Re:
Pipe line pressure drop is proportional to length, but inversely proportional the 5th power of the internal diameter. Increasing pipe ID from 10” to 12” will reduce pressure drop by over 50% if the pipe length also increases by 20%, nearly 60% if the overall pipe length and bend ratios are unchanged.
Flow induced noise is proportional to pressure drop, all other things being equal.
Yup, and going back to the original contention, the primary requirement of natural circulation within nuclear reactors is to reduce friction flows. Given, one can increase pipe diameter but as I have mentioned and you have questioned, one can also reduce piping.
If piping design has been significantly improved in Virginias, the assumption can be made that the S9G is likely to use natural circulation as well.
And the corrollary is that it undermines the basis that the S8W is actually the quietest reactor. I don't think there is sufficient public information to confirm either way.
Nobody uses a 2 loop BWR because the turbine will be exposed to radioactive steam and become too radioactive to access, let alone perform repairs, except using remotes. It will also have to be inside the primary containment
And nobody uses a BWR on board a ship because you have to use a reactor design with a 0 [zero] void coefficient, or be subject to core irregularities very time the vessel rolls, pitches, or accelerates in any direction.
That will probably explain why the Russkis are crazy enough to use a single loop arrangement for the Juliets. My sole reason for highlighting the BWRs is just to rebut the view that the 3 loop system is the sole loop arrangement for nuclear reactors.
If we're on the topic of submarine nuclear reactors, the russkis use single/four or six loop arrangements.
As to BWR application to ship propulsion, one can read this.
http://www.energyfromthorium.com/pdf/NSP_chap07.pdf
THE APPLICATION OF BOILING WATER REACTORS TO SHIP PROPULSION - MATHIEU - 2009 - Journal of the American Society for Naval Engineers - Wiley Online Library
Your rationale is a very 1950s point of view. There's a bit of research out there addressing the issue.
The only reason why only light water reactors are used by the USN is because of the Defense Authorisation Act that requires a standard reactor type for all naval vessels. The Act itself does contradict the contention that the S9G is that much fundamentally different from the S8W though.
Commercial Gen III reactor designs (all types) only rely strictly on natural circulation to dispose of residual heat after a shutdown (7% of output immediately after shutdown, less than 1% after 1 hour). They all use pumps during normal operation.
Commercial Gen III reactor designs that use water as a moderator are much large, around 1000 MWe, and the cores are larger than equivalent Gen II designs to permit greater spacing between the tubes to reduce pressure drop. Height has also become important to increase the ‘chimney effect’ that drives natural circulation.
Yup, but we know that commercial power generators operate at high/max power most of the time for max cost efficiency. In a ship/submarine case, nuclear reactors do not need to operate at max power. Power usage is equate to the speed required.
We know that natural circulation will occur in a PWR primary loop (in the absence of pumped flow) whenever buoyant forces caused by differences in loop fluid densities are sufficient to overcome the flow resistance of loop components (steam generators, primary coolant pumps, etc.).
The reason why natural circulation is able to be achieved in gen III designs is simply because the loop fluid densities are a lot higher than in the past achieved by several technologies eg coolant, design etc.
That's why hints in FAS like the S9G has higher "energy density" in the reactor core indicates the likelihood that natural circulation is also a capability in low power operations.
S9G Next Generation Reactor
Same thing with 3rd gen and 4th gen reactors in russki subs.
Chap. 2: Nuclear-powered vessels - The Russian Northern Fleet
It is interesting to note that if natural circulation is also used in Russki subs, why aren't their subs that much quieter... the reason could be that its not just the cooling pumps that create noise.
The land based reactor was a test rig, like a test stand for an automobile engine. When the testing was finished they reused it to test the S6W because they have the same output rating. The S6W was designed for attack subs, the S8G was designed for ballistic missile subs. The outputs are nearly the same, but other design requirements are different.
It is only your assumption and your word alone that the design requirements are different. I'm not so sure anyone can justify that attack subs do not require acoustic stealth as much as SSBNs.
It can also be argued that if the new design is easier to find and track than an Ohio that it is a failure. If the S9G can meet the requirement for silent operation, then by all means use it. But major design guideline for the S9G was to make it more compact to fit into a smaller hull, NOT silent operation as it was for the S8G.
The OK-650 is used for both the Sierra attack sub (single reactor) and the Typhoon SSBN (dual reactor). Why can't the S9G can't be used in the same manner?
Are you saying attack subs don't operate silently? It is only your assumption that the S9G is a noisy reactor.
The refueling problem may only be solvable with a new reactor design, which will probably be larger, requiring a larger hull. Sometimes you can only choose between the least worst solutions.
Agreed. However, I would remind your contention is that the S8W should be used to reduce development cost. The whole debate is predicated on the assumption that the development cost of a new reactor is a constraint ie which existing reactor can be used. I am merely highlighting that the S9G would be a better candidate than the S8W on the reasons mentioned.
The Sherman tank used an aircraft engine, which meant that they had to use gasoline for fuel. The crews nicknamed them ‘Ronsons’ because “It lights every time” (advertising jingle). The Germans called them ‘Tommy Cookers’ for the same reason.
Not the best idea. A lot like using a powerplant design for a SSN in a modern SSBN.
The example is merely to highlight cross-use of equipment. Same thing with the OK-650 reactors used for both attack subs and SSBNs. I agree it may not be the best solution. But the so called best solution may also be the most expensive solution.
I will agree to disagree here if you will refrain from using noise comparisons between the Los Angeles class and the Virginia class as argument that the S9G is as good or better than the S8W in that area.
Actually that was gf who compared it. My contention is merely that the Virginias are not noisy subs. I also provide an explanation of why the Virginias are quieter than the LAs but no comparisons made.
