I was thinking the same thing when reading the intro - remember reading one of the stories in Digital -er- Analog SFM (ca 1974).
A few years ago, Scientific Amrican published a piece on possible space propulsion methods. One was using lasers and a "solar sail" credited to Robert Forward. I wrote the editor saying that Niven and Pournelle came up with the idea in the early 70's - Niven used it in a short story - and it was used in "The Mote in God's Eye" (noted that someone else made reference to escaping the Coalsack). The editor came back with a very lame reply about Forward being the first "scientific" inventor (completely ignoring the fact that Pournelle has a PhD and that Forward and Pournelle undoubtedly know each other) - that's when I gave up subscribing to SciAm.
Solar Sail: my first exposure to that was A.C. Clarke's "Sunjammers" (AKA "Wid From the Sun") that appeared in the June (?) 1964 issue of Boy's Life. CLarke predicted that computers in the 1980's would be the size of a box of kitchen matches...
SMES (Superconducting Magnetic Energy Storage) probably does have an advantage over ultracaps for the moment, but there are enough interesting applications for ultracaps that they will soon pull ahead of SMES.
IANAL, but from reading both the EFF webpage and the PDF of the FCC report and order - it would seem that one loophole is for devices sold only intrastate. I would presume that CA would probably ban the manufacture of such devices, but some states may not give a rat's behind about the MPAA.
As far as "who is responsible", do you honestly think that AccuWeather or Landmark Communications (Weather Channel) would be in business if you could sue them for incorrect forecasts?
This is probably the strongest argument against an exclusively private weather service. The private companies are probably better off with the public having free access to NWS forecasts just for reducing liability.
As I've mentioned elsewhere, the functions of the NWS are entirely consistent with the "general welfare" and "interstate commerce" clauses of the Preamble to the US Constitution (and also the "National Defense" caluse as well - weather is important to military operations).
IMHO, the information provided by the NWS clearly falls into the categories of promoting "general welfare" and "interstate commerce" as mentioned in the preamble of the US Constitution.
The gent from Accuweather wrote an article for Scientific American a few years ago. His arguments for privatizing weather don't make any more sense now than they did a few years ago.
We can get really high Isp's with electric propulsion, but a lot of the advantage is lost when the mass of the power source is figured in (solar cells or nuclear). With microwave power, it is easy to make a low-mass, very efficient power collector.
I am neither a physicst nor a nuclear engineer, but something about that statement just doesn't look right. I'm pretty sure that being at the critical point is just a nudge away from "an earth-shattering kaboom."
I got my MS degree in Nuclear Engineering and can say that critical is the normal state of operation for a nuclear reactor. It is not a nudge away from an earth shattering boom.
"Crtical" means that the reactor is generating exactly one neutron for every neutron that is absorbed or escapes - it means the reactor is running at constant power. Virtually all power reactors are designed so that any "nudges" will tend to cause an increase in neutron absorption or leakage and thus causing to power to decrease.
One really, really important concept to grasp is "delayed neutrons" - approximately 0.65% of the neutrons from fissioning U-235 are delayed slightly - so a slight increase in reactivity translates into a doubling time of minutes or hours instead of milliseconds (without delayed neutrons, operating a reactor would be a lot like Heinlein's "Blowups Happen" - nobody knew anything about delayed neutrons when the story was written in 1940).
Chernobyl - the reactor was near the end of core life, which meant that the primary fissile material was Pu-239, which has a delayed neutron fraction of 0.2%. The combination of Pu-239 loading, that day's operating history and the design of that reactor meant that it had a positive void coeffiecient. To make matters worse, the scram rod actually increased reactivity during initial insertion. The reactor was scrammed, and power levels increased, which led to more boiling, which led to more reactivity (remember positive void coefficient), which led to more power, which led to more boiling - which in a short time led to the reactivity equalling the delayed neutron fraction (called "prompt critical") and that's when the serious shit started happening. And one more thing - since the reactor was graphite moderated and the graphite was not in good thermal contact with the fuel (as in the case with an HTGR) - the only thing that would stop the reaction was fuel melting or graphite melting - the result is history.
The standard light water reactors use the water as both coolant and moderator - get too many voids in the coolant and the reactor shuts down.
600 years, by the way, is how long it would take the waste to be *less* radioactive than the ore it was mined from IF we recycled the usable fuel.
