16/5/2010 - Member of the Public Overexposure (sleeping with a source)
This is taken from the IAEA event log.
The Incident - Member of the Public Overexposure (20/04/2010)
(Note: the incident was reported to IAEA 23/04/2010)
|(USA). The potentially overexposed individual may have spent a significant amount of time visiting his fiancée who was receiving a temporary implant of Cs-137 and Ir-192 seeds via low dose-rate remote afterloader brachytherapy on April 16-18, 2010. The licensee instructed the patient's visitor to visit no longer than 2 hours in a 24-hour period and to stay behind the bedside shield during these visitations.
On Tuesday, April 20, 2010, the Assistant Nurse Manager informed the licensee that the visitor claimed to have spent the night in the bed with the patient on two consecutive nights. Nursing Management personnel are in the process of interviewing staff members that were involved directly with the care of the implant patient to verify that the visitor was in the room overnight with the patient.
A preliminary and conservative dose estimate for the visitor is 60 mSv (6 rem) whole body exposure, based on a 16-hour stay time (8 hours each night for two nights) and an estimated distance of 15.2 cm (6 inches) from the sources. Investigation of the event continues.
The incident log can be read at the following link: IAEA News (You may need to log in as a guest).
Hmm - perhaps the wrong source of ‘hot' date?!
The mind boggles I guess when determining the visitor source distance of 6 inches (the report does not specify the area of treatment).
No data regarding the sources is given but they might vary between about 400 MBq and 3.7 GBq for Cs-137 (Ir-192 probably about the same).
2/5/2010 - My simple take on Election 2010
I said I would never do politics on this blog. But then again I have done cooking curries, progressive rock music, and theft analysis as well as radiation protection - so why not politics?
Actually, I'm not so interested in this up and coming UK election. I was interested to begin with, and I will vote, but I have lost a degree of faith in politics, the media and the electorate. Firstly, let us be clear that this is a race to the wining line and everyone wants to come first (although since this is not proportional representation it is not a simple linear race with the ‘popular vote' deciding the outcome). Therefore, no one party is going to say to the ‘people' we are totally *$&£^$ (insert appropriate word).
It rather annoys me when the media (TV interviews and the press) continually pester the politicians with questions like ‘tell us what you are really going to do after the election' or ‘what real cuts are you going to introduce' or ‘are you NOT going to increase VAT'. Do they really think they are going to get a straight (and indeed honest) answer?
The same can be said for radio interviews. I am amazed how many people (particularly members of the public) come on the radio to specify their own particular requirements or support for one party (be it NHS, schools, energy or green issues) without considering the bigger picture. Indeed, in one interview there was I believe a Labour supporter who stated ‘I will be voting for Gordon Brown again, since Labour came to power there has been such an improvement in the NHS where I work, we have a nice new clean building and lots more staff etc etc'.
The thing is - where does this person think the money has come from - does it grow on trees? Do they not realise that times have changed (perhaps for good?). It is very easy at this point to bash the bankers (I do like everyone else) and blame them for the lack of money and significant debt in the economy. However, when many (like me) have lived through 10 years of house price rises, reasonable standard of living, nice car (etc) did the population really care what the bankers were doing (right or wrong)? I do concede that there were also people much worse off than myself during that period, but then again, many also made an absolute mint way beyond my wildest dreams.
What worries me about this election is that many are blinded with regards the bigger picture. There have been many hints of ‘hard times ahead' - and each party has blamed the other for the possibility of excessive cuts (which might stall economic repair) or scaremongering. But if you look a little deeper you will see that all the cuts thus far discussed by any of the main contenders are completely and utterly trivial - a total drop in the ocean - insignificant - tiny - etc. When you look at the situation in that context I think you can then see that the individual party manifestos begin to blur together - yes each will say something slightly different about TV licensees for the aged, new jobs for young persons, help for small businesses, things for ‘hard working family', trident and so on. But this is where the point of this blog (and indeed it conclusion) begins. In my view none of these ‘little matters' really matter when looking at the big picture - and that is - we as a country are totally and utterly up to our necks in debt. The majority of the electorate in my view is not going to be dominated over the next few years by the ‘little matters' that one particularly party states in their manifesto. Instead, we are all going to be dominated by something that no party can avoid - and it matters not if there is a hung parliament either - CUTS and increases in direct and in-direct tax.
