The Nuclear Regulatory Commission (NRC) and Minnesota Department of
Health regulations require that all individuals who work in areas where
personal radiation monitoring is required, must receive radiation
protection training prior to using sources of ionizing radiation.
Therefore, training documentation is a prerequisite to obtaining
a radiation monitoring dosimeter.
Radiation Dose received by individuals must be
maintained as low as reasonably achievable within the radiation dose
limits specified by the NRC regulations, and University license
The following is a description of personnel
monitoring methods, and procedures for the measurement of radiation
doses received by individuals using sources of ionizing radiation.
Dose Assessment: Personal Monitoring Devices
The following are three types of external personal
monitoring devices (dosimeters) commonly used at the University.
- Thermo-Luminescent Dosimeter (TLD) Body
Used primarily for monitoring the radiation dose to the trunk of the
- TLD Rings: Used primarily for
monitoring radiation dose to the hands and wrist.
- Film Badges: A monthly body
dosimeter used to monitor exposure of declared pregnant employees.
Personal radiation monitoring dosimeters do not
protect individuals from the effect of radiation, but only record the
radiation dose an individual has accumulated.
Dose Assessment: Bioassay
When quantities of radioactive material used by
personnel presents a potential for internal contamination, or in the
event of a radioactive material spill, the Radiation Protection
Division (RPD) will require the necessary bioassay procedure to
determine the quantity of the internal disposition and the resulting
dose if any.
All bioassay procedures are performed by the
Department of Environmental Health and Safety, or by persons or
organizations approved by the RPD. RPD will maintain radiation
dose records on all personnel requiring bioassay for assessment of
possible internal deposition.
In general the following three bioassays
procedures may be used.
How to Apply for, and Obtain a Radiation Monitoring
- Urine Analysis: Will be
performed on any individual who uses more than 100 mill-Curies (mCi) of
tritiated water, gas or sodium borohydrade, or more than 10 mCi of 3H-Labeled
nucleotides per experiment within one week. If the above
quantities are used routinely, a weekly urine analysis (bioassay) is
- Thyroid counts: Performed on any
individual who uses 125I and 131I (Iodine 125,
131) in procedures where volatilization is likely (e.g. protein
labeling, column separation, dialysis) within one week following the
procedure. For continuing operations of the above procedures,
monthly thyroid counts are required.
- Whole Body Count: Required when
appreciable internal contamination is suspected or when the potential
for internal contamination warrants the procedure.
- Application request cards of appropriate
radiation dosimeters for assessment of personnel radiation dose are
available from the UMD Environmental Health and Safety Office, 31 DAdB,
- Completed request cards should be sent to the
RPD at the address listed on the request card.
- Personnel radiation dosimeters are not
necessary for individuals who use 3H, 14C. 35S,
33P, 45Ca or other low
energy beta emitters, because these radioisotopes present little or no
external radiation exposure potential. For 32P Users,
dosimetry is required only when the activity of the isotope used is at
or above 0.5 mCi, and a TLD Ring is also required if the activity is at
or above 1 mCi. Questions on when a personal dosimeter is
required should be referred to the Radiation Protection Division (612)
- The UMD EHS-Office will have replacement
dosimeters, and will be responsible for returning all exposed
dosimeters to the RPD on the designated monthly or quarterly change
- Individual dosimeter holders are responsible
for returning their dosimeters on the scheduled change date.
Failure to do so may result in a financial penalty issued by the