Radiation Physics Division 4902xC, 4903xC RPD-P-12

DOSE INTERPRETATION OF CUSTOMER-IRRADIATED 

NIST TRANSFER DOSIMETERS 

Version Date Author Approval Pages Filename

8.00 4/3/2023 IMP AKT 1 of 19 Procedure12v800

Purpose

The purpose of this procedure is to describe the setup, measurement, and 

reporting procedures for the absorbed-dose certification of customer-irradiated 

NIST transfer dosimeters.

Scope

NIST provides transfer standards in the form of sets of calibrated alanine pellets

packaged in polystyrene. The sealed, packaged dosimeters are sent to the 

customer for irradiation to nominal, agreed–upon absorbed dose levels in a 

prescribed geometrical arrangement. The unopened packaged dosimeters are then 

returned to NIST to be measured and evaluated and the results reported in the 

form of an absorbed-dose certificate. The absorbed dose range that is suitable for 

use with these transfer dosimeters is 20 Gy to 100 kGy.

Definitions

Absorbed dose to water: the energy absorbed from ionizing radiation per unit 

mass of water: 1 J/kg = 1 Gy.

Dosimeter batch: quantity of dosimeters made from a specific mass of material 

with uniform composition fabricated in a single production run under controlled 

conditions, and having a unique identification code.

Electron Paramagnetic Resonance (EPR): the process of resonant absorption of 

microwave radiation by paramagnetic ions or molecules in the presence of a static 

magnetic field.

Equipment

Essential Equipment Calibration Method Calibration 

Frequency

Location

60Co Gamma-Ray 

Sources

Comparison to Vertical 

Beam Source

Determined by 

control charts

Irradiation 

Facilities

Bruker EMXmicro EPR,

ER 070; SN: 807095

Dosimeter Check 

Standard Measurement

As needed H023

Bruker ECS 106 EPR,

B-E 25; SN: 25 89 436

Dosimeter Check 

Standard Measurement

As needed B0020

Bruker Benchtop EPR escan, SC0160Dosimeter Check 

Standard Measurement

As needed B0020

Microbalance External Service Annual H023

Bruker EPR systems use commercial software, WinEPR, to simplify bridge tuning, 

resonator calibration, and data collection.
Radiation Physics Division 4902xC, 4903xC RPD-P-12

DOSE INTERPRETATION OF CUSTOMER-IRRADIATED 

NIST TRANSFER DOSIMETERS 

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Health & Safety Precautions

Radiation safety

The 60Co sources used for system calibration are housed in secure areas.

Radiation safety, trainings are provided by the NIST Gaithersburg Radiation 

Safety Division.

Magnetic field safety

A Gaithersburg Office of Safety, Health and Environment survey of the vicinity 

of the EPR spectrometers determined that the magnetic field strengths are below 

actionable limits. However, as an extra precaution the room entrance has 

magnetic field warning signs; individuals with pacemakers should avoid rooms 

containing electromagnets associated with EPR spectrometers.

Procedures

1. Dosimeter Batch evaluation and testing

The evaluation testing provides data to assess influence quantities that may have 

significant effects on the performance of a dosimetry system. Data from all tests 

shall be recorded in the Dosimetry System Databook. 

1.1 Records should include a correlation between the unambiguous pellet 

identifier, its batch, and the container from which it was removed. The 

pellets will be stored in labeled containers.

1.2 Pellet Mass Test

1.2.1 Select and weigh pellets to the nearest 0.0001 g.

1.2.2 Plot a histogram of the mass distribution.

1.2.3 Determine the mean, standard deviation, and relative standard 

deviation (RSD) of the pellets measured.

1.2.4 RSD Acceptance Level: ≤ 10 %

1.3 Alanine-EPR Response Variation

1.3.1 Irradiate 4 pellets to each of the prescribed doses: 0.025 kGy, 0.200 

kGy, 1.00 kGy, 10.0 kGy, and 40.0 kGy.

