Dear Dr. George:
It was good to see you again last summer. Per our discussion, I am working as an independent consultant (Richard Sipos Consulting) to a large southern electric utility. Our project work scope is to change out reactor heads on the four nuclear units in the system. These are large tops to the reactor pressure vessels. The forgings are made at Japan Steel Works and are machined in France by Framatome.
The reason these are being replaced is a phenomenon called PWSCC (pure water stress corrosion cracking). The control rod nozzles are made of Inconel 600. This is susceptible to PWSCC over time, temperature, and exposure to stress. Consequently, all pressurized water reactors are susceptible to this type of cracking in the nozzle to head welds. Many of the utilities have opted to replace heads rather than to inspect and repair (which is technically complicated and costly). The new reactor head design incorporates Inconel 690 control rod drive nozzles which is known to resist PWSCC.
Recently on a trip to France (Framatome St. Marcel Manufacturing Facility) I met another Ole Miss graduate Jim Taylor Brown BSChE '65. Taylor is working for another southern utility getting a reactor head built also. He and I were surprised to see each other. We took the occasion to have our photo taken together. Our reactor heads are being manufactured in the same shop and are on a similar schedule.
Our first one will be replaced fall 2004. It will be shipped via Russian transport plane, Antonov 124. The shipping weight is around 100 tons which complicates movement from France and to the power plant. In addition, the replacement typically requires cutting an access opening in the reactor containment building. Two of our buildings and Jim Taylor Brown's are post tensioned structures. This is a civil engineering challenge to design and construction. It requires tendon replacement and special concrete mix design (7000 psi in three days).
The old reactor heads will be transported over land to final burial in Utah.
I have enclosed photos of interest.
Richard "Dick" Sipos
Jim Taylor Brown and me in France, January 20, 2004
This is a similar reactor head (not ours) coming off of a Russian transport plane. (October 2003)
Our first reactor head in the heat treat furnace (France, February 2004)