IIRC, that data point was from a paper by Pigford and Chen - and the timespan has been increased somewhat since the paper was published (a few thousnad years) - and please note that the course I took on fuel cycles was taught by Pigford.
Your point is valid - by isolating nuclear waste on a timescale that falls within human experience (think "King Tut's" tomb laying undisturbed for 3,000+ years) it will decay into something about the same toxicity as the original ore.
If the fuel is recycled into an Integral Fast Reactor (IFR), the time it takes for the decay prodcuts to drop down to the original ore levels will probably be close to 600 years - the IFR will convert the long-lived transuranics to short-lived transuranics. The IFR project has been closed down by the DOE, but it took a long time to close down.
Do the world a favor and whenever you see a site that relies on flash without an alternative, send an email to the owner of the site informing him that his web designer is an incompetent moron (though you might want word it a bit nicer than that).
If it is any kind of commerce site, it may be more effective to point out that the site may be covered by regulations requiring accessibility (e.g. ADA). The US government is requiring all government sites to be "accessible" and it is possible that having an accessible website will be required for doing business with the US government (though I wouldn't hold my breath on that).
The second piece of software, the back-end, was written by a guy named Jörg Schilling.
I believe Schilly also wrote "mkisofs" as the front end to "cdrecord" (or "cdrw -i" in my case). It might be a bit more effort to create the iso image before burning the CD, but I'd rather have error messages come up before trying roast a CD-R.
It has been amusing reading the comments Schilly makes about Linux and Linus making comments about Schilly's SCSI layer. Schilly has a copy of the source code for Solaris 8 (acquired from Sun) and states that it is a lot cleaner than Linux source code.
The American public was in no mood to go to war even as late as the eve of December 7th. The only reason that the US declared war on Germany was that Germany first declared war on the US - although FDR was flagrantly violating the Neutrality Act with his prodding of the German U-boats in late 1941.
There was a very good reason for the American public's reluctance to go to war - 82,000 US troops died in the 5 month period of June to November 1918 - the wartime propoganda machine told some real whoppers about what was going on in Europe that were later revealed for the lies that they were - Wilson had basically abolished the Bill of Rights for the duration - and after the war ended, France imposed conditions on Germany that virtually guaranteed another war. The sentiment was that the war was Europe's problem.
The Europeans had their chance to avert war in 1938 - Germany didn't have a chance before the Munich peace talks - The betrayal of the Czech's was a double win for Hitler - he didn't have to devote resources defending against the Czech army and he got some really nice arms factories.
Remember, the fighting in Europe started when Poland was invaded by Germany and the Soviet Union!
The war with Japan was another story - the US Navy had been planning for a Japanese attack since 1900. The public was aware of the war going on in China since 1931 - and some news of the Rape of Nanking made it to the US, which got about the same level of response as the Rwandan massacres...
Re:Real implications of cheap solar power
on
Solar Cells Get Boost
·
· Score: 2, Interesting
Let's look at what the real implications of cheap solar power are:
One very valuable use for cheap electricity is desalinating seawater. Normally arid areas bordering on an ocean or large sea (think places like Baja California, North Africa, even Saudi Arabia) will have access to significant amounts of very fresh water - probably won't be cheap enough for rice farming, but certainly cheap enough for moderately high-value crops.
Reverse osmosis is not as energy intensive as you might think - current technology needs 800 psi to desalinate sea water (about a 2,000 foot pressure head) - and 2,000' is about what the Colorado River aqueduct traverses to get to coastal souther California.
The real issue with solar energy isn't watts/m^2 of panel, but watts/$.
Watts/m^2 is still important...
The economics of solar power get really interesting when the price gets down to $1/w. For a 10% efficiency, the installed cost of the array needs to come in at $100/m^2 (~$10/ft^2) - at 50% efficiency we're talking $500/m^2 (~$50/ft^2). I would hazard a guess that the support structure and glazing would come in around $10/ft^2 (or more). The last point makes low efficiency cells kind of a non-starter, unless made to replace roofing materials.
what makes Robertson's better is that you can put a screw on the screwdriver and it'll stay there without falling at lower angles than the Philips... and the square shape is also less likely to fray, compared with the cross angles of the Philips.
