What are the major differences between reactors on subs and carriers, and reactors at power plants? Why is the government so secretive about its naval reactors?
There is little difference between the naval reactors and the USA land power station reactors. They are both all pressurised water reactors.
For example, Canada UK and Japan don’t use pressurised water reactors at all,
while the USA uses them exclusively. This highlights that “major difference” is due to the country operating them.
Is the USA government/Navy super secretetive about their reactors ?
There have been four designers of the naval use reactors,
“W” for Westinghouse, “G” for General Electric, “C” for Combustion Engineering, and “B” for Bechtel, and more for the land based reactors which are very very similar in design and operation.
So the government has provided details of what they want to four different companies, and the companies are the ones to actually design and build.
Here’s a photo of the old reactors being stored at the totally secretive trench 94.
Its such a secret thing, they decided to hide these things in plain sight !
Actually USA’s military strategy is more about informing the world about its power than to do things all hush hugh … “you must have been seeing things, we dont have that” ,etc.
Unlike civilian power reactors, U.S. and British naval reactors are fueled with weapons-grade uranium. Given access to that material, it would be straightforward to construct a rudimentary “gun type” fission bomb. By contrast civilian power reactors use low-enriched uranium which cannot easily be used for weapons.
U.S. and British naval reactors use this design because (1) They are compact, (2) It enables rapid power changes, and (3) It prolongs the refueling life.
It is possible to build a practical naval reactor without using highly enriched uranium and some countries have done this, but it entails tradeoffs.
Aside from this the general design of both naval and civilian power reactors are somewhat similar: they both generally use pressurized water and thin, zirconium-clad fuel elements. This was not necessarily the best architecture for civilian power reactors, but under Admiral Rickover, naval reactors were developed first and he convinced the commercial manufacturers to use a similar design.
My understanding, and I will confirm this later today, is that secrecy when it comes to our naval ships relates to safety systems/equipment/procedures.
My understanding, and this is just a wild-assed guess, is that the secrecy only involves things like high-efficiency low-noise pump impeller design.
Nuclear submarines were known to be noisier than submarines operating on batteries. The obvious difference is the noise of the nuclear reactor, which is the noise of the pumps, fluid, and turbines (??).
Low-loss fluid flow was a technically difficult design problem in cars, and pump impeller design was a technically difficult problem everywhere.
Do you suppose the navy reactors are considerably more advanced?
Could civilian nuclear reactors use U-235 HEU, and go decades without refueling as well?
(Yes, a very bad political idea, but technically/scientifically possible?)
I would assume the primary difference is the naval reactor is designed to minimize size and weight, while a civilian PWR is meant to be cheaper to maintain and it probably has more redundant cooling systems. The ultimate plan if a naval reactor catastrophically fails is there is a way to vent seawater into the core, and, apparently, it will not escape containment.
We know this from the 2 submarines lost on the bottom of the ocean - their reactor cores are not leaking. Probably this is because the pipes that burst when the pressure inside gets too high let seawater flow in and out, and convection must keep the core from melting through the side of the submarine.
To reduce size and weight, they use purer fuel, which is obviously a big problem for a civilian reactor, because the replacement fuel rods can be turned into a fission bomb quite easily if enough of them were stolen.
Another difference, from a friend who was a reactor tech, is naval reactor shielding is imperfect and you are not permitted to enter the reactor compartment while it is at power. Just the distance and the walls of the reactor compartment are part of the shielding.
I read that back in the day, Soviet submariners would have sperm samples frozen in the USSR prior to deployment, just in case a reactor mishap or radiation exposure made them infertile. Wonder if U.S. Navy submariners ever had to do that?
There are civilian research reactors that use HEU. They are typically smaller/lower power than naval reactors, and often focus on producing radiation for variety of research
Civilian power reactors are larger power. You don’t want them running on heu. When the USSR imploded, the US bought plutonium and possibly heu and blended it down for use in civilian reactors.
You have nuclear safeguard, cost and safety issues to worry about…
> the U.S. Navy and United Kingdom’s Royal Navy almost exclusively use an HEU enrichment that is as high as or
higher than that used in nuclear weapons.
> Other navies, such as the Russian Federation and the Indian Navy, typically use
HEU that is enriched in the 40 percent to 50 percent range, approximately one half that of the typical enrichment for nuclear
weapons.
> Finally, the remaining navies (France and China) that have nuclear-powered vessels use LEU fuel, most of which is enriched to a level of less than 10 percent.
The design approach behind naval reactors is different, focusing on space, weight, ability to respond quickly to varying power demand, noise and enabling long life between refueling. There are apparently other considerations also…Eg the fuel alloy claddings differ from research reactors, naval reactors may operate at higher temperatures and resist xenon ‘poisoning’ of the reaction (radioactive xenon builds up)
Etc.
Clearly they could be designed to do so.
Could an existing civilian design simply be fueled with very different fuel and still work correctly? IANA nuke anybody but it’s a pretty good bet the answer is “no”.
All these machines are a lot more complicated than a campfire. Even cooking over a campfire must be done differently depending on which wood, how big, or whether you’ve got some coal in there too.
At a bare minimum, the control systems are designed to manage a particular neutron and heat flux distributed a certain way. Very different fuel will produce different results. Some engineering margins someplace will be adversely affected by these differences. So you’ll either get burn-through, reaction instability, or flat inability to control the reaction. Imagine trying to drive your car where a mere 1/8" press on the gas pedal was enough to redline the engine. It’d be [del]darn hard[/del] impossible to control.
a minor point- GE commercial power reactors tend to be Boiling Water Reactors, which are a bit different despite also using pressurized water as the moderator, coolant, and working fluid. Biggest difference is they send steam directly from the reactor vessel to the turbines instead of having a separate loop with heat exchangers.