The UFSAR should not address scaffolding, as it is typicallynot part of the plant design. However, if scaffolding needs to remain installed in the plant for greater than 90 days, it is no longer temporary. It has now become a temporary modification, or a permanent design, depending on the purpose. It sounds like you are using the scaffolding to hang your shielding blankets. The 50.59 screening is the method of evaluating whether you need to seek NRC approval for this "modification". You need to evaluate the potential effect on Safety Related equipment and also the seismic qualification of the scaffolding. At our plant, we complete a configuration change package, with requisite 50.59 screening. If the scaffold needs to remain in place for a very long time (i.e. will not be removed by your next UFSAR update), you also DO need to have it added to your UFSAR, because it has now become plant design (even if "temporary"). Because this is a very cumbersome process, at our plant we normally direct that the scaffold be removed prior to 90 days, unless it is absolutely critical to remain longer, in which case we ask that the group request for a permanent/engineered design change be pursued. Maintenance has a database that tracks installed scaffolds and alerts them when the 90 days is approaching.
One other small caveat that is easy to miss...if you know on day 1 of installing the scaffold that it will be installed for greater than 90 days, you should completing the 50.59 screening immediately. It's hard to prove, but that can be fodder for a violation.
