radiation hardening 101
TRANSCRIPT
8/3/2019 Radiation Hardening 101
http://slidepdf.com/reader/full/radiation-hardening-101 1/6
Radiation Hardening 101: How To Protect Nuclear Reactor Electronics
Slashdot
Digg
StumbleUpon
delicious
POSTED BY: THE IEEE SPECTRUM EDITORIAL STAFF / TUE, MARCH 22, 2011
Tucked behind shielding, most of the electronics in a working nuclear reactor are no more exposed to radiation than
the humans that operate them. Problems like the loss of coolant in Japan’s damaged Fukushima reactors can
change that, boosting radiation to levels that can threaten control systems and robots that might be sent in for
repairs.
How do you protect or “harden” electronics to prevent radiation damage? And are the electronics at the Fukushima
Dai-1 nuclear power plant tough enough? IEEE Spectrum Associate Editor Rachel Courtland asked Dan Fleetwood ,
an expert in radiation-resistant devices at Vanderbilt University in Nashville, Tennessee, to take us through the
basics.
How does radiation pose a problem for electronics?
Radiation can ionize atoms and disrupt a semiconductor's crystal structure. For electronics that are very close to a
reactor, neutrons will create physical damage to the semiconductor crystal. But most chips will fail first because of
leakage that’s associated with the charging of insulators. In something like a metal-oxide-semiconductor device, for
8/3/2019 Radiation Hardening 101
http://slidepdf.com/reader/full/radiation-hardening-101 2/6
example, gamma rays and x-ray radiation will knock electrons off atoms in an insulator to create electron-hole pairs.
The resulting trapped positive charges will shift the operating characteristics. Devices are designed to turn on and off
at a well-defined point of operation, and if that operating voltage shifts, this can create difficulties.
How do you protect or “harden” electronics against radiation in a nuclear reactor?
It involves all aspects of design, process, and testing. At a power plant there are usually design criteria to keep the
most basic operating and control electronics relatively simple and relatively robust so that you can have an event likea loss of coolant and maintain control of the plant.
There are special processing techniques that are used to make the insulators more resistant to the consequences of
having electrons knocked out. There are ways to process insulators, for example, so that there are fewer defects,
which reduces the number of sites where positive charges can be trapped, and there are ways to dope the regions
between transistors to make devices more resistant to the effects of radiation.
Nuclear power plants may also have the most critical electronics shielded in enclosures made of lead or some other
very dense material that can help protect them from radiation.
How good can radiation hardening get?
The annual, whole-body limit for radiation workers is usually set in the range of 20-50 millisieverts, or 2-5 rads. Most
commercial electronics can survive radiation levels in silicon of at least 500 to 1000 rads. Some commercial devices
can survive levels higher than that but you’re just never sure when it’s going to lose functionality unless detailed
testing has been done in advance. The most radiation-hardened electronics can survive levels of radiation that are
hundreds of thousands of times greater than what a human can survive, more than a million rads.
The higher the dose the less likely you will be able to find a commercial integrated circuit to handle it. Radiation-
hardened electronics are typically anywhere from two to four generations behind commercial electronics in terms of
their performance. It takes extra time to do the additional engineering.
Can a reactor’s electronics survive a meltdown?
Certainly in the 1960’s [when the first Fukushima reactors were built], people were very aware of the risks due to
radiation and there were choices of electronics that could be made that would increase the resistance to radiation by
a lot.
Very basic control circuits can be made to withstand exceedingly high levels of radiation, but they’re very simple in
terms of function. They’re not the kinds of electronics that you could use to run the entire plant. They would just be
used to maintain the capability of being able at some point to turn cooling systems on or perform critical switching andcontrol functions.
Is it possible that electronics in the damaged Fukushima reactors could be used to boot the cooling system
back up?
That’s a question of how bad the damage is. My guess is the electronics are probably not the weak link there. The
mechanical systems could be the weak link just because of the physical damage that appears to have occurred as a
result of the explosions that have been reported. It’s also possible that there could be some failures in the electronics
that might recover with time. Not all the effects of radiation exposure are permanent.
TAGS: JAPAN // JAPAN NUCLEAR EMERGENCY // NUCLEAR EMERGENCY // EARTHQUAKE // NUCLEAR ENERGY // NUCLEAR POWER // RADIATION // RADIATION-HARDENED // TSUNAMI
Comment FAQ Comment Policy
Use my avatar from...
No avatar
My computer Top of Form
8/3/2019 Radiation Hardening 101
http://slidepdf.com/reader/full/radiation-hardening-101 3/6
Use my avatar from...
http%3A%2F%2
Bottom of Form
My Facebook Profile
My Google Profile
My Twitter Account
My Yahoo! Account
Gravatar email
Login
Login with:
My Facebook Profile
My Google Profile
My Twitter Account
My Yahoo! Account
My OpenID
Your name (
Share
Share with:
This Page
My Facebook Friends
My Google Friends
My Twitter Followers
My Yahoo! Friends
This Page
8/3/2019 Radiation Hardening 101
http://slidepdf.com/reader/full/radiation-hardening-101 4/6
<span s tyle="color: #808080;">W
Follow
Cancel Post
Leave a commentControls
Echo 6 Items
Admin
Log In
Edit My Profile
Follow
Moderation
General Settings
Admin Notices
–
Harold "Hal" Frost, Ph.D. This blog was a wonderful idea, having an expert like Dan, an IEEE 'servant', give a beginner's '101' tutorial onradiation hardening of engineering materials, electronics, and so on. He provided a common sense approach for usall, such as delineating the radiation responses of electrically insulating materials from those of semiconductor andindicating that radiation-hardened electronics performance levels are generations away from those of electronicsused in nominally rad-free environments. Some comments, though, to help expand the scope of the discussion:
It is harder to design and make rad-hard electronics packages to perform adequately in radiation environmentswhen these packages draw and control power-level currents as opposed to the much smaller signal-level currentsused to process data from sensors, hard disk drives, and keyboards for assembling and transmitting commands tocontrollers mounted on hardware such as motors, pumps, and valves. The scope of radiation effects on materialsis broader than just on dielectrics; mechanical and chemical properties can also be affected. And, it is possible tointrinsically 'design in' radiation hardness to materials used on electronics and other apps, such as by choosing themore stable crystalline structures of the fluorite type. Finally, there is a long history of research work on theeffects of nuclear radiation in all types on monolithic materials (and interfaces between dissimilar materials) whichincorporates not only rad damage expected in civilian nuclear fission reactors but also in civilian thermonuclearfusion reactors currently on the drawing boards, such as inertial confinement fusion and magnetic fusion energy.
