Round Robin Tests for WWER Heat Exchange Tubes

Abstract

One of the most affected components from the point of view of long-time operation of WWER reactors are heat exchanging tubes of steam generators. With the nominal tube wall thickness of 1,4 mm (WWER440) or 1,5 mm (WWER1000) only and significant consequences of many factors, such as; increasing units power output, the long-time operation, secondary water chemistry and, in some cases, mechanical impact due to dissimilar welds (DN1100) repair, steam generator tubing represents one of the most critical component significantly limiting overall lifetime of many units. New forms of degradations came into being in many of WWER unites, many of them specific for some units only. Therefore, there is a wide accepted need for applying new inspection techniques. As such, these techniques are now on the market, being partially used in some units. Pulled-out tubes from Jaslovske Bohunice units 1 and 2, with real defects, well documented from the point of view of historical eddy current results and results from last inspection, carefully stored and treated, provide the great opportunity for experimental verification of these new, state-of-the art inspection ET techniques (e.g., MRPC, X-Probe, High-speed MRPC etc.).