Gamma v X-ray

Date 07-06-2007 06:45

X ray is man made and definitly safe when switched off. check this site for more info http://www.ndt-ed.org/EducationResources/CommunityCollege/communitycollege.htm

By NDTIII

Date 07-06-2007 07:21

I am not sure if Gamma is faster than X-rays. It depends on the strength of the source and the strength of the X Ray Machine. The only real advantage of using a souce instead of X-Rays is the portability of the source.
The safe working distance will also depend on the strengths of each. If you use a collimator that cuts your safe working distance down drastically.

By hogan

Date 07-06-2007 14:49

i would have to agree. depending on KV and Ma, and Currie strength they are pretty much equal. they both can be made safer by using a collimator (gamma) or a directional tube (x-ray). X-ray would be safer in my opinion. Because you CAN turn it off. I've performed a lot of gamma and x-ray. I've carried tubes by the tube head, hundreds of times. with no skin damage, no rise in film badge density. The tube could be still getting some energy, but probably as much as your TV.

By 803056

Date 07-06-2007 21:33

When the tube is off, the tube is off and no ionizing radition is produced. There is no decay involved, so there is no radiation unless the target is Thoriated Tungsten, and even then, the Alpha particles emitted would be stopped by the "window" material.

Best regards - Al

By ndeguy

Date 08-27-2007 09:11

Hogan rightly says that a gamma source "can be made safer by using a collimator (gamma)"

True, but dont be lured into complacency here, especially if the environment you are working in is a busy one such as a plant during shutddown, as your safe working zone is not the perfect circle surrounding the collimator. You'll need to know the aperture angle of your collimator so that you will have an idea of the conical angle and geometry (intensity) of your emitted UNCOLLIMATED beam. Often the test material (pipe) itself will further attentuate most of the beam, but think in terms of small bore pipework e.g. 1 -2 inch OD, especially vertical pipes with horizontal welds. Now, with a source-to-film distance of say 18 inches only a small part of the collimated beam is incident upon the pipe itself -- much radiation travels on into the surroundings (as its a horizontal weld its not possible to safely direct the beam down to the ground or up in ot the sky) with an intensity exactly that of a corresponding uncollimated beam from an identical source at the same distance, except where the primary beam is incident upon some material such as surrounding pipework or pipe-supports.

In order to minimise this radiation "pollution" it is advisable to place a lead sheet immediately behind the radiographic film. This sheet should be of dimensions greater than the diameter of the beam at this point and sufficiently thick to reduce the barrier disatance to similar to that necessary for the collimated beam region. Now those who may be working beyond the shooting zone should be protected from any radiation.

By hogan

Date 08-27-2007 15:53

why would one shoot a 1" pipe weld at 18 inches?

By ndeguy

Date 08-28-2007 11:12

18 inches to get a good sharp image. Depending on your source dimensions and meeting Code requirements you could reduce the SFD to about 10 -12 inches but you would be close to exceeding Code unsharpness value (0.020 inches). So what SFD do you shoot a 1 inch DW Superimposed at? Or an ellipse?

By hogan

Date 08-28-2007 14:41

i don't remember going over 15". there would be less "pollution" ( i have not heard that one before), the job would be done quicker and everyone can go back to work (customer happier). with no problem meeting ug and showing IQI.

By ndeguy

Date 08-29-2007 02:24

Well I have no problems with that at all, in fact the greater percentage of the beam filled by the pipe then the less unwanted radiation there is - as long as the RI/AI are happy with the quality of the graphs. But this is a side issue to the X-ray versus gamma and the statements that came out regarding the use of collimators. My experience in the field is that the radiographers will quote the uncollimated and collimated barrier distances but ignore the uncollimated beam from the aperture which may have an opening angle of 20 to 30 degrees. Thats a lot of radiation kicking around the plant which should be either safely directed (earthwards, skywards though watch out for scatter) or absorbed through "stopper" shielding behind the pipe.

