NRC Regulations and 

Guidance for Interna

Dosimetry

Professional Training Programs

Oak Ridge Associated Universities
Objectives

To review the regulatory dose quantand limits.T i th l t i To review the regulatory requ ory requiremen

monitoring for internal dose.

To review relevant published guidan
TODE 

The dose to an organ is the sum of all dothat organ from radioactive material in it aother organs, plus dose from external irraThe result is called the total organ dose equivalent (TODE).
TODE

The TODE (other than lens of the eye) m<0.5 Sv/yr (50 rem/yr) for occupationally exposed adults. 10 CFR 20.1201(a)(1)(ii)The TODE must be <50 mSv/yr (5 rem/yroccupationally exposed minors. 10 CFR 2TODE = CDE + DDE
CDE

The internal dose component of the TOD50-year integrated dose, called the comm

year integrated dose, called the comm

dose equivalent (CDE) to an organ. 
TEDE

The total effective dose equivalent (Tis the sum of the weighted CDEs anexternal dose.TEDE = CEDE + DDE
TEDE

The TEDE must be:

– < 50 mSv/yr (5 rem/yr) for occupationa

< 50 mSv/yr (5 rem/yr) for occupationaexposed adults. 10 CFR 20.1201(a)(1)

– < 5 mSv/yr (500 mrem/yr) for occupatio

< 5 mSv/yr (500 mrem/yr) for occupatio

exposed minors. 10 CFR 20.1207

– < 5 mSv (500 mrem) to the embryo/fet

< 5 mSv (500 mrem) to the embryo/fetdeclared pregnant woman for the gestaperiod. 10 CFR 20.1208

– < 1 mSv/yr (100 mrem/yr) to a membe

< 1 mSv/yr (100 mrem/yr) to a membegeneral public. 10 CFR 20.1301(a)(1) 
CEDE

The CEDE is the sum of the weighted Cfrom significantly irradiated organs.Sensitive organs have larger weightingSensitive Sensitive organs have larger weighting weighting

factors.

The committed effective dose equivalen(CEDE) represents the same risk to the worker (from intakes) as uniform externirradiation.
Dose Quantities
Secondary Derived Limi

The previously discussed dose limits primary dose limits.There are two secondary derived limthat are useful for individual dose coand determining compliance with pridose limits.
Annual Limit on Intake (A

The Annual Limit on Intake (ALI) is t

amount of a single radionuclide that deliver a CEDE of 50 mSv (5 rem) o

CDE 0 5 Sv (50 rem)CDE

0.5 Sv (50 rem).

It is useful as a benchmark figure focontrolling dose.
ALI

Values of ALIs are listed in NRC regulations 10 CFR 20, Appendix B, 

30, or Federal Guidance Report No. 
Derived Air Concentratio

(DAC)

The DAC is the concentration of a single radionuclide in air that if breathed by refeman for a full working year (2000 hours), result in an intake of one ALI.It is also useful as a benchmark figure for controlling dose since measured concentof radionuclides in air are easy to obtain fsampling results.
DAC

Tables of DACs can be found in 10 CFR Appendix B, in ICRP 30, and in Federal 

Guidance Report No. 11.
DAC

The DAC fraction, or percent of the DAC, calculated by the following formula:
DAC

If more than one radionuclide is present iair, then the DAC fraction is calculated ussum of the fractions rule:
Controlling Dose with the D

A useful operational quantity is called DAA useful operational quantity is called DAhours (DAC hours (DAC-hrs), the product of the DAC 

hrs), the product of the DAC 

and the exposure (stay) time in hours.

