United States Nuclear Regulatory Commission - Protecting People and the Environment

Information Notice No. 96-57: Incident-Reporting Requirements Involving Intakes, During a 24-Hour Period that may cause a Total Effective Dose Equivalent in Excess of 0.05 Sv (5 rem)

                                         UNITED STATES
                                 NUCLEAR REGULATORY COMMISSION
                                     WASHINGTON, DC  20555

                                       October 30, 1996

                                        INVOLVING INTAKES, DURING A 24-HOUR
                                        PERIOD THAT MAY CAUSE A TOTAL EFFECTIVE                
                                           DOSE EQUIVALENT IN EXCESS OF 0.05 Sv             
                                           (5 rem)


All U.S. Nuclear Regulatory Commission licensees.  


The U.S. Nuclear Regulatory Commission (NRC) is issuing this information notice to remind
recipients of certain incident notification requirements found in 10 CFR 20.2202(b)(1)(i)
relating to intakes received during a 24-hour period that may cause a Total Effective Dose
Equivalent (TEDE) in excess of 0.05 Sv (5 rem).  It is expected that recipients will review the
information for applicability to their facilities, to ensure that this information is considered
when making a decision about the reporting of a radiation exposure incident.  However, this
information notice does not contain NRC requirements; therefore, no specific action nor
written response is required.  

Description of Circumstances

Recently, NRC was informed of, and responded to, two incidents involving phosphorus-32 
(P-32) and the resulting internal contamination of individuals at biomedical research facilities. 
P-32 is a radioisotope widely used in research institutions, as are many other radionuclides. 
Although only one of these events raised a question associated with reporting requirements
and is discussed below, our concerns regarding reporting of incidents involving internal
exposure extend to all facilities using licensed material.  

On October 16, 1995, a licensee informed the NRC that an incident involving internal
contamination of a researcher had occurred at its facility almost two months earlier.  The
licensee's final evaluation of the TEDE received by the individual was 0.048 Sv (4.8 rem)
which was within 5 percent of the annual limit of 0.05 Sv (5 rem).  An NRC Incident
Investigation Team analysis (NUREG-1535, "Ingestion of Phosphorus-32 at Massachusetts
Institute of Technology, Cambridge, Massachusetts, Identified on August 19, 1996")
concluded that the licensee's final dose assessment was appropriate, but further concluded 

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                                                                        October 30, 1996
                                                                        Page 2 of 3

that data available within the first week was sufficient to indicate that the event threatened to
cause an individual to receive a TEDE in excess of 0.05 Sv (5 rem).  Licensee officials told 
NRC staff that they had not reported the incident earlier because their analysis indicated that
the researcher's TEDE received during the first 24 hours did not require reporting, pursuant
to 10 CFR 20.2202(b)(1)(i).

The pertinent rule, 10 CFR 20.2202(b)(1)(i), states "...each licensee shall, within 24 hours of
discovery of the event, report any event involving loss of control of licensed material
possessed by the licensee that may have caused, or threatens to cause, any of the following

       (1) An individual to receive, in a period of 24 hours--
              (i) A total effective dose equivalent exceeding 5 rem (0.05 Sv);or..."

The licensee had interpreted this to mean that the dose actually received by the individual
during the particular 24 hours following the event had to exceed 0.05 Sv (5 rem) before the
24�hour notification was required.  This interpretation is not consistent with the definitions of
TEDE, committed effective dose equivalent (CEDE), and committed dose equivalent (CDE) in
10 CFR 20.1003.


As noted above 10 CFR 20.2202(b)(1)(i) requires 24-hour notification if a loss of control of
licensed material may have caused, or threatens to cause, an individual to receive, in a
period of 24 hours, a TEDE exceeding 0.05 Sv (5 rems).  NRC's interpretation of the rule is
derived from the definitions in 10 CFR 20.1003 as follows:  TEDE is defined as the sum of
the deep-dose equivalent (for external exposures) and the CEDE (for internal exposures),
CEDE is the sum of the products of the weighing factors applicable to each of the body
organs or tissues that are irradiated and the CDE to these organs or tissues, and CDE
means the dose equivalent to organs or tissues of reference that will be received from an
intake of radioactive material by an individual during the 50-year period following the intake.  

Licensees are required by 10 CFR 20.2202(b)(1)(i) to report the TEDE received by an
individual that is based on all doses received during the 24-hour period, including committed
doses (i.e., the CEDE) and not just the doses delivered during the 24-hour period.  For
internal doses, the 24-hour period specified in 10 CFR 20.2202(b)(1) refers to the period of
intake and not the period of dose delivery.  In the case described above, the CEDE from the
intake received during the event (in a period of 24 hours) threatened to exceed 0.05 Sv
(5 rem).  Because this case does not involve external exposure (rather, only ingestion),
CEDE is equal to TEDE.  In such a case, a licensee would be required by 10 CFR
20.2202(b)(1)(i) to notify NRC within 24 hours of discovery of the event.  

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                                                                        October 30, 1996
                                                                        Page 3 of 3

This information notice requires no specific action nor written response.  If you have any
questions about the information in this notice, please contact the technical contacts listed
below or the appropriate regional office. 

       signed by                                                 signed by

Thomas T. Martin, Director                                Donald A. Cool, Director 
Division of Reactor Program Management                    Division of Industrial and 
Office of Nuclear Reactor Regulation                        Medical Nuclear Safety
                                                               Office of Nuclear Material Safety     
                                                              and Safeguards

Technical contacts:   Cynthia G. Jones, NMSS
                      (301) 415-7853
                      Email:  cgj@nrc.gov

                      James E. Wigginton, NRR
                      (301) 415-1059
                      Email:  jew2@nrc.gov
Page Last Reviewed/Updated Thursday, November 21, 2013