Contents

Calibration Requirements for Radiochemistry

Effective Date: 07/2008
Point of Contact: Quality Engineer for Regulatory Programs

Instrument calibration should be performed as needed with nationally or internationally recognized standard agency sources and standards. Instrument calibration must be verified to ensure the instrument is properly calibrated and to confirm the accuracy of the calibration standards. The instrument response check must be performed routinely using the counter control standards to ensure that an instrument responds in the same manner after its calibration. Recalibration should be necessary only when the instrument or system has malfunctioned and the repaired equipment response exceeds the tolerance level on the quality control chart. Only well-defined standards shall be used, and care should be taken to prepare homogeneous standards in accurately defined geometries having exact (or correctable) radiometric characteristics of the sample matrix or geometry. Minimum calibration requirements for radiochemistry are given in the following tables:

Analytical techniques not addressed in this plan are developed according to the Procedures section with consideration given to the quality control requirements presented in the following tables and the Quality Control section.

Minimum Calibration Requirements for Alpha/Beta Counting

Calibration Requirements Calibration Parameters and Standards Criteria Corrective actions Frequency
Calibration Plateau checks as applicable Count one standard over a range of voltage in increments Plot voltage versus counting activity to estimate proper operating voltages for alpha and/or ß counting Set instrument at plateau voltage After repair or major maintenance if control of system cannot be reestablished
Cross talk or sensitivity(a) as applicable Count known alpha activity on ß counter, and known ß activity on alpha counter Cross talk of alpha in ß: less than 10% Cross talk or sensitivity of ß in alpha: less than 1% Investigate the system if cross talk criteria fail  
Counting efficiency to calculate activity in sample Count at one known level for each counting geometry at the appropriate energy Counting error 1% Investigate the system  
Weight of solids(b) to calculate sample activity when mass loading occurs Establish a curve for efficiency versus mass loading(b)    
Background counting Count detector background. Use contamination-free clean planchet Establish a background count rate value for total alpha and total ß As needed to meet data quality objectives Once per day as the system is used or per batch. See Radiochemistry Quality Control exhibit for routine background requirements

(a) When cross talk has an impact on data reduction.
(b) When mass loading is applicable.

Minimum Calibration Requirements for Alpha Energy Analysis

Calibration requirements Calibration parameters and standards Criteria Corrective actions Frequency
Calibration Energy calibration
Counting efficiency(a) Matrix- and geometry-specific		 Need at least two isotopes with resolvable energies.
Use at least 1 traceable alpha source.		 Not applicable After repair or major maintenance if control of system cannot be re-established
Background Count detector background to establish background level Represents the background at the time of calibration. As needed to meet data quality objectives See Radiochemistry Quality Control exhibit for routine background requirements

(a) The counting efficiency for alpha spectrometers is independent of alpha energy. Counting efficiency need not be directly determined for a detector, if the analyte is determined relative to an appropriate traceable internal tracer. The alpha energy peak used for calibration must be resolvable from other peaks in the spectrum or a peak fitting correction applied if integration is affected by tailing. Equally acceptable, the counting efficiency may be determined for the system and factored into the sample activity determination as long as the basis for the efficiency determination remains constant with the samples, i.e., reproducible counting geometries. At a minimum, one traceable alpha source is used to determine the detector counting efficiency.

Minimum Calibration Requirements for Gamma Energy Analysis

Calibration Requirements Calibration Parameters and Standards Criteria Corrective Actions Frequency
Calibration Detector energy calibration
Counting efficiency(a) Matrix- and geometry-specific		 Specific criteria depends on total channels and range of energy of desired nuclides Span energy range of nuclides of interest, unless calibration is for a single nuclide, then calibration is at that specific energy Not applicable
Not applicable		 After repair or major maintenance if control of system cannot be reestablished
Background Count detector background to establish background level Represents the background at the time of calibration As needed to meet data quality objective See Radiochemistry Quality Control exhibit for routine background requirements

(a) Only where counting efficiency is an analytical requirement

Minimum Calibration Requirements for Liquid Scintillation Counter

Calibration requirements Calibration parameters and standards Criteria Corrective action Frequency
Calibration External (instrumental) standardization Not applicable Not applicable After repair or major maintenance, if system control cannot be re-established
Method calibration (determining quench) 1. Quench curve(a) at least three points in the applicable energy range bracketing the sample quench characteristic
2. Internal standard		 Used for establishing quench level in the sample and to determine specific counting efficiency Investigate the system 1. If matrix or cocktail changes
2. Add to each sample type
Alternate calibration: batch approach (b) Minimum two matrix-matched standards and blanks Matrix matched standards must agree within ± 3 sigma counting uncertainty or ± 5%, whichever is greater Investigate One blank and one standard at the beginning and one blank and one standard at the end of the batch

(a) If applicable.
(b) This is an alternate calibration. If this approach is used, the above requirements do not apply.