Of course no party could go into this election and be bold and tell the whole story - but I get a little frustrated that there is so much debate (and indeed excitement ?!) when the end game is going to be the same for every individual in the UK. What if one party had said - we will cut jobs, raise basic rate of income tax to 26% in the pound, raise higher rate of tax for 60p in the pound... etc
I am an optimist so do not belong to the ‘tin hat brigade'. However, I think you only have to look to Greece to see the results of ‘difficult' cuts. I think there will be difficult times ahead with everyone having to consider a rethink of their expectations, rights and standard of living.
So for a radiation related site, you might have expected a comment on all things nuclear? Well, I am generally pro-nuclear but concede the industry has not been at its best in the past. However, I do not even think nuclear issues and energy would sway me one way or the other - I still nuclear issues - as important as they are - are small when compared to the massive changes that are going to take place post - election.
Who am I going to vote for - good question!
26/3/2010 - Worker Overexposure (Positron emitter / Fingers)
This is taken from the IAEA event log.
The Incident - Worker Overexposure (04/02/2010)
(Note: the incident was reported to IAEA 25/03/2010)
|(USA). The Licensee reported a potential overexposure based on a ring dosimetry report that indicated a dose between 119 and 40 mSv (11.9 and 4 rem). Licensee investigations indicated that a research technician is believed to have received between 0.5 to 4 Sv (50 to 400 rem) to his fingertips due to improper handling of bromine-76. The range of the 0.5 to 4 Sv dose estimate was based on interviews with the technician and the results of a Varskin computer calculation. There were no observable effects to the fingertips. The technician handled vials containing 1.18 GBq (32 mCi) of bromine-76 without the use of tongs, which was the approved method. The technician has approximately 6 years of experience handling this material and there was no apparent reason for the lapse in safety technique.
The incident log can be read at the following link: IAEA News (You may need to log in as a guest).
I confess I had to look up Br-76 as it is not something I have worked with. Transpires that it is a positron emitter with a 16 hour half-life. What is interesting in the above case is the difference between the ring dosimetry data and the estimated dose on the finger tips. For ‘conventional' beta emitters (i.e. P-32, S-35 etc) this difference is well know - it is one reason why I have never been that keen on ring TLD's if you want to measure beta doses to the finger tip. Clearly within the range of typical higher energy beta emitters you are going to find some considerable difference between that ‘seen' by the TLD worn in a ‘wedding ring position' vs that ‘seen' by your finger tip.
Normally when one talks about positron emitters there appears to be a general bias towards discussing the 511 keV annihilation radiation - particularly when considering shielding. Often the fact that the emitter is a ‘beta +' is forgotten - and this could be to the cost of those that work closely with the radioisotope (particularly in quality assurance / research etc). The same cannot be said for a pure ‘beta -‘ emitters like P-32 where the extremity hazards are generally well respected by users.
Compare the following beta spectra for P-32 and Br-76
What you can see above is that the Br-76 beta spectra is not trivial by any means. Cleary this demonstrates the difference seen between the dosimetry results and finger tip dose estimated in the above incident record. If we were only accounting for the 511 keV annihilation radiation then the expected difference would probably be negligible over the distances involved. This is why I prefer finger tip dosimetry for beta emitters whereas ring dosimetry is fine for x-ray / gamma emitters.
It is important to add that Br-76 also emits gamma rays - however for the purpose of this blog entry these are much less important when considering the extremity hazard. There are also '(-) electrons' emitted and these are considered in the calculation below.
