ML20035E037

Draft Rev 1 to Reg Guide 08.009,task DG-8009, Interpretation of Bioassay Data

ML20035E037
Person / Time
Issue date:	03/31/1993
From:	NRC OFFICE OF NUCLEAR REGULATORY RESEARCH (RES)
To:
References
RTR-REGGD-8.009, TASK-DG-8009, TASK-RE RE08.009-930331, RE8.009-930331, NUDOCS 9304140197
Download: ML20035E037 (29)

Text

.

U. S. NUCLEAR REGULATORY COMMISSION asson i March 1993 p su cg

/

T REGULATORY GUIDE g

e g%n f

OFFICE OF NUCLEAR REGULATORY RESEARCH o..e REGULATORY GUIDE 8.9, Revision 'l (Draft was issued as DG-Boo 9) p@

INTERPRETATION OF BIOASSAY DATA A. INTRODUCTION certain unusual circumstances, such as exposures at or near the limits, special consideration may Section 20.1204 of 10 CFR Part 20, need to be given to the specifics of an individual's

" Standards for Protection Against Radiation,"

retention and elimination in determining the intake.

i requires that each licensee, when required by 10 CFR 11 is not the intent of this regulatory guide to 20.1502, take suitable and timely measurements of constrain licensees from performing more quantities of radionuclides in the body, quantities of elaborate analyses when the licensee determines radionuclides excreted from the body, concentrations that the magnitude of the exposure warrants of radioactive materials in the air in the work area, or further investigation.

any combination of such measurements as may be necessary for detection and assessment of individual This guide describes a practical and intakes of radioactive material.

Furthermore, consistent method acceptable to the NRC staff for 120.1204(c)(1) allows for the use of specific estimating intake of radionuclides from bioassay information on the physical and biochemical measurements. Additionalprogrammaticguidance properties of the radioactive material deposited in the is presented in other documents, including ICRP body in determining an individual's intemal dose.

Report No. 54 (Ref.1) and NCRP Report No. 87 Also, as stated in 120.1703(3)(ii), if respiratory (Ref. 2).

protection equipment is used to limit intakes of airborne radioactive material, a licensee shall conduct Any information collection activities bioassay measurements, as appropriate, to evaluate mentioned in this guide are contained as actual intakes of airborne activity.

requirements in 10 CFR Part 20, which provides the regulatory basis for this gdde.

The Due to differences in physical properties and information collection requirements in 10 CFR Part metabolic processes, each individual's dose resulting 20 have been cleared under OMB Clearance No.

from an exposure is unique. In other words, the 3150-0014.

same exposure to multiple individuals will cause different doses to each individual. However, for the purpose of demonstrating compliance with dose limits, standard approaches for determining intake and calculating a dose have been developed. For USNRC 51GU1AToRY GUIDL's The gu60es are issued in ttw fobowong ten twood div6ssons:

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9304140197 930331 N

I PDR REGGD OB.009 R PDR h-

t B. DISCUSSIOld characteristics and biochemical processes may be' l

different.

In addition, the particulars of the i

Bioassay measurements include the analysis of exposuie situation, such_ as particle size

[

radioactive material in body organs or in the whole distribution, will affect the lung compartment j

body (in vivo measurements) and in biological deposition fractions and the resultant biological I

material excreted, eliminated, or otherwise removed clearances. For example, particles larger than 20 l

from the body (in vitro measurements). The in vivo pm will deposit mainly in the naso-pharyngeal (N-

[

measurements are made using a whole body counter, P) region and may show biological retention and 7

thyroid counter, lung counter, or other similar device.

elimination characteristics more typical of an The in vitro measurements involve collection of urine, ingestion intake than for an inhalation intake of

feces, or tissue samples accompanied by the default 1 pm AMAD'. This characteristic is radiochemical analysis using techniques such as due to the fact that a large fraction of particles gamma spectroscopy or chemical separation followed deposited in the N-P region is cleared by the.

I by alpha or beta analysis.

ciliated epithelial-cells to the throat and subsequently swallowed, thereby appearing to be ICRP Publication 30 (Ref.

3)

(with an ingestion intake.

Fitting an individual's accompanying addenda) has been used by the NRC bioassay measurement data for a particular as the basis for its Annual Limits on intake (All) and exposure situation to the standard modeling will, Derived Air Concentrations (DAC) f ound in Appendix however, provide reasonably accurate estimates I

B to il 20.1001 through 20.2401. Likewise, this for most situations.

same modeling serves as the basis for interpreting l

bioassay measurements found in NUREG/CR-4884, Contained within this guide are methods for

" Interpretation of Bioassay Measurements" (Ref. 4),

evaluating bioassay data that will result in

{

Since the issuance of ICRP-30 (Ref.

3),

calculated intakes that are acceptable for improvements in the metabolic modeling for a few evaluating compliance with the occupational dose i

radionuclides have resulted in better dosimetric limits of 620.1202.

Examples of specific modeling. For example, a model developed by Jones exposare situations and the physical and

[

(Ref.5) provides better estimates of urinary fractional biochemical processes considered in the j

eliminations of plutonium. Also, a tritium metabolic assessment of the exposure have been included in j

model developed by Johnson and Dunford (Ref. 6)

Appendix A.

Additional guidance on bioassay provides acceptable (and often improved) estimates measurements, interpretation of bioassay data, of time dependent tritium elimination. As additional and bioassay program components can be found l

research is conducted, it is expected that refinements in ICRP 30 (Ref. 3), ICRP 54 (Ref.1), NCRP 87 f

l in the metabolic modeling will further improve the (Ref. 2) and NUREG/CR-4884 (Ref. 4).

l methods available for correlating bioassay l

measurements to actual intake and resultant individual's dose.

C. REGULATORY POSITION Metabolic modeling, such as that of ICRP-30 (Ref. 3)

Each licensee, in accordance with l

and ICRP-54 (Ref.1), can be used for evaluating 620.1204, (20.1502, and 120.1703 shall take l

bioassay measurements through the development of suitable and timely measurements of workers' l

time dependent values for the bodily retention and/or exposures for determining compliance with the j

l elimination of the ingested or inhaled radioactive occupational dose limits.

As specified in l

I material.

NUREG/CR-4884 (Ref, 4) presents a 620.1204(a), measurements should be made of comprehensive set of data on intake retention and airborne radioactive material in the work area, elimination fractions developed from these models.

quantities of radionuclides in the body, quantities These data, and accompanying description of the of radionuclides eliminated or excreted from the i

modeling and methods, provide usef ul inf ormation f or body, or any combination of such measurements l

using bioassay measurements to estimate intake, in f as may be necessary for detection and l

addition, ICRP-54 (Ref.1) presents metabolic models assessment of individual intakes of radioactive i

j accompanied by data and figures of bodily retention material.

andz chmination for many of the radionuclides of I

importance to NRC licensees.

The regulatory positions in this regulatory j

l guide supersede the information contained in NRC l

l lCRP 30 (Ref. 3) and ICRP-54 (Ref.1) are IE information Notice No. 82-18, " Assessment of l

based on general considerations (i.e.,

standard intakes of Radioactive Material by Workers.'

i l

chemical forms and standard man or woman metabolic modeling).

Each individual's physical

1. BIOASSAY SERVICES 8.7-2

l

.The purposes of bioassay measurements are to 2.1. Routine Measurements confirm the adequacy of radiological controls and/or

,j to determine compliance with the occupational dose Routine measurements include baseline limits. Bioassay measurements should be performed measurement (s), - periodic measurements, and i

on:

termination measurement (s).

These measurements are conducted for the purpose of

1) workers whose internal exposures are confirming that appropriate controls exist.

monitored in accordance with the However, because of uncertainty in the time of requirements of E20.1502(b) and intakes and absence of other data related to the

2) workers who use respiratory protection for exposure (e.g., physical and chemical forms, limiting intakes of radioactive material in exposure duration), correlating positive results to

[

accordance with the requirements of actual intakes for these type analyses can be j

i20.1703.

difficult.

