July 2000 Highlight

Armenia Bulgaria Czech Republic Hungary

Kazakhstan Lithuania Russia Slovakia

Ukraine United States Cross-Cutting Activities Planned Activities

Cross-Cutting Activities

The first meeting of the International Atomic Energy Agency (IAEA) Intergranular Stress Corrosion Cracking Working Group 1 was held at Kursk NPP, Kurchatov, Russia, July 17 through 20. Working Group 1 is focused on improvements to the performance of, and qualifications for, inservice inspections in nuclear reactors. Nondestructive testing of cooling-water piping systems is aimed at discovering and repairing cracks before they cause leaks and ruptures that could result in the loss of cooling water to the reactor core.

Working Group 1 is led by a U.S. team member and nondestructive evaluation specialist from Pacific Northwest National Laboratory. Participants from RBMK reactors in Lithuania (Ignalina) and Russia (Leningrad, Smolensk, and Kursk) attended, along with experts from Gosatomnadzor and MinAtom in Moscow, the Nuclear Regulatory Department and the Nondestructive Examination Training and Certification Facility in Ukraine, and Mitsui Babcock Energy Limited in Scotland.

RBMK plant representatives described specific inservice inspection problems that they felt the working group should address. The Pacific Northwest National Laboratory specialist discussed approaches used in the United States. The problems at RBMKs include improving inspection techniques so as to more accurately reflect the depth and length of a crack, resolving issues of limited access to some welds and geometries that produce confusing signals, improving reliability of ultrasonic inspection and qualification of inspectors, and identifying techniques for inspection of repairs by the weld overlay technique. Working Group 1 will hold its next meeting early in 2001. (Grig Trosman, DOE, 301-903-3581; Tom Taylor, PNNL, 509-375-4331)

During the last week of July, a U.S. specialist from Argonne National Laboratory traveled to Kyiv, Ukraine, and Sofia, Bulgaria, to review two U.S.-supported projects: 1) computer code validation for application to VVER reactors and 2) special transient analysis. The U.S. team member met with analysts at Kyiv National Taras Shevchenko University (KU) in Kyiv on the first project. Specialists from Bulgaria’s Institute of Nuclear Research and Nuclear Energy (INRNE), Pennsylvania State University (PSU), and Kozloduy NPP met in Sofia to review the second project.

Topics discussed included

• KU’s definition and analysis of a standard problem based on transient data for Rivne NPP to validate RELAP5 for VVER reactors

• INRNE’s definition and analysis of a standard problem based on a natural circulation test at Kozloduy Unit 6 for the validation of RELAP5 for VVER reactors

• the exchange of standard problems between KU and INRNE to allow comparison of two independent analyses of each problem

• Attendance at the Obninsk Information Exchange Forum to be held in October 2000 – KU expects to present two or three papers at the forum; INRNE analysts expect to present a paper on their evaluation of the INRNE standard problem.

• the status of KU’s ongoing VVER special transient analysis project that includes use of the RELAP5-3D code at the Russian International Nuclear Safety Center (RINSC) – Remote connections are being used for visualization of results, and an on-site visit to RINSC, with associated model runs and file exchanges, is planned in conjunction with the October forum.

• INRNE, PSU, and Kozloduy NPP’s definition and analysis of a benchmark for coupled codes – A specific transient (startup of a loop after a pump trip) was tentatively selected. Kozloduy NPP management will verify that sufficient data are available; work is expected to start in late August. This work was also discussed with KU, which expressed an interest in performing the analysis of the benchmark with RELAP5-3D. (Walter Pasedag, DOE, 301-903-3628; Jordi Roglans, ANL, 630-252-3283)