It is not appropriate to try and model the above situation - beta doses will be very susceptible to position, attenuation through material containing the Br-76, gloves that might have be worn etc. Instead, we have also used the Varskin computer code to provide a dose prediction for the following basic case: a one minute exposure to the tip of the finger from 1.18 GBq (32mCi) of P-32 or Br-76. This calculation initially ignores dose averaging through the skin, protective clothing (e.g. gloves) and attenuation through the receptacle containing the radioactive material. The results are as follows:
- Br-76: 21.3 Sv (23.6 Sv if gamma is also included)
- P-32: 35.4 Sv
Clearly the results we have obtained are significantly more than that estimated in the incident report. However, for the case of Br-76, simply using a 3mm shield of 1gcm-3 density reduces the 1 minute exposure to < 3 Sv (i.e. same order of magnitude as reported in the incident). This considerable difference for a modest level of shielding (receptacle / gloves etc) shows why a model of the above incident is not possible without considerably more information.
Moreover, we have no knowledge regarding the duration of exposure - suffice to say that our results, and acknowledgement that there were no deterministic effects to the fingers, indicates that the duration of the exposure would have been short (probably much less than one minute).
In the above calculation for Br-76, no account has been taken of exposure from annihilation radiation. In other words, the exposures for Br-76 is the same order of magnitude as for P-32, indicating that equal respect should be given to both these radioactive substances with respect to external extremity hazards.
It is reported that there was no apparent reasons for the lapse in safety technique. I think this demonstrates the need for regular update training with a practical component. It is all too easy to become over familiar with a procedure which then leads to complacency.
Oh :-) , at last a blog entry !!
19/2/2010 - It may never happen to you... but it might
Blogs are written for all sorts of reasons - marketing, news analysis and comment, getting something off your chest and so on. This blog has served a number of purposes over the last few years - many articles have been clearly radiation protection related, but others have looked at my hobbies (e.g. cooking and music), and a few are of a more personal nature involving aspects of my family life (e.g. playing in the snow with the kids).
Whatever the driver for writing a blog post - there is an element of ‘therapy' involved - it feels good to write down thoughts and views, if there is an audience out there that likes to read those views then even better.
This entry is one of those ‘therapy' moments - we were burgled. Yes, this goes on all the time and perhaps some of you have experienced the same. However, it is only when it actually happens to you that you realise the effects it can produce - anger, ‘why me', stress, ‘if only' ....
I can say from the outset that the most important thing in the world is my family - my wife and the boys. Material possessions are important but way down the league table - the fact that the family came to no physical harm and were not present when this event occurred is a great relief. No physical harm is one thing - mental harm is something altogether more difficult to define and is perhaps longer lasting. The feeling of anger and resentment, the feeling that someone has been in your house and trashed it, is less tangible but no less painful. So what happened?
We live in a pleasant quiet residential road in Berkshire. We left the house locked up at 1615 on Monday afternoon to drop the kids off at their Grandparents. My wife and I were going to cook a late Valentine's Dinner - a spicy chicken dish I recall. We returned to the house at around 1845 and knew something was wrong before we even arrived back on the driveway - my wife could see the house from the main road and commented that my youngest son's bedroom light was on. As we got onto the driveway a feeling that I can only describe as nausea came over us. There was the house - every curtain and blind was drawn (not how we left it) and every light appeared to be on.
At this point I think I thought ‘something is missing here' - but could not define that thought further. We opened the front door (was all locked up and deadlocked). Upon opening the door we immediately knew the worst - we could see all the doors leading from the hall were open, all lights were on and items were strewn across the floor. Through this feeling of nausea, panic and a certain anxiety that someone might still be in the house (although for some reason I worried less about that at the time), we began to look around.
What we found
Kitchen - all the drawers were open and items all over the place. The rice tin (an old biscuit tin) was open and bent - does the thief still believe that cash is kept in a biscuit tin? If you still do this then please don't! The French Doors at the back of the kitchen were open - that was the point of entry. They had been forced open - we are talking about a modern high security 7 point locking door that was secured before we left earlier in the afternoon.
