Adult: > 18 Years ALARA: As low as reasonably achievable ALI:

Transcription

1 Health Physics

2 Adult: > 18 Years ALARA: As low as reasonably achievable ALI: Annual Limit on Intake. The amount of an isotope that if taken into the body over the course of a year would result in in a whole body dose of 5 rem, or an organ dose of 50 rem. Which ever value is smaller is utilized

3 Committed Dose Equivalent: Cumulative dose to organs or tissues from an intake over the 50 years following the intake Derived Air Concentration: The air concentration, that if breathed continuously would result in a worker intake equal to 1 ALI (work year =2000 hours, hours). Extremity: Hands/ Forearm/ Elbow/ Foot/ Calf/ Knee. Basically from the joint (knee/ elbow) down.

4 Source Material Ur or Th in any form other than special nuclear Special Nuclear Material Pl, Ur-233 or any substance enriched in Ur-233 or U235

5 Whole Body 5 Rem/ yr Eyes 15 Rem/ yr Individual Organ 50 Rem/ yr Skin and Extremities 50 Rem/ yr

6 Whole Body 0.5 Rem/ yr Eyes 1.5 Rem/ yr Individual Organ 5 Rem/ yr Skin and Extremities 5 Rem/ yr

7 Whole Body 50 mrem/ yr Spread evenly through a 10 month preganacy Eyes 15 Rem/ yr Individual Organ 50 Rem/ yr Skin and Extremities 50 Rem/ yr

8 Dose Limit 100 mrem/yr Dose Rate Limit 2 mrem/ hr

9 Several tables with different limits on it. ALI/ DAC and Effluent Concentrations? Effluent Concentration Limits : Generally speaking these are Gas/Water Concentration Limits that are released to the public, so they are based on the public limits (actually ½ the public limit, 50 mrem (instead of 100 mrem) for extra conservatism). These control how much we can release, the TS limit for Ar-41 comes directly from 10CFR20 Appendix B

10 1 x 10-8 μci/ml

11 Personal Monitoring (TLDs/ internal monitoring): Required if someone could reasonably expect to exceed 10% of the their limit/ali in 1 year

12 Several Areas need to be posted

13 > 5 30 cm, dose rate Posted as CAUTION RADIATION AREA

14 > cm, dose rate Posted as CAUTION or DANGER HIGH RADIATION AREA

15 Each Entry Point must be: Equipped with a control device that: reduces radiation <100 mrem / hr upon entry Or Alarms such that licensee or supervisor is made aware of entry and person entering area OR Must remain locked unless access is required and positive control over individuals is maintained *Access control must not prevent exiting the space *for areas established direct surveillance may be substituted for access controls

16 500 rads/ 1m Note exposure NOT dose Posted as GRAVE DANGER VERY HIGH RADIATION AREA Additional Restrictions Must meet requirements for High Radiation area and also must be protected to ensure not unauthorized access can occur

17 Listed 10 CFR 20 appx B Must be posted if exceed values on appx B or.6ali Posted as CAUTION or DANGER AIRBORNE RADIOACTIVITY AREA

18 Listed 10 CFR 20 appx C Posted as CAUTION RADIOACTIVE MATERIALS Must be posted in each room that licensed materials are stored and used (except natural Ur or Th)

19 Exposure amount of ionization per unit mass due to gammas or x-rays in air Unit: Roentgen Absorbed Dose Energy deposited by radiation/ Unit Mass of a material Unit: Rad Rad (1 rad=100erg/ gram)

20 Biological Dose Equivalent Absorbed does that produces the biological tissue damage equivalent to 200 Kev X-rays Unit: REM Rem= rad * QF

21 Quality factor Conversion factor between absorbed dose and dose equivalent for a given energy and type of radiation QF = Rem/ Rad NRC QFs X-rays, β, ϒ: 1 Ns & Ps: 10 α, fps: 20

22 Per the NRC 10CFR20 Definitions page TEDE: means the sum of the effective dose equivalent (for external exposures) and the committed effective dose equivalent (for internal exposures).