1.3.2 Measure the EPR response (see Section 4) of the individual pellets.

1.3.3 Determine the mean, standard deviation, and relative standard 

deviation of the measured pellets grouped by prescribed absorbed 
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dose.

1.3.4 RSD Acceptance Level: ≤ 1 %

1.4 Dose fractionation

1.4.1 Irradiate six pellets (groups 3A & 3B) to 1.0 kGy, wait 1 hour then 

irradiate the six pellets to an additional 1.0 kGy, remove three 

pellets (group 3B), wait 1 hour then irradiate the group 3A pellets to 

an additional 1 kGy, wait overnight (~20 hours), then irradiate 

group 3B to an additional 1.0 kGy. 

1.4.2 Irradiate three pellets (group 3C) to 3.0 kGy.

1.4.3 Irradiate six pellets (groups 30A & 30B) to 10 kGy, wait 1 hour 

then irradiate the six pellets to an additional 10 kGy, remove three 

pellets (group 30B), wait 1 hour then irradiate the group 30A pellets 

to an additional 10 kGy, wait overnight (~20 hours), then irradiate 

group 30B to an additional 10 kGy.

1.4.4 Irradiate three pellets (group 30C) to 30 kGy.

1.4.5 After a 24 h wait period from the last irradiation, measure the 

absorbed dose for all pellets.

1.4.6 Determine the mean, standard deviation, and relative standard 

deviation of the pellet groups measured, and compare fractionated 

doses to continuously applied doses.

1.4.7 RSD Acceptance Level: ≤ 2 %

1.5 Post-irradiation time dependence

1.5.1 Irradiate six pellets, three to 1.0 kGy and three to 10 kGy.

1.5.2 Measure the absorbed dose approximately every other day for 2 

weeks.

1.5.3 Plot the signal of the measured pellets as a function of time. 

Determine the mean, standard deviation, and relative standard 

deviation for the stabilized signal. Determine the time necessary for 

the signal to stabilize.

1.5.4 RSD Acceptance Level: ≤ 2 %

1.6 Irradiation temperature coefficient
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1.6.1 In the dewar irradiation geometry, irradiate pellets to 10 kGy at 

each of three irradiations conditions: ambient; 20 °C higher than 

ambient; and 20 °C lower than ambient.

1.6.2 Measure the EPR response of the individual pellets.

1.6.3 Compute the resultant temperature coefficient (slope of the percent 

change, relative to the predicted value at the ambient temperature, 

in response versus the irradiation temperature) and compare this 

value to the accepted value.

1.6.4 Computed temperature coefficient Acceptance Level: ≤ 30 %

1.7 Batch mean

1.7.1 Irradiate simultaneously (co-located) two pellets from the previous 

batch with two pellets from the batch undergoing evaluation to 

each of the following doses: 1.0 kGy and 10 kGy.

1.7.2 Measure the EPR response (not absorbed dose) of the individual 

pellets.

1.7.3 Determine the mean of the pellet groups and compute the percent

difference in response between the batches.

1.7.4 Batch response difference Acceptance Level: ≤ 20 %

2. Instrument maintenance

EPR Spectrometers are operated and maintained according to the 

manufacturer’s guidelines. Significant maintenance activities are recorded in the 

EPR spectrometer log book.

2.1 Record major maintenance activities in the EPR spectrometer log book.

2.2 As necessary, or before each new calibration curve is measured, the quartz 

sample tube should be cleaned.

2.2.1 Soak a long stick cotton swab with methanol/water mixture (a few 

drops of water in 1 mL to 2 mL methanol) and insert into the 

sample tube to clean the pellet resting area. Allow the swab to 

remain inserted for 5 hours to 7 hours.

2.2.2 Draw a vacuum until sample tube is dry. This step may take 1 day 

to 2 days to be complete.
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2.2.3 Maintain a log of the laboratory conditions, such as temperature 

and humidity. Long-term trends will be reviewed in a control 

chart.

3. Dosimeter system calibration

Once a batch of pellets has been characterized and passed all acceptance 

criteria, a calibration curve shall be established.

