U.S. NUCLEAR REGULATORY COMMISSION STANDARD REVIEW PLAN OFFICE OF NUCLEAR REACTOR REGULATION 15.6.2 RADIOLOGICAL CONSEQUENCES OF THE FAILURE OF SMALL LINES CARRYING PRIMARY COOLANT OUTSIDE CONTAINMENT REVIEW RESPONSIBILITIES Primary- Accident Evaluation B

This SRP section covers the radiological consequences of failures outside the containment of small lines connected to the primary coolant pressure boundary, such as instrument lines and sample lines. The review includes the following: 1. The identification of small lines postulated to fail and the isolation provisions for these lines, including the applicability of General Design Criterion 55 (Ref. 1), which requires isolation capability of the line inside and outside containment, and Regulatory Guide 1.11 (Ref. 2), which requires isolation capability outside containment for those lines that are exempt from GDC 55. The implementation of these regulatory positions and guidelines is reviewed by the Containment Systems Branch (CSB) under SRP Section 6.2.4. 2. The failure scenario, as described by the applicant, to assure that the most severe radioactive releases have been considered. 3. The models ad assumptions used by the applicant for the calculation of the thyroid and whole-body doses for the postulated failure. 4. An evaluation of the primary coolant iodine activity, including the effects of a concurrent iodine spike, and the technical specifications for the reactor coolant iodine activity. 5. An independent calculation by the staff of the thyroid and whole-body doses for the small line failure, including an evaluation of the isolation times and maximum leak rates of the isolation valves