ABOUT Absorbed Dose D

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Mitchell Cameron
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IONIZING RADIATION IS THE JOB & GOAL OF RADIATION PROTECTION

1 Slide 1 of 22 A DRAFT ABOUT Absorbed Dose D & Dose Rate D* CONTROLLED REDUCTION & PREVENTION OF THE UNWANTED EFFECTS OF IONIZING RADIATION IS THE JOB & GOAL OF RADIATION PROTECTION PROFESSION. Continuous improvement is the foremost prerequisite for survival. DeSegnac et al.

2 TELLING IS NOT TEACHING Thoughtfully organized, illustrated, and animated presentation, given by a classroom experienced, engaging SAT enabled trainer/instructor, could help students, especially the adult ones, understand the RP concepts and their applications in practice. The following PPT module covering ABSORBED DOSE, a part of our COMMON RADIATION PROTECTION EQUATIONS series, illustrates our abilities to create impressive and useful learning material that will keep the students aware, awake, and engaged in the process of acquiring new and/or reviewing and cementing their existing knowledge of the radiation protection science. Our team is, also, capable of incorporating similar PPT presentations into your existing, approved lesson plans and in an engaging way. We are, also, well qualified and capable of augmenting your training team at outages and other times of need. Please review our RP DOSE module and let us know if and, maybe, when we may be considered to help in your important efforts in RP training and qualifications of your workforce. We are standing by! Our references include RP Directors, Nuclear Power Plant Maintenance Managers, Maintenance Training Directors and Managers, and Lead Instructors. If and when you need our references, we will be glad to provide you with their s and/or phone numbers. Respectfully Dusan A. Radosavljevic Slide 2 of 22 desegnac@att.net Continuous improvement is the foremost prerequisite for survival.

3 ABOUT ABSORBED DOSE D Slide 3 of 22 & DOSE RATE D* The material that follows is an introductory presentation of two fundamental concepts in radiation protection: Dose and Dose Rate. It could help an RP technician build her/his understanding of other important concepts and tools that RP professionals are using in the field. Pictures and simple animations are used for visualization of the presented concepts. Formulas and numerical data are the bare minimum and should not present great difficulties while working a few numerical examples. As always, there are unintended mistakes and errors hidden within the material. These are my own and I would appreciate to be made aware of them so that they can be corrected. Please let me know your impressions and concerns regarding this presentation. Dusan desegnac@att.net

4 Slide 4 of 22 About Exposure X (R) & Dose D (J/kg, Gy, & rad) Content (A simplified term Dose D will be used instead of Absorbed Dose.) Slide 5 : Exposure & Dose Two Different Concepts Slide 10 : Of Dose D & Dose Rate D* Slide Slide Slide 13 : Specific Dose Constant D (Gym2 / TBqhr) 17 : Exposure & Dose d(istances) 21 : Summary of Units & Equations Compton Effect photoeletric effect

5 Slide 5 of 22 Exposure X & Dose D (air) photoeletric effect Compton Effect Continuous improvement is the foremost prerequisite for survival. DeSegnac et al.

58 10-4 Coulombs/kg air photoeletric effect Dose D is given in joules / kg 1J / kg ~ 6.

6 About Exposure X & Dose D Slide 6 of 22 The terms Exposure X and Dose D, reflect two distinct concepts: Exposure represents ionization of air! Dose is energy absorbed per kg of any material! Exposure X is given in roentgens R ~ Coulombs/kg air photoeletric effect Dose D is given in joules / kg 1J / kg ~ MeV/kg The SI energy unit joule, 1 J ~ Mev Absorption of 1 J by a drop of water, ~ 50 mg, will raise its temperature by ~10 0 F

7 About Exposure X & Dose D Slide 7 of 22 Exposure X and Dose D (air) could be related in the following way: If one free e-charge (ion) carries ~ Coulomb, how many ions is represented by 1 R ~ Coul./kg air? Compton Effect 1 R ~ C/kg air ~ ions If ~34 ev is necessary to free 1 e charge in air, what energy in MeV is needed for ions? 1 R ~ MeV Because 1 J ~ MeV, & 1 R ~ MeV, how many R(oentgens) per J(oule) & J / R? J ~ 114 R 1 R ~ J/kg air

About Exposure X & Dose D J/kg Slide 8 of 22 1R ~ 7/8 10-2 J/kg air 1 R ~ 5.

8 About Exposure X & Dose D J/kg Slide 8 of 22 1R ~ 7/ J/kg air 1 R ~ MeV/kg air 114 R ~ 1 J Dose represents energy deposited per kg of any material (joule/kg) The energy unit joule J is, also, defined as 1 J = erg ~ 2.2 mg grain of fine sand moving at 1 ft/s delivers ~ 1 erg to a solid target. If a 0.26 Ci 60 Co source delivers? R/hr at 1ft (?). How many ergs and MeV is absorbed in a target of 7.3 1ft, which retains only10% of the available energy? What is the Dose? ~ erg, ~ MeV, D ~ J/kg

Slide 9 of 22 About Dose in J/kg, gray Gy, & rad 1 J/kg is the measure of the SI unit of dose. It is named gray Gy 1 J/kg = 1 Gy 1 J/kg = 1 10 7 erg/kg 1 J/kg ~ 6.

