Do NERVAs have radioactive propellant?

[jwenting]

Don't forget this was designed in the same era America nuked themselves about 900 times just to **** off the soviets. As long as the astronauts were protected, I doubt they had much concern what kind of radiation they'd be pumping into the upper atmosphere.

and so did the Soviets, and the Chinese, and the French. What was your point again, apart from "evil Americans"?

[Idobox]

I never said it would catch fire. I said that it might release radioactive particles into the atmosphere.

The explosion of the fuel of a Saturn V on the pad would be devastating. 500kT of TNT equivalent, a 2600°C fireball. A nuclear reactor located on top, even if it was protected by a casing, would be obliterated and any fuel rods inside would end up blown to pieces all around the pad. It would be the equivalent of a dirty bomb that would shut down pad operations for years.

It's a solid block of ceramic, on top of the rocket. A launchpad explosion would likely occur in the main stage, so it shouldn't get the worst of the blast. And even if it breaks, it's a solid chunk of ceramic, it might break, even crumble, but it's going to fall on the ground pretty quickly.

On the dirty bomb part, assuming NERVA runs on uranium (couldn't find a source), it would be almost not radioactive at all in the beginning. Highly enriched uranium can held in your hands with just a pair of rubber gloves. Even if it runs on plutonium, it would be quite safe in the beginning.

The thing will be much more dangerous after a few hundred hours of operation, as short lived fission products (the real killers) accumulate.

Dirty bombs would use spent fuel or medical radiation sources, which are much more radioactive and volatile. Blowing up a chunk of enriched uranium would cause some chemical toxicity, probably not much more than what is found on a battlefield (depleted uranium ammo), which is significant (heavy metals are bad), but negligible in the face of an exploding Saturn V (I'm sure there's plenty of nasty stuff in it). The worst effect would probably be public backlash and anti-nukes bleating for years.

[Kryten]

and so did the Soviets, and the Chinese, and the French. What was your point again, apart from "evil Americans"?

NERVA was an american program. Try actually reading the thread before pulling out a strawman.

[shynung]

The worst effect would probably be public backlash and anti-nukes bleating for years.

Not to mention a really heavy blow to the national ego, along with close to 2 years worth of repair work.

When N1 blew up, it took 18 months to rebuild the launch pad. If the same N1 has an NTR upper stage, there could be years before the same pad can ever be used again.

[Sirrobert]

Not to mention a really heavy blow to the national ego, along with close to 2 years worth of repair work.

When N1 blew up, it took 18 months to rebuild the launch pad. If the same N1 has an NTR upper stage, there could be years before the same pad can ever be used again.

And how the hell is that different than any other rocket exploding?

An exploding launch pad has nothing to do with some uranium sitting on top of it or not.

As Idobox just explained, a fresh Nerva/NTR would radiate almost no radiation. Or did you skip over that part?

[xcorps]

Dirty bombs would use spent fuel or medical radiation sources, which are much more radioactive and volatile. Blowing up a chunk of enriched uranium would cause some chemical toxicity, probably not much more than what is found on a battlefield (depleted uranium ammo), which is significant (heavy metals are bad), but negligible in the face of an exploding Saturn V (I'm sure there's plenty of nasty stuff in it). The worst effect would probably be public backlash and anti-nukes bleating for years.

Only when rendered to particles by high speed impact, and then only when ingested, and then due to acute toxicity, not radiation. The mere presence of DU munitions on a battlefield is not harmful.

[sal_vager]

I dunno, having a lump of radioactive material, enough to be fissile and produce enough heat to propel a rocket, sitting on a 105m tower of fuel that happens to explode and collapse does not sound easy to clean up after.

[Sirrobert]

I dunno, having a lump of radioactive material, enough to be fissile and produce enough heat to propel a rocket, sitting on a 105m tower of fuel that happens to explode and collapse does not sound easy to clean up after.

Besides being radioactive (which it's not even that much radioactive), it's also very solid.

It's not ganna turn to ash just because of a little temprature increase

[lajoswinkler]

Saturn V had kerosene, LOX and LH2 in separate containers. I don't see how that would cause an extremely devastating explosion capable of dispersing ceramic material encased in steel. This is not a tank full of premixed compounds and it is not SRB which contains solid fuel, which is prone to cracks and violent explosions.

The reaction would be violent as the tanks break and spill LOX, there would be a fireball, no doubt about that, but I think some of you are imagining something akin to a small yield nuclear device. That would not happen.

When you see a liquid fueled rocket exploding in midair, it is not actually exploding. It's a fireball, a deflagration made by disintegrating structure. If the rocket turns in a wrong direction, the aerodynamic forces are too high and it is ripped to pieces, spilling fuel. This is not a detonation.