}

if bicassay measurements are not required,it may be appropriate to make provisions for bicassay I

services should atypical situations arise where individual monitoring may be needed.

Bioassay 2.1.1 Baseline Measurements services should be available if the types and quantities of radioactive material licensed for use at Baseline measurements of existing intemal the facility could, under normal operational depositions should be made for allindividuals for i

occurrences, result in airborne levels in normally whom assessment of intakes is required (20.1502 occupied areas exceeding DACs. Provisions should or 20.1703).

An individual's baseline be made for the collection of appropriate samples, measurement of radioactive material within the analysis of bioassay samples, and the evaluation of body should be conducted prior to initial work the results of theae analyses to determine intakes, activities, involving exposure to radiation and/or radioactive materials, for which monitoring is

{

required.

2. FREQUENCY OF BIOASSAY MEASUREMENTS As a minimum, baseline measurements should Determining the appropriate frequency of routine be conducted at least annually. These annual bicassay measurements depends upon the exposure baseline measurements provide additional pctential and the physical and chemical information on any long term accumulation and characteristics of the radioactive material Elements retention of radioactive material in the body, that should be considered include: 1) the potential especially for exposures to concentrations of exposure of the individual, 2) the retention and airborne radioactive material below the threshold excretion characteristics of the radionuclide,3) the requiring more frequent bioassay measurements, sensitivity of the measurement technique, and 4) the acceptabie uncertainty in the estimate of intake and committed dose equivalent. Bioassay measurements 2.1.2 Periodic Measurements used for demonstrating compliance with the 7

occupational dose limits should be conducted on a in addition to the baseline measurement (s),

[

frequency sufficient to identify and quantify potential periodic bioassay measurements should be exposures and resultant intakes that, during any year performed if cumulative intakes in one monitoring collectively, could exceed 0.1 times the Annual Limit year are likely to exceed 10% of All. These on intake routine bioassay measurements should be 2

Two separate categories of bioassay conducted on a time frequency consistent with an measurements have been specified for further individual's cumulative exposure of 0.02 All (40 defining the frequency and scope of measurements:. DAC-hours).

Determining the frequency of periodic measures should be made on an a priori

1) Routine Measurements and basis, considering the likely exposure of the individual. The determination of the worker's

2) Special Measurements.

likely exposure should consider such information as the worker's access, work practices, measured levels of airborne radioactive material, and i

8.7-3

exposure ti nes.

Noble gases and airbome radioactive material resulting from 1: censed particulates with a radioactive half-life less than 2 activities. The scope of the evaluation should be i

hours may ie excluded from the evaluation since commensurate with the potential magnitude of the r

i external exposure is g?')erally controlling for these intake.

For individual exposures where the

[

radionuclides.

resultant intake is less than 0.02 ALI, minimum bioassay measurements are needed for providing l

2.1.3 Termination Measurements a reasonab!e approximation of intake. Repeated, follow-up measurements and/or additional

+

When n individual is no longer subject to the exposure data reviews are not necessary provided i

bioassay program due to termination of employment a reasonable estimate of the actualintake can be or change in employment status, a termination made based on available data.'

bioassay measurement should be made to ensure that any unknown intakes are quantified.

2.3.1 Evaluation Level if exposure data, including initial bioassay 2.2 Special Monitoring measurements, indicate that an intake is greater than an Evaluation Level of 0.02 All, additional Abnormal and inadvertant intakes, resulting from available data should be included in the j

situations such as as failed respiratory protectise assessment.

Other data, such as airbome oevice, inadequate engineering controls, inadvertant measurements and/or additional bioassay ingestion, contamina. ion of a wound, and skin measurements, should be used to obtain the best absorption,* should be evaluated on a case-by-case estimate of actualintake.

basis.

Some circumstances that should be 2.3.2 investigation Level considered when determining if p-tential htakes should be evaluated include:

If a potential intake exceeds an Investigation i

Level of 0.1 All, a mora thorough investigation

1) presence of unusually high levels of facial and/or should be conducted for quantifying the intake, j

nasal contamination; Multiple bioassay measurements and an evaluation of available workplace monitoring data should be

2) inadvertent entry into airborne radioactivity areas conducted.

If practical, daily measurements without appropriate exposure controls; should be made until a pattern of bodily retention i

and elimination can be established.

Such a

3) operational events where a reasonable likelihood determination may be feasible after as few as

[

exists that a worker was exposed to unknown three measurements; however, in some cases, quantities of airborne radioactive material (e.g.,

physiolugically relate' c ariations and uncertainties l

loss of system / container integrity);

may require that measurements continue over a longer period of time. For potentialintakes near or

4) known or suspected incidents of worker's exceeding the Alls, the scope of the bioassisy inadvertent ingestion of radioactive material; data evaluations should consider any additional i

data on the physical and chemical characteristics l

5) incidents resulti:.i s. contamination of wounds or and the exposed individual's physical and j

other skin absorptions; and biokinetic processes.

f

6) evidence of damage to or failure of a respiratory protective device.

3. TYPE OF MEASUREMENTS j

l Bioassay measurements provide one means for Bioassay measurements should provide for the evaluating the significance of these events and, as a quantification of all radionuclides to which the i

minimum, should be performed for any inadvertant ; workers are exposed. Characteristics, such as intake likely to exceed 0.02 All.

mode of intake, uptake and elimination, and mode l

of radioactive decay should be considered in selecting the most effective and reliable types of measurements. For example, in vivo lung or total i

2.3 Estimating intakes - Evaluation and body measurements shortly following exposure l

Investigation Levels generally provide reliable estimates of intakes for most gamma-emitting radionuclides.

In vitro l

Licensees should estimate the intake for any measurements should be used for most particle-2 bicassay measurement indicating internally deposited emitting radionuclides. However,in vitro urine or 8.7-4

t fecal measurements for the first voiding following assessment of a worker's dose. However, for exposure, while providing important information for exposures that are potentially important for

[

assessing potential significance, may not represent purposes of quantifying the actual intake (i.e.,

equilibrium conditions and thereby may not be useful greater than 0.1 ALI), the methods should not lead I

in evaluating actual intakes. ICRP Publication 54 to significant underestimation or overestimation of (Ref.1) and NCRP Report No. 87 (Ref. 2) provide the actual intake.

guidance for determining the types of bioassay measurements that should be made considering the Variations from predicted results for specific i

physical and biological characteristics of the individuals can be expected.

Excretion of radioactive material.

radionuclides may be influenced by the worker's diet, health condition, age, level of physical and metabolic activity, or physiological characteristics.

4.

INTERPRETATION OF BIO ASS AY The lung deposition and clearance of the inhaled i

MEASUREMENTS radionuclide, the particle size distribution, and the l

time of the excretion also influence the elimination The specific scope and depth of the evaluation of rate of radionuclides. Some of the important bioassay measurements, as discussed in section 2.3, physical and biological characteristics that should should depend on the potential significance of the be considered in evaluating bioassay intake. The methods presented below represent measerements include:

Appropriate measurement techmque (in vivo acceptable approaches for correlating bioassay and/or in vitro) based on'radionuclide decay measurements to estimates of intakes for the characteristics (i.e., types of radietion emitted) i purpose of demonstrating compliance with the and bickinetic characteristics (iie., systemic occupational dose limits of 120.1202.

uptake and retention and urine and fecal l

elimination fractions);

j 4.1 Time of Exposure j

- The effects of diuretics or chelation to reduce in order to estimate intake from bioassay systemic uptake and to increase excretion or measurements, it is necessary to know the time of elimination rates exposure.

