Radiological Monitoring and Measurement 1

OBJECTIVES Allow the participants to understand the concepts of measuring dose received by radiation workers Equipment used in measuring radiation exposure Method of measurement radiation dose Monitoring radiation dose of personnel and working areas 2

MONITORING OF PERSONNEL & WORKPLACE - LOGICAL Max permissible level not exceeded Limit exposure to individual radiographer /worker (as low as possible) Assist medical authority in making analysis in the case of accidental exposure Provide information about work practices & personal dose history 3

MONITORING WEB Radiation Contamination IndividualArea Film dosimeter TLD Pocket Dosimeter Integrating dosimeter Beta Ion chamber Film dosimeter Gamma Neutron Dose Eq. Meter (Rem meter) Film dosimeter TLD Ion chamberGM tube Survey meter installed monitor Individual Area Surface contamination Airborne contamination Survey meter Smear GM Probe Continuous Sample Lab counters (GM tube, Scintillation Counters WBC, Air Sampler Bioassay etc 4

RADIATION MONITORING Personal monitoring Area/Workplace monitoring 5

PERSONAL MONITORING Objectives: To estimate of external radiation received by workers To obtain estimate of internal exposures related to intake radionuclides      , β x-rays 6

PERSONAL MONITORING EQUIPMENT FOR EXTERNAL EXPOSURES Film badge Thermoluminescent dosimeter (TLD) Pocket dosimeter - Quartz Fiber Electrometer (supplement Personal Dosimeter) 7

FILM BADGE The PTW film badge for personal dosimetry type 8621 Open Window 0.05mmCu 0.3mmCu 1.2mmCu 0.8mmPb Open Window 0.05mmCu 0.3mmCu 1.2mmCu 0.8mmPb 8

FILM BADGE Measured doses between 0.2 mSv (20mR) - 50mSv (5000mR) depend on source energy. Disadvantage: sensitive to heat & humidity 9

THERMOLUMINESCENT DOSIMETER (TLD) For whole body and extremity monitors For whole body and extremity monitors Characteristics: Wide linear range, short readout time, lightweight, reusability & energy dependence (for phosphor) Characteristics: Wide linear range, short readout time, lightweight, reusability & energy dependence (for phosphor) Read using TLD Reader Read using TLD Reader TLD materials: LiF (phosphor), CaF 2 :Mn activated, LiB 2 O 3 :Mn, CaSO 4 (phosphor) TLD materials: LiF (phosphor), CaF 2 :Mn activated, LiB 2 O 3 :Mn, CaSO 4 (phosphor) 10 Whole body Extremity TLD-Chip

TL- READER SYSTEM TLD-Chip and TLD-card for personnel, extremity and area monitoring 11

Advantage of TLD over films: Can be reused. Not as sensitive to moderate heat as is film. More responsive to a wide photon energy range. More sensitive to radiation. Disadvantages over film: Expensive. Non-permanent record. COMPARISON OF TLD AND FILMS 12

POCKET DOSIMETER - QUARTZ FIBER ELECTROMETER “Pen dosimeter”/ ”Pocket Dosimeter” Direct Reading of dosimeter - contains magnifying glass window to observe reading on the meter enclosed in Aluminium case Consists of ion chamber & Quartz fiber electroscope as indicating element Dose range mGy (0-50mR) or up to 1000 mGy (100R) Can also be used to measure fast & thermal neutrons dose 13

Structure of Pocket Dosimeter 14

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GENERAL RULES FOR USING PERSONNEL DOSIMETER User must wear dosimeter all the time when working with & around radiation Dosimeter should be placed at the body location likely to receive the highest exposure, I.e., between waist & neck level Dosimeter should be worn only by person to whom it is issued Personnel should use film dosimeter with the same identification number for the whole working life otherwise notified. This is in order to facilitate recording & traceability 17

GENERAL RULE FOR USING PERSONNEL DOSIMETER (cont.) Never use holder other than recommended by Nuclear Malaysia Never use dosimeter without holder Never allow any object such as pens to shield the front of dosimeter Dosimeter should be prevented against damage by heat, moisture, pressure & contamination Dosimeter should not be worn during non-occupational exposure, such as during treatments with medical & dental x-rays Dosimeter not in use should be kept in uncontrolled area Dosimeter should be changed monthly regardless of exposure 18

