Is Alternative Nuclear Power Viable?
I read with interest the article, "Alternative Nuclear Power" by Rod Adams [April 2001, p.134]. I agree with Mr. Adams that the pebblebed modular reactor (PBMR) has some compelling characteristics and the potential to greatly improve nuclear energy safety and economy. However, some of Admiral Rickover's "attention to detail" is needed before we accept many of the ideas being sold in this article.
While much of the basic technology is proven, several engineering details still need to be worked out for a PBMR and gas turbine system. For example, PBMR power systems will require making millions of spherical fuel elements a year to the exceedingly high and uniform quality levels needed to ensure that radioactive fission products are retained in the fuel.
This is a substantial manufacturing and quality-control challenge. The degree of confidence in the fuel's ability to retain fission products with 100 percent reliability will undoubtedly affect safety and containment requirements, as well as the economics of a PBMR system. There are further challenges in nuclear analysis methods, system design, and instrumentation and control development.
Several past nuclear reactor concepts have fallen to engineering details, including the Russian RBMK (i.e., Chernobyl) and many earlier gas reactors. With the way PBMR is currently being oversold, another engineering failure and subsequent reactor failure would severely damage public confidence in nuclear power. It is therefore incumbent on Eskom and Excelon, its U.S. partner, to do their jobs right.
As for the small power units envisioned in the article, I doubt that PBMR technology will be infinitely scalable in the manner described. For example, the discussion of the NEREUS concept (8 MWe, or about 18 MW thermal, in an 18,000 cu. ft. plant volume) implies a reactor power density somewhat higher than envisioned for PBMR power stations. Higher power density will likely eliminate the inherent safety characteristics advertised for PBMR.
In addition, it is possible, and even likely, that the fuel-element manufacturing process will constrain achievable fuel and burnable poison loadings, and thus achievable reactor-energy density and size.
Furthermore, any nuclear reactor will inherently make enormous quantities of radioactivity that have to be contained by rigorous adherence to complex and nonintuitive principles of nuclear reactor physics. Regardless of the fuel system or whatever sophisticated (and costly) automatic controls and maintenance contracts you wrap around it, the responsibility associated with such radioactivity is something that the average homeowner will probably not want to deal with.
In my opinion, there is no future for the United States without nuclear power. The high-energy density economics and small, contained waste volume promised by PBMR are strong incentives to overcome the challenges where it makes sense to do so. PBMR is a concept in the right direction, and increased attention to this technology is long overdue. However, please recognize that a lot of hard work remains to be done to show that this power source is viable and to make it a reality.
Rod Adams replies:
Mr. Bell is obviously well versed in many of the details of nuclear power and provides some insightful comments. I hope that he remembers, however, that the article to which he is referring is a space-limited information piece aimed at a general audience. It is not a detailed technical article specifying all relevant details.
In fact, some of the details that Mr. Bell implies are open questions have been solved, but the solutions, quite logically, are not publicly available. The business of producing energy is, after all, quite competitive and lucrative to those with superior technology.
The team that has been established to develop the PBMR is extremely competent and experienced. Based on our contacts, I believe it is fully aware of the need for "attention to detail." In fact, many members of the team have years-to-decades' worth of involvement in the Naval nuclear power program and were quite well trained by Admiral Rickover.
It is also interesting that Mr. Bell accuses the PBMR of being "oversold." As far as I can tell, none of the plants have been offered for sale. Instead, the partners have simply provided a wealth of information about what they intend to build.
With respect to the scalability of the plant, Mr. Bell is simply wrong. The reactor power density of the NEREUS concept is essentially the same as that proposed for the PBMR; the space required by auxiliary equipment--there is no continuous fuel-handling system, for example--is simply less, allowing a more compact machine. As reactors get even smaller, the increase in surface area to volume ratio actually makes it easier to meet the physical requirements that lead to the plant's inherent safety.
With regard to his comments about rigorous control of radioactivity, Mr. Bell demonstrates exactly the attitude that I mentioned at the end of my article. He cannot allow himself to believe that one can engineer a tamper-proof black box that "contains no user-serviceable parts" so that we can entrust this phenomenal power source to an average person.
I have a different opinion. I believe that it will be relatively simple to design such a box. In 1900, automobile enthusiasts would have never have believed that there would be almost as many cars in the United States as people. Thirty years ago, one would have been hard pressed to find a programmer who believed that common people could ever learn to use a computer. Ten years ago, comedians joked about the inability of some people to program their VCR. Now there are millions of people who mix their own CDs.
My final comment to Mr. Bell is to reassure him that there are people who are working very hard to make pebble bed reactors real and available. Based on recent events, I am glad that they started that work several decades ago; the fruits of their labor appear to be needed almost immediately.