Session: CS-20-01 Master Curve Method and Applications

Paper Number: 128727

128727 - Surveillance Specimen Design Recommendations for Hfir Vessel Long Term Operation 

To ensure long-term and high-performance operation and operational flexibility of the High Flux Isotope Reactor (HFIR), it is essential to address the concerns with radiation embrittlement of the vessel. Due to historical concerns about radiation embrittlement, HFIR has operated at a power below that of the original design for several decades. It is commonly accepted understanding within the community that the current vessel should be replaced to permit safe and full power operation of the HFIR for one hundred years and beyond. When it comes to vessel replacement, the obvious path is the physical removal of the current vessel and installation of a new vessel that is resistant to radiation embrittlement. Another possible option is to repair/replace the existing vessel by mitigating harmful radiation embrittlement by means of thermal annealing. This thermal anneal option does not require physical replacement and would be more ecologically friendly than physical replacement since it will not create large volume of low activated waste in the form of a spent, replaced vessel. Lastly, a modern, state-of-the -art probabilistic failure analysis using the latest achievements in fracture mechanics has to be performed to remove all margin that were used back in 1960s when this reactor vessel was designed and build. 
Regardless which path will be selected, there is a need to develop recommendations for designing a surveillance specimens’ program that would monitor degradation of vessel material properties during long-term operation. This paper will consider various challenges and solutions in developing such program based on specific need of HFIR vessel.
 

Presenting Author: Mikhail Sokolov Oak Ridge National Laboratory

Presenting Author Biography: The presenter is a Senior R&D Staff Member at the Materials Science and Technology Division at ORNL for more than 30 years.

Authors:

Mikhail Sokolov Oak Ridge National Laboratory
William Server ATI Consulting
J. Brian Hall WEC
Henry Kmieciak ORNL