as the amount of radiation exposure by a TLD reader, a unit that heats the
crystal and reads the exposure as well. The TLD gives an accurate exposure
reading and can be reused after proper heating (annealing).
It should be noted that exposure resulting from medical procedures and
background radiations are not included in occupational dose limits. There-
fore, radiation workers should wear film badges or dosimeters only at work.
These devices should be taken off during any medical procedures involv-
ing radiation such as radiographic procedures and dental examinations, and
also when leaving after the day’s work. Also radiation workers should not
wear these badges for certain period of time after undergoing a diagnostic
or therapeutic nuclear medicine procedure or radiation therapy permanent
implant procedure.
Dos and Don’ts in Radiation Protection Practice
Do wear laboratory coats and gloves when working with radioactive
materials.
Dowork in a ventilated fume hood while working with volatile material.
Docover the trays and workbench with absorbent paper.
Dostore and transport radioactive material in lead containers.
Dowear a film badge while working in the radiation laboratory.
Doidentify all radionuclides and dates of assay on the containers.
Dosurvey work areas for contamination as frequently as possible.
Doclean up spills promptly and survey the area after cleaning.
Do noteat, drink, or smoke in the radiation laboratory.
Do notpipette any radioactive material by mouth.
Domonitor hands and feet after the day’s work.
Donotify the radiation safety officer (RSO) in the case of any major spill
or other emergencies related to radiation.
Bioassay
NRC Regulatory Guide 8.20 gives the details of bioassay requirements for
(^131) I and (^125) I radionuclides. Bioassays are required when the level of radioio-
dine activity handled (volatile or dispersible) exceeds the following values:
Open bench: 1 mCi (37 MBq)
Fume hood: 10 mCi (370 MBq)
Glove box: 100 mCi (3.7 GBq)
When the radioiodinated material is nonvolatile, the limits of activity are
higher by a factor of 10. Stricter limits may be imposed in the license by the
NRC.
For iodine radionuclides, bioassay is performed by the thyroid uptake test
within 72 hr and at 14 days after handling the radioactivity. Sometimes urine
analysis may also be required soon after the exposure. Bioassays may be
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