23 Effective Dose Equivalent (EDE): is the sum of the products of the dose equivalent to the organ or tissue (H T ) and the weighting factors (W T ) applicable to each of the body organs or tissues that are irradiated (H E = ΣW T H T ). Committed effective dose equivalent (CEDE): is a measure of the stochastic (i.e., probabilistic) health effect on an individual due to an intake of radioactive material into their body over the next 50 years after the intake. It takes into account the biological and radiological ½ lives of the isotopes and intended to carry the same effective risk as if the source had been external as in the DDE. Sometimes called organ dose

24 Total effective Dose Equivalent (TEDE): This is the NRC Term that once calculated is regulated by the Whole Body Dose used in limits listed in the 10 CFRs. For the actual calculation its is not possible to actually calculated EDE so something called Deep Dose Equivalent is used.

25 Deep Dose Equivalent: Applies to external whole-body exposure, is the dose equivalent at a tissue depth of 1 cm (1000 mg/cm 2 ) Can actually be determined with a TLD TEDE = DDE + CEDE Or TEDE= DDE + Organ Dose

26 The NRC formula Chart give the following equation. (combo of two equations) DR= (6CEn / R 2 ) Where: DR Rem Ci curies E Mev R feet

27 foot = 6CEn

28 Point source DRd 1 2 = DRd 2 2

29 A f = A i e λt Where A f = Activity Final A i = Activity Initial λ= Decay Constant = (Ln2/ half life) t= time Half Life Amount of time that it takes for decay to reduce the activity by ½ such that A f /A i =1/2

30 I f = I i 10 x/t 1/10 Where I f = Intensity Final A i = Activity Initial t 1/10= tenth thickness x= thickness of material Tenth Thickness Amount of a material that will reduce the activity by 1/10 such that I f /I i =1/10

31 Half Thickness Amount of a material that will reduce the activity by 1/2 such that I f /I i =1/2

32 μ x I = I i e Where I f = Intensity Final A i = Activity Initial μ= linear attenuation coefficient x= thickness of material

33 Up to 75 Rem to save a life/ 25 Rem to mitigate consequences of an accident Once in a lifetime only Preference given to the oldest able-bodied person. Authorized by the Onsite Manager

34 During an Emergency, the RS-OEC may authorize personnel voluntary whole body exposure up to 75 rem dose equivalent per individual for life saving actions. This individual is authorized to receive up to 75 rem dose equivalent per: a. annual basis b. each emergency c. twice in a lifetime d. once in a lifetime Answer D

35 An area in which radiation levels could result in an individual receiving a dose equivalent in excess of 100 mrem/hr is defined as: a. Radiation area b. Restricted Area c. High Radiation Area d. Very High Radiation Area Answer C

36 A radioactive source reads 10 Rem/hr on contact. Five hours later, the same source reads 1.0 Rem/hr. How long is the time for the source to decay from a reading of 10 Rem/hr to 10 mrem/hr? a. 10 hours b. 15 hours c. 20 hours d. 25 hours Answer B

37 The radiation from an unshielded source is 1 rem/hr. When a 60 mm thickness of lead sheet is inserted; the radiation level reduces to 125 mrem/hr. What is the half-value-layer of lead? (HVL): thickness of lead required so that the original intensity will be reduced by half)? a. 10 mm b. 20 mm c. 30 mm d. 40 mm Answer B

38 A small radioactive source is to be stored in the reactor building. The source is estimated to contain 10 curies and emit 100% of 110-Kev gamma. Assuming no shielding used, how far is a distant that reads 100 mrem/hr? a. 8 feet b. 24 feet c. 75 feet d. 257 feet Answer A

39 Which one of the following is the definition of Total Effective Dose Equivalent (TEDE) specified in 10 CFR Part 20? a. The sum of thyroid dose and external dose b. The sum of the external deep dose and the organ dose c. The sum of the deep dose equivalent and the committed effective dose equivalent d. The dose that your whole body is received from the source, but excluded from the deep Dose Answer C

40 Which type of following radiation will travel through air with the shortest distance? a. neutron b. alpha c. beta d. Gamma Answer B