Successfully reported this slideshow.
We use your LinkedIn profile and activity data to personalize ads and to show you more relevant ads. You can change your ad preferences anytime.

51

Share

Download to read offline

Radiation Dosimeters

Download to read offline

Related Books

Free with a 30 day trial from Scribd

See all

Related Audiobooks

Free with a 30 day trial from Scribd

See all

Radiation Dosimeters

  1. 1. General requirements for dosimeters #Dosimeter is a device that measures directly or indirectly • Exposure • Kerma • Absorbed dose • Equivalent dose • Or other related quantities. #The dosimeter along with its reader is referred to as a dosimetry system.
  2. 2. A useful dosimeter exhibits the following properties: • High accuracy and precision • Linearity of signal with dose over a wide range • Small dose and dose rate dependence • Flat Energy response • Small directional dependence • High spatial resolution • Large dynamic range
  3. 3.  Accuracy specifies the proximity of the mean value of a measurement to the true value.  Precision specifies the degree of reproducibility of a measurement. Note: High precision is equivalent to small standard deviation.
  4. 4. Examples for use of precision and accuracy: High precision High precision Low precision Low precision and and and and High accuracy Low accuracy High accuracy Low accuracy
  5. 5. Note: The accuracy and precision associated with a measurement is often expressed in terms of its uncertainty.
  6. 6. New Concept by the International Organization for Standardization (ISO) "Guide to the expression of uncertainty in measurement“  This new guide serves as a clear procedure for characterizing the quality of a measurement.  It is easily understood and generally accepted.  It defines uncertainty as a quantifiable attribute.
  7. 7.  Standard uncertainty: is the uncertainty of a result expressed as standard deviation.  Type A standard uncertainty is evaluated by statistical analysis of a series of observations.  Type B standard uncertainty is evaluated by means other than statistical analysis. This classification is for convenience of discussion only.  It is not meant to indicate that there is a difference in the nature of  the uncertainty such as random or systematic.
  8. 8.  Combined uncertainties: The determination of the final result is normally based on several components. Linearity:  The dosimeter reading should be linearly proportional to the dosimetric quantity.  Beyond a certain range, usually a non-linearity sets in.  This effect depends on the type of dosimeter.
  9. 9. Two possible cases Case A: • linearity • supralinearity • saturation Case B: • linearity • saturation
  10. 10. Dose rate dependence :  M/D may be called the response of a dosimeter system  When an integrated response is measured, the dosimetric quantity should be independent of the dose rate dD/dt of the quantity.  Other formulation: The response M/D should be constant for different dose rates (dD/dt)1 and (dD/dt) 2. M = 􀀁 (M / D)(dD / dt)dt M = (M / D)􀀁 (dD / dt)dt
  11. 11.  Energy: The response of a dosimetric system is generally a function of the radiation energy.  The term "radiation quality" is often used to express a specific distribution of the energy of radiation.  Therefore, a dependence on energy can also be called a dependence on radiation quality.  Since calibration is done at a specified beam quality, a reading should generally be corrected if the user's beam quality is not identical to the calibration beam quality.
  12. 12. A small radiation monitoring device worn by persons entering environments that may contain radiation . # Desirable characteristics  Should be lightweight, durable, and reliable  Should be inexpensive
  13. 13.  Healthcare or laboratory workers in non- emergency environments that may contain radiation  Examples: radiology, nuclear medicine, and radiation oncology department staff  Workers in emergency environments that may contain radiation  Examples: first responders and first receivers  Workers in industrial environments where radiation is used  Examples: nuclear power plant workers or employees at radiation sterilizing facilities
  14. 14.  Flat badges are usually worn on the torso, at the collar or chest level, but can be worn on the belt, or forearm  Ring shaped badges can be worn on the finger when dose to the finger may exceed dose to the badge worn elsewhere on the body  First responders and first receivers  Wear water-resistant personal dosimeters on the outer layer of personal protective equipment (PPE).  Should be able to easily see and hear a dosimeter alarm while wearing PPE  May wear a personal dosimeter underneath waterproof outerwear
  15. 15.  Film badge  Pocket ionization chambers  Thermo luminescent dosimeters (TLD)  Optically stimulated luminescence (OSL)  Solid State
  16. 16.  Most widely used and most economical  Consists of three parts:  Plastic film holder  Metal filters  Film packet  Can read x, gamma, and beta radiation  Accurate from 10mrem - 500rem  Developed and read by densitometer  A certain density value equals a certain level of radiation  Read with a control badge  Results generally sent as a printout
  17. 17.  Lightweight, durable, portable  Cost efficient  Permanent legal record  Can differentiate between scatter and primary beam  Can discriminate between x, gamma, and beta radiation  Can indicate direction from where radiation came from  Control badge can indicate if exposed in transit  Only records exposure where it’s worn  Not effective if not worn  Can be affected by heat and humidity  Sensitivity is decreased above and below 50 keV  Exposure cannot be determined on day of exposure  Accuracy limited to + or - 20%
  18. 18.  The most sensitive personnel dosimeter  Two types  Self-reading  Non self-reading  Can only be read once  Detects gamma or x-radiation
  19. 19.  Small, compact, easy to use  Reasonably accurate and sensitive  Provides immediate reading  Expensive  Readings can be lost  Must be read each day  No permanent record  Susceptible to false readout if dropped or jarred
  20. 20.  Looks like a film badge  Contains a lithium fluoride crystal  Responds to radiation similarly to skin  Measured by a TLD analyzer  Crystal will luminescence if exposed to radiation, then heated  More accurate than a film badge
  21. 21.  Crystals contained in TLD interact with ionizing radiation as tissue does  Determines dose more accurately  The initial cost is greater than that of a film badge  Can only be read once  Records exposure only where worn
  22. 22. • “Captures” information in an Aluminum Oxide matrix • Releases information by laser stimulation • Can be reread after processing • Durable • Landauer Only
  23. 23.  Provides instantaneous information regarding dose accumulation  Simple to use  Not a “legal” record  Dose range device dependent
  • SouravBarman22

    May. 4, 2021
  • ShashankKothari15

    Apr. 22, 2021
  • geethap15

    Feb. 19, 2021
  • SMajeed3

    Dec. 21, 2020
  • andrewchristopher20

    Dec. 21, 2020
  • AbuSayeed37

    Dec. 18, 2020
  • SheebaBhardwaj

    Jun. 24, 2020
  • AungThu55

    May. 12, 2020
  • ShaikhFatima1

    Mar. 22, 2020
  • Rbakshi1

    Mar. 4, 2020
  • NandiniM19

    Dec. 30, 2019
  • SushmaTanniru

    Oct. 11, 2019
  • Kamal1240

    Sep. 18, 2019
  • badushavp

    Jul. 10, 2019
  • PoojaGupta370

    Jun. 3, 2019
  • BishwoDangol

    May. 30, 2019
  • BalpinderBharaj

    May. 20, 2019
  • MaliniChinnu1

    Mar. 28, 2019
  • BharatSingh289

    Dec. 30, 2018
  • khaledelorfi

    Dec. 8, 2018

Views

Total views

22,469

On Slideshare

0

From embeds

0

Number of embeds

17

Actions

Downloads

901

Shares

0

Comments

0

Likes

51

×