8/3/2019 Radiation Hardening 101
http://slidepdf.com/reader/full/radiation-hardening-101 5/6
Concerning this fourth point, ITER is a machine of the latter type for which an international facility is currentlybeing built in France. Would it not it be nice, then, if IEEE took the bull by the horns, so to speak, and organizedthe disparate engineering societies into a mega-society large enough to allow cross-fertilization of ideas andexchange of data on rad effects on materials, whether used (for ex.) in producing energy, exploring space viasatellites or deep space probes, hardening national power grids from potential damage from solar-induced EMPs, oradvancing medicine via improved imaging machines for diagnosing illnesses in patients? Thanks for theopportunity to comment on a topic important to the future energy security of the globe, let alone of just one
country like Japan, the U.S. or France, for example. Indeed, in decades ahead, materials engineering and sciencewill be found to be even more crucially important to realizing safer and more sustainable ways of generatingelectric power via either type of nuclear energy.Today, 12:45:32 AM
– Flag – Like – Reply – Delete – Edit – Moderate
Scaliger Q1: GPS antenna is necessarily exposed. It is also crucial for outdoor autonomous navigation.
- Can it be hardened, especially for perfect performance also while being irradiated, then?Q2: Can Consumer Electronics survive the Neutron beams recorded yesterday at Fukushim?Yesterday, 5:42:07 PM
– Flag – Like – Reply – Delete – Edit – ModerateLiked by
stan
Calvin H Woosnam Dan Fleetwood got most of it right here. The true cause of the Reactor loss of control was a combination of theEarthquake and the Tsunami severing power and control between the Control Room and the individual Reactors.After more than 14 yrs of Loss Investigation work and 40+ years in computers and electronics I discovered the real
failure behind most disasters is not the Critical Electronic Components, but instead the failure of the power andcommunications circuits we spend so little time on insuring can survive the most basic of everyday disasters. Thenew CSA C22.2 No. 267-10 Life Safety Wiring Standard and the original FHIT 17 CI lev 3 UL Specification whichdrove this New Standard clearly identifies that off the shelf current (Riser, Plenum, 90C, Mil-Spec) solutionsdeemed fire safe are infact wholly inadequate. This led UL, ULC, BRE, LPCB and CSA to agree a New WiringStandard was necessary for this all important category of Life Safety. My company therefore set out to not only
assist in writing this New ASPCA standard but also getting it Publicly Published November 26, 2010. NEC, CEC andIEC Code Book Organizations are in the process now of including this new Life Safety Standard in all applicationsthey deem needing better protection. Imagine a cable supplying power, control and communications to the
Reactors that is not only Radiation Resistant, but also able to withstand 2600+ lbs of stress and more than 500+lbs of crush resistant while able to withstand more than 1000 C, this would not have failed in this case loosingcontrol and power to the cooling systems that are at the heart of this current problem. Support the New ASPCAStandard and lets call for end to this gambling with life. Yesterday, 2:10:37 AM
– Flag – Like – Reply – Delete – Edit – ModerateLiked by
stan
3 Guests
Jorma Nieminen In order to provide any further comment or idea there is a need for information of the actual radiation intensityinside the reactor building at the control room.
In my understanding, based on the above physical description of the failure mechanisms of irradiatedsemiconductors, instead of annual dose more useful would be data about the maximum intensity of radiationaround the location of control electronics with all those components. Does such information exist on Fukushimareactors? What order of magnitude compared to the risk levels given above?
My very heuristic guesstimate, based on diverse general information from world media, is that in Fukushima wewould be quite far from any real risk level. Is this correct initerpretation of the situation?
Jorma Nieminen
8/3/2019 Radiation Hardening 101
http://slidepdf.com/reader/full/radiation-hardening-101 6/6
Yesterday, 1:31:12 AM
– Flag – Like – Reply – Delete – Edit – ModerateLiked by
stan
haghgoo The U.S. media's story is absolutely not the truth about the radiation levels. Japanese media as well as RussiaToday have reported that radiation levels are 1,600 times the "normal" level outside the evacuation perimeter andthis radiation is bio-accumulating in the soil.Yesterday, 8:48:00 PM
– Flag – Like – Reply – Delete – Edit – ModerateLiked by
stan
Natan Weissman I recommend following the situation via the website of the International Atomic Energy Agency, www.iaea.org.
They use their own monitoring teams as well as data supplied by the Japanese. Once releases of radiation stop,one would expect the radiation levels around Fukushima to start decreasing (through both decay and dispersal),but further away the levels may continue to increase, albeit from a lower base (due to dispersal). The IAEA datashows levels are elevated, but doesn't support the view that they are 1,600x normal outside the evacuation zone.I'd sooner trust the IAEA on this than Russia Today.Yesterday, 9:24:43 PM
– Flag – Like – Reply – Delete – Edit – Moderate