It is also home to seven out of ten of the world's most polluted cities and is the second largest carbon dioxide emitter.

All of which puts China on the horns of a dilemma regarding nuclear power. Nuclear power is not only less expensive, but it is much cleaner than coal-fired power, which is responsible for most of China's pollution. But nuclear power must be properly controlled and its wastes safely disposed.

As China seeks to expand its nuclear power capabilities, its leaders are drawing upon the international nuclear power expertise of Vanderbilt's Frank L. Parker, Distinguished Professor of Environmental and Water Resources Engineering. Professor Parker heads up the Radiation Safety of the Biosphere Project (RAD) of the Laxenburg, Austria-based International Institute for Applied Systems Analysis (IIASA), and he has served for decades as one of the leading experts helping both the United States and Russia to clean up after the accidents and inadequate handling of nuclear wastes during the Cold War.

It was his work co-editing and writing part of Radiation Legacy of the Soviet Nuclear Complex that initially piqued the interest of Pan Ziqiang, Deputy Director of the Chinese National Nuclear Corporation (CNNC). Dr. Pan asked Professor Parker to help him update his 1991 book, Radiation Environmental Impact Assessment of the Nuclear Industry in China in the Three Decades (1955-1985).

"I recommended that they expand the scope and technical depth of the book, and to truly update it to include recent decades," Professor Parker says. "Ultimately they didn't take that recommendation, but they did revise the book to address numerous other specific issues I had raised."

Nonetheless pleased with Professor Parker's input, the CNNC enlisted his help in comparing Chinese nuclear remediation techniques with those of the West. Professor Parker led visits to China and U.S. sites and co-authored a 2003 paper with Chinese nuclear experts on reclamation of China's decommissioned uranium mining and milling facilities.

Next, the CNNC asked Professor Parker to evaluate the model Chinese scientists developed to determine the path of atmospheric releases of radioactive materials from nuclear power facilities would most likely take under different weather conditions.

Last summer Professor Parker directed the work of IIASA Young Scientist Summer Program post-doctoral student Rentai Yao in modeling these pathways from two Russian nuclear submarine bases and two Chinese nuclear power plant stations, based on 2003 weather data. They then compared the Chinese model with the Danish model used in their previous studies.

"These findings are interesting," Professor Parker says. "The two models have produced discrepant results. This was a surprise, since assessments of the Chinese model using tracer data from several years ago showed that the Chinese model performed as well as the Western model."

The discrepancy could be due to different release heights or meteorological conditions. However, if the reason is found to be in the models themselves, it could be important since these models are used to assess the impact of nuclear power facility accidents on China and on other countries.

"There is no public knowledge of accidents in China similar to Three Mile Island and Chernobyl," Professor Parker says. "But so far our knowledge of the Chinese nuclear complex operations is still sketchy. However, China had the benefit of starting its program approximately ten years later than the US and Soviet Union and benefited from the experience in those programs."

Professor Parker is accustomed to dealing with government projects shrouded in secrecy, having led international teams in several environmental assessment projects in the former Soviet Union and Russia. In addition to helping the Russians determine what to do with the waste generated by the Northern Fleet's decommissioned nuclear submarines, Professor Parker conducted several projects related to Lake Karachai, the most contaminated known area on earth. He also studied the radiation doses due to the radioactive wastes released in the Siberian Yenesei and Tom Rivers and analyzed the known and potential impact of injecting radioactive waste into deep geological formations in Siberia.

This "deep well injection" practice is one of the techniques the Chinese are interested in having Professor Parker assess in China.

Deep well injection is one of several techniques of disposing of liquid radioactive waste throughout the nuclear fuel cycle. "In modern times in the West, this practice has been largely replaced by solidifying radioactive wastes," Professor Parker says. "There are large uncertainties in our knowledge of the behavior of liquid wastes in geological strata, and as a result there is a potential for migration of substances from the place of its disposal to the accessible environment. However, in more recent times and under much stricter regulation, the technique has performed well with hazardous chemical wastes."

Radioactive wastes are produced at each stage of the nuclear power generation process. The international community is

currently developing final-disposition techniques for nuclear wastes. Final disposal has been delayed to allow the radioactivity to decay, making it much safer to handle. Canisters of waste are currently stored near processing sites in dry concrete containers or in water filled basins set aside for this purpose. The US claims it will begin to dispose high level radioactive wastes by 2010, with the waste expected to be in the forms of vitrified (glass) wastes encased in steel canisters or spent fuel rods contained in copper or stainless steel. However, most nations, except Sweden and Finland, will not begin disposal until later. These containers will be buried deep underground in stable rock structures.

Meanwhile, Chinese leaders are interested in eliciting Professor Parker's help in remediating sites that have used in situ leaching, a modern uranium-extraction technique which brings the uranium to the surface in solution, directly from the underground ore. Ordinarily surface or underground mining are used to obtain uranium in a solid form.

Professor Parker's role in helping China improve techniques in various stages of the nuclear fuel cycle is still evolving. The IIASA decided this summer to extend the Chinese cooperative projects for another two years, and Professor Parker expects to visit more Chinese nuclear facilities.

But first he will host a major international workshop to assess the global nuclear legacy: "Solutions to Security Concerns about the Radioactive Legacy of the Cold War that Remain in Urban Environments," to be held at Vanderbilt in November.

"The workshop will evaluate typical critical situations in Russia, China and the West and will search for solutions to security concerns about the radioactive legacy in urban environments," Professor Parker says.