You're missing one of the chief advantages of the Phillips - that the screwdriver will cam-out when the screw is all the way in. For situations where cam-out is undesirable, typical American practice is to use hex pattern and Allen wrenches (which are available in both "english" and metric sizes).
The advantage of the 'Metric' paper sizes is obvious, the mill only makes one size stock (A0) and (someone) can cut it to any requested size without loss.
Say what?!
You can do exactly the same thing with US customary paper sizes. Cutting an 11 by 17 shet in half gives you 8.5 by 11 - a 17 by 22 will yield two 11 by 17 - and so on.
Unfortunately we've all been lied to by our physics teachers.
In my case it was my fluid mechanics professor - the textbooks made it very clear that pounds were a unit of force, e.g. pounds per square inch. To remove ambiguity, references were made to "pound mass" (lbm) versus "pound force" (lbf). As you said, there is precedence for using pounds as mass units - which isn't as disgusting as using grams/kilograms as force (weight) units.
You are correct in stating that a balance beam measures mass, but I will assert that a spring scale (strain gauge included) measures weight. The conversion does require agreeing on a "standard gravity".
I swear, I don't know which was worse: learning the truth about Santa or or the truth about slugs
Slugs can be very useful: 1 pound of force is required to accelerate a mass of 1 slug at a rate of 1 foot per second squared. This is exactly equivalent to saying 1 newton of force is required to accelerate 1 kg of mass at a rate of 1 meter per second squared. The metric system would have been much nicer had the meter been defined to be a factor of 9.80665 longer - then a kilogram would have weighed one newton at a standard gravity.
Along these lines, there are several other non-SI units that will take a long while to go away:
Measuring atmospheric pressure in mm or inches of mercury (latter is standard for aviation).
Oil is sold in units of barrels (42 US gallons).
Most states in the US regulate the sale price of natural gas in price per 10e6 BTU (which is approximately 1,000 cu. ft.)
Relay racks will be 19 inches wide, height in multiples of 1.75 inches and use 10-32 screws.
And the "what were these guys smoking?" award goes to HO scale: 1'=3.5mm
4 by 8 foot plywood sheets will be here a long time (in the US).
Plumbing will remain in inch sizes for the forseeble future (in the US)
RR track guage will remain 4'8.5" (a standard that's too entrenched to be replaced by better (read wider - 1.8m?) choices)
There are too many things in the US that have been standardized on "English" units for it to go completely metric in the next half century. Metric is creeping in where convenient, e.g. 2 liter soda bottles and metric pitch for surface mount components. On the other hand, the US uses 120V/60Hz power, Europe uses 230V/50Hz and I don't see either Europe or the US making changes. I suspect we will see a true paperless economy before the US switches from letter to A4 size paper.
Unfortunately, this is like the other fsck'ing Disney sites that only allows entry if you have the latest and greatest in Flash players - which don't seem to be available in anything but WindBlows.
But 110V transformers and motors tend to run somewhat hotter than their 220V cousins.
That would be true if the 110V motors and xfrmrs used the same conductor size as their 220V brethren, typically a 110V unit will have half as many turns and twice the individual conductor area as a 220V unit (copper losses would be identical). Transformers designed to run on both 110 and 220 with dual windings end up with exactly this case - windings are in parallel for 110 and series for 220.
A transformer designed for 50/60 Hz will have lower copper losses at 60 Hz and possibly lower core losses (depends on whether the higher frequency or higher peak flux hurts the most).
I think it's fair to [say] 220V is less likely to lead to fire than 110V (reduced current).
If the wires are properly sized, then there should be no difference between fire potential of 110 versus 220. Also bear in mind that 220 should have thicker electrical insulation than 110 and good electrical insulators are usually good thermal insulators (notable exceptions are BeO and diamond).
One project I've worked on a couple of years ago involved making damn sure that wiring was being operated well within the thermal limits (a couple of the cables were carrying 90+ amps continuously). A fire in this case would have been -um- messy.
The B-36 got two to three years of extra operational life for the simple reason that the first generation of fusion weapons were too big to fit in a B-52. Later generation fusion weapons were smaller - figure the warhead on Titan II was on the order of two meters diameter and maybe two meters high.
A 10 MT Hf bomb would be putting out about 100 KW of heat - which would make it pretty easy to spot. All-in-all, even if a Hf bomb was possible, it would much simpler building a conventional nuke.
