Thermal-Hydraulic Analysis of a Hypothetical Complete Failure of One Shroud Access Hole in a Boiling Water Reactor

Cracks have been observed in the welds of the shroud support access hole cover plates at Peach Bottom Unit 3 as well as at the Chinshan nuclear power plant. The cracks could potentially result in complete weld failure and, as a consequence, a coreflow bypass. Analysis of the postulated complete weld failure of the Chinshan nuclear power plant shroud support access hole cover plate is performed with RETRAN-02/MOD3. The results show that some confusing phenomena could be observed. The reactor operator should be aware of the phenomena to avoid the likelihood of misoperation. Also, a special procedure needs to be established to deal with this event.