9 Slide 9 of 22 About Dose in J/kg, gray Gy, & rad 1 J/kg is the measure of the SI unit of dose. It is named gray Gy 1 J/kg = 1 Gy 1 J/kg = erg/kg 1 J/kg ~ MeV/kg A much smaller unit of dose is 1/100 Gy 1 rad = Gy rad (=) radiation absorbed dose How much of, J, erg, MeV (/kg), and roentgen R, corresponds to 1 rad? 1 rad = 0.01 J/kg = erg/kg = MeV/kg ~ 1.14 R

10 Slide 10 of 22 Dose Rate D* (air) Gy/hr & rad/hr photoeletric effect Compton Effect Continuous improvement is the foremost prerequisite for survival. DeSegnac et al.

11 About Dose Rate D* (air) in Gy/hr & rad/hr Dose rate D* is deposited energy/kg per unit of time, i.e. per hour: 1 J/kg hr = 1 Gy/hr ~114 R/hr 100 rad/kghr MeV/kghr Slide 11 of 22 1 rad/hr = Gy/hr ~ 1.14 R/hr A 1.8 Ci 75 Se source delivers? R/hr at 1ft distance. What is the dose rate in rad/hr, Gy/hr, J/kghr, MeV/kghr? Compute the 3.75m ~3.3 rad/hr ~0.033 Gy/hr ~ J/kghr ~ MeV/kghr ~2.2 x 10-2 rad/hr ~ Gy/hr ~ J/kghr ~ MeV/kghr

12 Slide 12 of 22 COMMON RADIATION PROTECTION EQUATIONS Dose D & Dose Rate D* air - Exercises 50 R/hr ~ 1.6 Ci of 60 Co reads? R/hr at 1 meter. Compute dose rate in Gy/hr and erg/kghr. ~ Gy/hr ~1.75 x 10 5 erg/kghr A ~4.5 Ci 18 F m read ~? R/hr. Compute dose after 1.75 min in J/kg & rad. ~9.2 mj/kg ~0.92 rad The same 3.3 ft delivers? R/hr. Compute dose after 0.27 hr Gy ~ 0.85 Ci m makes? mr/hr. Compute dose rate rad/min and dose after ¾ hr ~5 mrad/min ~ 2.25 mgy

13 Slide 13 of 22 Specific Dose Constant photoeletric effect D Gym 2 /TBqhr Compton Effect Continuous improvement is the foremost prerequisite for survival. DeSegnac et al.

Slide 14 of 22 COMMON RADIATION PROTECTION EQUATIONS Specific Dose Constant D Gym 2 /TBqhr The Specific Exposure Constant X (Rm 2 /Cihr), the unit of Exposure Rate is for 1Ci @ 1m computed as X ~ 0.

14 Slide 14 of 22 COMMON RADIATION PROTECTION EQUATIONS Specific Dose Constant D Gym 2 /TBqhr The Specific Exposure Constant X (Rm 2 /Cihr), the unit of Exposure Rate is for 1m computed as X ~ 0.5 sum EN The Specific Dose Constant D (Gym 2 /Bqihr), the unit of Dose Rate for 1 1m, could be derived from X in this way. X in Rm 2 /Cihr and D in Gym 2 /Bqhr, are, for air, related by: 1 Rm 2 /Cihr ~ Gym 2 / Bqhr ~ Gym 2 /Bqhr For 1 TBq = dps 1Rm 2 /Cihr = 0.24 Gym 2 /TBqhr For E N = 1, X ~ 0.5 sum (E N) ~ ~ 0.5 Rm 2 /Cihr Thus: Gym 2 /TBqhr ~ 0.12 Gym 2 /TBqhr, thus D ~ 0.12 sum (E N) Gym 2 /TBq hr 1 Bq Ci 1 meter

15 Slide 15 of 22 COMMON RADIATION PROTECTION EQUATIONS Specific Dose Constant D Gym 2 /Bqhr Specific Dose Constant in terms of Gym 2 /TBqhr (~27 Ci) is given by: D ~ 0.12 sum E N Gym 2 /TBqhr T = Tera Radioactivity is, also, expressed, in Giga and Mega Bq, thus D ~ EN Gym 2 /GBqhr G = Giga 10 9 D ~ EN Gym 2 /MBqhr M = Mega 10 6 Find ~ D for 1 GBq 137 Cs point source E = % per decay. D ~ ~ Gym 2 /GBqhr Convert to x by dividing D with because 1 Rm 2 /Cihr = Gym 2 /GBqhr. Tus: 1 Bq Ci X ~ D / ~ 0.28 Rm 2 /Cihr air X and D are constants of rates at 1 m! air 1 meter