What had DARPA excited was the possibility of a fuel with much higher energy content than chemical fuels without the neutron shielding problems of a conventional reactor. 2.45 MeV photons are basically stopped by Compton scattering, so while you would want a lead shield around the reactor, the primary gamma ray absorber could be any goor refratory material.
Doesn't that mean that a ten megaton hafniabomb would be the size of one million golf balls? That's pretty big...
That would be my assumption as well. Remember a volume of 1 million golf balls would be a sphere 100 times larger than a golf ball - which is maybe a factor of 2 to 4 larger than a 10 MT nuke.
Anyway, reason for size
Splitting U-235 releases 207 MeV
Gamma from Hafnium is 2.45 MeV
Slashdot Mirror
Funny, I've been seeing these asymmetric brown creatures running around - and things seem to be working better - the coffee is simply wonderful.
A few years ago, Scientific Amrican published a piece on possible space propulsion methods. One was using lasers and a "solar sail" credited to Robert Forward. I wrote the editor saying that Niven and Pournelle came up with the idea in the early 70's - Niven used it in a short story - and it was used in "The Mote in God's Eye" (noted that someone else made reference to escaping the Coalsack). The editor came back with a very lame reply about Forward being the first "scientific" inventor (completely ignoring the fact that Pournelle has a PhD and that Forward and Pournelle undoubtedly know each other) - that's when I gave up subscribing to SciAm.
Solar Sail: my first exposure to that was A.C. Clarke's "Sunjammers" (AKA "Wid From the Sun") that appeared in the June (?) 1964 issue of Boy's Life. CLarke predicted that computers in the 1980's would be the size of a box of kitchen matches...
SMES (Superconducting Magnetic Energy Storage) probably does have an advantage over ultracaps for the moment, but there are enough interesting applications for ultracaps that they will soon pull ahead of SMES.
To make things even more interesting, Solaris 10 is built on top of SunOS 5.10 - naive version checking algorithms are going to choke on that.
IANAL, but from reading both the EFF webpage and the PDF of the FCC report and order - it would seem that one loophole is for devices sold only intrastate. I would presume that CA would probably ban the manufacture of such devices, but some states may not give a rat's behind about the MPAA.
But once "their" IP hits the airwaves, the rules do get changed a bit.
And isn't an airport something that's used in Interstate Commerce???
Technically they have no authority to govern intrastate radio emissions.
One question - just WTF is the difference between intertstate and intrastate radio emissions??
Use of the Radio spectrum is covered by international agreements - which pretty much guarantees that this is a Federal not state matter.
This is probably the strongest argument against an exclusively private weather service. The private companies are probably better off with the public having free access to NWS forecasts just for reducing liability.
As I've mentioned elsewhere, the functions of the NWS are entirely consistent with the "general welfare" and "interstate commerce" clauses of the Preamble to the US Constitution (and also the "National Defense" caluse as well - weather is important to military operations).
The gent from Accuweather wrote an article for Scientific American a few years ago. His arguments for privatizing weather don't make any more sense now than they did a few years ago.
We can get really high Isp's with electric propulsion, but a lot of the advantage is lost when the mass of the power source is figured in (solar cells or nuclear). With microwave power, it is easy to make a low-mass, very efficient power collector.
I got my MS degree in Nuclear Engineering and can say that critical is the normal state of operation for a nuclear reactor. It is not a nudge away from an earth shattering boom.
"Crtical" means that the reactor is generating exactly one neutron for every neutron that is absorbed or escapes - it means the reactor is running at constant power. Virtually all power reactors are designed so that any "nudges" will tend to cause an increase in neutron absorption or leakage and thus causing to power to decrease.
One really, really important concept to grasp is "delayed neutrons" - approximately 0.65% of the neutrons from fissioning U-235 are delayed slightly - so a slight increase in reactivity translates into a doubling time of minutes or hours instead of milliseconds (without delayed neutrons, operating a reactor would be a lot like Heinlein's "Blowups Happen" - nobody knew anything about delayed neutrons when the story was written in 1940).