3.1 Irradiate dosimeters to specified doses as detailed in RPD Procedure 11.

3.1.1 Selection of dose range of interest (Dose minimum is denoted as 

Dmin and the Dose maximum is denoted as Dmax).

3.1.2 To determine the minimum number of dose points, the equation 

Q = log(Dmax/Dmin) should be used. If Q is equal to or greater 

than 1, calculate 5 × Q, and round this up to the nearest integer 

value. If Q is less than 1, then 5 dose points may be sufficient.

3.2 Measure pellets

3.2.1 After all irradiations are completed, measure the pellets as 

described in Section 4.

3.3 Analyze the measurement data.

3.4 Record the calibration curve and any supporting information in the 

Dosimetry System Databook

4. Customer-irradiated absorbed-dose certification for alanine pellets

4.1 Upon receipt of a shop.nist.gov order, calibration service staff will evaluate 

whether the calibration service can be completed. If accepted, the 

calibration service staff will change the status to “Accepted” within the ecommerce platform. Calibration service staff will log the order in the 

Electronic Calibration Log Book with a unique HD number. After 

confirmation from the e-commerce platform concerning the payment status, 

the customer will be notified of the status by the calibration service staff.

4.1.1 An Electronic Test Folder (ETF) is created for record 

maintenance of the calibration order. Store all relevant 

documents from the e-commerce platform in the ETF. Start a 

new paper file (HD folder) to hold all printed documents until 

they can be digitized into the ETF and destroyed.

4.2 Mail dosimeters for requested test (service) numbers with an instruction 
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letter to the customer (Appendix A). This step is not applicable to service 

code 49030C.

4.2.1 Each dosimeter consists of four alanine pellets in a polystyrene 

vial or in a disc, upon customer request [2].

4.3 After receiving the returned customer dosimeters, verify that irradiator and 

irradiation information (target dose, temperature, etc.) on instruction letter 

has been provided by customer and reconcile the dosimeters returned with 

the list cited in the accompanying documents.

4.3.1 Customer letter for service code 49030C must contain the 

lot/batch number for the dosimeters provided.

4.4 Opening only one vial at a time, remove pellets from vials, unambiguously 

labeling each pellet consecutively (top to bottom) as each one is removed

from the vial. 

4.4.1 An additional sequential mark is placed on the service code 

49030C pellets as a visual aid.

4.4.2 The pellets will be stored in labeled containers with appropriate 

labeling.

4.4.3 Weigh pellets and input masses into Excel spreadsheet. Create 

Excel spreadsheet to record data from measurements.

NOTE: Empty vials are cleaned by immersing in ethanol with agitation, 

allowing them to remain immersed overnight, then dried in a fume hood 

overnight. Service code 49030C vials are not cleaned by NIST; they are 

returned to the customer. 

4.5 Operate EPR Spectrometer

4.5.1 Turn on magnet cooling water chiller.

4.5.2 Turn on magnet.

4.5.3 Check that the micrometer on the ruby reference device is at set 

value.

4.5.4 Logon to the EPR computer using the appropriate login 

credentials.

4.5.5 Tune spectrometer.
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4.5.5.1 For ECS106 Press F5/F3. Once the standby light changes 

from red to green, use the right arrow key to change to tune mode.

4.5.5.2 With a pellet in the EPR sample tube, use the page-up key 

to perform the auto-tune procedure at least twice and allow 

approximately one hour for the spectrometer to warm up, then run 

the auto-tune procedure once more.

4.5.5.3 For the EMX, select the autotune option under the 

microwave dialogue box.

4.5.5.4 Open VBS code for data collection.

4.6 Ensure that the spectrometer is operating at an expected level of 

reproducibility (<1 %) by recording alanine pellet and ruby spectra at 

regular intervals.

4.7 Excel spreadsheet setup

4.7.1 Verify that the Parameter worksheet contains the EPR 

Spectrometer parameters matching those of the corresponding 

calibration file. 

4.7.2 The measurement worksheet includes the date, vial number, 

pellet number, pellet mass, alanine signal max/min peak height 

and ruby signal max/min peak height, peak-to-peak amplitude, 

and mass-ruby normalized signal amplitudes (response).

