The NRC has another meeting scheduled for tomorrow January 16 at 9am EST to discuss post-Fukushima safety changes to US reactors. The meeting will allow for public comment and will be webcast. Details of the safety changes to be discussed at the end of this post.
One of the issues to be covered at the meeting is the vent systems for BWR reactors (the same design as Fukushima). The NRC has been considering requiring filtered vents after it was found that the venting systems at Fukushima released large amounts of contamination to the atmosphere. The US nuclear industry is fighting these vent systems, wanting instead to either not install them at all or create a complicated process to re-invent the wheel and create different filter systems at each reactor. Europe has had these standardized vent systems for decades. This is the standard system used in Europe, it consists of an outside water tank that can be used to filter venting gasses from both the suppression chamber and the containment structure. Currently the containment structure has no filtering mechanism. The suppression chamber when appropriately filled with water can act as a sort of filter but many conditions during an accident can cause the suppression chamber to not have water in it, removing that filtering ability.
The standard filtration system used in Europe involves a water tank housed outside the reactor.
Filtered vent system at Chooz nuclear plant, France.
Filtered vent system at Leibstadt nuclear plant, Switzerland.
Filtered vent system diagram at Leibstadt nuclear plant.
Tier 1 recommendations :
2.1 Seismic and flood hazard reevaluations
2.3 Seismic and flood walkdowns
4.1 Station blackout (SBO) regulatory actions
4.2 Equipment covered under Title 10 of the Code of Federal Regulations (10 CFR)
5.1 Reliable hardened vents for Mark I and Mark II containments
7.1 SFP instrumentation
8 Strengthening and integration of emergency operating procedures, severe
accident management guidelines (SAMGs), and extensive damage mitigation
9.3 Emergency preparedness regulatory actions (staffing and communications)
The second tier consists of those NTTF recommendations which could not be initiated in the near term due to factors that include the need for further technical assessment and alignment, dependence on Tier 1 issues, or availability of critical skill sets. These actions do not require long-term study and can be initiated when sufficient technical information and applicable resources become available.
The Tier 2 recommendations:
7 SFP makeup capability (7.2, 7.3, 7.4, and 7.5)
9.3 Emergency preparedness regulatory actions (the remaining portions of Recommendation 9.3, with the exception of Emergency Response Data System (ERDS) capability addressed in Tier 3)
The third tier consists of those NTTF recommendations that require further staff study to support a regulatory action, have an associated shorter-term action that needs to be completed to inform the longer-term action, are dependent on the availability of critical skill sets, or are dependent on the resolution of NTTF Recommendation 1. The staff has focused its initial efforts on developing the schedules, milestones, and resources associated with Tier 1 and Tier 2 activities. Hence, information regarding the Tier 3 recommendations is not included in the enclosure. Once the staff has completed its evaluation of the resource impacts of the Tier 1 and Tier 2 recommendations, it will be able to more accurately
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