Chernobyl - the reactor was near the end of core life, which meant that the primary fissile material was Pu-239, which has a delayed neutron fraction of 0.2%. The combination of Pu-239 loading, that day's operating history and the design of that reactor meant that it had a positive void coeffiecient. To make matters worse, the scram rod actually increased reactivity during initial insertion. The reactor was scrammed, and power levels increased, which led to more boiling, which led to more reactivity (remember positive void coefficient), which led to more power, which led to more boiling - which in a short time led to the reactivity equalling the delayed neutron fraction (called "prompt critical") and that's when the serious shit started happening. And one more thing - since the reactor was graphite moderated and the graphite was not in good thermal contact with the fuel (as in the case with an HTGR) - the only thing that would stop the reaction was fuel melting or graphite melting - the result is history.
The standard light water reactors use the water as both coolant and moderator - get too many voids in the coolant and the reactor shuts down.
IIRC, that data point was from a paper by Pigford and Chen - and the timespan has been increased somewhat since the paper was published (a few thousnad years) - and please note that the course I took on fuel cycles was taught by Pigford.
Your point is valid - by isolating nuclear waste on a timescale that falls within human experience (think "King Tut's" tomb laying undisturbed for 3,000+ years) it will decay into something about the same toxicity as the original ore.
If the fuel is recycled into an Integral Fast Reactor (IFR), the time it takes for the decay prodcuts to drop down to the original ore levels will probably be close to 600 years - the IFR will convert the long-lived transuranics to short-lived transuranics. The IFR project has been closed down by the DOE, but it took a long time to close down.
If it is any kind of commerce site, it may be more effective to point out that the site may be covered by regulations requiring accessibility (e.g. ADA). The US government is requiring all government sites to be "accessible" and it is possible that having an accessible website will be required for doing business with the US government (though I wouldn't hold my breath on that).
I believe Schilly also wrote "mkisofs" as the front end to "cdrecord" (or "cdrw -i" in my case). It might be a bit more effort to create the iso image before burning the CD, but I'd rather have error messages come up before trying roast a CD-R.
It has been amusing reading the comments Schilly makes about Linux and Linus making comments about Schilly's SCSI layer. Schilly has a copy of the source code for Solaris 8 (acquired from Sun) and states that it is a lot cleaner than Linux source code.
There was a very good reason for the American public's reluctance to go to war - 82,000 US troops died in the 5 month period of June to November 1918 - the wartime propoganda machine told some real whoppers about what was going on in Europe that were later revealed for the lies that they were - Wilson had basically abolished the Bill of Rights for the duration - and after the war ended, France imposed conditions on Germany that virtually guaranteed another war. The sentiment was that the war was Europe's problem.
The Europeans had their chance to avert war in 1938 - Germany didn't have a chance before the Munich peace talks - The betrayal of the Czech's was a double win for Hitler - he didn't have to devote resources defending against the Czech army and he got some really nice arms factories.
Remember, the fighting in Europe started when Poland was invaded by Germany and the Soviet Union!
The war with Japan was another story - the US Navy had been planning for a Japanese attack since 1900. The public was aware of the war going on in China since 1931 - and some news of the Rape of Nanking made it to the US, which got about the same level of response as the Rwandan massacres...
One very valuable use for cheap electricity is desalinating seawater. Normally arid areas bordering on an ocean or large sea (think places like Baja California, North Africa, even Saudi Arabia) will have access to significant amounts of very fresh water - probably won't be cheap enough for rice farming, but certainly cheap enough for moderately high-value crops.
Reverse osmosis is not as energy intensive as you might think - current technology needs 800 psi to desalinate sea water (about a 2,000 foot pressure head) - and 2,000' is about what the Colorado River aqueduct traverses to get to coastal souther California.
Watts/m^2 is still important...
The economics of solar power get really interesting when the price gets down to $1/w. For a 10% efficiency, the installed cost of the array needs to come in at $100/m^2 (~$10/ft^2) - at 50% efficiency we're talking $500/m^2 (~$50/ft^2). I would hazard a guess that the support structure and glazing would come in around $10/ft^2 (or more). The last point makes low efficiency cells kind of a non-starter, unless made to replace roofing materials.
You're missing one of the chief advantages of the Phillips - that the screwdriver will cam-out when the screw is all the way in. For situations where cam-out is undesirable, typical American practice is to use hex pattern and Allen wrenches (which are available in both "english" and metric sizes).
US surveyors typically use tapes marked in units of 0.01 foot (slightly smaller than 1/8 inch).
Say what?!
You can do exactly the same thing with US customary paper sizes. Cutting an 11 by 17 shet in half gives you 8.5 by 11 - a 17 by 22 will yield two 11 by 17 - and so on.