Generally, intakes should be readily identifiable considering work activities and other Representativeness of measurements such as monitoring data, such as air sample data. Therefore, 24-hour or accumulated urine or fecal

}

time of intake should be known for all but unusual measurements, situations. Where exposures are not monitored, the time of intake can often be determined based on The appropriate lung clearance class (D, W, or

)

information provided by the individual. For situations Y), if known, if no information on the where information is insufficient for determining time biological behavior or chemical form is of intake, it is acceptable to assume that the intake available, the most restrictive clearance class t

occurred at the mid-point of the time period since the relevant for the particular element should be i

last bioassay measurement. This initial assumption assumed (i.e., that class that gives the lowest j

may be refined using any available information such value of ALI).

as the individual's work schedule, facility operations data, historical air monitoring data, and the effective Particle size distribution, A

half life of the radionuclides detected. (Refer to Chemical toxicity as in the case of uranium.

Appendix A, Example 2.)

Refer to f 20.1201(e).

4.2 Acceptable Biokinetic Models ll The metabolic models in ICRP-30 (Ref. 3) (and l

Determining a worker's intake based on bioassay accompanying addenda) and ICRP-54 (Ref.1) measurements involves comparing the measured present acceptable bases for estimating intake '-

bodily retention or elimination to the expected value.

from bioassay measurements. Other models may

[

The models and methods used for evaluating be used provided it can be demonstrated that the bioassay measurements should provide a reasonable results are con parable or provide better estimates.

assessment of the worker's exposure. For intakes Examples of other acceptable models include the that are a small fraction of the limit, greater tritium model developed by Johnson and Dunford inaccuracy in the estimate of intake can be accepted (Ref. 6) and the plutonium urinary excretion model

[

without having a significant impact on the overali developed by Jones (Ref. 5).

j 8.7-5

.p

5 Other applications of these models (e.g.,

computer codes) are also acceptable for evaluating tA, = C E (t, - 1,_3)

Equation 2 3

bioassay measurements, ' provided it can be demonstrated that the models and methods employed A, = A A[ t AA +. AA, Equation 3 l

2 provide results that are consistent with the acceptable models. There are several commercially available computer codes for interpreting bioassay where:

l measurements. These codes may be used aslong as the licensee can demonstrate that the software application is based on acceptable models and 4 A, =

Activity or amount of radioactive provides results that correctly implement the models.

material _

sample, normalized to in No specific computer codes are endorsed by NRC standard parameters staff. The licensee is responsible for ensuring that The sequence number of the sample i

=

computer codes are appropriate for use in their The radionuclide concentration in urine C,

=

individual circumstances.

(activity / liter) or feces (activity / gram) of sample i, decay corrected to the time of j

4.3 Intake Retention and Elimination Functions for sampling l

Calcu*ating Intakes Daily excretion rate (use measured rates E

=

when available, or assume values of 1.4 The Intake Retention Fractions * (IRFs) contained liters / day.for urine and 135 grams / day in NUREGICR-4884 (Ref. 4) represent an acceptable f r feces for standard man or 1.0 basis for correlating bioassay measurements to liter / day, urine and 110 grams / day, estimates of intake. To apply the use of IRFs for feces for standard woman) calculating an individual's radionuclide intake from a The time (days) after intake that sample t,

=

single bioassay measurement, divide the total activity e as collected in 24-hour urine, 24-hour feces, accumulated urine, Accumulated activity up to time t, 4

or accumulated feces *; or the radionuclide content in A,

=

?

the total body, systemic organs, lungs, nasal pas-This method is applicable only if spot samples sages, or GI tract by the appropriate IRF value in are collected on a frequency that is consistent NUREG/CR-4884 (Ref. 4),

with the significance of changes in the excretion

rates, in general, spot samples should be Equation 1 demonstrates this method:

collected on a f requency corresponding to no more than a 30% increase in the accumulated fractions Equation 1 over any tirue period.

For example, if the

)

accumulated urinary excretion fractions increase j

3*g by a rate of 30% per day, daily spot samples rap (n should be collected. If the rate is 10% per day, where:

once every 3-day spot samples would be desired.

Estimate of intake with units the same Also, the rapid clearance and elimination of I

=

as A(t),

inhaled particles from the N-P region of the lung Alt) =

Value of the bioassay measurement makes it important that at least one spot sample f

obtained at time t, decay corrected to be collected within the first 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> post

[

time of sampling for in vitro exposure.

Otherwise, the reliability of using measurements or to time of accumulated.,amples and elimination fractions for measurement forin vivo analyses, with calculating intakes should be examined; appropriate units (gCi, Bq. or gl.

calculations based on spot samples correlated to IRF(t) =

Intake Retention 24-hour samples may provide better estimates.

Fr a c1 i o n ;:

corresponding to type For spot samples correlated to an l

of nr.ssurement for equivalent 24-hour sample, correcting for s.

time t after estimated abnormal conditions of high or low fluid intake or

' f time of intake, excessive loss of fluids by perspiration may be i

required. NCRP-87 (Ref. 2) presents the following j

If spot samples are collected (i.e., 24-hour or method based on a relationship between the l

accumulated samples not collected), the following specific gravity (sp. gr.) of the sample to the i

equations may be used to estimate the accumulation average sp. gr. of urine (1.024 g/ml).

l of activity in urine or feces.

8.7-6 iP

(

may be used. Several methods are available for i

Equation 4 estimating the variance of measurements. One I

approach, applicable to radioactivity I

low / a.f measurements, is to assume that the variance is cm, c,,nc,.,m cm, m e r k / *d) proportional to the value of the measurement 4

l itself. Another is the assumption that the variance i

is proportional to the expected value (Ref. 7).

l An alternative to this method is a correction 1

based on the expected creatine excretion rate of 1.7 in selecting the statistical method to be i

j grams / day for men and 1.0 grams / day for women.

used for evaluating multiple measurements,

[

Refer to NCRP-87 (Ref. 2) for additionM r,ddance, consideration should be given to available i

information, particularly observed variability of the

(

)

Logarithmic interpolation should be used for data and reliability of individual measurements.

interpolating retention and elimination fractions. For Other statistical methods may also be used j

example, using the NUREG/CR-4884 (Ref. 4) data, an provided it can be demonstrated that the results IRF value for 2.8 days post intake may be calculated provide reasonable estimates of intake.

by a logarithmic interpolation between the 2-day and the 3-day IRF values.

4.4 Adjusting intake Estimates for Multiple and Continuous intakes Examples of the application of intake retention and elimination functions based on the in practice, a worker may receive repeated j

NUREG/CR-4884 data set are provided in Appendix exposures to the same radioraclide over a period A.

of time. These intakes should be treated as separate acute intakes if measurements collected i

through the period allow for the individual

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4.3.1 Evaluating Multiple Bioassay Measurements quantification of each exposure. As a general I

rule, if intakes are separated in time such that the When multiple bioassay measurements are retained or eliminated fraction from an earlier

[

made, a statistical evaluation of the data should be intake is less than 10% of the retent'on or i

j performed.

Numerous statistical methods are elimination fraction for the next intake, each i

available for evaluating multiple measurements.

intake may be separately evaluated without regard However, the results will be no better than the to any previous intakes.

reliability of the data set. Measurements that are j

d suspect or known to be inaccurate should be Continual intakes that are distributed excluded from the ant ysis.

Additional equally in size and time may be approximated measurements should be used for identifying an using a relationship based on time integration of 3

appropriate data set for evaluation.