4.7.3 The summary worksheet includes the company name, date, 

calibration function and the corresponding solution formula, 

coefficients of the calibration curve being used, the calculated 

mass-ruby normalized signal (from the measurement 

worksheet), the calibration temperature and temperature 

coefficient, and the customer-reported irradiation temperature 

and estimated dose (from the customer instruction letter).

4.7.4 The summary worksheet calculates the irradiation temperature 

corrected response and absorbed dose.

4.8 EPR measurement

4.8.1 The mean response and RSD are calculated for each group of 

four pellets within a vial. Check the RSD for each grouping, 

perform an outlier test and/or repeat measurements as needed.

The mean response is the value used to calculate the absorbed 

dose. 
Radiation Physics Division 4902xC, 4903xC RPD-P-12

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4.8.1.1 An increasing pellet response trend that exceeds a 1 % RSD 

across the stack of four alanine pellets in the vial is considered to 

be a significant absorbed dose gradient. In this case, the absorbed 

dose shall be calculated and reported for each pellet.

4.8.2 The dose determination for service code 49030C is preceded by 

an analysis of the check standard dose repeatability and alanine 

pellet anisotropy.

4.8.3 Determine the mean response and RSD for the pre- and postcustomer pellet measurements of the four check-dose pellets. A 

dose value is interpolated and the pre- and post-check standard 

dose deviations from the established absorbed dose must agree 

within 1 %. If the deviation percentages differ by 1 % or more, 

the measurement session must be repeated. Note that the 

absolute deviation from the established absorbed dose can be 

greater than 1 %.

4.8.4 The mean response and ruby-normalized alanine signal 

anisotropy is calculated for each customer dosimeter. If any 

dosimeter has an anisotropy difference greater than 1 %, that 

dosimeter must be remeasured. If repeated measurements 

continue to exceed 1 %, a special comment should be appended 

to the certification report.

4.8.5 Calculate dose by using the coefficients from the applicable 

calibration curve (refer to Dosimetry System Databook).

4.9 Above 5kGy, the Dose Rate Effect (DRE) may be evident. Check standard 

dosimeters irradiated to > 5 kGy with < 1 Gy/s will be adjusted using an 

experimentally determined DRE. DRE-adjusted Check standard dosimeters 

can be used to establish EPR performance but all calibration curves above 

5 kGy shall be completed with higher dose rates (> 2 Gy/s).

4.10For service code 49030C and for doses below 200 Gy, an additional step is 

added to adjust for the check-dose-offset value.

4.10.1 When the calibration curve is created, a 25 Gy reference dose 

value is established to relate all future check-dose 

measurements to the calibration curve. That value is the 

interpolated dose from the fitted equation derived from the 

mean response of the 25 Gy dosimeter group of the calibration 

set.

4.10.2 The average dose value of the pre- and post-check standard dose 

is calculated. The difference of that average check standard dose 
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value to the previously established reference dose value is then 

calculated (in Gy). This difference is recorded as the dose-offset 

value for the measurement session and is added/subtracted from 

each customer pellet calculated dose.

4.10.3 Uncertainty analysis is modified, if needed.

4.11Check the spreadsheet cell links/functions and entered data for accuracy.

4.11.1 Print copies of data, and insert in Transfer Dosimetry Databook

4.11.2 Copy Transfer Dosimetry Databook pages and insert into HD 

folder

4.12Report and test closure

4.12.1 A checklist, Appendix B, for HD irradiation services is filled 

out and included in the ETF.

4.12.2 Create an “Absorbed Dose Measurement Certificate” report 

from a template. Include an annotated draft of the certificate in 

the ETF checking the company information, order number and 

Transfer Dosimetry Databook references (footnote), and the 

final dose values into the report template (see Appendix C)

4.12.3 The preparer sends the ETF and the electronic certificate for 

review. They are sequentially routed to the reviewer, Group 

Leader and Division Chief (as designated on the certificate) for 

review and an electronically certified signature. 

