MSR Upgrade at Duane Arnold Uses Modularization to Cut Radiation Exposure and Erection Time

When the BWR at Duane Arnold went on-line, it was rated at 565.7 MWe. Some time ago, due to operational and other problems it was determined that it would be economical to isolate the HP reheaters from service in the double-stage two Moisture Separator Reheaters (MSRs). Duane Arnold is now undergoing an extensive and lengthy life-extension and uprating program, targeted at 16 percent involving many components. After a detailed study involving several alternative approaches to upgrading the MSRs in conjunction with a new, larger HP turbine, they have now been completely redesigned and reconstructed using essentially the original configuration — 2-pass LP and HP reheaters with chevron moisture separator sections, but using advanced technology throughout and in conjunction with the optimization of the uprated turbine generator. In order to minimize component installation time and reduce personnel radiation exposure, the modern Moisture Separation (M.S.) components were “modularized” — installed as four completely preassembled M.S. sections replacing the need for the in-shell installation of multiple small components. This paper covers the many alternative choices considered and details all elements and phases of the final MSR upgrade design and installation process selected. The installation of a new main turbine, oversized in anticipation of an increase in thermal power, was expected to result in a decrease of about 10 MWe due to throttling losses across the turbine control valves. The refurbished MSR with restored second stage reheat was expected to just offset this loss. Post installation testing showed a gain of 4 MWe beyond the offset of the turbine control valve throttling losses. As a result, the net gain over previous operation is therefore 4 MWe even though the new MSR is responsible for gain of about 14 MWe.