By hogan

Date 08-29-2007 16:06

that is a common issue, more for 1104 work than 31.1 or 31.3 in my opinion

By CWI555

Date 07-07-2007 02:21 Edited 07-07-2007 02:23

Gamma would be faster when allowed. The exclusion zone is not necessarily greater for one or the other. It depends on the source/energy of the unit in question, shielding available and many other factors.
Contrary to popular belief, there are x ray tubes capable of creating low level short half life ionizing isotopes. They are not very common, but I have worked with a 10.5 Mev unit.
Pair production starts at 1.022MeV which is a necessary process for creation of radioisotopes.
A linear accelerator (LINAC) at 10Mev or above will be strong enough to accomplish this. The LINAC I used was for heavy wall Pressure vessel heads 10" thick.
At 10.5 a full power shot for a maximum time would create low level radioisotopes that took around 20 minutes to half life out to a safe level.
This may be where your boss got the idea that they still emit some radiation. However; the average tube just will not get any where near that level and therefore when turned off, there will be no emitting radiation without the required pair production.

http://en.wikipedia.org/wiki/LINAC
http://en.wikipedia.org/wiki/Pair_production

By prasad

Date 07-07-2007 14:09

Hi CWI555 from your link

http://en.wikipedia.org/wiki/Pair_production

Pair production is the chief method by which energy from gamma rays is observed in condensed matter.

http://en.wikipedia.org/wiki/LINAC

Medical linacs utilise monoenergetic electron beams between 4 and 25 MeV, giving an x-ray output with a spectrum of energies up to and including the electron energy. The x-rays are used to treat both benign and malignant disease. The reliability, flexibility and accuracy of the radiation beam produced has largely supplanted cobalt therapy as a treatment tool. In addition, the device can simply be powered off when not in use; there is no source requiring heavy shielding

What is the difference between medical LINAC safe after shutdown at 25 Mev and Industrial LINAC dangerous after shutdown at 10.5 Mev as it creates radioisotopes .

Thanks in advance for your answer

By CWI555

Date 07-07-2007 14:30 Edited 07-07-2007 14:43

Difference in Linacs is the amount of time operated. Making something radioactive even for a brief time requires time and energy. Not just energy alone, which is one of the reasons medical use it to begin with. They are high energy short time frame.

As for pair production. and radioisotopes.

http://en.wikipedia.org/wiki/Radioactive_isotope

"Artificially produced radionuclide's can be produced by nuclear reactors, particle accelerators or by radionuclide generators"

I never said they where "dangerous" that is an assertion of your own, safe was meant as in 0 dose not as in it will fry you. They do produce low level fast decaying sources if you leave it on long enough. They are not however, on the order of anything near being called "dangerous" at least for the time frames and energies used for industrial radiography needs.

The reason for the delay was not that it was going to "contaminate or irradiate" the tech (namely me) it was simple alara. No point in taking dose when a 15 to 20 minute hold can drop the dose to zero.

As far as the references are concerned, I quote wikipedia as it's convenient and easy to read. If you want more details, they are readily available on the net.

By prasad

Date 07-07-2007 18:42 Edited 07-07-2007 19:37

Cwi 555

The laws of physics will never change. The principals of x ray whether for medical use or industrial will not change. I hope you agree with me.I want to know how radioisotopes are created from xrays.I will be glad to have a full explanation to satisfy my academic needs. one more thing as you are a expert ? on RT Is a LINAC a cyclotron

Naturally occurring radionuclides fall into three categories: primordial radionuclides, secondary radionuclides and cosmogenic radionuclides. Primordial radionuclides originate mainly from the interiors of stars and, like uranium and thorium, are still present because their half-lives are so long that they have not yet completely decayed. Secondary radionuclides are radiogenic isotopes derived from the decay of primordial radionuclides. They have shorter half-lives than primordial radionuclides. Cosmogenic isotopes, such as carbon-14, are present because they are continually being formed in the atmosphere due to cosmic rays. Despite their relatively "short" half-lives, they are found in nature because their supply is always being replenished.

