1 - Alaska Energy Data Inventory

M. Transient Background and Summary.(1) The design of the surge tank and calculation of waterpressures for the Crater Lake project has been an ongoi ng evo 1 ut ionaryprocess with a wide variety of modifications which include:a. Changes in surge tank design from the original 350 ft highvented surge tank (10 ft in diameter) to an air chamber surge tank and thenon to the recommended vented tank which is approxmately 950 ft high (10 ftdiameter for the horseshoe tunnel and 12 ft diameter for a machine boredtunnel).b. Turbine characteristics changed from the original LOllg Lakemodel with a throat diameter of 52.32 inches and synchoronous speed of 514rpm to the Oworshak model with 600 rpm synchronous speed and then back tothe Long Lake model (synchronous speed equal 600 rpm and throat diameter of54 inches). The final recommended turbine is based on the Long Lake modeland has a synchronous sreed of 600 rpm with a throat di ameter of 51.5inches.(2) Figure 10 in Hydraulic Appendix B2 shows an abridged summaryof the transients for a small cross section of the calculations that weredone for the project. The table shows that the transients are onlymoderately sensitive to even major changes in the system; for instance, thepiezometer elevation at the turbine (for a vented tank) varies from ami n imum of 1,237 ft to a max imum of 1,303 ft. The compressed air surgetank produced a maximum piezometer elevation at the unit of 1,218 ft and amaximum hydraulic gradient at the surge tank of 1,129 ft. Our recommendedsystem produced a maximum piezometer elevation at the unit of 1,256 ft andmaximum hydraulic gradient at the surge tank of 1,075 ft. [The original OM26 of October 1983 indicated a maximum piezometer elevation at the unit(reject condition) of 1,329 ft, but this was based on the combined use ofcomputer programs "MSURGE" and "MSRWH", which, when their maximum gradientsare added together produce more conservat i ve resu 1 ts than "WHAMO" does. ]The transient analysis for the system shown in OM 23 (1973) which includedBl-38