For the the IRF. The total intake may be estimated by l

evaluation of multiple measurements, NUREG/CR-dividing the measured activity by the appropriate l

4884 (Ret 4) recommends the use of unweighted, time-integrated retention or elimination fraction.

minimized chi-squared statistics, assuming all An example using the IRF values from NUREG/CR-l a

variances are the same (i.e., a least squares fit). This 4884 (Ref. 4) would be to perform a numerical f

l method represents an acceptable approach that is integration over the individual IHF values covering simple and straightforward for evaluating multiple - the time period of interest. Any one of a number j

bioassay measurements. The equation is as follows:

of standard integration techniques, including l

numerical and analytical solutions, can be used.

j Equation 5 For example, using the trapezoidal rule yields the following method:

1 For bioassay measurements taken during

)

{ IRFft) w /Qt) an exposure time interval, the equation is' l3 j

{ IRFftf Equation 6 l

5 i

46 = T l

Other statistical analyses of the data may provide a i.

for a < r better fit of the data considering the particulars of g

the measurements. For example, a minimized che, squared fit weighted by the inverse of the variance l

t 8.7-7 d

i I

=

4.5 Correcting intake Estimates for Particle Size

.j Using the trapezoidal rule to solve Equation 6 yields Differences j

the following approximation:

The model used for deriving intake retention l

and elimination fractions, such as those in t

Equation 7 NUREG/CR-4884, are typically based on a 1-micrometer activity median aerodynamic diameter (AMAD) particles. For certain unusual situations, l

A(r) x r = =

l=

it may be appropriate to correct intake estimates

1. M'l

• IM'"0A d"") + Ima )+ +IMu) for particles of different sizes. These corrections tx i

may help explain retention or elimination rates j

different than that expected, such as would occur i

For bioassay measurements taken after an exposure for larger particles preferentially deposited in the -

interval, the equation is:

upper region of the respiratory tract (N-P region) with more rapid clearance times. Guidance for determining AMADs is provided in Regulatory

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Equation 8 Guide 8.25 (Ref. 8),

i i

Equation 9, taken from NUREG/CR-4884 (Ref.

?

4), Appendix B, may be used for revising the total A(r) x r ps a r body IRFs in NUREG/CR-4884 (Ref. 4) to particle I

1. ~

4 l

[ IMu) du size distributions between 0.1 to 20 pm AMAD.

j er

?

l i

Likewise, Equation 8 may be approximated using the trapezoidal rule which yields equation 9:

Equation 9 8

A(r) a j

f.

.' M '* )

• M')

• Imu,) +.

• IRr(u,.,)

2 t

I i

where:

t Total intake during period T

~

l

=

Amount of activity in j

A(t)

=

compartment or whole body at time t following onset of intake r

T Duration of intake (exposure time

=

period)

Time from onset of intake to time t

=

of measurement Intake retention fraction at time u in j

IRF(u)

=

compartment or whole body for a single intake of a radionuclide l

Variable time between integration u

=

limits number of increments n

=

I The number of increments to be used for a numericalintegration should be selected to minimize i

unnecessary errors associated with the particulars of

[

f the IRF values over which the integration is being performed. In general, errors associated with the integration technique should be limited to less than 7

10 %

8.7-8

)

i

EOUATION 10

',, Q#[ -

m(=m up ** L t

j

~, nn.

b*' L %w, Dst >%

i

%W,. DA*A g

L %w, 041 cmD where:

Total body IRF for inhalation of IRF(AMAD)

=

Class D, W, or Y compounds for activity median aerodynamic diameter (AMAD) of interest Total body IRF for inhalation of f

IRF(1 m)

=

1 pm AMAD aerosols (these IRFs are given in Appendix B to NUREG/CR-4884 (Ref. 4))

{

Summation over all tissues (and I,

=

organs) T.

The compartments or regions of N-P, T-B, P

=

deposition of the respiratory tract: the nasopharyngeal passage region (N-P),

the tracheobronchial region (T-B),

j and the pulmonary region (P)

The fraction of committed dose f.,,,, f r.1, f,,,

=

u equivalent in the tissue T resulting from deposition in the N-P, T-B, and P regions, respectively (values for j

individual radionuclide are l

contained in the Supplements to l

Part 1 of ICRP-30 (Ref. 31) 6 i

Committed dose equivalent for H,

=

tissue (or organ) T Tissue (or organ) weighting l

W,

=

f actor, from 10 CFR 20.1003 l

Regional deposition fractions for Do,D,,,D,

=

i an aerosol entering the..

respiratory system.

(Values "

l presented in Table 1, below) f 8.7-9 i

Table 1 i

Aeroso! AMAD l

0.2pm 0.5pm 0.7pm 1.0 pm i

D,,,

0.05 0.16 0.23 0.30.

l 7

D, 0.08 0.08 0.08 0.08 i

D, 0.50 0.35 0.30 0.25 Total 0.63 0.59 0.61 0.63 Deposition 2.0 pm 5.0 pm 7.0 pm 10.0 pm j

D.,

0.50 0.74 0.81 0.87 i

Du 0.08 0.08 0.08 0.08 l;

D, 0.17 0.09 0.07 0.05 l

Total 0.75 0.91 0.96 1.00 Deposition 20 pm, complete deposition in the N-P region can be assumed.

Equation 9 does not provide valid corrections for time periods shortly following intakes. For Class

[

D compounds, the time after intake for which Equation 9 begins to yield satisfactory results is less than 1 day. For Class W compounds, this time is 6

about 7 days following intake, and for Class Y 4.6 Use of Individual Specific Biokinetic Modeling compounds, about 9 days following intake.

Individual specific retention and elimination The above equation 9 for revising the IRF for rates may be used in developing biokinetic models different particle sizes is applicable for the total body that differ from the standard man modeling IRF. ICRP-54 (Ref.1) provides graphs of IRF values (20.1204(c)). The quality and quantity of data j

for 0.1 m,1 pm and 10 pm AMAD particles for required for this type of individual specific modeling other tissues and excreta.

Intake retention and should be sufficient to justify the revised model.

elimination functions may be derived for other AMAD Licensees should not attempt to develop individual i

particles based on the acceptable biokinetic modeling specific retention and elimination rates in the as discussed in Sections 4.2 and 4.3.

absence of actual biochemical and particle size information. Individual specific modeling is not The estimate of intake for different particle required but may be developed; the modeling as sizes may be compared with the ALis in Appendix 8 presented above in section 4.2 is acceptable for to 10 CFR 20.1001 through 20.2401 which are evaluating regulatory compliance.

i based on a particle re of 1 micrometer for

[

t demonstrating compliance with intake limits.

5.0 CALCULATING DOSE FROM ESTIMATES OF However, to modify the All values for different INTAKE particle size distributions requires prior NRC approval Once the intake is determined, refer to j

(120.1204(c)(2)).

l Regulatory Guide 8.34 (Ref. 9) for additional I

Particle size distribution and its effect on lung guidance on determin'ing doses based on calculated l

deposition and transfer may be considered in intakes.

evaluating an individual's dose. ICRP-30 (Ref. 3)

(with supplements) provides data and methods that l'

may be used for evaluating the lung deposition and I

resultant doses for particle sizes between 0.1 and 20 pm AMAD. For particles with AMADs greater than 8.7-10 I

6.0 RECORDKEEPIMG REFERENCES Records of measurement data, calculations of 1.

International Commission on Radiological intakes, and methods for calculating dose sha!! be Protection,

• Individual Monitoring for intake of maintained as required by i 6 20.1204 (c),

Radionuclides by Workers: Design and Inter.

20.2103(b), and 20.2106(a).

For additional pretation,* ICRP Publication 54, Pergamon information on recordkeeping and reporting Press, New York,1988.

occupational exposure data including intakes, refer to Regulatory Guide 8.7, Revision 1 (Ref.10).

2. National Council on Radiation Protection and I

Measurements, *Use of Bioassay Procedures for Assessment of internal Radionuclide D. IMPLEMENTATION Deposition," NCRP Report No. 87, February The purpose of this section is to provide 1987 information to applicants and licensees regarding the NRC Staff's plans for using this guide.

3. International Commission on Radiological Protection,

• Limits forintakes of Radionuclides Except in those cases in which an applicant by Workers," ICRP Publication 30, Part 1, and proposes an acceptable alternative method for ICRP Publication 30, Supplement to Part 1, complying with specified portions of the Appendix A, Pergamon Press, New York, Commission's regulations, the methods described in 1978.

this guide wi!! be used in the evaluation of applications for new licenses, license renewals, and 4.

Lessard, F.

T.,

et.

al.,

• Interpretation of license amendments and for evaluating compliance Bioassay Measurements,* NUREG/CR-4884, with 10 CFR 20.1001-20.2401.

U.S. Nuclear Regulatory Commission, July 1987.