Dose is easily determined by multiplying Dose is easily determined by multiplying hrs by a dose conversion of 2.5 mrem pehrs by a dose conversion of 2.5 mrem pehr for a stochastic DAC value or 25 mrem nonstochastic DAC value.
Controlling Dose

The following formula represents the calculation for a stochastic DAC.
Controlling Dose

DAC and ALI values may be used to determine the individual’s dose and demonstrate compliance with the occupational dose limits 10 CFRoccupational occupational dose limits. 10 CFR

20.1201(d)
Determining Internal Dos

Internal dose may be assessed usin

– measured air concentrations measured air concentrations– measured activity in the body measured activity in the body

measured activity excreted from the bo

– measured measured activity activity excreted excreted from the bo– combinations of the above 10 CFR 20.

combinations of the above 10 CFR 20.(a)
Using Air Concentration

It is assumed that an individual breaair at the measured concentration, urespiratory protection is used. 10 CF20.1204 (b)However, the licensee must also demonstrate that the measured concentration is representative of thworker’s breathing zone.
Individual Monitoring (Inter

The RSO must evaluate which workneed to be monitored for intakes.It i ft i t id tif th It is often easier 

to identify these wo

ese wo

than to identify the group of workers must wear dosimeters. 
Who must be monitored

NRC regulations (10 CFR 20.1502) requi

monitoring for the following workers:

– workers likely to receive workers likely to receive an intake greater tha

of the applicable ALI in table 1, columns 1 an

A di B 10 CFR 20

Appendix 

B, 10 CFR 20

– declared pregnant women likely to receive a 

declared pregnant women likely to receive a greater than 1 mSv (100 mrem) during the pr
Who should be monitored

The RSO should examine the following types of identify individuals who may need to be in an intmonitoring program:

– airborne radioactivity areas airborne radioactivity areas– heavily contaminated or dusty areas heavily contaminated or dusty areas– areas where resp areas where respirators are used– areas where large quantit areas where large quantities of tritium are ha

s of tritium are ha

– Laboratories where volatile Laboratories where volatileradioactive mater

radioactive mater

such as many radioiodines, are handled
Who should be monitored

Reviewing the information on the license or permissued under the license can give the RSO an idwhere intakes could occur.A surve

y of monitorin of monitorin

g criteria indicated that few criteria indicated that few 

y g

institutions used the 10% of the ALI criterion.No consistent criteria were identified, but some w

– radioactivity, independent of form radioactivity, independent of form– radionuclide and form radionuclide and form– activity present in a single use, single order, or over a activity present in a single use, single order, or over a 

designated time span (week,months,year)
Internal Monitoring Progra

Once workers to be monitored have been identified, the RSO must design a programonitoring them.NRC regulations (10 CFR 20.1204) allow 

estimates of intakes to be made from air sampling results or bioassay. sampling results or bioassay. The RSO m

The RSO m

determine the best method to use for eacsituation or group of workers.
Internal Monitoring Progra

The internal monitoring program must be a documented part of the RPP. It must include:

– the type of monitoring performed the type of monitoring performed– the frequency of bioassay the frequency of bioassay– the length of the monitoring period the length of the monitoring period

The frequency and length of the monitoring peheavily dependent on the capabilities of the anlaboratory analyzing the results. 
Training

The RSO is responsible for training each monitored worker.The training should be standardized andThe training training should be standardized standardized and

documented.
Training

The training should include:

– why monitoring for intakes for this worker is necessary why monitoring for intakes for this worker is necessary– the types of monitoring to be performed (air sampling 

the types of monitoring to be performed (air sampling bioassay)

– the worker's responsibility to provide requeste

the worker s worker s responsibility responsibility to provide provide requeste

requeste

bioassay samples

– the worker's responsibility the worker's responsibility to notify the RSO i

is occupationally exposed is occupationally exposed outside of work (pa

outside of work (pa

jobs, etc.)

– the worker's responsibility not the worker's responsibility not to contaminate

or tamper with bioassay samples
Training

– the worker's responsibilit the worker's responsibility to notify the RSO o

previous exposure during the year while with employer, allowing the RSO to obtain these rand include the accumulated dose in the wor

yearly total.y y

– encouraging women to declare pregnancy ea

encouraging women to declare pregnancy eaallowing the RSO to adequately plan for and the dose to the fetus.
Records

Examples of important records are: 

– monitoring results monitoring results– declarations of pregnancy declarations of pregnancy

incident reports

– incident reports
References

NRC (1992). Nuclear Regulatory Commis“Monitoring Criteria and Methods to CalcuOccupational Radiation Doses,” Reg Gui(NRC, Washington, DC).O’Brien, S.L. et al., Howard Hughes MedInstitute Dose Assessment Survey. HealtPhysics 71(6):966 71(6):966-969;1996. 969;1996.