Author Topic: Lead-cooled nuclear reactors in space?  (Read 576 times)

Offline Nilof

  • Full Member
  • ****
  • Posts: 889
  • Liked: 357
  • Likes Given: 537
Lead-cooled nuclear reactors in space?
« on: 11/26/2017 11:59 PM »
So basically, improvements in corrosion-resistant steels have made it possible to build liquid metal cooled nuclear reactors using pure molten lead as a coolant, and there is a company with significant funding pursuing this for mini-reactors that can be shipped to remote locations by airplane:

http://www.leadcold.com/index.html

So I was naturally wondering about possible space applications? Afaik, all nuclear reactors that have flown in space so far have been of the liquid metal cooled type. Lead-cooling has the advantage of using a coolant that can not be neutron activated, so the coolant itself can double as radiation shielding, and the pool of lead will naturally solidify and contain the fuel in the event of an anomaly. For powering a large HSF base, the hands off nature and inherent safety seems quite desirable.
« Last Edit: 11/27/2017 04:11 AM by Nilof »
For a variable Isp spacecraft running at constant power and constant acceleration, the mass ratio is linear in delta-v.   Δv = ve0(MR-1). Or equivalently: Δv = vef PMF. Also, this is energy-optimal for a fixed delta-v and mass ratio.

Online john smith 19

  • Senior Member
  • *****
  • Posts: 6184
  • Everyplaceelse
  • Liked: 825
  • Likes Given: 5143
Re: Lead-cooled nuclear reactors in space?
« Reply #1 on: 11/30/2017 07:40 PM »
So I was naturally wondering about possible space applications? Afaik, all nuclear reactors that have flown in space so far have been of the liquid metal cooled type. Lead-cooling has the advantage of using a coolant that can not be neutron activated, so the coolant itself can double as radiation shielding, and the pool of lead will naturally solidify and contain the fuel in the event of an anomaly. For powering a large HSF base, the hands off nature and inherent safety seems quite desirable.
Lead cooled (or Lead Bismuth Eutectic) have been used on various  Russian submarine designs since the 1960's

In space it's been Sodium, Sodium Potasium Eutectic. But AFAIK a lot of those are not pipes full of molten metal but heat pipes, with much smaller amounts of metal liquid/vapor in sealed tubes.

Point being one tubes weld fails it vents 1 tubes Sodium. Rest of system continues to operate.

Lead's attractive because it's cheap (about 1/10 the cost of Bismuth) and could (hypothetically) run with natural convection, eliminating the (very) expensive metal pumps needed to make the fuel move. Running lead only significantly reduces (but does not elmininate) the Polonium, which is an intense Alpha emitter.

Not to mention that no fast reactor has made it to commercial service and all need fuel that's much more enriched (19.9% is is actually low by fast standards) by normal LEU standards (most PWR run around 3-45% U235 enriched Vs 0.7% natural). BTW IRL most PWR do breed some of their U238 (it's i]fissile[/i] and can be bread to fissionable)  and have done for some time.

Anyone looking to design a new reactor should be thinking about the Balance-of-Plant problems. PWR Steam turbines are about 10x the price of normal 550c turbines that are driven by pretty much all non gas turbine combustion systems. That's why the British AGR systems of the 70's were targeted around that operating temperature. The technology is available from multiple mfgs and is well understood. It's why modern combustion power plants can run 40-45% efficient (and more if you can harvest the "waste" heat for district heating systems).
[EDIT BTW the lat people to try this were Toshiba with their 4S fast spectrum, Sodium cooled external moderator design.

IIRC one of the environmental pressure groups killed it with a letter pointing out how much power it would need to start it from cold once it got to site.

Lead's melting point is much higher than Sodium or NaK eutectic or PbLi, so will need a lot more electricity to bootstrap it.

Unless attitudes have changed a lot the same letter will kill this system as well.  :(

TBH all of these SMR's seem to come from people with large pre-existing agenda which are trying to shoe horn their notions into what's needed, rather than starting from the position "What's the cheapest way to do this as a system" None of which seem to be addressing those issues.

IOW "The random punishment beatings will continue until morale improves" to coin a phrase.   :( ]
« Last Edit: 12/04/2017 07:35 PM by john smith 19 »
"Solids are a branch of fireworks, not rocketry. :-) :-) ", Henry Spencer 1/28/11  Averse to bold? You must be in marketing."It's all in the sequencing" K. Mattingly.  STS-Keeping most of the stakeholders happy most of the time.

Offline stefan r

  • Member
  • Posts: 62
  • pennsylvania
  • Liked: 7
  • Likes Given: 12
Re: Lead-cooled nuclear reactors in space?
« Reply #2 on: 12/05/2017 08:32 PM »
...
Lead's attractive because it's cheap (about 1/10 the cost of Bismuth) and could (hypothetically) run with natural convection, eliminating the (very) expensive metal pumps needed to make the fuel move...

How does natural convection work in space?

Online john smith 19

  • Senior Member
  • *****
  • Posts: 6184
  • Everyplaceelse
  • Liked: 825
  • Likes Given: 5143
Re: Lead-cooled nuclear reactors in space?
« Reply #3 on: 12/06/2017 06:35 AM »
...
Lead's attractive because it's cheap (about 1/10 the cost of Bismuth) and could (hypothetically) run with natural convection, eliminating the (very) expensive metal pumps needed to make the fuel move...

How does natural convection work in space?
Badly of course.  :)

However if the OP meant "Off Earth" then in Mars, Venus or Titan it will work fine.

The vast bulk of Lead or Lead Bismuth Eutectic experience is powering Russian submarines, where natural circulation eliminates pump noise.  In space that's not an issue and nor is the pump costs. Note that a submarine reactor is around 40-60MW and huge by current space nuclear standards (SNAP10a was c30Kw thermal). OTOH stationary power plants typically start at 250MW and run to 1GW+ levels.
"Solids are a branch of fireworks, not rocketry. :-) :-) ", Henry Spencer 1/28/11  Averse to bold? You must be in marketing."It's all in the sequencing" K. Mattingly.  STS-Keeping most of the stakeholders happy most of the time.

Tags: