- External/Internal Exposure Limits for Occupationally Exposed Individuals
Adult ($18 yrs) Minor (< 18 yrs) Whole body* 5000 mrem/yr 500 mrem/yr Lens of eye 15000 mrem/yr 1500 mrem/yr Extremities 50000 mrem/yr 5000 mrem/yr Skin 50000 mrem/yr 5000 mrem/yr Organ 50000 mrem/yr 5000 mrem/yr
*Effective dose equivalent
- For the purpose of external exposure, whole body includes the head and trunk area (i.e., arms above the elbows, legs above the knee, and the gonads). Extremities include the hand, elbow, arm below the elbow, foot, knee, or leg below the knee.
- The whole body limit requires that internal and external exposures be summed. External exposure is determined by the use of personnel monitoring. Internal exposure may be determined by calculation and/or by the performance of bioassays (see PERSONNEL MONITORING - Bioassays). Compliance with NRC regulations is determined by comparing the amount of radioactivity in the body to the appropriate Annual Limit on Intake (ALI) in 10 CFR20, Appendix B. The limits for individuals under 18 years of age are 10% of the adult limits.
- Limits for the Embryo/Fetus of Declared Pregnant Workers
A number of studies indicate that the risks associated with radiation exposure to the embryo/fetus are greater than those to adults (see NRC Reg Guide 8.13 in Appendix CC). In keeping with this information, the NRC has established a regulatory limit of 500 mrem to the embryo/fetus of a "declared pregnant woman" for the entire gestation period. In addition, this dose must be distributed evenly throughout the gestation period (i.e., approximately 50 mrem per month). Pregnant women who are occupationally exposed to radiation have the option to "declare" their pregnancy by completing an A-7, Notice of Pregnancy, form. When pregnancy is declared, the RSO will review any previous exposures the employee may have received as well as the potential for future exposures during the pregnancy. Based upon the review, the RSO will provide specific recommendations and/or implement any additional precautions. If the pregnant employee does not declare pregnancy, the exposure limits for occupational radiation users apply.
- The ALARA Program
The RSO evaluates radiation exposures for adherence to the University's program for maintaining exposures As Low As Reasonably Achievable (ALARA). Any excessive exposures and/or deviations from the ALARA program are investigated by the RSO and reported to the RRSC. The investigation levels and the basic procedures for maintaining the ALARA program are as follows:
INTERNAL EXPOSURE Level I Level II 10 % of the applicable 30% of the applicable Annual Limit on Intake (ALI) Annual Limit on Intake (ALI) EXTERNAL EXPOSURE Level I Level II Whole body 125 mrem/qtr 375 mrem/qtr Lens of eye 375 mrem/qtr 1250 mrem/qtr Extremities 1250 mrem/qtr 3750 mrem/qtr Skin 1250 mrem/qtr 3750 mrem/qtr Organ 1250 mrem/qtr 3750 mrem/qtr
- Exposures < Level I:
Except when deemed necessary, no further action will be taken in those cases where an individual's exposure is less than those listed under Level I.
- Exposures > Level I but < Level II:
Each individual whose exposure equals or exceeds Level I will be asked to complete an Investigation of Elevated Exposure form. The RSO will then review this form and the individual's exposure history. The RSO will report the results of this review at the first RRSC meeting following the quarter when the exposure was recorded. If the exposure does not equal or exceed Level II, no action related specifically to the exposure is required unless deemed appropriate by the RSO and/or RRSC. The RRSC will, however, consider each exposure in comparison with those of others performing similar procedures as an indication of the ALARA program quality and will record the review in the RRSC minutes.
- Exposures > Level II
Each individual whose exposure equals or exceeds Level II will be asked to complete an Investigation of Elevated Exposure form. The RSO will then review this form and the individual's exposure history. The RSO will investigate in a timely manner the cause(s) of all personnel exposures equaling or exceeding Level II, and if warranted, take action. A report of the investigation, actions taken, if any, and a copy of the individual's exposure history will be presented to the RRSC at the first quarterly meeting following completion of the investigation. The details of the investigation will also be made available to NRC inspectors for review at the time of inspection.
- Establishment of higher ALARA levels:
In cases where a worker's or a group of workers' exposures are expected to routinely exceed an ALARA Level, a new, higher Level may be established if it is consistent with good ALARA practices for that individual or group. Justification for a new ALARA Level will be documented. The RRSC must review and approve all revisions of ALARA Levels.