Exploring further we looked in the lounge and the flat screen TV was gone - the French Doors in the lounge had been opened from the inside using keys that we had ‘hidden'. Things got a whole lot worse as we moved up stairs. Every item in every one of the four bedrooms had been turned upside down. Three laptops had been taken from one room, my wife's jewellery (valuable, sentimental and both) had been taken. The IPod had gone. Every drawer had been emptied on the bed - the place was wrecked.
What do they expect to find in a 6 year / 3 year old boys room??
The most upsetting thing for both of us was the boys' rooms - thankfully they are too young to be reading this blog and we have kept this information from them. Their rooms had been turned upside down - all the drawers of clothes, books, toys were emptied onto the floor. Why - I guess they were looking for hidden objects - but why - do they not have kids.... were they not kids themselves at some point in the past?
I said earlier that ‘something was missing here' - My car, an Audi A5 with registration ‘RPA 418' - that had gone too - stolen from the driveway. They must have found the hidden set of spare keys.
Initial Police Response
The look around the house took less than a minute - less time than it is taking to read this blog. We phoned the police - 999. Was immediately told they would ring back as this number was only for emergencies... (how many of you keep your local police station number to hand for an event like this ??). From this point on I cannot fault the initial response of the police at all. Two officers arrived within less than 10 minutes - they were courteous, professional with an appropriate degree of empathy - my only comment is that I think they had seen this many times before. They checked out the house, phoned for the forensics team, examined the outside of the property and made door to door enquiries.
They were shocked at the lack of damage to the rear forced door - damage was clearly visible but the robbers had not broken the door - simply appeared to have forced the two halves of the door apart enough to disengage the locking mechanisms (also doing the same top and bottom). We were actually able to close and relock the door - which is not reassuring since you know that the exact same thing could happen again. [We have had the doors examined by two separate experts and they concede that this could happen to anyone with similar doors - please do not assume that this type of modern UPVC door is secure, if they want to get in they will].
What goes through their mind (they do have a mind??)
The police were not able to get any finger prints (burglars were wearing gloves it seems). They were able to identify four different sets of foot prints on the kitchen tiled floor. So there were four of them it seems - four sad, selfish, worthless individuals. Did these four individuals not see:
- the Valentines day cards they dropped into the sink as they closed the front kitchen blind
- the pictures of our boys, either side of the TV they took
- the family pictures, the smiles and happy faces
They did and they clearly felt nothing. I wish I could understand the mindset of these people - what drives them? Is it the recession - are they on the poverty line and need to steal goods to buy bread and milk for their poor family? Are they a modern day Robin Hood - stealing from those who are apparently ‘doing ok' (i.e. working very hard as a family) to buy meal vouchers for those less fortunate? Are they feeding a drugs habit and need the goods to fund their next fix?
Or, are they simply selfish and want something for nothing? I have no idea which it is - but I wish I knew. I wish I could understand what drives someone to take a risk and do this on a late Monday afternoon with people coming home from work. We could so easily have come back whilst they were midway through their break in.
So, it is now Friday Morning. Today is the first day where I can honestly say I intend to ‘work'. My clients have been understanding and there has been so much to sort out - new locks and a lot of learning to do (more of that in a moment). The boys know ‘a man has taken the TV and daddies car' - and that is it, how I envy their innocent mind. My oldest son is already interesting in looking for a new car for me (the police incidentally do not hold out much hope of getting it back). I spent an hour yesterday with just my youngest son playing rough and tumble on the floor. How I love them both - they will grow up to be honourable, kind and caring adults.
My wife has taken this as well as can be expected. I think she finds the violation of her family and house hard to accept. She had spent most of Monday doing housework and making the family home what it is - a great place to be. To come home and find all that turned upside down is hard to take. I know she worries they will come back again - I need to now work on reassuring her that they will not. Many items of sentimental value were taken from her and I know that hurts.
So, to some learning points. Everything in this blog has been communicated to the police and therefore to the insurance company. I put the following points down in the full knowledge that this is public.
