UConn prof writes clear PBMR overview

Pelindaba, South Africa, pebble bed work site

Professor Lee Langston writes in Mechanical Engineering
University of Connecticut retired professor Lee Langston has just published a very clear, readable history of the pebble bed modular reactor project underway in South Africa. Pebbles Making Waves is the feature article in the April, 2008, issue of Mechanical Engineering, published by the American Society of Mechanical Engineers.

I encourage you to read this overview of the history and status of the Pebble Bed Modular Reactor project in South Africa.

MIT drives much pebble bed reactor research

MIT, the Massachusetts Institute of Technology, is a great institution. For example, the MIT Department of Nuclear Science and Engineering has led the study of basic nuclear processes and nuclear engineering for a half century. In light of the fact that the US has not built a nuclear power plant since the 1970s, we are fortunate that the science lives on with in faculty of 28 and senior research staff, 101 graduate and 48 undergraduate students.

Andrew Kadak has the unusual title of Professor of the Practice in this department. He has served the US government looking into issues of nuclear waste and safety. His pre-MIT career within the nuclear power industry included being the CEO of Yankee Atomic Electric. This nuclear power plant in Rowe, Massachusetts was decommissioned in 1992. Click Yankee Rowe to see before and after pictures and learn the fate of the spent fuel.

Much of the current interest in pebble bed reactors sprang from an MIT student summer project in January 1998 advised by faculty advisors Ronald Ballinger and Andrew Kadak. Nuclear Power Plant Design Project involved 6 students and 10 guest lecturers. The students reviewed:

1. Westinghouse AP600 advanced pressurized light water reactor (LWR)
2. ABB System 80+ LWR
3. GE Advanced Boiling Water Reactor (ABWR)
4. General Atomics high temperature gas reactor (HTGR)
5. German AVR pilot pebble bed reactor (a HTGR)
6. Lead bismuth reactor
7. Thorium breeder reactor
8. Liquid metal breeder reactor

They evaluation process considered 26 criteria such as safety, economics, construction time, modularity, efficiency, and lifetime. The process selected the small, modular pebble bed high temperature gas reactor. Some of the identified unique features of the PBR are:

• Inherent safety: no operator actions nor automated systems needed
• Proliferation resistance: reprocessing spent fuel pebbles is impractical
• Short, 36 month construction time
• Modular growth: 100 MW units
• Refueling: no shutdown
• Fuel disposal: spent fuel ready for disposal on removal from core
• High thermal/electric efficiency: no water cooling needed
• On-site assembly/disassembly: components shipped intact to/from factory

Subsequently a number of research projects were conducted and documented at the MIT Pebble Bed Reactor web site. Marc Berte and Andrew Kadak prepared the interesting Modularity Approach of the Modular Pebble Bed Reactor which contains a physical design for a PBR, including designs for all component parts that permit construction in a factory, shipment by rail and truck to a job site, and on-site assembly with no welding required.

I am pleased that in the recent three-decade dark ages of US nuclear power plant construction the US government has funded and MIT has continued research and development in nuclear engineering. Unfortunately it appears that US-sponsored funding of pebble bed reactor research projects at MIT has dropped off in recent years. China and South Africa are both developing pebble bed reactors, attracting the attention of university scientists and engineers. MIT is cooperating and sharing information with Tshinghua University in China. The university now has an operational pilot PBR. Kadak has traveled to China to observe the plant's fail-safe testing, and he is now consulting with the South African project.