This section addresses the question of whether the SGRP is needed and, if needed, when it should be performed. The parties agree that the original steam generators will need to be replaced if SONGS is to continue operating to the end of its license lives.
The timing of the SGRP is dependent upon the degradation of the original steam generators, and the availability of replacement steam generators. SCE states that Refueling and Maintenance Outage (RFO) 16, which may begin as soon as 2009, is the earliest that the SGRP can be performed because of the approximate five-year lead time for steam generator fabrication.7 No party disputes this claim.
SCE states that there is a 25% probability that the Unit 2 steam generators will not be able to operate beyond RFO 16. It also says that there is a 15% probability that the Unit 3 steam generators will not be able to operate beyond RFO 16. SCE argues that it would be irresponsible to wait beyond RFO 16 to perform the SGRP because the probability of an unplanned shutdown would be too great.
The Utility Reform Network (TURN) states that SCE has not justified why its estimated 25% probability of shutdown in RFO 16 justifies performing the SGRP at that time. TURN points out that other utilities have requested and received higher plugging limits from the NRC.8 TURN, therefore argues that SCE has not addressed this possibility. TURN also states that due to the uncertainty in the steam generator tube degradation forecast, the tube plugging limit, and the point at which the probability of shutdown justifies that the SGRP be performed, it is possible that SONGS could operate until at least one or two RFOs later.9 TURN, therefore, recommends that such a possibility should be modeled.
SDG&E states, based on steam generator tube degradation forecasts prepared by Dominion Engineering, Inc. (DEI) for SCE, that there is a 67% probability that Unit 2 will operate until RFO 17 in 2011 and a 56% probability that Unit 3 will continue to operate until RFO 20 in 2016.10 Therefore, SDG&E recommends that the SGRP, if it is to be performed, be delayed by at least one RFO for Unit 2, and up to three RFOs for Unit 3. In the interim, the replacement steam generators would be stored.
The SGRP is needed if SONGS is to continue operating through the end of its license lives. If the SGRP is to go forward, any delay in doing so would result in more monies being spent to repair and maintain the original steam generators, and store the replacement steam generators, without a corresponding decrease in the cost of the SGRP. The replacement steam generators will not be available before 2009. If the SGRP is to be performed, it makes no sense to spend additional funds to keep the original steam generators in operation. Therefore, if the SGRP is to go forward, it should do so on the schedule proposed by SCE.
7 An RFO is when a unit is taken out of service to refuel the nuclear reactor, and perform repairs and maintenance. RFOs for each unit are generally performed sequentially so that both units are not out of service at the same time.
8 If failing steam generator tubes can't be repaired, they are removed from service by inserting plugs (plugging). If they can be repaired, the repair is accomplished by inserting a sleeve inside the tube that spans the problem area (sleeving). Since a sleeve restricts coolant flow through the repaired tube, a specified number of sleeved tubes is considered equivalent to a plugged tube. The plugging limit is the maximum number of plugged tubes (including equivalent sleeved tubes) that would still allow adequate coolant flow through the steam generator. For SONGS, the coolant is water.
9 RFOs occur at approximately 18 month intervals for each unit.
10 See section VII.I for a more complete discussion of tube degradation forecasts.