Radiation

[timfinch]

Why would I deign answer such a silly question?  Who do you think I am that I should answer to your whims?  The question has nothing to with the matter at hand and My knowledge of the submarine is not a matter that is pertinent.  Stay focused.  Be concise and you might lean from your elders.

[timfinch]

I have had a change of heart and I am ready to to make amends on one condition.  The condition is the group answer one single question.  If you were planning a lunar mission what  value would you assign to GCR background radiation,  what would you derive this value from and would it be an daily average?  If the group should answer this question truthfully.  Then I will apologize and in turn answer any and all questions asked of me.

I wouldn't. I would assess the risk and balance those risks against crew safety. I'd test my vessel to make sure it could do what I asked it to do. There is no point assigning an average value: an average of 5 can be derived by values of 4, 5 and 6, or 1, 5 and 9. What you need is an assessment of the probability that your safety values will be exceeded and what you do about it if they are.

I submit you have to have some level of expectation or you could not have any estimation of your ability to protect the safety of your men.  Having some Idea then you could establish a safety margin but to do so without any idea of what to expect is ludicrous.  It was a valiant attempt but comes across as disingenuous.  I respect you more for the attempt than I do the response and as such I will in turn honor it.

[MBDK]

I have had a change of heart and I am ready to to make amends on one condition.  The condition is the group answer one single question.  If you were planning a lunar mission what  value would you assign to GCR background radiation,  what would you derive this value from and would it be an daily average?  If the group should answer this question truthfully.  Then I will apologize and in turn answer any and all questions asked of me.

I wouldn't. I would assess the risk and balance those risks against crew safety. I'd test my vessel to make sure it could do what I asked it to do. There is no point assigning an average value: an average of 5 can be derived by values of 4, 5 and 6, or 1, 5 and 9. What you need is an assessment of the probability that your safety values will be exceeded and what you do about it if they are.

Correct, and a little more explicitly, the mission would be designed with expected doses deigned by the general radiological conditions of the belts (as we know, they can be influenced by a LOT of factors), but more importantly, there would be action level limits if their doses reached certain values (normally still WELL below standard legal limits for radiation workers).  If such an event occurred, there would already be plans to mitigate the astronaut's risk as derived by Health Physicists.  This could range anywhere from keeping a closer watch on current exposures to aborting the mission altogether.  It just depends on so many variables, including mission length, spacecraft designs, space environment (seems like an oxymoron, but it isn't), mission status, etc.  There is also the possibility that the astronauts' yearly limit could be allowed to be exceeded due to special circumstances.  The legal yearly limit is there to minimize the risk associated with exposure.  It is not a line in the sand where people start dropping like flies.

[smartcooky]

I agree that ANY person versed in the operation of a nuclear submarine would know that answer.  Off the top of their head, too.

Well I'm not at all versed in the operations of nuclear submarines, but I can hazard a guess as to where it would be placed and why.

[MBDK]

I agree that ANY person versed in the operation of a nuclear submarine would know that answer.  Off the top of their head, too.

Well I'm not at all versed in the operations of nuclear submarines, but I can hazard a guess as to where it would be placed and why.

Based on the insights I have read in the comments you have posted, I would bet money that you would probably be close to the where and spot on to the why.

[nomuse]

I wouldn't try to find such an average. Plus as someone who has flirted with astronomy, I hate the way extra-solar cosmic rays (essentially stable value and anisotropic, except for the not-small interaction with our own sun's magnetic field) are getting lumped in with solar particles.

Yeah, you could separate out the GCR and plot it over solar cycle and deal with things like Earth and Moon shadow and get some decent numbers. But that still is particle/flux. No way in heck to do a straight-line conversion to "this many grays to a person inside a spacecraft." Even the orientation of the spacecraft matters. Even the duty station of the astronaut matters. And it is different for every energy range.

[nomuse]

I'm still going to point a finger at the NASA report Tim himself linked to, where GCR was one of four potential radiological hazards to be quantified...with another of the four being the glow in the dark switches in the cockpit.

Yeah, this is the sixties. Even the Army started shying from those comparable tritium night sights. But still...!

[timfinch]

I'm still going to point a finger at the NASA report Tim himself linked to, where GCR was one of four potential radiological hazards to be quantified...with another of the four being the glow in the dark switches in the cockpit.

Yeah, this is the sixties. Even the Army started shying from those comparable tritium night sights. But still...!

Don't be quick to dismiss the radiation from old syle glow in the night devices.  They would set off alarms on the submarine the radiation was so high.

