Brush-up. Radiation Safety Radiochemistry 07/12/

Transcription

1 Brush-up Radiation Safety Radiochemistry 07/12/

2 Agenda 1. Why this meeting or why is it necessary to have this kind of Brush-Up meetings? Why care about safety? 2. Appetizer 3. A fast introduction to radiation safety. 4. Status for whole body and finger doses for the radiochemistry group. 5. Examples of possible improvements 6. BEK Details to be respected and followed! 7. Radioactive gas release at the limit. 8. New procedure for upscaling from experiments with low activity to full scale routine productions Page 2

3 1: Why this meeting? Ionizing radiation can be dangerous. Many new employee and students. Increasing number of research and development projects. Are our labs over crowded and do we have to many projects and/or staff? Work with new and longer lived isotopes ( 89 Zr, 111 In, ) Examples of contaminations where people did not know how to handle the decontamination process. Cases of high doses and reports to the authorities. A self-inspection has revealed a terribly mess and disorder in the lab. Several repairs and modifications will be necessary if we do not want to have troubles with SIS. Our radioactive releases are at the limit. Cases where staff denied to follow basic rules for working in a isotope laboratory. Apparently necessary to emphasize that the rules/legislation are not for discussion. Page 3

4 Agenda 1. Why this meeting or why is it necessary to have this kind of Brush-Up meetings? Why care about safety? 2. Appetizer Page 4

5 2: Appetizer Typical producers of PET isotopes have production capacities of GBq 18 F and 100 GBq 11 C. Some facilities are approaching 1000 GBq 18 F. Can this be dangerous? YES Effective dose rate D from a 18 F point source, A = 1 MBq, at a distance of r=30 cm is D = msv/h For 500 GBq we obtain D = msv/h = 905 msv/h or the allowed annual dose in 20/905*60 = 1.3 minutes! This is a good argument for this safety lecture Page 5

6 Agenda 1. Why this meeting or why is it necessary to have this kind of Brush-Up meetings? Why care about safety? 2. Appetizer 3. A fast introduction to radiation safety. Page 6

7 3: IAEA text book Nuclear Medicine Physics Side 7

8 3: Recommended dose limits Page 8

9 3: Background radiation/dose: Page 9

10 3: What is the risk? Estimated riskfactor P = 0,00005/mSv Statistically it is expected to find 5 death in a population of inhabitants if they each receive 1 msv. With 5 million inhabitants in Denmark and a background of 4 msv/year (50*4*5=) 1000 death per year is expected. (Radon is the big killer). A received dose of 6 msv gives 0,3 permille risk of developing a mortal cancer. This corresponds to: Going on canoe vacation for 5 days Being 60 years old in 4,5 days Drinking 20 bottles of vine Smoking 15 packs of cigarettes We are safe if we follow the rules! Page 10

11 3: But it can be dangerous! Just in case if the ladies at the back seats has forgotten already! Effective dose rate D from a 18 F point source, A = 1 MBq, at a distance of r=30 cm is D = msv/h For 500 GBq we obtain D = msv/h = 905 msv/h or the allowed annual dose in 20/905*60 = 1.3 minutes! At our cyclotrons the neutron dose rates are much worse! Page 11

12 3: Medical examination? Dose limits at Rigshospitalet: Effective WB dose: 6 msv/y Equivalent skin dose: 150 msv/y Equivalent dose for hands and feet: 150 msv/y Why these special limits? Simply to avoid medical examinations and formal radiation permits for the staff Should we have a written examination on a regular basis rather than the medical examinations? Page 12

13 Examples of links, procedures, graphs, data,, 3: Legislation, procedures, A collection of the most important laws, procedures and results can be found at: In order to be allowed to work with open radioactive sources it is requested by the Danish Legislation to read and understand major parts of the open source legislation: BEK_954_231000_aabne_kilder but also the documents: 90 Vores gældende isotoptilladelse - part B 95 BEK_954_231000_aabne_kilder 38 PET_Cyklotron_Sikkerhedsinstruks.pdf RH.0.01 Dekontaminering.pdf 41 Forskrift for opbevaring af radioaktive kilder.pdf 43 Haandtering og bortskaffelse af radioaktivt affald.pdf 106 Helkropsdoser_Cyklotron 107 Helkropsdoser_Kemi 108 Helkropsdoser Plot 116 Fingerdoser_ Doser pr maaned Page 13

