etudiant said:
Thank you for the additional clarification.
This makes the industry's reluctance to install or retrofit such scrubbers more puzzling to me.
It seems like a fairly inexpensive retrofit/upgrade well worth the hassle in regulatory grief avoided.
I still do not understand how this can be effective while venting a megawatt power steam plume.
Is the vent path changed to include this unit if/when the cooling water runs out?
As someone who works in a design department for a nuclear power plant, this type of modification is drastically more complex than it looks on the surface.
For one, you are extending containment to a location outside of the plant. You also have to add new penetrations to the containment which have a design to fail the containment in a controlled fashion. Fun fact, the primary containment is one of the only pressure vessels in all of the ASME code which is allowed to have no overpressure protection, due to the fact that it is contrary to nuclear safety for design basis accidents. There is no regulatory guidance or analysis which even supports doing something like this in the US, and if any plant did go out of their way to install it, it is very likely that it would cost easily 15-20 million dollars, and would require a rework if/when the NRC finally decides to put together regulatory guidance which explains what they think containment venting should look like.
Some design considerations that would have to be looked at (if I was preparing this engineering change authorization). Soil below where the vent unit is going to go will need geological reviews. A seismically capable pad needs to be built. The entire pipe route from containment to the vent unit and back to the elevated release point (which extends outside of secondary containment) needs seismic and weather/severe accident proof enclosures around it, and every piece of that needs calculations to determine the maximum theoretical force it can withstand to prove that it can exceed severe accident scenarios. All my leak rates for my primary and secondary containment need to be recalculated, and leak rate testing needs to be reperformed (which is challenging on the containment). The penetration work on the containment cannot be performed online, and would likely require an extended outage (not to mention that new containment penetrations have a potential risk of going bad...see crystal river 3). A lot of this work will have to go out to large external engineering firms who have the experience doing a lot of this analysis.
For me to replace a single section of pipe, or replace a single indicator in the control room, it takes about 70-80 pages of paperwork total (forms, drawing updates, authorizations, reviews, licensing analysis, testing requirements, parts list, programs impacts, procedure/training impact reviews, new vendor manuals, update forms for the master equipment list and the design basis database). For something like this, a new filter, it would likely be several thousand pages, cost over 10 million dollars in just engineering services, and take about 2 years to complete. At that point it doesn't matter if it is a "small" or "Simple" filter, the overhead cost in making changes to ASME pressure boundaries and extending containment outside of the plant is relatively astronomical. Plus when all is said and done, I need the NRC to agree to a license amendment and safety review, as this change absolutely is more than a minimal increase in the consequences of an accident (see 10CFR50.59). It takes about 1 year for the NRC to review these things, and they charge about 272 dollars per hour right now.
That's my view of it based on my experience as a design engineer at a nuclear power plant.