Firstly - the house was secure and locked up. However, as we were in a rush to leave we did not set the alarm. We normally do - but on this occasion we simply did not - this is, by the way, on the very day that the alarm was serviced and tested. We can say or think the ‘if only' phrase for evermore but it does not change the fact. Therefore, if you do have a house alarm please ensure you use it every single time you leave the house - this includes late afternoon when you are only planning to be out for an hour.
Secondly - it is a sad fact but you have to think like a burglar. Where will they look? What are they after? What is their motive (small items, expensive items). Hiding spare car keys, door keys etc has got to be very carefully planned - if they do get into the house then they are going to look in all the obvious (and perhaps less obvious) places. I have not thought this one through yet so if you have any ideas feel free to pass them on.
Thirdly - think about security starting outside and working in - from the perimeter of the property. Each security measure / inconvenience / time delay that you put in place between the perimeter of the property (i.e. the road / garden inwards) and your home should make it less attractive.
Forth - pardon me if this is going to sound unjust - we have had several sets of workman doing work around the house over the last view weeks (home office etc etc). Please do not assume anything and be careful what you say. There is no direct evidence to suggest that anyone had ‘motives', but when you look at the specifics of our case (many of which I have deliberately left out of the blog), you cannot help wondering how did they ‘know certain things'.
- The type of gate lock
- The lighting (which we now know was deliberately disabled a few days before the event)
- The type of back door
- The contents of the house (e.g. TV could only be seen from the back garden)
- The time of day we come and go - the routine
Now this has happened we are perhaps going overboard with security and I am of course not going to describe that all in detail - suffice to say .. security lights, more locks, new rear security doors, a new way of storing valuables and keys etc are all part of the mix. I know that nothing offers a guarantee that theft is preventable, but it lowers the risk. Indeed, it is similar to the radiation ALARP principle really - or ASARP (as secure as reasonably practicable).
Finally - just to say - I really hope this does not happen to you, it is a truly awful experience. Do have a look at your physical security measures and think about where you store your valuables and similar.
Blog articles on radiation protection, Asian cooking and progressive rock music will return shortly...
10/2/2010 - Risk comparison - does it work for you with radiation?
Of late there have been many stories in the media regarding ionising radiation. Some have been related to new build nuclear power stations, others have looked at the excessive use of CT scans in the US, and yet others have discussed the use of back scatter security technology at airports. Indeed, I cannot remember when so many stories were circulating at the same time. Furthermore, if you have checked out our blog entries below you will see were have also got in on the act - particularly concerning recent articles from the two camps ‘radiation is not as bad for you as you think' all the way to ‘radiation does much more damaged than you think'.
One theme which runs through many of these stories / articles is risk comparison - i.e. trying to relate one unfamiliar risk with one that we all find more familiar. Of course that is an open statement because I am familiar with radiation risk (it is my job), whereas I am much less certain about financial risk (even though the basic principles may well be similar). Therefore a comparison between two or more risks will not work for everyone in the same way - particularly if the individual has an agenda, is a stakeholder, or perhaps has had a bad experience which muddies the water. This can be developed further by considering an individual's ‘irrational response' to risk, and comparing to someone else that finds the same risk familiar (and which can be placed in context with other surrounding risks).
Mark Ramsay and flying
Take my experience of flying - I have to fly quite a lot as a consultant and it is something I am familiar with. That said, to say I do not particularly enjoy flying in an understatement. I am not one of those individuals who grips the seat in terror, sweats and never leaves the seat - but I do have some traits that some of you might find irrational. Here are some of them:
- I always book flights with specific seats
- I always check-in online as soon as it is open - to get an aisle seat
- I do this as soon as I can to be near the front of the plane
- During take-off I have fingers crossed - always released once we get airborne
- I avoid drinking too much (little use of toilet)
For some that fly a lot for business or pleasure, my traits above might seem excessive - but apart from admitting them on line (gulp), I am pretty certain I do not look any different to any other calmer passenger. Once we are cruising I tend to relax and get on with work - resigned to the fact that should something go wrong then I am unlikely to know much about it!