5. Jones, S. R., " Derivation and Va:idation of a Urinary Excretion Function for Plutonium Applicable Over Ten Years Fost intake,"

Radiation Protection Dosimetry. 11(1):19-27, 1985

6. Johnson J. R., and D. W. Dunford, GENMOD -

A Pronram for Internal Dosimetry Calculations, AECL - 9434, Chalk River Nuclear Laboratories, Chalk River, Ontario,1987

7. Skrable, K. W., G. E. Chabot, C. S. French, and T. R. LaBone, " Intake Retention Functions and Their Applications to Bioassay and the Estimation of internal Radiation Doses,' Health -

Physics Journal, Volume 55, No. 6,1988

8. US Nuclear Regulatory Commission, Regulatory l

Guide 8.25, " Air Sampling in the Workplace,*

Rev.1, June 1992

9. US Nuclear Regulatory Commission, Regulatory Guide 8.34,

• Monitoring Criteria and Methods to Calculate Occupational Radiation Doses,"

i July 1992

10. US Nuclear Regulatory Commission, Regulatory Guide 8.7, Revision 1,

• Instructions for Recording and Reponing Occupational Exposure Data" June 1992 2

8.7-11

1.Activ'ity Median Aerodynamic Diameter (AMAD): The diameter of a unit density sphere with the same terminal settling velocity in air as that of an aerosol particle 3

I whose activity is the median for the entire aerosol.

2.The 10% All criteria is consistent with 520.1502(b), which.equires licensees to monitor intakes and assess occupational doses for exposed individuals who are likely to exceed 10% of the applicable limit (i.e., intakes likely to exceed 0.1 All for adults).

i 3.The skin absorption of airborne tritium has been included in the determination of l

4 its All and DAC values for occupationalinhalation exposures in Appendix B to ss20.1001 - 20.2401.

5 4.The purpose of this guidance is for describing the scope of the bioassay -

measurements that should be considered for assessing intakes. It is not for limiting the types of reviews that may be warranted for purposes of assessing the overall significance of an intake on the health physics program.

l

(

5.

For purposes of this guide and for application of the data from l

NUREG/CR-4884, the parameter IRF shall be used to denote both intake retention fractions and intake elimination fractions.

I 6.The term "24-hour urine" refers to the total urine output collected over a 24-hour period, and the term "24-hour feces" refers to the total fecal output collected over a 24-hour period. " Accumulated urine" and " accumulated feces" refer to the total output since time of exposure.

7.An IRF can be expressed as a sum of exponential terms and can vary by approximately 2 orders of magnitude in the first 1000 days following an exposure (refer to models and data in Ref.1). The composite trapezoidal rule can be used to numerically evaluate an integral that is equally partitioned. For example, using this rule to evaluate the integral f e" dx yields a relative error of 3.6% for 8 intervals, 2.7% for 9 intervals; and 2.2% for 10 intervals.

I

?

e i

8.7-12

?

i APPENDIX A 3

EXAMPLES OF THE USE OF INTAKE RETENTION FRACTIONS The following examples illustrate the use of retention and elimination functions for calculating intakes based on bioassay measurements. The data used for these examples are taken from NUREG/CR-4884. The purpose of these examples is not to define the total scope of a bioassay j

program. These examples do not illustrate the use of all possible bioassay or health physics i

measurements that may be available (e.g., excreta and air sampling measurements)'during a j

specific exposure incident. Rather, these examples demonstrate the use of the calculational

{

techniques presented in Section C.4 of the guide for correlating measurements to intake. The examples demonstrate the use of retention and elimination fractions to:

t Use of standard rnan metabolic models (intake retention and elimination fractions) for evaluating bioassay measurements, Estimate intake from one or several bioassay measurements, Adjust intake estimates for multiple or continuous intakes, and Correct intake estimates for particle size differences.

l The examples that have been developed are as follows:

i Example 1:

Calculating intake Following an inadvertant Exposure Based on a Single Bioassay Measurement Example 2:

Calculating intake with Unknown Time of Intake Example 3:

Using Multiple Measurements to Calculate intake Example 4:

Uranium intake Example S:

Comparison of Air Sampling and Bioassay Meas.irements and Results Example 6:

Correcting intake Estimates for Particle Size Difference Example 7:

Adjusting intake Estimates for Multiple and Continual intakes l

l l

j f

e 9

i A-1

EXAMPLE 1 Calculating intake Following an inadvertent Exposure Based on a Single Bioassay Measurement Determination that Intal <e Occurred Section 35.315(a)(8) requires licensees to perform thyroid burden measurements for all occupationally exposed individuals who were involved in the preparation and/or administration of therapeutic or diagnostic dosages of I-131. These measurements are to be performed within three days following the preparation or administration.

Following a patient iodination, the required bioassay measurements are conducted for allinvolved individuals. It is identified that the Radiation Protection Technologist (RPT) who prepared the dose has a measured thyroid content of 0.08 pCi of *l. It is determined that the RPT most likely received an inhalation intake when a difficulty was encountered during the preparation of the dosage. At the time, this abnormal situation was not considered significant. The time of measurement is determined to be 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> post estimated time of intake.

Evaluation Procedure I

The lung clearance class for all chemical compounds of iodine is class D. Since no information is available on particle size distribution, a 1 um AMAD particle size is assumed. Using Equation 1 from 3

Regulatory Position C.4.3 for estimating intake from a single bioassay measurement, the intake can be estimated as follows:

i l

A ('1.

IRF (t) 3 where:

Estimate of intake in units the same as Att) i I

=

Time interval between intake and bioassay measurement i

(t)

=

Thyroid content decay corrected to time (t) of measurement Att)

=

intake Retention Fraction for measured *l at time interval (t) after l

IRF(t)

=

1 estimated time of intake.

The table of thyroid IRF values for I-131 is found on page B-103 of NUREG/CR-4884. The value for i

time after intake equals 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> (t=24 hours)is 0.133.

l Substituting the measured thyroid content and the corresponding thyroid IRF value into the above i

equation and solvmg yields the following:

l 4

0.08 pCi g

= 0.6 pCi 0.133

(

l As discussed in Regulatory Position C.2.3, if a bioassay measurement indicates that the potential intakes is greater than the Evaluation Level of 0.02 All, additional exposure data and/or additional l

bioassay measurements should be examined for determining the best estimate of intake. The All for class D *l is SE + 1 pCi (from Appendix B to 1120.1001 - 20.2401); therefore, the Examination Level is 1.0 pCi (0.2 times the All value of SE + 1 pCi). Since the estimated intake is less than this level, no further evaluation is necessary.

A-2 I

EXAMPLE 2 Calculating intake with Unknown Time of Intake Determination that intake Occurred '

While conducting a routine termination bioassay measurement of a maintenance worker at a nuclear power plant, a whole body content of 0.26 Ci of

• Co is measured. Since the worker had entered a contaminated area earlier in the day, she was instructed to shower and don disposable coveralls to ensure that no external contamination of her skin or clothing was present. A second bioassay measurement is conducted and a whole body content of 0.26 Ci of

• Co is confirmed.

Evaluation Procedure The Health Physics Supervisor is notified, in an attempt to determine the cause and time of exposure, an examination is conducted of plant survey data, including airborne activity measurements for areas of the plant where she had recently worked. This examination fails to identify a source of exposure; all areas to which the maintenance worker had access over the past several days were found to be minimal 8y contaminated and no elevated levels of airborne radioactive material have been experienced.

This information, in addition to the determination that the worker is not externally contaminated, indicates that the intake did not occur during the past several days. In the absence of any other information, the licensee assumes that the intake occurred at the midpoint in time since the worker's previous bioassay measurement. This assumption allows for an initial assessment of the potential significance of the intake. In this case, the most recent bioassay measurement was one conducted six months ago (180 days) which represented her initial baseline measurement performed at the time of hire. Using these assumptions, the calculation of intake is as follows:

J A(r) g IRF (t) where:

Estimate of intake in units the same as A(t)

I

=

Time interval between intake and bioassay measurement (t)

=

Whole body content decay corrected to time (t) of measurement A(t)

=

Intake Retention Fraction for measured

• Co at time interval (t) after IRF(t)

=

estimated time of intake (half of 6 months or 90 days).

