NRC SFST ISG-14: Supplemental Shielding

Guidance regarding supplemental shielding that may be installed at an independent
spent fuel storage installation (ISFSI) to meet the requirements of 10 CFR 72.104(a).

Recent design reviews of dry cask storage systems have identified the possible installation of
supplemental shielding by general or site-specific licensees to meet the requirements of 10
CFR 72.104(a) regarding the dose limits for normal conditions of operation. Supplemental
shielding, such as an earthen berm or concrete wall surrounding the general licensee’s ISFSI,
is not a part of the cask system design approved under 10 CFR Part 72, Subpart L. The staff
considers engineered features for shielding purposes, such as berms or shield walls, to be
important to safety. This staff guidance addresses supplemental shielding that may be installed
by a general licensee and its classification as an important to safety component. Moreover,
supplemental shielding at an ISFSI for a site-specific licensee would be included in the Safety
Analysis Report (SAR).