Thanks for the sobering analysis. I would not have expected that. Fortunately you have to be very persistent to override all the interlocks on an in-house system. I do know on our Agilent instrument that the backscatter from a crystal at full power with the doors open is only 3 times background--learned that from the installer during commissioning. With the doors closed you can't measure any stray radiation.
Roger Rowlett On Jul 12, 2013 3:57 PM, "Mark van der Woerd" <mjvdwo...@netscape.net> wrote: > My first reaction to this question was "well, it depends". The effect of > X-rays depends on (among other things) the energy (wavelength) and the > intensity (and of course the dose). But I decided not to write about this > until... > > In response to Michael's note below, I want to point out that instruments > constantly improve: > > I just re-wrote our safety plan because we have to renew our radiation > license for our new in-house instrument. On this plan, they ask you to > write a worst-case scenario. For an in-house sealed tube instrument, > producing CuKa radiation, we calculated (with the help of the friendly > manufacturer, thank you) that if you had a direct exposure to the beam, for > example because your hand would be in the wrong place at the wrong time, > you would burn a 7mm deep hole in your hand. Interestingly and > surprisingly, when compared to our old rotating anode generator, the > estimated worst case scenario for the old setup was an order of magnitude > less severe (less than 1 mm deep burn). The constant improvement of > instruments also makes them just a little more dangerous. The old days of > 'tingle' are long gone and you *really* need to watch yourself, even on > in-house instruments. > > Indeed, if you do not tinker with the safety system and have shielding in > place at all time, as you say, the exposure is never above background. So: > obey all the rules and worry very little. > > At the synchrotron, if I recall my safety training correctly, the worst > case scenario (which is very nearly impossible to accomplish, even if you > tried, which of course you should not), is instant death. So yes, that gets > you kicked out, but not the way you imagined. There are many less severe > variations, but probably all are much more severe than the in-house case. > There is a reason for all the safety systems. > > The original question (what happens and how bad is it), is not that easy > to answer. Apart from burns, there are of course the known effects of DNA > damage etc. Since we share a building with people who call their profession > "radiation health physics", I was reminded with an interesting discussion > that there are people who study how you can use radiation for your benefit > - use enough to kill bad things, but not so much to badly harm the good > things - and these people make a living that way, quite successfully. > > In the end, it is hard to know what anything does to your body and it is > best to stay on the safe side. Remember ALARA and observe it. It is > possibly the most sensible safety rule I have seen in my life. > > Hopefully now nobody will be tempted to see if it tingles when you stick > your finger in the beam. > > Mark > > > > -----Original Message----- > From: R. M. Garavito <rmgarav...@gmail.com> > To: CCP4BB <CCP4BB@JISCMAIL.AC.UK> > Sent: Fri, Jul 12, 2013 10:14 am > Subject: Re: [ccp4bb] Harmful effect of X-ray > > Most modern textbooks have sections on the proper protections and > measures to take, although the information may be dated. See chapter 6 in > Volume III of the International Tables for X-ray Crystallography. With the > modern equipment and regulatory measures in most countries, you really have > to work hard to be exposed at dangerous levels (which can lead to skin > lesions and burns). However, you can get yourself exposed if you > intentionally circumvent the safety measures and interlocks. In my > experience, X-ray exposure in crystallography labs is very low and not > dangerous. Our radiation safety people find our labs to be very "clean" > with respect to scattered radiation around the sample compared to medical > X-ray labs. Talk to your institute's safety people for advice. > > For in-house equipment, you are most at risk of exposure during aligning > the equipment. If you talk to the old crystallographers (or > their students who are now +50 year old), you might hear stories of > aligning collimators and cameras by the "tingle" on your eye as you look > into the beam. By the time protein crystallography came around (50s-60s), > phosphors and film were used for alignment so the "danger" comes mostly > from scattered radiation and poor shielding. In all the years I have > worked with X-rays without protection (I only wore a lab coat to prevent > film developer from staining my clothes), neither I nor my colleagues have > ever had X-ray exposures above background as determined by film badges and > ring badges. In fact, we once exposed a film badge intentionally to see if > anyone cared. We caught hell for doing that. > > For synchrotron sources, chances of being exposed as a general user are > now nil unless you really work hard to subvert the safety measures (which > will get you kicked out). > > Hope this helps, > > Michael > > ****************************************************************** > *R. Michael Garavito, Ph.D.* > *Professor of Biochemistry & Molecular Biology* > *603 Wilson Rd., Rm. 513** * > *Michigan State University * > *East Lansing, MI 48824-1319* > *Office:** **(517) 355-9724 Lab: (517) 353-9125*** > *FAX: (517) 353-9334 Email: rmgarav...@gmail.com* > ****************************************************************** > > > > > On Jul 12, 2013, at 11:14 AM, diptimayee mishra wrote: > > Dear All, > Can anyone please tell me regarding the harmful effects of X-ray , we > are using for protein crystallography, on human being and what are the > precautions we should take. > > Thanks > > >