Substituting the measured body content and the corresponding IRF value into the above equation and f

solving yields the following:

0.26 pc I

- 4.07 pCi 6.39E-2 r

s The All for class W 66Co is 2E + 2 pCi; therefore, the Evaluation Level is 2E + 2 times 0.02 pCi or 4 pCi.

Since the calculated intake is greater than the 4 pCi Evaluation Level, additional information should be l

sought.

As part of the additional review, the Health Physics Supervisor conducts a further review of the individual's worker activities in an attempt to determine the actual time of exposure. A review of air i

sample data and worker access failed to indicate any abnormal exposure conditions. For unknown situations, the exposed individual is most often the best source of information when attempting to define A-3 er

the exposure conditions. The individual may remember unusual circumstances that at the time may have i

seemed acceptable, but upon further examination could have resulted in the unexpec1ed exposure. In

[

this case, the maintenance worker remembers breaching a contaminated system to remove a leaking valve. The system was supposed to have been depressurized and drained. However, she remembers that when the system was breached a slight pressure relief was experienced and a small amount of water was drained. Following a review of the Radiation Work Permit (RWP) log and the containment entry log, it is determined that this incident occurred 28 days prior to the time of the measured body content. Prior to and since that time, her other work activities have been in areas only moderately contaminated; an additional intake would have been unlikely. Based on these data, the most likely time 3

of intake is determined to have occurred during the contaminated system breach 28 days ago.

{

The appropriate IRF values for this exposure should be for a time of 28 days post intake. Also, the " Total Body" 1RF values shoukt be used since the body content has been determined by an in vivo total body i

measurement. A 28-day IRF value is calculated by performing a logarithmic interpolation between the

[

20-day value and the 30-day value.

IRF (day X) - exp x (day X - day Y) + In(IRF(day Y))

f fin (IRF (day Z)) - In (IRF (day Y)) '

(day 2) -(day Y) t 5

where-Interpolated IRF value, calculated at day X, which lies between two IRF values l

(RF (day X)

=

occurring at days Y and Z; in this case, X = 28 days, Y - 20 days, and Z = 30 days IRF value occurring at day Y, in this example, 20 days 1RF (day Y)

=

IRF value occurring at day Z, in this example,30 days i

1RF (day Z)

=

i Solving this interpolation yields:

'In(IRF(30 days))-In(IRF(20 days)) '

IRF(28 days) = exp x (28 days - 20 days)+ In(IRF(20 days))

30 days - 20 days l

t 3

in(0.123) - In(OM) '

I

- exp x 8 days + In(0.140) 10 dgs i

- 0.126 2

r i

i i

i Substituting this interpolated IRF value into the equation for calculating intake and solving yields:

y, 0.26 pCi 0.126 I

2-i

- 2.1 Ci (7.6E+04 Bq) i I

Since this calculated intake is less than the Exaministion Level (i.e., less than 0.02 times the ALI value of 4 uCi for 1 pm AMAD, class W, "Co) and the data reviews to date did not indicate any other source of.'

6 exposure, no further examination is needed. However, had this calculated intake exceeded the Evaluation Level of 4 pCi, additional bioassay measurements over the next several days should be considered. This intake value is recorded in the worker's exposure records and provided to the worker as i

a part of her termination exposure report, for which NRC Form 5 may be used.

i A-4 l

I i

~-

EXAMPLE 3 l

Use of Multiple Measurements for Estimatina intake i

Determination tha.L ntake Occurred l

A laboratory worker accidentally breaks a flask containing a volatile compound of *2P. The worker exits the work area. Contaminated nasal smears indicate that the worker may have received an acute inhalation intake. The results of work area air sampling measurements are reviewed, indicating increased airborne levels. Bioassay measurements are initiated to assess the actual intake.

Evaluation Procedure 2

From a review of the biokinetics for inhalation intakes of 'P, it is determined that urinalysis followed by liquid scintillation detection would provide the best bioassay data for calculating intake. For the volatile

'2P compound involved, class D represents the appropriate the lung clearance class. Also, lacking other 4

data, a particle size distribution of 1 pm AMAD is assumed.

The first voiding is analyzed and results verify the occurrence of an intake. However, due to particular characteristics of the sample (e.g., collection time relative to time of exposure), the results are not considered reliable for calculating an intake. Follow-up 24-hour urine samples are collected. The results i

of a second day 24-hour sample indicate a total activity, decay corrected to end of the 24-hour sample collection period, of 1.5 pCi. Using Equation 1 from Regulatory Position C.4.3, an initial estimate of the intake is calculated as follows:

g A(t)

IRF(t) 1.5 pCi 4.17E-02

- 36 pCi (1.3E+6 Eq) where:

l Estimate of the P intake, l

=

Intake Retention Fraction for 24-hour urine collected 2 days post intake, which IRF(t)

=

equals 4.17E-02 (NUREG/CR-4884, page B-25),

1.5 pCi, value of the second day 24-hour urine sample.

i A(t)

=

The All value for inhalation intakes of class D compound of 82P is 9E + 2 pCi. The initial estimate of l

intake of 36 Ci exceeds the Evaluation Level of 0.02 All, which is the recommended level above which multiple bioassay measurements should be considered for assessing actual intake. Follow-up-measurements are made it is determined that 24-hour urine samples should be collected for the third day, fifth day and 10 day.

Note: Daily measurements should be considered if the initial assessment indicates an intake greater than the Investigation Level of 0.1 All. The selection of the time periods above is used for A-5

l purposes of demonstrating the calculational method. In actuality, one would typically examine the third day results before deciding on the need and frequency of additional measurements.

The following table summarizes the results of the 24-hour urine sample measurements, the corresponding IRF value from NUREG/CR-4884, and the calculated intake based on the individual measurements using the above method.

(t )

(A,)

(i)

Time After Decay Corrected IRF Estimated Intake intake Activity in 24-Hour' Based on Single

{

(Days)

Urine Sample (pCi)

Sampics (pCi) t 2

1.5E + 0 4.17 E-2 3G

)

10 1.3 E-1 4.34 E-3 30

+

20 6.0E-2 1.55 E-3 39 t

The best estimate of intake is calculated using Equation 5 from Regulatory Position C.4.3.1 to obtain the chi-squared statistical estirnate of the intake. This estimate is calculated from the bioassay measurements obtained on three different days following the incident:

g, { IRF, x A,

{ IRF,2 1

3, (4.17E-2 x 1.5) + (4.34E-3 x 1.3E-1) + (1.55E-3 2 6.0E-2)

(1.55E-3)2 (4.17E-2)2 (4.34E-3)2

+

+

I - 36 pCi P-32 i

The data and results for this evalaution are placed in the worker's exposure records and included on the worker's NRC Form 5 report.

1 l

i r

f i

A-6

l

?

'I EXAMPLE 4 2

Uranium Intake

~

Determination that intake Occurred An accident at a facility that produces UF, (uranium hexafluoride) results in a worker being exposed to an I

unknown concentration of UF, with a natural uranium isotopic distribution. Based on information in l

Appendix B to i120.1001 - 20.2401, the UF,is identified as a inhalation lung class D compound.

j i

i Evaluation Procedure j

i The Health Physics Supervisor examines the significance of the exposure. _ Based on potential airborne j

radioactive material levels, it is determined that bioassay measurements should be conducted. Examining j

the biokinetics and decay characteristics for uranium isotopes, the Health Physics Supervisor determines i

that urine sample collection and analysis should be performed.

Spot urine samples are collected over the following few days with the results presented in the following tab le.

Time of Concentration

)

Sample of Uranium in Urine (days post intake)

(pg/l)

)

J

]

0.2 990

{

0.6 1,400 1

l 2.0 210 3.0 140 4

J

-1

(

Evaluation Procedure j

1 Using the results of the spot samples, accumulated urine activities can be calculated using Equations 2 i

and 3 from Regulatory Position C.4.3. The concentration of uranium in the urine samples in presented in i

the units of micrograms per liter Because of the long half-lives of uranium isotopes, decay correction in time of sample is not required.

