Round robin tests on DHCV and hydrogen concentration in Zr-2.5Nb CANDU pressure tubes

This study summarized the results of the round robin tests on Delayed Hydride Cracking Velocity (DHCV) and hydrogen concentration in Zr-2.5Nb tubes carried out as the coordinated research program of the International Atomic Energy Agency in which 10 research labs participated. Using the procedure suggested by the Chalk River Laboratory of the Atomic Energy Canada Limited, DHC tests were conducted at 144 to 283 .deg. C on CANDU and RBMK Zr-2.5Nb tubes. Round robin test on hydrogen concentration was performed using the hydrogen analysis procedure and analytical equipment of each participant on the Zr-2.5Nb pellets whose hydrogen concentration was controlled to 46.9 μg/g. We determined a temperature dependence of DHCV for the CANDU and RBMK Zr-2.5Nb tubes whose activation energy was 49 KJ/mol and 56 KJ/mol, respectively. Surprisingly, our data agreed perfectly with the activation energies for DHC of CANDU and RBMK that were determined using all the DHCV data produced by all the participants. Among all the participants, KAERI's data of the hydrogen concentration excellently agreed with the standard hydrogen concentration set up by AECL. As a conclusion, the round robin tests on DHCV and hydrogen concentration confirm that KAERI can determine the DHCV and hydrogen concentration in Zr-2.5Nb tubes with high accuracy. Comparing all the DHCV of CANDU and RBMK Zr-2.5Nb tubes, a difference in the activation energy of DHCV for both tubes was discussed