4.12.4 The certificate with the electronically certified signatures is 

returned to the preparer. The preparer submits the report to the 

e-Commerce platform and notifies the Calibration 

Administrative Staff of the completion of the work. The order 

status changes to “Completed”. Upon customer request, the 

preparer may send the electronic certificate by email or/and 

send a printed copy of the electronically signed certificate. 

4.12.5 The Administrative Staff will change the order status to 

“Closed”.

5. Quality control

5.1 Absorbed-dose check standards

Approximately every month, or as needed, dosimeter pellets are irradiated 
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to the following doses: 0.025 kGy, 0.20 kGy, 1.0 kGy, 10 kGy, and 40 kGy

as detailed in RPD Procedure 11. These check standards are routinely 

measured ~24 hours to 72 hours after irradiation, as well as prior to service 

measurements. Data from these check standards are archived in working 

spreadsheet files for reference availability. A control chart is updated and 

included into the ETF. Check standard dose measurements that measure 

outside of set limits must be resolved through re-measurement, repetition of 

the check standard process, or a complete recalibration of the dosimetry 

system.

5.2 Transfer dosimetry controls

Each set of transfer dosimeters shipped to a customer is paired with a 

control vial that is packaged separately and marked “Do Not Irradiate”.

Control vials contain pellets of the same type that have been previously 

irradiated to a calibrated dose. These dosimeters are typically check 

standards that have exhibited good stability after repeated measurements. A 

continuous history of these data is recorded. Any nonconformance shall be 

reported; action to be taken is at the discretion of the calibration staff.

5.3 International comparisons

Upon mutual agreement, dosimetry comparisons are performed with the 

high-dose calibration facility of the National Physical Laboratory of the 

United Kingdom. Dosimeters from each facility are exchanged, measured, 

and the results compared. The RPD participates in larger international 

comparisons, such as those organized by the BIPM, when available 

(approximately every ten years) [3, 4]. These data are summarized in the 

High-Dose International Comparisons Databook.

6. Traceability

6.1 Dose rate transfer

The SI unit of absorbed dose is the gray (Gy). For this service, the Gy is 

realized through water calorimetry measurements in the Vertical Beam

60Co Source. These measurements are transferred to the lowest dose rate 

Gammacell calibration source a by source-rate ratio measurements using 

alanine dosimetry. Similarly, the source-rate ratio from the lowest dose rate 

Gammacell is then transferred to the higher dose rate Gammacell and 

GR420 irradiators. These transfer measurement protocols are described in 

NIST SP250-44 [5]; the traceability scheme was later modified [6].
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Determination of Uncertainties

The basis for the determination of uncertainties associated with High-Dose 

calibrations is the Guidelines for Evaluating and Expressing the Uncertainty of 

NIST Measurement Results [7]. The purpose of this section is to explain the 

derivation of the various components of uncertainty for absorbed-dose 

certification. Examples of the values for the uncertainty components are listed in 

Appendix D.

Water Calorimetry: uncertainty from realization of the Gy [8].

Source Ratio Data: uncertainty from source dose-rate transfer (water calorimetry 

rate to high-dose calibration source rate) through ratio measurements.

Field Uniformity: radiation field uniformity within a dosimeter volume.

Environmental Effects: temperature control during irradiation.

Timer: uncertainty of timer readout relative to shortest irradiation time interval.

Decay Correction: half-life correction factor uncertainty.

Mass: uncertainty of microbalance relative to pellet mass.

Repeatability and Reproducibility: standard deviation of replicate pellet

measurements.

Interspecimen Contamination: cross contamination of pellets during the 

measurement process.

Ruby Correction: uncertainty resulting from EPR spectrometer fluctuations during 

the time interval between the alanine pellet measurement and the reference (ruby) 

measurement.

System Drift: uncertainty arising from temporal EPR spectrometer response 

fluctuations.

Temperature Correction: uncertainty from alanine dosimeter temperature 

coefficient measurement.

Calibration Curve: fit uncertainty from alanine dosimeter calibration curve.