)

i 1

1 I

i l

l 4

A-7 I

g

r i

i Using Equation 2, the amount of uranium in the first sample would be calculated as follows:

AA2 - C x E x (t2-8-1) 2 2

t

= 1,400 x 1.4 x (0.6 - 0.2)

= 780pg

{

M i

where:

Activity or amount of uranium in the first sample AA,

=

Concentration of uranium in the first sample C,

=

Daily excretion rate of 1.4 liter / day for urine for reference man (reference woman E

=

rate is 1.0 liter / day)

Time (in days) after intake when the first sample was taken t,

=

Time (in days) after intake when the previous sample was taken t.,

=

i (i.e., O days in this case)

The accumulation for the second sample is calculated in the a similar manner:

2 = C X E X (t2-1.,)

AA 2

2

= 1,400 X 1.4 X (0.6 - 0.2)

= 780pg

[

i Accumulations for the remainder of the sample times are similarly calculated.

The accumulated urine through the fourth spot sample collected on day 3 is calculated by summing all the accumulations.

A - A A, + AA + AA + A A, 4

2 3

i

- 280 + 780 + 410 + 200 4

i

= 1,670 pg l

I where:

A, =

Accumulated activity up to time 1 of the 4"' sample collected on the 3"' day post intake.

l' Using the calculatico of ac;umulated urine activity, the intake may be calculated by applying the method of Equation 1 from hoguiatory Position C.4.3. The IRF for this calculation would be that for the 5

A-8 2

i e

t

. =

7 I

accumulated urine for uranium, class D, from Appendix B tu NUREG/CR-4884 (page B-163). Because of the long radiological half-lives, the IRFs for all of the uranium isotopes are essentially the same; the -

values for U have been used for this example.

A(t) l j,

IRF(t) r

, 1,670 l

0.'4 91

- 5,700 pg i

where:

t i

= Estimate of intake with units the same as A(t),

Intake Retention Fraction for uranium, Class D inhalation for the accumulated urine IRF(t)

=

in the third day following time of intake, Value of the calculated accumulated urine based on the four spot samples (pg).

A(t)

=

A conversion from a mass (pg) to activity ( Ci) for the different percentages of the uranium isotopes can be performed based on isotopic specific activity. Natural uranium is composed of three isotopes: 8U at 0.0056% atom abundance,236U at 0.72%, and 2*'U at 99.274%. Based on these abundances, the 2

286 corresponding weight to activity correlations are as follows: 3.5E-01 pCi/g for **U,1.5E-2 pCi/g for U,

and 3.3E-01 pCi/g for 288U. Using these conversions, the following activity intakes are calculated:

1 Th x pCi/g conwrsion Acthity = Um e

ab i

- 5,700 pg x 0.35 pCi/g x 1E-06 g/pg = 2.0E-03 pCi U-234 oy

= 5,700 pg x 0.015 pCi/g x 1E-06 g/pg = 8.6E-05 pCi U-235 e-cal

- 5,700 pg x 0.33 pCi/g x 1E-06 g/pg - 1.9E-03 pCi U-238 cul at ed i

ac tiv i

ity int ak es for i

the uranium isotopes are much less than the Examination Level of 0.2 All where additional evaluations (e.g., measurements) should be considered. Therefore, considering the significance of the radiation exposure, the bioassay measurements conducted provid9 an acceptable calculation of the ir'aK6.

A separate limit of 10 milligrams in a week for soluble uranium is contained in 120.1201(e) and Appendix B to i120.1001 - 20.2401. This limit is based on the chemical toxicity and should be evaluated in addition to the radiation exposure. The above evaluation determines that the total intake was 5,700 pg (5.7 mg). Therefore, the 10 mg/wk limit of 120.1201(e) was not exceeded.

A-9 l

t I

i EXAMPLE 5 i

Comparison of Air Samplina and Bioassav Measurements and Results t

Determination that intake Occurred l

During fabrication of a '87Cs source, sampling of the airborne radioactive material levels to which the worker is exposed is performed using a continuous low volume air sampler. At the end of the 8-hour

{

shift, the health physicist counts the filter and calculates that the average airborne activity during the sample period was 5.4E-7 pCi/ml (20,000 Bq/m ) of Cs. The elevated levels were unexpected and the 8

health physicist compares the measured levels with the Cs DAC value from Appendix B to 1120.1001 l

-20.24016. The 8-hour average concentration is nine (9) times the DAC value for '*'Cs of SE-8 pCi/mi.

The worker was not wearing a respiratory protective device during the fabrication process as elevated 4

airborne radioactive material levels were not anticipated.

i The health physicist evaluates the significance of the exposure by calculating the intake (based on the air 4

i sample data) and comparing the result with the All value for '87Cs from Appendix B to 1620.1001 --

i 20.2401 ('3'Cs, inhalation ALI = 200 pCi).

{

As a first approximation, the health physicist assumes that the worker was exposed to the average j

s airborne Cs concentration represented by the activity on the air sampler filter for the entire 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> of i

the work shift. A worker breathing rate of 1.2 m*/ hour (light work activity) is also assumed. The following intake is calculated; f

Inuke = 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> x 1.2 x 5.4E-7 E x 1E6 hours mi 3

m 3

i i

1

= 5.2 pa (1.9E5 Bq) 1 j

This calculated intake is greater than the Evaluation Level of 0.02 -ALI. The health physicist orders an in

{

vivo bioassay measurement to be performed on the worker.

I 1

Evaluation Procedure j

The in vivo measurement is performed the following morning, approximately 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> after time of l

intake. The results indicate a total body activity of 0.21 Ci of '87Cs. The corresponding intake may be l

estimated by using Equation 1 from Regulatory Position C.4.3. Inhalation class D is assigned for all l

i chemical compounds of cesium (refer to Appendix B to 1120.1001 - 20.2401). The table of inhalation l

l IRFs for '87Cs rnay be found on page B-111 of NUREG/CR-4884. The IRF value for the total body,0.5 1

day after intake, is 6.31E-01. Substituting these values into Equation 1, yields the following calculation 3

of the intake:

A(t) l l.

IRF(t) l 0.21 pa = 0.33 pa ( 12,000 Bq )

6.31E-01 i

i A-10 e

6

The two calculated estimates of "'Cs intake are significantly different. The health physicist discusses the work activities leading to the exposure with the individual. It is determined that the differences could have been attributable to several factors:

Difference in the breathing rate assumed for reference man and that of the worker, Difference in the levels of airborne radioactive material as sampled by the low volume sampler and the levels as breathed by the worker, and Difference in exposure time assumed for the worker (i.e., actual exposure was less than a full 8-hour shift).

The available data cannot resolve the difference between the results of air sampling and the in vivo bioassay analysis: additional bioassay ineasurements and a review of the worker's exposure relative to the workplace ambient air sampling should be conducted for resolving the difference.

The estimate of intake to be used as the dose of record should be the value considered to better represent the actual exposure situation. In general, bioassay measurements will provide better estimates of actual worker intakes, provided the data is of sufficient quality. Air sample results typically represent only an approximation of the level of radioactive material in the air breathed by the worker.

Appropriately collected and analynd, bicassay results can provide better indication of actual intakes.

This example does nnt address the health physics issues concerning the elevated airborne levels and potential worker exposure to levels Dreater than DACs.

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EXAMPLE G l

_C_ orrectino intake Estimates for Particle Size Difference Annual Limits on intake, and the intake Retention Fractions (in NUREG/CR-4884) are based on a 1 pm AMAD particle size distribution. Rarely (if ever) will the actual distribution of airborne particulates be completely characteristic of 1 pm AMAD particles. Evaluating different particle size distributicas can assist in explaining retention and elimination rates that are different than would be exper 19d based on the standard modeling.

r' in this example, it is assumed that the actual particle size dis' tribution has been determined to be characterized as a 2 pm AMAD of Class Y compound of "Co. It is assumed that the intake occurred 20 days before the bioassay measurements were made.