Artificially produced radionuclides can be produced by nuclear reactors, particle accelerators or by radionuclide generators:

Radioisotopes produced with nuclear reactors exploit the high flux of neutrons present. The neutrons are used to activate elements placed within the reactor. A typical product from a nuclear reactor is thallium-201.
Particle accelerators such as cyclotrons accelerate particles to bombard a target to produce radionuclides. Cyclotrons are used to accelerate protons at a target to produce positron emitting radioisotopes e.g. fluorine-18.
Radionuclide generators contain a parent isotope that decays to produce a radioisotope. The parent is usually produced in a nuclear reactor. A typical example is the technetium-99m generator used in nuclear medicine. The parent produced in the reactor is molybdenum-99.
Trace radionuclides are those that occur in tiny amounts in nature either due to inherent rarity, or to half-lives that are significantly shorter than the age of the Earth. Synthetic isotopes are not naturally occurring on Earth, but they can be created by nuclear reactions.

By CWI555

Date 07-07-2007 22:45

You seem to be knowledgeable in it all, I don't claim any expertise in nuclear physics other than what my training has shown me.
I can tell you directly observed effects, and unless the companies rad safety techs where complete idiots as well as
their RSO I have to side with the information and instructions as found in their SOP's. I waited 20 minutes per procedure,
as I really didn't have any wish to be fired for violation their standard rad safety procedure.

"one more thing as you are a expert ? " Dunno, maybe I don't know what I am talking about, I was trying to help out with Shane's original question.

Then again maybe these people don't know what they are talking about either.
http://book.nc.chalmers.se/KAPITEL/CH13NY3.PDF
Refer to 13.9 Areas of application for accelerators.
"Accelerators in the 10 MeV range are very useful producing radionuclide's, which either cannot be made through (n,y)-reactions in nuclear reactors or are very short lived"

A cyclotron is a particle accelerator. However the cyclotron does so in a circular manner verses a linear manner. So to answer your question, no they are not one and the same, but they do work on near the same principle.

BTW, last I checked I didn't have to "satisfy" your academic needs with a full explanation. Can I back up what I say? Yes. Do I need to do so to every fresh poster? who comes through this site? no.

By prasad

Date 07-08-2007 06:26

CWI555

I will quote ASM
X rays are produced when electrons travelling at high speed are stopped by matter. In the usual type of x ray a filament (like that of a ordinary light bulb)is heated to incandescense . this supplies the electrons and forms the cathode or negative electrode of the tube . The anode or positive electrode of the tube usually contains a tungsten button on the surface( forming the target ) and this is surrounded by copper to dissipate heat generated by the electron collisions. a high voltage of the order of thousands of volts ( or Kilovolts ) when applied between the cathode and the anode attracts the electrons away from the filament ( cathode) and drives them at high speed to the target in the anode . The rapid interaction of these fast moving electrons at the surface and near subsurface of the tungsten button in the anode results in the generation of x rays of many wave lengths. The design and spacing of the electrode and degree of vaccum are such that in normal operation no flow of electrons between cathode and anode is possible until the filament is heated to incandescense and high voltage is applied between the cathode and anode.

As far as LINACs are concerned
Low and medium voltage x ray units so called because the voltage between anode and cathode may range from 5000volts to perhaps 400000 volts . All the low and medium x ray units are of the linear type. This means that the electrons produced at the filament follow an essentially linear path towards the target. The tubes designed for the high and supervoltage classes of x ray equipment range from 1 million volts and except for betatrons operate on the same principles although the design of the tube becomes quite sophisticated in the application of the high voltage to the electron stream. The linear acceleration principle applies to one and two million volt units as well as to a variety of x ray units known as linear accelerators or linacs ranging from one million to twelve million volts.

CWI555 as far as you statement of not answering any new poster let me saythat whenever you speak on a subject so sensitive you should have the full knowledge to back up on it.

