunately, the specific technologies needed for the Hyperion design - liquid metal (Pb-Bi) cooling and uranium nitride fuel elements - are not in commercial use. They hve been used in several specialized reactors and proven to work reliably and safely, but starting up a new supply chain is just one of the many hurdles that Hyperion is diligently working to overcome. The Toshiba 4S sodium cooled power system faces similar challenges, but both concepts have their fans and both are moving forward.

A trio of project teams has recognized that the concept of small does not mean that you have to start from scratch with the supply chain, training programs, and safety analysis; it is possible to do a redesign of light water reactors from the ground up to produce an economical design that achieves economy by both simplification and increased unit volume. All three of the teams - NuScale, B&W and Westinghouse - have designed systems that put the entire primary plant into a single pressure vessel. This choice eliminates the potential for a large pipe break loss of coolant accident. They have all chosen to include a large volume of water - relative to the core power output - that provides operators with lengthy interval between any conceivable accident and required operator action. They also have chosen passive safety systems that do not require any outside power sources to operate, so they expect to be able to prove that they can meet existing safety criteria without redundant power sources. All of the iPWR systems envision using fuel assemblies that are essentially the same as commercial nuclear plant fuel elements - but they will be shorter and there will be fewer assemblies in each core. All of the systems have been designed for the post 911 security and safety considerations including the aircraft impact rule through the use of below grade installation.

...The integrated pressurized water reactor (iPWR) that is gaining the most buzz from the business community and political leaders, however, is the 125 MWe mPowerâ„¢. Yesterday, Bechtel Corporation, one of the largest privately held companies in the United States, with 57,000 employees and $30.8 billion in 2009 revenue, announced that it was joining with B&W as a 20% partner in an exclusive alliance that they have branded as Generation mPower to build complete, turn-key power plants.

B&W has an already existing and ASME 'N-stamp' certified US manufacturing base and 50 years worth of experience in building nearly all of the components required for the small, modular light water reactors that power ships and submarines. Bechtel has either built or participated in major renovation projects at 64 of the 104 nuclear plants operating in the United States.

The mPowerâ„¢ modules will be about the same size as the NuScale modules, but each module will produce about 2.5 times as much power as a NuScale module because they include submerged reactor coolant pumps to provide forced flow through the core. The system is designed to supply a sufficient quantity of natural circulation to provide core cooling after shutdown without any pumps running, thus maintaining the passive safety characteristic. Like NuScale, Generation mPower expects that customers for its plants will probably want to plan to install multiple units on a single site, though they might start with just one or two and add additional units gradually over time. Generation mPower has informed the NRC that it will be submitted a design certification application by the end of 2012; that application might be filed at the same time as a construction and operating license for the first of a kind unit.... _TOD

Once the US Nuclear Regulatory Commission finally gets to work certifying the best of the SMRs, the small-scale nuclear renaissance should come into play. As the safety, reliability, affordability, and prompt delivery and installation are all proven, the number of applications for these reactors will almost certainly multiply rapidly.



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