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NEWS &
INFORMATION
Bioassay Program
As part of the recent U.S. NRC license renewal, the criteria for bioassay
have been changed. Previously, urine bioassays were required for all uses
of radioactive material involving greater than 10 mCi of activity. Thyroid
probes were required for experiments involving greater than 1 mCi of
I-125. For many radionuclides, these amounts did not reflect the true
potential for ingestion or risk of exposure.
The new program is based upon risk using the ALI (Annual Limit of Intake)
concept. Ingestion of one ALI of a radionuclide will result in an exposure
equal to the annual limit of 5000 mRem committed effective dose. The basic
criteria for the program is that a bioassay is required when 25 ALI are
used in either a single experiment or over the course of one month's time.
For the radionuclides in common use, this equates to 1 mCi of I-125; 15
mCi of P-32; 50 mCi's of C-14, Ca-45, or Cl-36; 250 mCi of S-35; 1000 mCi
of Cr-51; 2000 mCi of H-3. It may be seen that except for I-125 and P-32,
these amounts are much greater than typically purchased. ALI values for
all other radionuclides are greater than the amount typically purchased.
A summary of requirements in the program follows:
Experiments using greater than 25 ALI's of material require prior approval
from the RSO. A written description of the experimental protocol must be
submitted to the RSO on Form RSO-BIO1.
Bioassays must be conducted within 72 hours of a single use exceeding 25
ALI's. Personnel are required to deliver bioassay samples to the Radiation
Safety Office within this time period. For urine samples, 100 ml is
required. Thyroid probes are required for iodine users.
For laboratories where more than 25 ALI's is utilized over a month, but
not used in a single experiment, the Authorized User will be contacted to
identify individuals for whom bioassays may be required. Purchase records
will be used to determine which laboratories fall into this category.
Post procedure contamination surveys will no longer routinely be performed
by Radiation Safety Office personnel. Lab personnel will be responsible
for this survey, in accordance with the procedure and documentation
requirements of the "Documented Radiation Laboratory Survey
Program" outlined in the training manual. If unusual radiation levels
or contamination are determined, contact the RSO for assistance. Records
of these surveys should be maintained with other lab surveys. They are
subject to inspection by both RSO staff and NRC inspectors.
Implementation of this program has begun. The "Radiation
Safety Training Manual" and the "Regulations Regarding the Safe
Use of Sources of Ionizing Radiation" manual have been revised to
reflect this program change. If our monthly review of purchases indicates
that your lab personnel may be subject to the bioassay program, you will
be contacted and further details provided.
Iodinators will be receiving an additional notification of changes
specific to iodine labeling experiments.
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