hideout return evaluations are either performed or reviewed to determine crevice conditions and extent of crevices present sludge analyses are reviewed and assessed for aggressive impurities historical tube inspections are further reviewed to ascertain the types of degradation mechanisms which occurred and the extent of tube repairs performed as discussed previously thermodynamic data is then obtained for the plant different corrective action scenarios for the nuclear steam generator are then to be evaluated 130 as an example a scenario may include performing an enhanced upper bundle flush sludge lancing every other outage ibl every 4 th outage and full dmt every 6 th outage using the deposit heat transfer model described herein and the resulting net electrical power projections coupled with estimates of tube degradation nuclear power plant outages and other pertinent costs and benefits for the different corrective action scenarios the net present value and other economic measures are developed for each scenario within the deposit management plan the modeled thermal resistance of the deposit layer is a key element of these evaluations and is periodically recalculated to account for planned maintenance activities or unanticipated changes in plant operating behavior a base scenario is chosen as a reference for judging the efficacy of the other options 140 this base case is compared in terms of payback period irr and or net present value to each of the alternative.