By CWI555

Date 07-08-2007 17:13

As I recall, and as posted by yourself, your original argument was can a LINAC of sufficient energy produce low level radionuclide's. You argued that it could not. I can and have proven via a quote from a reputable source that it can. The operation of a standard x ray tube never came into the picture as all agreed the standard tube could not produce radionuclide's due to insufficient energy. I do not see in your recent post where you acknowledge that.
You also asked "on RT Is a LINAC a cyclotron"
I replied "A cyclotron is a particle accelerator. However the cyclotron does so in a circular manner verses a linear manner. So to answer your question, no they are not one and the same, but they do work on near the same principle. "
That answer is correct, and anyone willing to check into it will find the same.

I've answered accurately 1.) what is the difference between a cyclotron and a LINAC, 2.) can a LINAC of 10 MeV or above create low level radionuclide's 3.) can a standard x ray tube of low energy produce radionuclide's.
http://en.wikipedia.org/wiki/Cyclotron refer to my original explanation then refer this link in the section "problems solved with a cyclotron"

Your first post lead off with (and I quote) "The laws of physics will never change. The principals of x ray whether for medical use or industrial will not change. I hope you agree with me. I want to know how radioisotopes are created from xrays."

You did not believe it possible, and decided to make an attempt at proving me wrong leading off with a sentenced designed to trap me into an admission "I hope you agree with me" as in if I didn't I was an idiot. Well, I have backed myself up, yet you persist. When your wrong your wrong, and you sir are wrong.

Your last post dileberately avoided the original questions.

I will give you this, you did say one thing that was right.
"as far as you statement of not answering any new poster let me saythat whenever you speak on a subject so sensitive you should have the full knowledge to back up on it. "

I would ask that you listen to your own advice.

I will say again, the original post from Shane asked a question, I answered in an attempt to help, you have turned it into a debate which I will end now. Post as you wish, My facts speak for themselves. I will not post again on the subject.

By prasad

Date 07-08-2007 17:32 Edited 07-09-2007 07:39

CWI555 ,

If you dont post on this subject who is the loser . You are talking nonsense .If you see my first post in reply to Shane Feder,s question I have clearly told him that to the best of my knowledge no xray mc is dangerous after it is switched off . I stand by this . I deliberately did not answer his other question as I am not a practising radiographer and I believed it would be better that some else with field experience answer the question on whether gamma is better than xray etc. Of course its a different matter that I could have referred to my books and done that too.

I still dont believe that xrays from commercial mcs even LINAC,s used for medical and industrial radiography ( accelerating electrons ) create radioisotopes with half life of 20 minutes after it is switched off and unless you give me strong scientific valid data from a reliable source my view will not change. By the way do you know what is a isotope ? I am providing a link from your favourite site http://en.wikipedia.org/wiki/Isotope
Isotopes are any of the several different forms of an element each having different atomic mass (mass number). Isotopes of an element have nuclei with the same number of protons (the same atomic number) but different numbers of neutrons. Therefore, isotopes have different mass numbers, which give the total number of nucleons--the number of protons plus neutrons.

A nuclide is any particular atomic nucleus with a specific atomic number Z and mass number A; it is equivalently an atomic nucleus with a specific number of protons and neutrons. Collectively, all the isotopes of all the elements form the set of nuclides. The distinction between the terms isotope and nuclide has somewhat blurred, and they are often used interchangeably. Isotope is best used when referring to several different nuclides of the same element; nuclide is more generic and is used when referencing only one nucleus or several nuclei of different elements. For example, it is more correct to say that an element such as fluorine consists of one stable nuclide rather than that it has one stable isotope.

How do x ray mcs accelerating electrons add nuetrons to atoms in air ?

none of the links you have provided in your post mention a commercial xray system even Linac,s as used for medical and industrial use do this.

What must have happened at your job when they asked you to avoid going near the tube for 20 mins is difficult for me to say. We will have to speak to the Level III who prepared the procedure. But I will not agree with this theory of it creating radioisotopes .

By ssbn727 (*****)

Date 07-09-2007 07:40

Must be the full moon we had recently!!! ;) ;) ;)

Respectfully,
Henry

By prasad

Date 07-09-2007 09:19 Edited 07-09-2007 14:54

Henry,

That was a good one . I will not venture outdoors on full moon nights henceforth. I may crash into a radioisotope or two.