You can watch what happens with liquid fuel spillage in this famous youtube video.

[shynung]

As Idobox just explained, a fresh Nerva/NTR would radiate almost no radiation. Or did you skip over that part?

Radiation or not, having uranium nuclear fuel rod fragments scattered on any location would warrant holding back on its further use. Heavy metals have a negative effect, both on the environment and on people living on it. Most likely, some sort of nuclear waste cleanup would have to be conducted, which takes some time, especially in the middle of a launch pad rubble, the result of a 105m rocket exploding.

Edited May 12, 2014 by shynung

[Sirrobert]

Radiation or not, having uranium nuclear fuel rod fragments scattered on any location would warrant holding back on its further use. Heavy metals have a negative effect, both on the environment and on people living on it. Most likely, some sort of nuclear waste cleanup would have to be conducted, which takes some time, especially in the middle of a launch pad rubble, the result of a 105m rocket exploding.

There would be the usual amount of rubble, and some of it would be a little radioactive.

The only precaution needed would be radiationsuits while they clean it up.

Now offcourse that's not counting the public's usual reaction to anything radioactive, but that's not part of the discussion here

[shynung]

There would be the usual amount of rubble, and some of it would be a little radioactive.

The only precaution needed would be radiationsuits while they clean it up.

That may be true. However, I read somewhere else in the science lab that used radiation suits are considered low-level radioactive waste. I'm assuming that most of the waste and rubble that comes close enough to the fuel rod fragments themselves are within this category, though I may be wrong.

Also, I object calling the amount of rubble from an exploding rocket the size of Saturn V as 'usual'. It'd be devastating, NTR or not.

Edited May 12, 2014 by shynung

[Jeff Bird]

A good video about nuclear rockets from 1968.

[Sirrobert]

That may be true. However, I read somewhere else in the science lab that used radiation suits are considered low-level radioactive waste. I'm assuming that most of the waste and rubble that comes close enough to the fuel rod fragments themselves are within this category, though I may be wrong.

Also, I object calling the amount of rubble from an exploding rocket the size of Saturn V as 'usual'. It'd be devastating, NTR or not.

Usual for an exploding rocket.

As in, there being an NTR doesn't change how much debris and destruction there is

[cantab]

I'm quite sure no rocket engineers are stupid enough to expose nuclear fuel rods directly into an expansion chamber that has a direct access to everything outside the rocket. Therefore, I don't think we should expect any significant radioactive materials coming out of an NTR's exhaust gas.

There are some nuclear thermal designs that WOULD severely leak the radioactive fuel, like the open-cycle gas core designs mentioned. Nobody's yet been silly enough to build one though.

Of course, it's a fair point that nuclea-phobia would probably stop a NERVA-like engine flying today. With the possible exception of military purposes where F YEAH 'MURICA can trump OH NOES NUCULAR RADIATION.

The reaction would be violent as the tanks break and spill LOX, there would be a fireball, no doubt about that, but I think some of you are imagining something akin to a small yield nuclear device. That would not happen.

The N1 explosion was huge, reckoned to be among the largest non-nuclear explosions in history, and it was RP-1/LOX. True, it may not be a detonation strictly speaking, but with enough of the stuff that doesn't really matter, so long as it mixes reasonably well. Fuel-air bombs are plenty explosive enough to see military use - and indeed, raise the point that in a rocket failure the fuel can still react with the surrounding air even if it doesn't mix well with the oxidizer.

[shynung]

Usual for an exploding rocket.

As in, there being an NTR doesn't change how much debris and destruction there is

How usual? Last time a rocket comparable to Saturn V exploded on the pad was the N1 disaster, and that created one of the biggest non-nuclear explosions ever made. The presence of an NTR on top of it may not change much of the explosion, but makes the resulting cleanup more complicated.

Edited May 13, 2014 by shynung

[Nibb31]

Saturn V had kerosene, LOX and LH2 in separate containers. I don't see how that would cause an extremely devastating explosion capable of dispersing ceramic material encased in steel. This is not a tank full of premixed compounds and it is not SRB which contains solid fuel, which is prone to cracks and violent explosions.

The reaction would be violent as the tanks break and spill LOX, there would be a fireball, no doubt about that, but I think some of you are imagining something akin to a small yield nuclear device. That would not happen.

The Soviet N-1 explosion was estimated to be equivalent to 0.5 kT of TNT. The W54 nuclear warhead (used in the Davy Crocket nuclear bazooka or the AIM-26 air-to-air missile) ranged from 0.01 to 0.25kT of TNT. So yes, a Saturn V pad explosion would have been akin to a small yield nuclear device.

