Document: NRC Regulatory Guide
Document ID: de79d411-4fc9-456e-a5a0-f4a910ca4c9a
Document Type: regulatory_guide
Title: Assumptions Used for Evaluating a Control Rod Ejection Accident for Pressurized Water Reactors (Rev. 2)
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML2111/ML21119A157.pdf
Revision Date: 2023-05
Chapter: 
Section ID: RG-1.77
CFR Part: 
CFR Title: 

Content:
r within the guidelines of Table 2 located at a nearby stationary facility; (2) the largest shipping container within the guidelines of Table 2 that is frequently transported near the site; or (3) the largest container stored on site. For multiple shipping containers of equal size, the evaluation should consider failure of only one container unless the failure of that container could lead to successive failures. For the largest container stored on site, the evaluation should consider the total release from this container unless the containers are interconnected in such a manner that a single failure could cause a release from several containers. ACAs result in a long-term, low-leakage-rate, continuous release. Most onsite chlorine releases experienced to date within NPPs have been ACAs, involving leakage from valves or fittings and resulting in a long-term release with a leakage rate from near zero to less than 1 pound of chlorine per second. Given warning, the CR operator needs only a breathing apparatus to be protected from ACAs. However, because such a release might continue unabated for many hours, a self-contained breathing apparatus, a tank source of air with manifold outlets, or equivalent protection capable of operation for an extended period should be available. For example, the continuous release of hazardous chemicals from the largest safety relief valve on a stationary, mobile, or onsite source within the guidelines of Table 2 should be considered. For both types of accidents, MCAs and ACAs, the evaluation should consider release of contents during an earthquake, tornado, or flood for chemical container facilities that are not designed to withstand these natural events. In the evaluation of CR habitability, it may also be appropriate to consider hazardous chemical releases coincident with the radiological consequences (e.g., a design-basis loss-of-coolant accident for plants that are vulnerable to both events simultaneously) and demonstrate that such