Document: NRC Regulatory Guide
Document ID: c458fb43-5ee6-4e14-a33d-808ec974115a
Document Type: regulatory_guide
Title: Instrument Lines Penetrating Primary Reactor Containment + HISTORY - HISTORY 09/2009 – DG-1225 , Proposed Revision 1 Prior to the issuance of Revision 1, RG 1.11 was entitled "Instrument Lines Penetrating Primary Reactor Containment (Rev. 1)
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML0909/ML090970530.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-1.11
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CFR Title: 

Content:
guide contains information collection requirements covered by 10 CFR Part 50 that the Office of Management and Budget (OMB) approved under OMB control number 3150-0011. The NRC may neither conduct nor sponsor, and a person is not required to respond to, an information collection request or requirement unless the requesting document displays a currently valid OMB control number. B. DISCUSSION Valves provided for each instrument line that penetrates the primary reactor containment and that is part of the reactor coolant pressure boundary or that penetrates the primary reactor containment and connects directly to the containment atmosphere should be chosen with consideration of the importance of the following two safety functions: 1. the function that the associated instrumentation performs, and 2. the need to maintain containment leak-tight integrity. The likelihood of achieving the first function is enhanced by the presence of fewer valves (e.g., one valve rather than two), whereas the likelihood of achieving the second function is enhanced by having multiple valves in the line. In the event of a rupture of any component in an instrument line outside of the primary containment, it is important to ensure that the integrity and functional performance of the secondary containment and its associated air treatment systems (e.g., filters and the standby gas treatment system) are maintained. For those instrument lines that are part of the reactor coolant boundary, it is also important to ensure that the rate and the extent of coolant loss from the ruptured component are within the capability of the normal reactor coolant makeup system. Because the likelihood of such a rupture is assumed to be high, the system is designed to result in calculated radiation doses from just such an instrument line failure during normal operation being substantially below the guidelines of 10 CFR Part 100, “Reactor Site Criteria” (Ref. 2) and GDC 19, “Control Room.” The rate of coolant