Additional uncertainties are applied to irradiations in electron beams and 137Cs, or 

for absorbed dose to silicon conversions.
Radiation Physics Division 4902xC, 4903xC RPD-P-12

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References

1. Sleptchonok, O.F., Nagy, V., Desrosiers, M.F., 2000 Advancements in accuracy 

of the alanine dosimetry system. Part 1. The effects of environmental humidity, 

Radiat. Phys. Chem. 57, 115-133.

2. Radiation Processing Dosimetry Calibration Services: Manual of Calibration 

Procedures, Humphreys, J.C., Puhl, J.M., Seltzer, S.M., McLaughlin, W.L., 

Desrosiers, M.F., Bensen, D.L., Walker, M.L. 1998 NIST Special Publication 

250-45.

3. Burns, D.T., Allisy-Roberts, P.J., Desrosiers, M.F., Sharpe, P.H.G., Pimpinella, 

M., Lourenço, V., Zhang, Y.L., Miller, A., Generalova, V., Sochor, V. 2011 

Supplementary comparison CCRI(I)-S2 of standards for absorbed dose to water in 

Co-60 gamma radiation at radiation processing dose levels, Metrologia, 48, Tech. 

Suppl. 06009 1-18.

4. McEwen, M.R., Sharpe, P.H.G., Pazos, I.M., Miller, A., Pawlak, E., Ninlaphruk, 

S., Zhang, Y., Kessler, C. 2022 Supplementary comparison CCRI(I)-S3 of 

standards for absorbed dose to water in Co-60 gamma radiation at radiation 

processing dose levels, Metrologia, 59, 06012.

5. Radiation Processing Dosimetry Calibration Services and Measurement 

Assurance Program, Humphreys, J.C., Puhl, J.M., Seltzer, S.M., McLaughlin, 

W.L., Desrosiers, M.F., Bensen, D.L., Walker, M.L. 1998 NIST Special 

Publication 250-44.

6. Desrosiers, M.F., Puhl, J.M., Cooper, S.L. 2008 Discovery of an Absorbed-Dose / 

Dose-Rate Dependence for the Alanine-EPR Dosimetry Systems and Its 

Implications in High-Dose Ionizing Radiation Metrology, NIST J. of Res., 113,

pp. 79-95.

7. NIST Technical Note 1297, Guidelines for Evaluating and Expressing the 

Uncertainty of NIST Measurement Results, 1994.

8. Domen, S.R., A sealed water calorimeter for measuring absorbed dose, NIST J. of 

Res., 99, pp. 121 – 141, 1994.

Records

Record Contents/Purpose Location

Electronic Calibration Log 

Book

Login all tests to obtain test folder number In the 

High Dose 

folder 

Dosimetry System Databook Records dosimetry system calibrations and 

dosimeter batch characterization

245/

B0020

Internal Calibrations Source ratio measurements and data 

analysis

245/

B0020

EPR Spectrometer User Log 

Book

Usage and maintenance records 245/

B0020
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Record Contents/Purpose Location

Transfer Dosimetry Databook Records all transfer dosimeter certification 

data

245/

B0020

High-Dose International 

Comparisons Databook

Interlaboratory measurement comparison 

data summaries

245/

B0020

Filing and Retention

All paper copies of customer files are stored in the test folder for that service until 

they can be digitized and stored in ETF at which time it can be destroyed. The 

ETF is stored in OneNote. All customer-related electronic files are stored in the 

“High Dose” folder on the shared network drive.

The RPD Quality Manager shall maintain the original and past versions of this 

RPD Procedure.
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Appendix A – Sample Transfer Letter

June 20, 2021

HD0000

Ms. Gray 

RAD Sterilizers

Return Shipments to:

NIST High-Dose Service

Building 245

100 Bureau Drive, Stop 8460

Gaithersburg , MD 20899-8460

USA

Dear Ms. Gray,

Enclosed are the alanine transfer dosimeters that you requested for irradiation in your facility. There are six

vials for irradiation (9901-9906), each filled with four alanine pellets from the batch T030901. The other 

vial (#44) is a control and should not be irradiated. Do not open the vials. The useful life of the dosimeters 

is approximately 30 days from the date of receipt at your facility. If dosimeters are not used within this time 

frame, please contact NIST for further instruction. Please complete the table on the following page and 

return it with the dosimeters.