So where has the above come from - a bad experience flying? Not that I can remember - for me it is just one of those things. I have tried to make myself feel better by looking at air accident statistics - that did not help much. I have also looked at the physics of flying ... ‘how do they keep up in the sky'. That has not helped much either. It is not as if I am a nervous or anxious person - whilst I always get psyched up before I start training, I do not feel stressed or anxious about this - and I know many who have openly said they could not stand for three days in front of a group of people and be the focus during that time. So I have to stick with the fact that flying in an irrational fear that I deal with - 'safest form of transport' they all say - well whatever you say!!
Ionising Radiation Risk
So I turn to something that is more familiar to me - ionising radiation risk. Whilst I know many who have a healthy respect for radiation, and do not ‘fear it', I know of many that find it troubling. Some find it troubling even when you start to use risk comparators to place the risk in a more familiar context - others find this approach comforting. Take smoking as an example - I often use the following comparison (which numerically could be contested but is in the right ball park):
Fatal cancer risk from smoking 40 cigarettes - comparable to receiving a whole body dose of 1mSv of ionising radiation (1000 μSv).
You can develop the comparisons in many ways (which make all sorts of assumptions about LNT etc):
- UK average annual exposure to background / medical ionising radiation is 2700 μSv (108 cigarettes)
- 20/day smoker over a year - comparable to receiving 183 mSv whole body dose in same period
- Fire Fighter dose to save a life (100mSv) = 4000 cigarettes (200 days for 20/day smoker)
- Annual legal limit (20mSv) = 800 cigarettes
You get the general idea - this helps some, but does little to help others. I do not think this has anything to do with being a smoker or not, or the fact that smoking is something you do by choice. I think it is simply that smoking is a tangible thing you can understand, whereas ionising radiation is not.
Back scatter x-ray systems
The Rapiscan Secure 1000 Single Pose - for info go here.
Back scatter x-ray technology has been in the news of late - driven mainly by the ‘underpants' bomber. Those that have an anxiety about using such a device tend to fall into the privacy camp, the radiation safety camps - or both. The UK Department for Transport (DfT) has just released a document by the UK Health Protection Agency (HPA) which looks at back scatter radiation risk comparisons. This document can be found at the link below:
Assessment of comparative ionising radiation doses from the use of rapiscan secure 1000 x-ray backscatter body scanner
They acknowledge that statistics in the form of ‘1:20' or ‘5% per Sv' are not a lot of help to many. They have taken a different approach and compared familiar (likely and not so likely) risks as ‘equivalent number of scans'. For example, the claimed dose per single scan from a back scatter machine discussed in the above report is 0.02 μSv. The risk of this scan has been compared in the following way (only some examples are shown below, read the above report for the rest):
|| Cause of death
|| Fatality risk
|Risk of accidental death in a school pupil while at school (UK annual rate, ref. ROSPA data)
|| Fatal accident
= 1 in 2,300,000
Risk = x70 backscatter scan risk
|Average annual background radiation in the UK
Effective radiation dose =2,700 µSv
|Fatal lifetime cancer risk induced by exposure to background radiation (assumed to be 0.05 (5%) per Sv)
= 0.01 %
= 1 in 10,000
Risk = x 16,600 backscatter scan risk
|Risk of a mother dying during pregnancy or soon after in the UK
(UK Office for National Statistics)
|All causes directly and indirectly related to the pregnancy
= 0.015 %
=1 in 6,700
Risk = x 25,000 backscatter scan risk
(In the second line entry I believe the risk should be written as 1 in 7400 - rounded - but perhaps they have rounded to 1 in 10,000 for good measure?).
So, notwithstanding a couple of suspect figures in the above table, they have taken a familiar tangible risk and compared directly to a tangible security back scatter scan. Do you think this helps - it would help me (if I were worried).
Using my own data above for cigarettes, here is another one to finish:
1 scan (assumed 0.02 μSv) = 0.08% of a cigarette, which is < 0.1mm (average length) or a PUFF (but only if you inhale).
(Note: you should seek specific dose information from the scanner supplier direct - the figures above are for illustration only)
PAGE 18 OF 44