14 3: Radio nuclide groups Isotope Z Half-life Radionuclide group Limits with a S2 permission Storage Simple wet operations *1 Wet operations *2 [GBq] [GBq] [GBq] [GBq] Nuclide specific permission, K414 *3 11 C min N min F min Cu h % 68 Ga min , Rb 37 86,2 d ,5 % 84 Rb 37 32,77 d ,5 % 89 Zr h ,5 % 111In 49 2,8047 d ,5 % Cont. limit Cont. limit Decay properties [Bq/cm2] [Bq/cm2] EC β+ β- Eγ 11 C %, MeV 99,76%, 0,9602 MeV ,52%, 511keV 13 N %, MeV 99,80%, 1,1985 MeV ,6%, 511 kev 18 F ,27%, MeV 96,73%, 0,6335 MeV ,46%, 511 kev 64 Cu ,00%, 1,675 MeV 28,5%, 1,6734 MeV 39,00%, 0,5794 MeV 0,473%, 1345,77 kev 68 Ga %, MeV 89,1%, 2,9211 MeV Rb %, 0,910 kev ,7%, 520,389 kev 29,3%, 529,591 kev 16,0%, 552,588 kev 84 Rb ,20%, 2,681 MeV 3,80%, 0,894 MeV 4%, 0,894 MeV 69,0%, 881,6041 kev 89 Zr ,3%, 2,832 MeV 22,7%, 0,9015 MeV ,6%, 909,15 kev 111In %, 0,865 MeV Page 14 94,0%, 245,40 kev 90,2%, 171,28 kev

15 3: Surveillance and reporting Thermo Luminescence based Dosimetry (TLD): Whole body dose: 1 month Finger dose: 2 weeks. Electronic RAD-60 Dosimeter: Online monitoring and alarm function Page 15

16 3: Equipment Always check staff, tools and equipment for contaminations before leaving a isotope laboratory. Report to Daniel Dahan (or me) if they are not functioning. Page 16

17 3: The decay law of radioactivity Radioactive material: number of decays/disintegrations ΔN per timeunit Δt must be proportional to the number of nuclei N: N ΔN = λ N Δt = λ N N t = N t 0e λt The activity is given as the number decays/disintegrations of nuclei N per time unit: A(t) = dn = λ N dt 0e λt = λ N t A t = A 0 e λt Halflife T ½ and decay constant λ is related by λ = ln(2) / T ½ and are good given nuclear physics constants that can not be changed. Activity law expressed in powers of ½ : A t = A 0 e λt t ln 2 = A 0 e T½ = A 0 (e ln 2 t ) T½ = A t T½ Side 17

18 3: The decay law of radioactivity Activity law expressed in powers of ½ : A t = A 0 e λt t ln 2 = A 0 e T½ = A 0 (e ln 2 t ) T½ = A t T½ Example: 11 C, T ½ =20min, A 0 =64 GBq, what is the activity A after 2 hours? A t = 2h = A t T½ = A 0 ( 1 2 )120/20 = A 0 ( 1 2 )6 = 64 GBq 1 64 = 1 GBq If you have an accident and need to clean up wait until the activity has decayed. This is if you are working with short-lived isotopes. If you are not please make sure you have NO accidents! Side 18

19 Radiation Protection Data Handbook F 18 O + e + + ν T ½ = 109,728 m 2h ISBN RADIATION PROTECTION DOSIMETRY Vol. 98 No 1, 2002 Published by Nuclear Technology Publishing Side 19

20 3: Radiation Protection Data Handbook Do not forget the β-dose! H β = 120 μsv/h or H γ /H β = 1/66 H γ = 1,81 μsv/h Side 20

21 3: Time factor Received dose is proportional to time: ΔE = E Δt You should always estimate expected dose before any new task. Train the work cold or with experimental activities only. If you are in doubt do not take any risk and ask for help! Example: Point source, 11 C r = 30 cm, A = 1 MBq, E = 1, msv/h For 100 GBq we have E =187 msv/h In 2 minutes you will receive ΔE = 187 msv/h 2/60 h = 6,2 msv corresponding to the allowed annual dose. Side 21

22 3: Distance square law Received dose is inversely proportional to the distance squared: E (r) = E (r=a) ( a r )2 and I do not dare to ask you for a simple explanation! Example 1: Double distance = one forth dose 10 times distance = reduction to 1% Keep distance. Use tweezers, tongs, If possible use/develop automation of the labelling procedure. Example 2 (100 GBq 11 C, a= cm): E (r) = E (r=a) ( r a )2 = 187 msv/h ( 0,3 1,0 )2 = 16,8 msv/h Now the annual dose is received in 21 minutes rather than in 2 minutes as in the former example. Side 22

