Document: NUREG-0800
Document ID: 7e9d3620-7a94-488e-b2d5-992282113080
Document Type: srp
Title: NUREG408OO
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0523/ML052350480.pdf
Revision Date: 2023-06
Chapter: 7
Section ID: 7
CFR Part: 
CFR Title: 

Content:
r-operated isolation valve (MOIV) and two check valves are provided in series between each safety injection tank and the reactor coolant (primary) system. The MOIVs must be considered to be "operating bypasses" because, when closed, they prevent the safety injection tanks from performing the intended protec- tive function. IEEE Std 279 has a requirement for "operating bypasses" which states that the bypasses of a protective function will be removed automati- cally whenever permissive conditions are not met. This Branch Technical Position provides specific guidance in meeting the intent of IEEE Std 279 for safety injection tank MOIVs. It should be noted that BTP ICSB 18 (PSB), "Application of the Single Failure Criterion to Manually-Controlled Electrically-Operated Valves," also applies to these isolation valves and should be used in conjunction with this position. B. BRANCH TECHNICAL POSITION The following features should be incorporated in the design of M0IV systems for safety injection tanks to meet the intent of IEEE Std 279: 1. Automatic opening of the valves when either primary coolant system pressure exceeds a preselected value (to be specified in the technical specifications), or a safety injection signal is present. Both primary coolant system pressure and safety injection signals should be provided to the valve operator. 2. Visual indication in the control room of the open or closed status of the valve. 3. Bypassed and inoperable status indication in accordance to Regulatory Guide 1.47. | 4. Utilization of a safety injection signal to remove automatically (override) any bypass feature that may be provided to allow an isolation valve to be closed for short periods of time when the reactor coolant system is at pressure (in accordance with provisions of the technical specifications). C. REFERENCES 1. Arkansas 1, Unit 1, Safety Evaluation Report, January 23, 1973. 2. IEEE Std 279, "Criteria for Protection Systems for Nuclear Power Generating Stations." 7A-5