Average msv/yr = 1.34 msv/yr

Transcription

1 Radiation Shielding guidelines do you really need ALARA or source constraints? Robert L. Dixon Wake Forest University it School of Medicine i

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3 Natural Background in USA- Exclusive of Radon (NCRP #45 & #94) Atlantic & Gulf Coastal Plain msv/yr Middle America- Rocky Mountain Plateau msv/yr 1.45 msv/yr Denver Colorado msv/yr Population-weighted average-1.09 msv/yr Average msv/yr = 1.34 msv/yr

4 Despite the variation in natural background, most locales l in the US are below 6 msv per annum. So where would logic dictate setting thepublicdoselimit? limit?, perhaps5msv? Au contraire they picked 1 msv per year They evidently don t believe it s safe to live in Denver, CO

5 The 1 msv per yr public dose limit is Down in the noise 4.0 msv 3.5 Avg +1 msv Avg

6 Public Dose Limit 1 msv/yr

7 But the Lords of Protection (ICRP) secretly yearned to set it even lower, so they turned to a little trickery to try to accomplish the same thing With constraints they could create a new and even lower de facto dose limiti

8 Public Dose Limit- simplified Rule one : 1 msv/yr Rule two : Now Divide Rule one by 3

9 Source Constraints An ICRP fantasy The Myth of Multiple Sources which fails to consider: Most sources do not converge to a single location (short range, inactive at night) A given person cannot be in more than one place at a given time This argument is developed in much greater detail in our paper in published in Radiation Protection Dosimetry(2005),v.115, No. 1-4, pp

10 1 msv

11 1 msv 1 1 This 1

12 ICRP SPEED LIMIT SOURCE CONSTRAINTS SPEED LIMIT- 60 MPH BUT WE MUST CONSTRAIN YOU TO 20 MPH SINCE YOU MAY OWN MORE THAN ONE AUTO, OR DRIVE ON MORE THAN ONE HIGHWAY This logic is closely analogous to that used for source constraints - ignoring simultaneity

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14 The International Council for Radiation ( ) p Protection(ICRP) in 2003 expanded its charter to protect animals as well They choose the duck as their animal model

15 But we can still shoot the ducks, right? No problem, we just can t nuke em

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17 Cost per (hypothetical) Life-year saved 1 Radiation Emission Standards for Nuclear Power Plants: $100 Million/life-yr Radionuclide Emission Control at NRC- licensed facilities: $2.6 Billion/life-yr Widen lanes on Rural Roads by 2 ft: $120,000/life-yr 1. Tengs et al., Risk Analysis 15,, , 390, 1995

18 rld15 Thinking Inside the Box Lower is always better in here

19 Slide 18 rld15 1. only hazard is radiation 2. no coupling between the box and the outside world 3. money is no object rdixon;

20 I can readily prove that most of you are inside the box thinkers How many of you drove here ALARA?

21 Driving ALARA* Keep your Speed ALARA *As Low As Reasonably Achievable

22 Driving ALARA would inarguably reduce the risk of death - not only to you, but to other members of the public in your path. A definite, it proven benefit to you and the public. Saves on fuel It seems a no-brainer

23 ALARA? Sure it ll cost more, but don t forget we re dealing with deadly radiation here. Hey, It doesn t apply to driving just radiation! I m not driving ALARA (or Miss Daisy)!

24 Secret ICRP training camp Behold! multiple sources!

25 So how did I get involved in this Orwellian world? We presented our final report to NCRP, and were called before the Pope (like Gallileo) BEN ARCHER, JOEL GRAY, BOB DIXON, DOUG SIMPKIN

26 Thou shalt design all thy shielding to ¼ msv per annum whether thou believest or not, for it is thus written in NCRP 116 chapter one, verse 122 Zip it! Our reply pyto NCRP But.. It is futile to resist

27 Administrator It s going to cost you $250,000 to upgrade your vault to 0.25 msv/yr for a slight (hypothetical) increase in protection for the 5 or so members of the public who work in its immediate vicinity Also, those 5 people will be getting more radiation from natural radioactivity inside their own bodies than from your accelerator And by the way, every pizza parlor, ice cream shop, home or business in the Denver region will have a higher radiation level than that just outside your expensive new leaded accelerator walls-

28 Many developing countries who cannot afford modern medical x-ray equipment, waste their precious resources on shielding to the ICRP suggested limit of 1/3 msv/yr blindly adopted by their regulators.

29 Predictions if Designing Shielding to msv per year An estimated additional 10 9 kg g( (1/2 billion pounds) of lead would be required for medical x-ray alone (50% of total annual production).

30 (hypothetical) annual risk from 3/4 msv/yr 4x10-5 (real) annual risk to 2 : metal miners & smelters 56 x 10-5 Construction workers 14 x Wilson and Crouch, Risk-Benefit Wilson and Crouch, Risk Benefit Analysis, Harvard 2001.

31 Recent NCRP report series for shielding medical x-ray sources NCRP has concluded that a suitable source control for shielding individuals in uncontrolled areas in or near medical radiation facilities is an effective dose of 1 msv in any year. 1 msv.y-1 to the maximally exposed individual in an uncontrolled area will provide adequate protection to the employees and the members of the public that access the uncontrolled o areas.

32 Reconfirms Source Control of 1 msv per year

33 IAEA Training Material on Radiation Protection in Diagnostic and Interventional Radiology RADIATION PROTECTION IN DIAGNOSTIC AND INTERVENTIONAL RADIOLOGY L12: Shielding and X Ray room design

34 Radiation Shielding - Calculation Based on NCRP 147 Assumptions used are very pessimistic, so overshielding is common Various computer programs are available, giving ii shielding hildi in thickness thik of various materials IAEA continued 33 12: Shielding and X Ray room design

35 Radiation Shielding Parameters () (I) P - design dose per week usually based on 5 msv per year for occupationally exposed persons (25% of dose limit), and 1 msv for public occupational dose must only be used in controlled areas i.e. only for radiographers and radiologists i IAEA continued 34 12: Shielding and X Ray room design

36 Implications of 1/3 msv per annum Constraint Attempting to increase public protection by forcing the doses allowed from medical X-ray sources to Heroically low levels (10% of natural background) limit is likely to represent net harm to the patient population (the same public) in terms of both increased healthcare costs as well as increased health risk to individual patients, with no proven benefit whatsoever.

37 How re they gonna find enough duck A-bomb survivors to figure risks, Eh? I guess we ll have to nuke a bunch of them They re not gonna like that, t Eh?

38 And the duck rebellion is already beginning The ICRP is next- bring it on Lars-Erik Two can play this decoy game

39 The risk coefficient The End is Here

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42 This is my lucky day, I m from upstairs, and am conducting an NCRP - type investigation-so where do you live or go after work? Is anybody else irradiating you besides me?

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