23 3: Distance square law Distance and/or geometry is VERY important for received dose. Example: E point source / E syringe = 1/1600 Side 23

24 3: Shielding I 0 Δx absorbed I 0 * e -mx detected scattered S. Holm. Reduction in intensity ΔI per thickness Δx is proportional to the incoming intensity I 0 : I ΔI = μ I Δx = μ I I x = I x 0e μx Linear attenuation coefficient µ and half-thickness X ½ is related: μ = ln(2) / X ½ Side 24

25 3: Shielding γ I x = I 0 e μx μ = ln(2) / X ½ I x = I x X½ The linear attenuation coefficient µ is a material constant and depends on both radiation type and energy. Linear- (µ) or mass attenuation - (µ/ρ) coefficients for γ rays can be found at: X ½ (E γ =511keV) = 0,4 cm for lead X ½ (E γ =511keV) = 3,4 cm for concrete X ½ (E γ =511keV) = 7,2 cm for water/tisue Side 25

26 3: Shielding γ Example: Hot-celle, ΔX = 70 mm, X ½ (E γ = 511keV) = 3,8 mm for lead X ½ (E γ =1.0 MeV) = 8,6 mm for lead X ½ (E γ =1.5 MeV) = 11,7 mm for lead 511keV: 1500keV: I x I I x I , 8 = 70 11, 7 = = = 1 63 If the dose rate from a 511 kev source is 1 µsv/h on the out side of the hot-celle it will be 350 msv/h in side the hot-cellen. Never open a hot cell with a full batch inside. But if E γ =1.5 MeV the dose rate will be 5,6 msv out side the hot-cell Be careful the shielding is VERY energy dependent. Side 26

27 3: Shielding α and β Linear- (µ) and/or mass attenuation - (µ/ρ) coefficients for α and β can be found at: R β (0,5 / 1 MeV) = 1,6 / 4,1 m in air R β (1 MeV) = 2,3 mm in pyrex glass R β (1 MeV) = 2,1 mm in aluminum Glasses are good for protecting your eyes. Side 27

28 3: Shielding α and β Linear- (µ) and/or mass attenuation - (µ/ρ) coefficients for α and β can be found at: R β (0,5 / 1 MeV) = 1,6 / 4,1 m in air R β (1 MeV) = 2,3 mm in pyrex glass R β (1 MeV) = 2,1 mm in aluminum Glasses are good for protecting your eyes. Side 28

29 3: Shielding α and β Linear- (µ) and/or mass attenuation - (µ/ρ) coefficients can be found at: We are now talking about µm and mm. External radiation is no problem, but inhalation and/or ingestion can be VERY serious. Side 29

30 Agenda 1. Why this meeting or why is it necessary to have this kind of Brush-Up meetings? Why care about safety? 2. Appetizer 3. A fast introduction to radiation safety. 4. Status for whole body and finger doses for the radiochemistry group. Page 30

31 4: Whole body dose Average = 1,2 ±1,1 and max. = 4,0 for Chemistry in Average = 1,7 ±1,5 and max. = 5,5 for Cyclotron in Page 31

32 4: Finger dose A Sum Middel Stdafv Max Min. 0,0 0,0 0,1 0, Page 32

33 4: Finger dose B Large variations for several experimental chemists! D finger 20 msv implies a report to the authorities! Each time I have to argue this is the last time! Are our procedures good enough? Do we have the necessary equipment? Do we know and respect what we are working with? Do we have the work/ development in K414 under control? Permission to work with radioactivity? Page 33

34 Agenda 1. Why this meeting or why is it necessary to have this kind of Brush-Up meetings? Why care about safety? 2. Appetizer 3. A fast introduction to radiation safety. 4. Status for whole body and finger doses for the radiochemistry group. 5. Examples of possible improvements Page 34

35 5: Possible improvements/ recommendations/ requirements/ A More teaching. Should we have a written examination on a regular basis? Read BEK954 and understand your responsibilities. Use of WB TLD Use of finger TLD Change of WB- and finger TLD in time. Use personal electronic dosimeter (RAD-60S). Check that it is functioning correct. Log your radiation dose compare from day to day and with your colleagues. Use of lab coats with long sleeves. (Further instructions by Jacob Madsen and Anne Sørensen). Use of gloves. Change shoes when entering a isotope laboratory. Always check your self, tools and equipment for contaminations before leaving a isotope laboratory. Use Troel s list for contamination limits. Page 35 BEK_954_231000_aabne_kilder