Evaluation Procedure The IRF may be adjusted for a 2.0-pm AMAD particle size using Equation 9 of Regulatory Position C.4.5.

The approximation relationship of this equation is applicable to the total body IRFs for particle sizes between 0.1 m and 20 pm AMAD.

Values for D,,,, D,4, and D, derived from the data in Part 1 of ICRP Publication 30 (pages 24 and 25) are presented in the following table. (Note: the deposition fractions presented in Table B.8.1 of NUREG/CR-4884 (page B-801) contains errors and should not be used.)

Regional Deposition Fractions for Aerosol with AMADs Between 0.2 and 10 pm 0.2 pm 0.5 pm 0.7 pm 1.0 pm D.,

0.05 0.16 0.23 0.30 l

D, 0.08 0.08 0.08 0.08 D,

0.50 0.35 0.30 0.25 h

Total Deposition 0.63 0.59 0.61 0.63 j

2.0 pm 5.0 pm 7.0 pm 10.0 pm Do 0.50 0.74 0.81 0.87 D,

0.08 0.08 0.08 0.08 D,

0.17 0.09 0.07 0.05 Total Deposition 0.75 0.91 0.96 1.00 i

4 l

The values of fu, fu, and f, needed for the above equation are listed in the Supplement to Part 1 of ICRP Publication 30 (page 40). These values, as pr,esented in ICRP Publication 30 are given as i

percentages and must be converted to decimal fractions before use. The decimal fractions for each l

tissue, along with its weighting factor and committed dose equivalent factor, are presented in the following table.

l s

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Input Values Tissue f,

fu f,

W,'

Hw,,2 (Sv/Ba)

Gonads 0.35 0.21 0.44 0.25 4.0E-09 Breast 0.19 0.17 0.64 0.15 4.2E-09 Red Marrow 0.20 0.17 0.63 0.12 4.2E-09 Lungs 0.02 0.02 0.96 0.12 3.6E-08 Thyroid 0.03 Bone Surface 0.03 LLI Wa!I 0.45 0.15 0.40 0.06 8.2 E-09 I

i Liver 0.21 0.19 0.60 0.06 9.2E-09 Remainder 0.10 0.09 0.81 0.06 8.0E-09 I

The following equation is used to estimate the IRF for 2 pm particles.

"#(^

IRF(AMAD) = IRF(1 pm) {7 f +'r

+

u

{7 H W,

Du_p(1 pm) m i

H W Dr,(AMAD) m r Dr-,(1 pm) i

~ * '

{7 HmW7 t

D (AMAD) l H AV e

3c 7 j

U (1 YE))

{7 #sedVT P

Substituting into the above equation from the table of input values results in the following:

Total Body IRF(2 pm) @ 20 days after intake = 8.5 E-02 i

This 1RF could be used to estimate intakes as i!!ustrated in previous examples.

j

' Tissue weighting factors adapted from 10 CFR 20.1003 as further clarified by ICRP-30.

Committed dose equivalent. Example data taken from ICRP Publication 30, 2

Supplement to Part 1.

i A-13

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)

i The above method for revising the IRF for different particle sizes is' applicable for the total body IRF.

ICRP-54 provides graphs of IRF values for 0.1 pm,1 pm, and 10 pm AMAD particles for other tissues -

and excreta.

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- L

EXAMPLE 7 Adiustino Intake Estimates for Multiple and Continual intakes The following is a simplified example showing the application of the numerical integration of IRFs over a continual exposure period. It is recognized that most exposure situations do not involve chronic exposures to airborne radioactive material; most intakes can be reasonably characterized as acute exposures. However, when exposures extend over a longer period of time (i.e., more than a few days) it may be necessary to adjust the IRFs, which are based on single, acute intakes, to account for the extended exposure period.

Urinalysis for a worker, performed on a Friday, indicated an uptake of 'H. It was determined that the worker was continually exposed to 'H as HTO (water vapor) for the five work days of the prior week (i.e., Monday through Friday of the previous week). Results of the 24-hour urine sample reveal 10 pCi (3.7E + 05 Bq) of 'H.

Evaluation Procedure Since the exposure occurred over an extended period of time and the measurement taken after the exposure interval, the methods of Equation 8 from Regulatory Position C.4.4 should be used.

A(t) n j,

+ I W jg ygg,y,,, jgjyy,_,y i

2 where:

Amount of activity in compartment or whole body at time i following onset of Att)

=

intake Total intake during period T 1

=

Duration of intake (exposure time period)

T

=

Time from onset of intake to time of measurement t

=

Variable time between integration limits u

=

IRF(u) =

Intake retention fraction at time u in compartment or whole body for a single intake of a radionuclide number of increments n

=

For this example, the time interval values are:

5 days (period of intake)

T

=

11 days (number of days following onset of intake) 1

=

The integration period is for the time (t-7) to t; therefore the interval consists of a total of 6 days. For purpose of the numerical integration, the 6-day time interval has been divided into 6 equal one-day increments.

The IRF values, taken from NUREG/CR-4884 (page B-711), for the calculation are listed in the following,

table. If IRF values are not presented for the day of interest, a logarithmic interpolation should be perform to calculate the value.

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1 3

l J

l EXAMPLE 7 i

Adiostino intake Estimates for Multiple and Continuallntakes i

The following is a simplified example showing the application of the numericalintegration of IRFs over a f

continual exposure period. It is recognized that most exposure situations do not involve chronic j

exposures to airborne radioactive material; most intakes can be reasonably characterized as acute exposures. However, when exposures extend over a longer period of time (i.e., more than a few days) it j

may be necessary to adjust the IRFs, which are based on single, acute intakes, to account for the extended exposure period.

Urinalysis for a worker, performed on a Friday, indicated an uptake of 'H. It was determined that the worker was continually exposed to 'H as HTO (water vapor) for the five work days of the prior week (i.e., Monday through Friday of the previous week). Results of the 24-hour urine sample reveal 10 pCi (3.7E + 05 Bq) of 'H.

Evaluation Procedure Since the exposure occurred over an extended period of time and the measurement taken after the exposure interval, the methods of Equation 8 from Regulatory Position C.4.4 should be used, i

l Je 4t) n I

• I

'5 + IRF{u,) +..

• 1RF(u,.,)

2 where:

l A(t)

Amount of activity in compartment or whole body at time t following onset of f

=

intake I

Total intake during period T

=

T Duration of intake (expasure time period)

=

Time from onset of intake to time of measurement t

=

Variable time between integration limits u

=

IRF(u) =

Intake retention fraction at time u in compartment or whole body for a single intake of a

(

radionuclide number of increments n

=

For this example, the time interval values are:

l l

T 5 days (period of intake)

=

t 11 days (number of days following onset of intake) r

=

The integration period is for the time (t-7) to t; therefore the interval consists of a total of 6 days. For i

purpose of the numerical integration, the 6-day time interval has been divided into 6 equal one-day increments.

The (RF values, taken from NUREGICR-4884 (page B'-711), for the calculation are listed in the following table, if IRF values are not presented for the day of interest, a logarithmic interpolation should be

~-

perform to calculate the value.

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r-Time Intervals From (r-7)

IRF to t (24-hr Urine)

(in 1 day increments) -

6 2.85E-02 7-2.66E-02 8

2. 48E-02 9

2.31 E 10 2.16E-02 11 2.02E-02 Substituting the IRFs and the interval length into the above equation yields the following:

10 pCi x 6 2.85E-02 + 2.02E-02 + 2.66E-02 + 2.48E-02 + 2.31E-02 + 2.16E-02 2

= 5.0E+02 pCi (1.8E+07Bq)

This calculated intake is less than 0.2 All for 'H (i.e.,500 Ci < 0.2 times the All value of 8E4 pCi).

Additional bioassay measurements would not be necessary for determining the intake. However, additional radiation safety measures may be needed for evaluating the incident and preventing future occurrences.

i;

~.

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