Dosimeter Date(s) of irradiation

Target Dose, kGy

(approximate)

Average Irradiation 

Temperature (°C)

9901

9902

9903

9904

9905

9906

Control Vial 

(#44) DO NOT IRRADIATE 0

How would you like for us to identify your irradiator on the certificate? 

Any other information you wish to be noted on the certificate?

Sincerely,

Calibrations Technician

Dosimetry Group

Physical Measurement Laboratory

PHONE: 301-975-xxxx FAX: 301-869-7682 E-MAIL: caltech@nist.gov

Enclosures
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Appendix B – QM Checklist for 49020C and 49030C

NIST ID:

Date:

Checklist for 49020C and 49030C:

____ The Spectrometer was set up with the spectral parameters that were used 

for the corresponding calibration curve.

____ ECS106

____ EMX

____ The spectral parameters were noted in the Excel spreadsheet.

____ The pellet masses are paired correctly with the corresponding pellet number.

____ The Excel spreadsheet reflects the appropriate NIST ID, company name, irradiation 

temperatures, etc.

____ The Excel spreadsheet reflects the appropriate file names and dates for both the data 

file and calibration file.

____ The correct calibration curve coefficients were used in the dose calculation and 

noted on the spreadsheet. 

____ All mathematical calculations embedded in cells have been checked for accuracy 

and correct cell linkage.

____ The appropriate correction factors were applied (i.e., temperature, dose-to-water, 

dose-to-silicon, 137Cs, etc.) to the calculated dose.

Signed by: ______________________________ Date: ____________
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Appendix C – Example Certificate

National Institute of Standards and Technology

Absorbed-Dose Measurement Certificate

NIST Service Identification Numbers 49020C and 49022C

IRRADIATOR

MDS Nordion Gammacell XXX

CUSTOMER

RAD Sterilizers

7 Electron Avenue

Mega Rad, LA 99817

ATTN: Ms. Gray

Reference: PO # 5678

Measurements made by Ileana M. Pazos

Report reviewed by Lonnie Cumberland

Report approved by 

Michael G. Mitch, Leader

Dosimetry Group

Approved by

James M. Adams, Chief

Radiation Physics Division

Physical Measurement Laboratory

For the Director of the National Institute of Standards and Technology

Information on technical aspects of this report may be obtained from Ileana M. Pazos, NIST, 100 Bureau Drive 

Stop 8460, Gaithersburg, MD 20899, 301-975-4121, ileana.pazos@nist.gov.

REFERENCE HD0000

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NIST DB 2000/000

July 23, 2021

Page 1 of 3 Pages
Radiation Physics Division 4902xC, 4903xC RPD-P-12

DOSE INTERPRETATION OF CUSTOMER-IRRADIATED 

NIST TRANSFER DOSIMETERS 

Version Date Author Approval Pages Filename

8.00 4/3/2023 IMP AKT 17 of 19 Procedure12v800

Transfer dosimeters were sent to RAD Sterilizers for irradiation in their facility. The 

dosimeters were NIST alanine pellets of FWT batch T030901; four each in a polystyrene 

vial. The dosimeters were analyzed on July 8, 2021, using a Bruker EMXmicro 

spectrometer. Dose interpolations are based on a NIST calibration of batch T030901 alanine 

dosimeters performed January 1, 2021 and include the influence of the customer-reported 

irradiation temperature. The results are summarized in the following table. 