[molesworth]

Correct, and a little more explicitly, the mission would be designed with expected doses deigned by the general radiological conditions of the belts (as we know, they can be influenced by a LOT of factors), but more importantly, there would be action level limits if their doses reached certain values (normally still WELL below standard legal limits for radiation workers).  If such an event occurred, there would already be plans to mitigate the astronaut's risk as derived by Health Physicists.  This could range anywhere from keeping a closer watch on current exposures to aborting the mission altogether.  It just depends on so many variables, including mission length, spacecraft designs, space environment (seems like an oxymoron, but it isn't), mission status, etc.  There is also the possibility that the astronauts' yearly limit could be allowed to be exceeded due to special circumstances.  The legal yearly limit is there to minimize the risk associated with exposure.  It is not a line in the sand where people start dropping like flies.

Very well put, and I'm sure the people designing flight profiles for the eventual manned Orion missions are taking just such an approach.  The broader scope of use for Orion means there will be a lot more complexity in mission planning, but the dose calculations will use the virtually the same data we've been going over here ad nauseam - probably just more up to date and accurate.  (It would be interesting to know if any of those thoughts or calculations are available yet.)

Every space mission, whether manned or unmanned, goes through the same sort of process to determine the likely radiation risks to people and equipment.  It's not rocket... oh hang on! 

[Jason Thompson]

That is not a nuke question.  A nuke question would be...

Evasion of simple question noted.

[Jason Thompson]

I have had a change of heart and I am ready to to make amends on one condition.

No, that's not how this works. You have been given conditions to satisfy here. You don't get to dictate what we have to do to earn your apology.

If you were planning a lunar mission what  value would you assign to GCR background radiation,

Irrelevant. You're the one who decided what the background level should be, you're the one who insists on using an average as a minimum (such a fundamental error I can only assume it is deliberate), and furthermore you are the one using an average derived from data collected on the Apollo missions to declare the data from the Apollo missions bogus. Again, such a simple error that I can only assume it is deliberate.

If the group should answer this question truthfully.

I will answer no questions as long as you are the one arbitrarily deciding on if the answer is truthful, since you have already demonstrated a total lack of interest in the actual truth.

Then I will apologize and in turn answer any and all questions asked of me.

Really not how this works.

[Jason Thompson]

I agree that ANY person versed in the operation of a nuclear submarine would know that answer.  Off the top of their head, too.

Hell, I've never even set foot on a submarine, nuclear or otherwise, but even I know where they put the tanks and why on a nuclear one. Tim's evasion of a simpler question and the suggestion he can do the more complex ones is not only not helping his credibility, it's not even written in a credible manner. Looks more like someone using word salad to sound clever than actually a genuine question. For one thing I'm pretty damn sure that emergency shutdown mechanisms are not 'chemical' and are integrated into the reactors, given that all the actual reacting takes place in a sealed and shielded compartment. In an emergency shutdown scenario I wouldn't want to be going to a store somewhere else to get something, then opening the reactor up to use it. This isn't like Spock restarting the Enterprise engines in Star trek II, after all....

[MBDK]

For one thing I'm pretty damn sure that emergency shutdown mechanisms are not 'chemical' and are integrated into the reactors, given that all the actual reacting takes place in a sealed and shielded compartment.

You may want to research that a bit more.

From: http://www.nuclearsafety.gc.ca/eng/reactors/power-plants/nuclear-power-plant-safety-systems/index.cfm

"All nuclear reactors in Canada have two independent, fast-acting and equally effective shutdown systems.

The first shutdown system is made up of rods that drop automatically and stop the chain reaction if something irregular is detected.

The second system injects a liquid, or poison, inside the reactor to immediately stop the chain reaction.

Both systems work without power or operator intervention. However, they can also be manually activated."

NOTE:  Edited to add source and quote, after finding them.

[Northern Lurker]

For one thing I'm pretty damn sure that emergency shutdown mechanisms are not 'chemical' and are integrated into the reactors, given that all the actual reacting takes place in a sealed and shielded compartment. In an emergency shutdown scenario I wouldn't want to be going to a store somewhere else to get something, then opening the reactor up to use it.

Those chemicals are neutron poisons https://en.wikipedia.org/wiki/Neutron_poison. They can be pumped into reactor as a part of SCRAM or in some reactors to help moderating the huge difference in reactivity between new and nearly spent fuel loads, whcich  would be unpractical to control with only control rods.

[Jason Thompson]

Ah, well I stand corrected, thank you, Lurker. I also withdraw my criticism of Tim's question about chemicals for shutdown purposes.

See how easy that was, tim?