In my case it was my fluid mechanics professor - the textbooks made it very clear that pounds were a unit of force, e.g. pounds per square inch. To remove ambiguity, references were made to "pound mass" (lbm) versus "pound force" (lbf). As you said, there is precedence for using pounds as mass units - which isn't as disgusting as using grams/kilograms as force (weight) units.
You are correct in stating that a balance beam measures mass, but I will assert that a spring scale (strain gauge included) measures weight. The conversion does require agreeing on a "standard gravity".
I swear, I don't know which was worse: learning the truth about Santa or or the truth about slugs
Slugs can be very useful: 1 pound of force is required to accelerate a mass of 1 slug at a rate of 1 foot per second squared. This is exactly equivalent to saying 1 newton of force is required to accelerate 1 kg of mass at a rate of 1 meter per second squared. The metric system would have been much nicer had the meter been defined to be a factor of 9.80665 longer - then a kilogram would have weighed one newton at a standard gravity.
Along these lines, there are several other non-SI units that will take a long while to go away:
Measuring atmospheric pressure in mm or inches of mercury (latter is standard for aviation).
Oil is sold in units of barrels (42 US gallons).
Most states in the US regulate the sale price of natural gas in price per 10e6 BTU (which is approximately 1,000 cu. ft.)
Relay racks will be 19 inches wide, height in multiples of 1.75 inches and use 10-32 screws.
And the "what were these guys smoking?" award goes to HO scale: 1'=3.5mm
4 by 8 foot plywood sheets will be here a long time (in the US).
Plumbing will remain in inch sizes for the forseeble future (in the US)
RR track guage will remain 4'8.5" (a standard that's too entrenched to be replaced by better (read wider - 1.8m?) choices)
There are too many things in the US that have been standardized on "English" units for it to go completely metric in the next half century. Metric is creeping in where convenient, e.g. 2 liter soda bottles and metric pitch for surface mount components. On the other hand, the US uses 120V/60Hz power, Europe uses 230V/50Hz and I don't see either Europe or the US making changes. I suspect we will see a true paperless economy before the US switches from letter to A4 size paper.
Unfortunately, this is like the other fsck'ing Disney sites that only allows entry if you have the latest and greatest in Flash players - which don't seem to be available in anything but WindBlows.
That would be true if the 110V motors and xfrmrs used the same conductor size as their 220V brethren, typically a 110V unit will have half as many turns and twice the individual conductor area as a 220V unit (copper losses would be identical). Transformers designed to run on both 110 and 220 with dual windings end up with exactly this case - windings are in parallel for 110 and series for 220.
A transformer designed for 50/60 Hz will have lower copper losses at 60 Hz and possibly lower core losses (depends on whether the higher frequency or higher peak flux hurts the most).
I think it's fair to [say] 220V is less likely to lead to fire than 110V (reduced current).
If the wires are properly sized, then there should be no difference between fire potential of 110 versus 220. Also bear in mind that 220 should have thicker electrical insulation than 110 and good electrical insulators are usually good thermal insulators (notable exceptions are BeO and diamond).
One project I've worked on a couple of years ago involved making damn sure that wiring was being operated well within the thermal limits (a couple of the cables were carrying 90+ amps continuously). A fire in this case would have been -um- messy.
The B-36 got two to three years of extra operational life for the simple reason that the first generation of fusion weapons were too big to fit in a B-52. Later generation fusion weapons were smaller - figure the warhead on Titan II was on the order of two meters diameter and maybe two meters high.
A 10 MT Hf bomb would be putting out about 100 KW of heat - which would make it pretty easy to spot. All-in-all, even if a Hf bomb was possible, it would much simpler building a conventional nuke.
What had DARPA excited was the possibility of a fuel with much higher energy content than chemical fuels without the neutron shielding problems of a conventional reactor. 2.45 MeV photons are basically stopped by Compton scattering, so while you would want a lead shield around the reactor, the primary gamma ray absorber could be any goor refratory material.
That would be my assumption as well. Remember a volume of 1 million golf balls would be a sphere 100 times larger than a golf ball - which is maybe a factor of 2 to 4 larger than a 10 MT nuke.
Anyway, reason for size
Splitting U-235 releases 207 MeV
Gamma from Hafnium is 2.45 MeV