You can watch what happens with liquid fuel spillage in this famous youtube video.

There are some definite high-energy pad explosions in that video. Detonation or explosion, the payloads of those rockets get a heavy beating. If an NTR had been on top of a Saturn V in the same situation, I would be hard pressed to guarantee that the reactor would survive in one piece.

There would be the usual amount of rubble, and some of it would be a little radioactive.

The only precaution needed would be radiationsuits while they clean it up.

Now offcourse that's not counting the public's usual reaction to anything radioactive, but that's not part of the discussion here

Hazmat suits protect from alpha and beta radiation, not gamma rays which are the worst. The main reason they use hazmat suits is to avoid contamination of skin and clothes. They throw them away after use and they still have to limit exposure to gamma radiation.

The only way to safely clean up in a radioactive environment is to rotate crews while limiting exposure time. That's why most of the Chernobyl liquidators survived by only working for a few minutes each on the site. They brought in thousands of men by train for only a few minutes work. It requires organization and lots of manpower and it's expensive.

Some of the public's reaction to nuclear energy is irrational, but that's not a reason to blankly dismiss the real dangers and precautions that are necessary.

Edited May 13, 2014 by Nibb31

[Kryten]

Hazmat suits protect from alpha and beta radiation, not gamma rays which are the worst. The main reason they use hazmat suits is to avoid contamination of skin and clothes. They throw them away after use and they still have to limit exposure to gamma radiation.

Then it's a good thing there wouldn't be any gamma, isn't it? Fresh reactor=no fission products=only alpha emitters, this has been pointed out twice already. Comparisons to Chernobyl are ridiculous.

[Red Iron Crown]

The only way to safely clean up in a radioactive environment is to rotate crews while limiting exposure time. That's why most of the Chernobyl liquidators survived by only working for a few minutes each on the site. They brought in thousands of men by train for only a few minutes work. It requires organization and lots of manpower and it's expensive.

I'm thinking remotely controlled cleanup robots could help immensely here. Who cares how much radiation the robot accumulates, as long as it keeps functioning? I don't think the technology was mature enough for the Chernobyl cleanup, but today it could be different.

[YNM]

Who cares how much radiation the robot accumulates, as long as it keeps functioning? I don't think the technology was mature enough for the Chernobyl cleanup, but today it could be different.

Really ? Then why radiation-hardened electronic hardwares are "old" in terms of specs compared to anything else ?

[Sirrobert]

How usual? Last time a rocket comparable to Saturn V exploded on the pad was the N1 disaster, and that created one of the biggest non-nuclear explosions ever made. The presence of an NTR on top of it may not change much of the explosion, but makes the resulting cleanup more complicated.

I don't know, and I don't give a hoot. "Usual amount" just means the precense of an NTR won't add a substantional amount of debris.

Then it's a good thing there wouldn't be any gamma, isn't it? Fresh reactor=no fission products=only alpha emitters, this has been pointed out twice already. Comparisons to Chernobyl are ridiculous.

It's amazing how little people know about radioactive stuf, versus how much they THINK they know.

This is one awesome example of people knowing gamma rays exist, and asuming it's the default

Really ? Then why radiation-hardened electronic hardwares are "old" in terms of specs compared to anything else ?

He said AS LONG AS IT KEEPS FUNCTIONING.

Radiation will wreck electronics, but if you have those shielded, than there are no problems

[Red Iron Crown]

Really ? Then why radiation-hardened electronic hardwares are "old" in terms of specs compared to anything else ?

Radiation hardening has been mature for a long time, true. I meant that remote-controlled robot technology was not mature enough then. It existed, but probably not cheap enough to be treated as disposable. Look at the relatively recent proliferation of remote-controlled robots for surveillance and ordnance disposal, the tech has gotten much more affordable and reliable in the last decade or two.

[Psycix]

One of the fun things regarding reactor safety is that the NERVA is practically a nuclear reactor cooled by liquid hydrogen.

Can you imagine a more effective way to cool something than pumping cryogenic liquid hydrogen through it with a rocket engine's turbopump?

[Red Iron Crown]

Can you imagine a more effective way to cool something than pumping cryogenic liquid hydrogen through it with a rocket engine's turbopump?

Pumping water through it? Liquid hydrogen is quite cold, but its specific heat is very low compared to water.

[Psycix]

Nice point, but remember that the leidenfrost effect will form an isolating barrier of steam

This is one of the main challenges in conventional nuclear reactor design, the hotter the reactor is, the better the bubbles insulate the core.