HFIR Pressure Vessel and Structural Components Materials Surveillance Program- Supplement 3

Abstract

New sets of dosimetry data (2004) and vessel material surveillance data (2005) have been obtained since the new (enlarged) HB-2 and HB-4 beam tubes and new Key 2 and Key 4 surveillance-capsule mounts were installed over the period May 2001 to April 2002. Also, upgrades to the dose-rate calculational models have been made over the period 2000 to 2009. This information has been used to improve the accuracy of the calculated dose rates for the surveillance specimens and for critical areas of the vessel (HB-2 nozzle, etc.) and for updating the HFIR vessel radiation embrittlement trend curve (delta-NDTT vs dpa`). This curve and the improved calculated dose rates were used to establish the schedule for removal of the remaining 63 surveillance capsules and the testing of the Charpy V notch (CVN) specimens therein. (The updated calculated dose rates and radiation embrittlement trend curve are also used in the periodic reevaluation of the HFIR vessel structural integrity, but that is the subject of another study and report.) The data obtained thus far indicate a somewhat higher dose rate than previously estimated. As a result, the previously published schedule for removal and testing of CVN specimens was updated to specify earlier removal of a few of the remaining surveillance capsules.