Dosimeter 

Identification

Absorbed Dose 

kGy(H2O)

9901 0.325

9902 0.678

9903 0.989

9904 1.21

9905 2.22

9906 3.25

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NIST DB 2000/155

July 23, 2021

Page 2 of 3 Pages
Radiation Physics Division 4902xC, 4903xC RPD-P-12

DOSE INTERPRETATION OF CUSTOMER-IRRADIATED 

NIST TRANSFER DOSIMETERS 

Version Date Author Approval Pages Filename

8.00 4/3/2023 IMP AKT 18 of 19 Procedure12v800

UNCERTAINTIES AND RELATED FACTORS IN HIGH-DOSE MEASUREMENTS

Absorbed Dose Evaluations Based on Use of

Mailed Alanine Pellet Transfer Standard Dosimeters Irradiated Using 60Co

(Expanded uncertainty: ± 1.8 % at a 95 % confidence level)

The customer’s use of NIST-certified transfer standard dosimeter measurements to 

determine their radiation-source dose rate is subject to limitations and precautions described 

in the letter accompanying the dosimeters. The customer must follow the prescribed 

procedures carefully in order to ensure that the results obtained from the transfer dosimeters 

are valid. The uncertainty value cited above may be assumed as long as suitable care is 

exercised. That value does not include uncertainty in the customer-reported irradiation 

temperature or non-uniformity in the customer’s irradiation field.

The absorbed dose in water evaluation is based on NIST alanine pellet dosimeters that are 

traceable to primary standard water calorimeter measurements and are corrected by certain 

modifying factors (such as the geometry attenuation factor and source decay factor). The 

absorbed dose value(s) given in this report can be used to check the accuracy of customer 

measurement systems and to verify the capabilities of those systems to both transfer and 

maintain traceability of measurement results. The absorbed dose value(s) relate only to the 

dosimeters in this report.

A detailed list of the various sources of uncertainty and estimates of the magnitude of 

those uncertainties that make up the overall uncertainty given above may be obtained 

through the Internet (https://www.nist.gov/programs-projects/basic-metrology-high-dosedosimetry-uncertainty-tables) or by requesting this information from NIST. The 

uncertainties are divided into two types: A and B. Type A uncertainties are those 

evaluated by statistical methods, often associated with random effects. Type B 

uncertainties are those evaluated by other means, often associated with systematic effects.

Type A Uncertainties

The combined standard uncertainty evaluated by statistical methods is ±0.66 % at an 

approximate level of confidence of 68 %.

Type B Uncertainties

The combined standard uncertainty based on scientific judgment is estimated to be ±0.59

% at an approximate level of confidence of 68 %.

Expanded Uncertainty

The Type A and Type B uncertainties have been combined in quadrature (the square root 

of the sum of the squares) and multiplied by a coverage t-factor of 2.05 to yield an 

expanded uncertainty of ±1.8 % at an approximate level of confidence of 95 %.

REFERENCE HD0000
Radiation Physics Division 4902xC, 4903xC RPD-P-12

DOSE INTERPRETATION OF CUSTOMER-IRRADIATED 

NIST TRANSFER DOSIMETERS 

Version Date Author Approval Pages Filename

8.00 4/3/2023 IMP AKT 19 of 19 Procedure12v800

682.02/O-00123456789-21

NIST DB 2000/155

July 23, 2021

Page 3 of 3 Pages

Appendix D- Example Uncertainties Table for Transfer Dosimetry Service

High-Dose Alanine Response, Far West / Gamma Service Alanine Pellets

Uncertainty Source Type A (%) Type B (%)

Repeatability and Reproducibility 0.30

Mass Determination 0.20

Interspecimen Contamination 0.10

Ruby Correction 0.05

System Drift 0.10

sqrt(sum) 0.36 0.15

Alanine Pellet Dosimeter Transfer Dose(water), Gamma/X-Ray, >100 Gy

Uncertainty Source Type A (%) Type B (%)

Alanine Dose Rate (GC207 Center) 0.25 0.55

Alanine Response 0.36 0.15

Temperature Correction 0.10

Dose Rate Effect 0.10

Calibration Curve 0.50 0.10

sqrt(sum) 0.66 0.59

combined in quadrature 0.89

t-factor for 45 d.f at 95.45 % 2.06

Expanded Uncertainty at 95.45 % conf. 1.8