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
CFR Part: 
CFR Title: 

Content:
power is lost. Not having an isolation valve inside containment makes it even more important that there be a high degree of assurance that the instrument line from the containment out to and including the outside valve retains its integrity during normal reactor operation and under accident conditions. This assurance can be provided by taking the following four actions: 1. locating the valve as close to containment as practical, 2. adopting a conservative approach in the design of this section of the line, 3. implementing suitable quality assurance provisions, and 4. performing suitable visual inservice inspections. Performing periodic visual inspections should not increase the probability of damaging the instrument lines. In addition, provisions may be needed to protect against accidental damage of the lines and to ensure that pipe whip, missiles, or other mechanisms created by the failures of one line will not induce failures of any other line. Sufficient experience with valves of a similar type should be available that demonstrates a high likelihood a valve will not close when the instrument line is intact and its safety function is required but that it will close if the instrument line is ruptured downstream. In the event of a rupture downstream of the valve, the valve should close automatically or be capable of being readily closed during normal reactor operation and under accident conditions. In addition, the valve should reopen or be capable of being readily reopened under the conditions that prevail when reopening it is appropriate. It should not be necessary to externally backfill an instrument line to reopen a closed isolation valve with an intact downstream line. It is desirable to have an indication of the valve position status (opened and closed) in the control room because without such an indication, a valve may remain closed, thus impairing instrument functions for an excessive period of time. For remotely operable valves, the operator needs