36 5: Possible improvements/ recommendations/ requirements/ B Read and understand our de-contamination procedures. Avoid panic. Call for assistance. Be familiar with our de-contamination equipment and where you find the equipment. Report to Danial Dahan (5-1890) if the equipment is not functioning correct. Clean up in the lab and put up warning signs if necessary. Report in our log-books. Inform responsible physicist and/or chemist. Discuss the accident with the responsible physicist and/or chemist. Equipment, tools, books, staff, that are not necessary for the work are NOT allowed in a isotope laboratory. Clean up in the laboratories regularly. Keep order. Self inspections can be VERY useful. Page 36

37 5: Possible improvements/ recommendations/ requirements/ C H 2 bottle will be moved and installed in a more correct and safe way. Shielding of the filter unit has been ordered and will be mounted again. A new COMO170 contamination instrument has been ordered. Damage of the floor will be repaired. Hotcell doors and spindles will be repaired/services. Plans for some new storage rooms/shelfs under the hotcells. Help us and report your observations to the responsible chemist (and/or physicist), so it can be fixed. Page 37

38 5: Possible improvements/ recommendations/ requirements/ D Read (and understand) and follow procedures for radioactive waste handling. Sorting of waste. Labelling, storage and logging of waste. Consider if your setup and procedures could be shielded better. Also remember to consider the dose rates at the corridor and for the general public. Check the shielding when new isotopes are introduced γ, β, E γ, Be familiar with expected dose rates all over the lab and for all processes. Calculate expected dose (D t) before all active work and compare with measured dose when the work is finished. If you are in doubt you should stop the work rather than playing hero and taking a big risk. Keep a careful eye at your WB and finger doses. I do not want to write more reports to the authorities. Page 38

39 5: Possible improvements/ recommendations/ requirements/ E Long lived isotopes may require different procedures, planning, waste and contamination handling, Check your procedures regularly. Are they optimal? Only work will low activities for development/experimental work. Cold = no activity training. Automation of the process. Development of new tools and procedures Ask for help and advice from older and more experienced chemists! Upscaling from experiments with low activity to full scale routine productions will be covered later. Page 39

40 Agenda 1. Why this meeting or why is it necessary to have this kind of Brush-Up meetings? Why care about safety? 2. Appetizer 3. A fast introduction to radiation safety. 4. Status for whole body and finger doses for the radiochemistry group. 5. Examples of possible improvements 6. BEK Details to be respected and followed! Page 40

41 6: Bekendtgørelse nr. 954 af 23. oktober Read BEK954 and understand your responsibilities. BEK_954_231000_aabne_kilder 8-21: Holger. As an example I should guarantee that the staff knows and follows and and 59-69: YOUR responsibility! Kapitel 6, 7 and 8: also relevant for YOU. Bilag 1, 2, 6, 8 and 9: also relevant for YOU. Most relevant sections marked with yellow Page 41

42 Agenda 1. Why this meeting or why is it necessary to have this kind of Brush-Up meetings? Why care about safety? 2. Appetizer 3. A fast introduction to radiation safety. 4. Status for whole body and finger doses for the radiochemistry group. 5. Examples of possible improvements 6. BEK Details to be respected and followed! 7. Radioactive gas release at the limit. Page 42

43 7: Radioactive gas release at the limit We have a permission to release 1000 GBq activity per 26 weeks via our chimney/stack systems. We are at the limit and we need your help to reduce the release. Another argument for doing experiments with low activity. Page 43

44 7: Radioactive gas release at the limit Use the PAMS screen to monitor the success of your experiment. Record normal values at each step and react if these changes. In worst case we will have to stop all experiments until we have the release under control. Page 44

45 Agenda 1. Why this meeting or why is it necessary to have this kind of Brush-Up meetings? Why care about safety? 2. Appetizer 3. A fast introduction to radiation safety. 4. Status for whole body and finger doses for the radiochemistry group. 5. Examples of possible improvements 6. BEK Details to be respected and followed! 7. Radioactive gas release at the limit. 8. New procedure for upscaling from experiments with low activity to full scale routine productions. Page 45

46 8: Upscaling New procedure for upscaling from experiments with low activity to full scale routine productions. We are open for suggestions. Upscaling Page 46

47 Finito, basta, Finito, basta, cyclotrons are fun, radiation safety less fun. Side 47