By Stephan (***)

Date 08-02-2007 12:14

Gerald,

honestly I have found this - Shanes - topic rather coincidentally and I am truly and deeply impressed by your outstanding expertise!

It was an enjoyment to read your(*) explanations and by the way, great link you have attached!

Best Regards,
Stephan

(*) Brilliant! I am certain, whenever I may have a question on material testing - now I know where I will post it!

By 803056

Date 08-06-2007 05:29

I thick I hear some ice cracking!

Al

By Joseph P. Kane (****)

Date 08-07-2007 22:50

I think I have learned a lesson here. If Prasad speaks, don't question or comment unless you have a PhD. I still think his area code is 202.

By CWI555

Date 08-07-2007 22:51

No kidding

By rodofgod (**)

Date 08-10-2007 08:56

Eh?

By rodofgod (**)

Date 08-10-2007 09:09

Hi All!

At risk of being shot down, and trying to answer the original question by shane!

Gamma is faster!

X-Ray will leave slight residue of radioactivity, but no way near danger levels! as will gamma!

Regards

By CWI555

Date 08-11-2007 04:12

At great risk of offending the self appointed gods of physics, Industrial radiography gamma sources in general do not leave residual radioactivity.
x ray will only do so in 10Mev units or above. The standard units ranging from 120kev to 2mev do not have the punch to do so.
As for which is faster it depends on the application. For mobile source, the gamma projectors can't be beat. For a fix unit using real time, a tube is faster.

By 803056

Date 08-11-2007 17:57

Hello Shane;

I have to agree with CWI555.

Here's a quote from ASNT's Nondestructive Testing Handbook: "Unlike radioisotopes which emit radiation continuously, X-ray generators can be energized or turned off at will."

I am not familiar with any hazards due to isotopes being produced by a gamma source or electronic source of X-ray radiation used for typical industrial radiography.

Which is faster is dependent on the equipment available. High-energy electronic radiation sources (X-ray tubes, betatrons, linear accelerators, etc.) can have more penetrating power than a radioisotope. The energy (penetrating power) of the radioisotope is fixed and the activity (quantity of gamma rays) is constantly decaying, thus the source has to be replaced periodically. The energy (penetrating energy) of the electronic radiation sources is dependent on the acceleration voltage and the quantity of radiation is dependent on the current of the X-ray tube.

Higher energy levels usually translate into less exposure time assuming the energy level is sufficient to penetrate the part being tested.

The common way a non-radioactive material can become radioactive is if it is subjected to neutron radiation such that it becomes a radioactive isotope or it is a byproduct of a fission reaction. The electronic sources of radiation do not produce neutrons. Cesium 137 is a byproduct of a fission reaction. Many radioactive isotopes are produced by subjecting the source material to neutron bombardment in a nuclear reactor built for that purpose. Cobalt-60, Thulium-170, and Iridium-192 are examples of isotopes produced by being subjected to neutron bombardment. Other than Radium, I don't know of any naturally occurring materials that are use for practical industrial use today.

Neutron radiography can use high-energy accelerators, nuclear reactors, etc. to produce neutrons for use in industrial radiography. However, it is rather specialized and shouldn't be a factor or consideration in your discussions with your boss relative to typical industrial radiography.

Best regards - Al

By tomas Date 07-14-2008 21:52

Hi, I'm coming in late on this discussion, but here goes.

Gamma radiography allows techs "portability". Carrying a radioisotope camera into a power or chemical plant is much quicker than an x ray system.
You need no power to use an isotope. With an x ray system you have to plug in. So, yep, in the field gamma is faster.
All results of the two methods are the same except a bit of sensitivity and contrast advantage to x ray.
When you power off the x ray machine all radioactivity will cease. No danger of radiation exposure. At this point you only need worry about electrocution from those residual charge holding HV cables.
As far as my physics knowledge takes me... you need NEUTRON bombardment and capture of an isotope to begin decay or radioactivity. Not some high speed, high energy uber electron!
So get your beers Shane! Better late than never. Toss me a Guiness if you would!
TJ