16 Slide 16 of 22 Specific Exposure, X & Dose, D Constants ~ X (Rm 2 /Cihr) ~ 0.5 sum (E N) ~ D (Gym 2 /TBqhr) ~ 0.12 sum (E N) X (Rm 2 /Cihr) ~ D / 0.24 D (Gym 2 /TBqhr) ~ 0.24 X ~ X R m 2 / Ci hr air 60 Co 192 Ir 137 Cs 75 Se 131 I Am 198 Au 18 F 99m Tc 24 Na ~ D Gy m 2 / TBq hr air 60 Co 192 Ir 137 Cs 75 Se 131 I Am 198 Au 18 F 99m Tc 24 Na Approximate (±20%) values of the Specific Exposure and Specific Dose constants in air are determined here for the distance of 1 meter and activities of 1 Ci for X and 1 Tbq (10 12 Bq ~27 Ci) for D. The values of X and D used in actual dose computation may differ from the given in the table. Ci/TBq 1 meter

17 Slide 17 of 22 Exposure & Dose Rates air at a d(istance) photoeletric effect Compton Effect Continuous improvement is the foremost prerequisite for survival. DeSegnac et al.

18 Slide 18 of 22 Of Exposure & Dose Rates at a d(istance) air For point sources of different activities and any distance d in meters, the exposure rate X* and dose rate D* are computed as follows: X* (R/hr) ~ { X (Rm 2 /Cihr) C(Ci)} / d 2 ~ ( X C ) / d 2 D* (Gy/hr) ~ { D (Gym 2 /TBqhr) T(TBq)} / d 2 ~ ( D T ) / d 2 Ci/TBq Example: Use the reading of? mr/hr at 1 m from a 60 Co source to compute dose rate at 1 ft and the activity of the source in Ci and TBq. Use: D ~ 0.24 X 1 meter X ~ 0.5 EN ~ ~ 1.25? D ~ 0.24 X ~ ~ 0.3? 4.2 R/hr ~ (1.25 C)/1 2 C ~ 3.36 Ci T ~ TBq D*(Gy/hr) ~( D T )/d 2 ~ ( 0.3 x ) / ~ 0.11 Gy/hr

19 Dose D & Dose Rate D* - Exercises Slide 19 of R/hr ~? Ci of 131 I reads? R/hr at 1 m meter. Compute dose rate in Gy/hr and rad/hr at 0.5 m ~0.86 Gy/hr ~ 86 rad/hr A ~? Ci 192 Ir 1 m read ~? R/hr. Compute activity. Find rad/hr & D after ft. 15 Ci, ~ 600 rad/hr, ~ 0.2 Gy The same m delivers? R/hr. Compute dose after 1 sec. ~ 0.7 Gy ~? Ci m makes? ~R/hr. Compute D*rad/hr and dose after ¾ hr. ~43 rad/hr ~ 0.3 Gy

20 Slide 20 of 22 Summary of Units & Equations photoeletric effect Compton Effect Continuous improvement is the foremost prerequisite for survival. DeSegnac et al.

21 Slide 21 of 22 Summary of Units & Equations Exposure, X, roentgens R ~ Coulombs/kg air SI unit of energy joule ; 1 J = erg ~ MeV Dose, D, joules/kg 1 J/kg = erg/kg ~ MeV/kg Dose, D, joules/kg 1 J/kg = 1 Gy gray = 100 rad R vs Gy, & rad : 1R ~ 7/ Gy ~ 7/8 rad X (Rm 2 /Cihr) ~ 0.5 sum (E N) ~ D / 0.24 photoeletric effect D (Gym 2 /TBqhr) ~ 0.12 sum (E N) ~ X 0.24 Compton Effect X* (R/hr) ~ X C (Ci ) X (R) ~ X* t (hr) D* (Gy/hr) ~ D T (TBq ) D (Gy) ~ D* t (hr) X* d) ~ ( X C ) / d 2 X d) ~ ( X* t ) / d 2 D* d) ~ ( D T ) / d 2 D d) ~ ( D* t ) / d 2

22 Slide 22 of 22 Perseverance deserves congratulations! CONTROLLED REDUCTION & PREVENTION OF THE UNWANTED EFFECTS OF IONIZING RADIATION IS THE JOB & GOAL OF RADIATION PROTECTION PROFESSION. The pictures and animations are applied under the rules of non commercial use. Continuous improvement is the foremost prerequisite for survival. DeSegnac et al.

ABOUT RADIATION EXPOSURE X

Slide 1 of 29 A DRAFT ABOUT RADIATION EXPOSURE X & EXPOSURE RATE X* CONTROLLED REDUCTION & PREVENTION OF THE UNWANTED EFFECTS OF IONIZING RADIATION IS THE JOB & GOAL OF RADIATION PROTECTION PROFESSION.