Small Modular Naval Reactors

[gmax137]

It isn't clear to me what exactly is meant by SMR in this thread. See the latest news in the thread on NuScale's SMR, https://www.physicsforums.com/threa...reactor-project-in-idaho.1057305/post-6983730

 

[Astronuc]

It isn't clear to me what exactly is meant by SMR in this thread. See the latest news in the thread on NuScale's SMR, https://www.physicsforums.com/threa...reactor-project-in-idaho.1057305/post-6983730

US NRC - "The NRC refers to light water reactor (LWR) designs generating 300 MWe or less as small modular reactors (SMRs)."
https://www.nrc.gov/reactors/new-reactors/smr.html

Typically a reactor would be coupled to its own power conversion system. I do not see a common power conversion system. A larger capacity unit might share containment with another unit, but there are issues with refueling then.

In the case of nuclear scale, the original idea was to have up to 12 reactors in a shared containment, with each reactor in a bay. They reactor module sits in a large pool of water in common to all 12 units. For refueling, the plan was/is to decouple the reactor from it's power conversion system, bring the reactor module to a refueling bay, open the reactor and refuel, then return to its operating bay, reconnect to the power conversion system, and voilà startup and run.

NuScale had in mind an inherently safe reactor design, so small plant footprint and emergency planning zone (EPZ), and economy of order couple of units, then a couple more, until the site is filled out to the desired number. They could have done 12, 8, or 6, or 4, which would be up to the utility. In small towns, maybe 1 or 2 would suffice.
For example - https://www.nrc.gov/reactors/new-re.../current-licensing-reviews/nuscale-us460.html (6 * 77 MWe = 462 MWe)

Different size concepts have very different ideas. So much for standardization.

 

[gmax137]

Thanks, @Astronuc !
But still, what is it about say NuScale's SMR that would make it a better marine reactor than the S9G or whatever the US navy is using in the current submarines?

 

[Astronuc]

Thanks, @Astronuc !
But still, what is it about say NuScale's SMR that would make it a better marine reactor than the S9G or whatever the US navy is using in the current submarines?

I don't think NuScale's design would be better than an S9G, or whatever the Navy uses. They are two different animals - different purposes - different operating environment.

Perhaps as a merchant marine propulsion reactor, it might work.

NuScale's design is a derivative of LWR (PWR) technology, which like the NS Savannah's reactor back in the day.
https://en.wikipedia.org/wiki/NS_Savannah#Reactor
I think mPower and a W design were closer in concept to the Savannah reactor - basically putting the steam generator on top of the core, or as close to it as possible. Still the main issue is neutron leakage and activation of the surrounding structures (the RPV and containment). Refueling is another issue.

 

[Vanadium 50]

Submarine reactors are very complicated things, and kind of tangential to this discussion. I'll just say that the S2G reactor design was....wow. Just wow.

It is also worth pointing out that submarines are dangerous beasts. The Bonefish fire, on a modern non-nuclear submarine, is an excellent example. The fact that only three lives were lost and not the entire boat was nothing short of miraculous.

As for shipping, most vessels are registered or "flagged" in countries other than their corporate base. Panama is the most popular, but also Liberia, the RMI, Mongolia, Bolivia, among others. Note that some of these countries are landlocked. The UK has about a fifth as many ships as Panama, the US 10% of the UK, and Australia 10% of that (14 ships).

 

[gmax137]

Submarine reactors are very complicated things, and kind of tangential to this discussion. I'll just say that the S2G reactor design was....wow. Just wow.

Yes, but at least back in the 1950s there was a willingness to try lots of new ideas.

 

[Vanadium 50]

Liquid sodium in an underwater vessel? What could possibly go wrong? (And the Alfa showed that people didn't learn)

Other stupid idea: Soviet Quebec ("Zippo") class - carrying liquid oxygen on board. What could go wrong there?
Hey, let's put radar on a submarine (USS Triton).
US Barbel class. Who needs nuclear power when you have diesels? And, for extra credit, lets put more torpedo tubes where the sonar goes. With enough ammo, you don't need to be able to find your target!

 

[gmax137]

I don't know much about the S2G reactor (other than the sodium). The Wikis on Seawolf, S2G, and S1G are interesting. How about this (https://en.wikipedia.org/wiki/USS_Seawolf_(SSN-575)):

On 18 April 1959, the Navy disposed of the radioactive S2G plant by sealing it in a 30-foot high stainless steel containment vessel, towing it out to sea on a barge, and then sinking the barge at a point about 120 miles due east of Maryland in 9,100 feet of water. Twenty-one years later, the Navy was unable to relocate the container, but said that the radioactive materials inside should decay before the containment vessel deteriorated.

As Lou Reed said, "those were different times..."

 

[Vanadium 50]

Probably better than grinding it up and disbursing the dust over an unfriendly nation.

 

[Astronuc]

IAEA has a publication on Small Modular Reactors for Marine-based Nuclear Power Plant

https://aris.iaea.org/Publications/2023 IAEA Marine Based SMR Booklet.pdf

 

[Astronuc]

I just happened to read a CNN article on SMRs.
https://www.cnn.com/2024/02/01/clim...russia-china-climate-solution-intl/index.html

This technology is also being used below sea level. Dozens of US submarines lurking in the depths of the world’s oceans are propelled by SMRs, as the compact reactors are known.

No, not really, or at least, not entirely accurate. Perhaps using a lose definition of 300 MWe or less, which the NRC uses for land-based reactors. Most references mention 'naval reactors'.
https://www.nrc.gov/reactors/new-reactors/smr.html

The NRC does not regulate naval reactors, which are under DOE/NNSA and DOD/Navy.
https://www.energy.gov/nnsa/powering-navy

the Naval Nuclear Propulsion Program, a joint Department of Navy and Department of Energy organization responsible for all aspects of the Navy’s nuclear propulsion, including research, design, construction, testing, operation, maintenance, and ultimate disposition of naval nuclear propulsion plants.

https://www.navy.mil/Press-Office/News-Stories/Article/3476093/naval-reactors-celebrates-75-years/

From the CNN article

At the COP28 climate talks in Dubai in December, the US led a pledge to triple the world’s nuclear energy capacity, which 25 nations have now signed onto. And the US government has earmarked $72 million to its international SMR program, known as FIRST, to provide countries with a whole suite of tools — from workshops to engineering and feasibility studies — to provide them with everything they need to buy an SMR fleet made in America.

But bigger money is coming in the form of loans from state financial institutions, like the US Export-Import Bank and its International Development Finance Corporation, which have offered up $3 billion and $1 billion, respectively. Those have gone to two SMRs in Poland designed by GE Hitachi Nuclear Energy, a US-Japanese partnership headquartered in North Carolina.