GENERAL RULE FOR USING PERSONNEL DOSIMETER (cont.) Continue using the old dosimeter until the new one received & return immediately the used dosimeter to Nuclear Malaysia dose evaluation Finger ring dosimeter should be worn if hands are likely to receive higher radiation exposure than other part of the body For those wearing lead apron, dosimeter should be worn at the neck outside the apron A unique identification number is issued by Nuclear Malaysia for each personal In case of accident/suspected accident in which personnel likely to receive high dose, send dosimeter immediately to Nuclear Malaysia for dose evaluation Nuclear Malaysia should be informed ONE month prior to termination of usage of dosimeter 19

RULE OF WEARING PERSONAL DOSIMETER 20 Film Badge and Pocket Dosimeter worn by a radiation worker

PERSONAL MONITORING FOR INTERNAL EXPOSURES EXTERNAL MEASUREMENT of internal contamination using Whole Body Counter, Lung Counter & Thyroid Counter BIOASSAY of excreta & Body fluid using Scintillation counter    21

Example – Whole Body Counter 22 Chair typeBed type Lung + Thyroid Counter Spectra

INITIATION OF PERSONAL MONITORING FOR INTERNAL EXPOSURE When there is indication of air contamination which may lead to significant inhalation (Uranium mine) When personnel involved in accident of unsealed sources Simple test of skin & nose indicating internal contamination Personal air sampling placed at the nose via filter indicates internal contamination 23

Example Bioassay – Alpha preparation 24

AREA/WORKPLACE MONITORING AREA/WORKPLACE MONITORING Routine monitoring Operational monitoring Special Monitoring 25

ROUTINE MONITORING Monitoring intended to show that workplace environment is satisfactory No significant changes/ review in the procedures or operation necessary Continuous monitoring 26

OPERATIONAL MONITORING Monitoring intended to provide checks on a Monitoring intended to provide checks on a particular operation If necessary, provide basis for immediate decision on conduct of an operation 27

SPECIAL MONITORING Monitoring situation in working environment when insufficient information available to achieve adequate control of operation Monitoring carried out when there was an abnormal circumstances/ accidents/ suspected accidents 28

RADIATION MONITORS Installed area radiation monitors Portable radiation monitors (Survey meters) Radiation monitoring devicePassive type dosimeter 29

PORTABLE RADIATION MONITORS (SURVEY METERS) Ionization chamber Geiger Muller (GM) probe (  particle detector with thin window) 30

CALIBRATION OF SURVEY METER Example of calibration certificate and striker 31

CONTAMINATION MONITORS Surface contamination monitors Airborne contamination monitors 32

SURFACE CONTAMINATION MONITORS Two techniques: – –Probe monitor or – –smear monitor the surface with tissue and count using Alpha,  contamination - Scintillation detector (ZnS), Proportional Counter Beta-gamma,  - , contamination - GM detector, Scintillation counter 33

AIRBORNE CONTAMINATION MONITORS Use Air Sample Collector (e.g. Cellulose filter paper) via vacuum suction equipped with flow meter Cellulose filter paper send to laboratory to measure trapped radioactive particles Particles include - radioactive particles in air - radioiodine in air - radioactive gas in air 34

RECORD KEEPING Health register - kept for 30 years after last entry Source/Equipment register - contains source/equipment particulars & results of leakage test - kept for 5 years after last entry Instrument register - record on results & test of instrument & kept for 2 years after last entry Report of unusual occurrence - kept for 30 years Waste disposal record 2 years- temporary & permanent disposal 35

RECORD KEEPING of worker exposures Purpose of keeping records: To demonstrate company compliance to regulations Administrative control of worker exposures Benefit of employee with regard to his future employment in working with radiation Classes of records Temporary Permanent 36

RECORD KEEPING of worker exposures Content of record of personnel Identification Information of company or organization keeping the record All date, day, month & year relevant to the record The dose received (mSv) by personnel Information to indicate period of measurement 37

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