Quality Assurance Requirements for 36Cl and 129I Accelerator Mass Spectrometry

PRIMELab QA samples Sample Custody Change Wheel Tune Beam Nist Standard Certificates 36Cl Phy-Chem treatment 10Be,26Al Phy-Chem treatment

Introduction

Chlorine-36 is a radioactive isotope of chlorine, produced by naturally occurring and anthropogenic processes; it has a half-life of 301,000 years. Iodine-129 is a radioactive isotope of iodine, and is produced predominately as a result of neutron-induced fission of uranium. Its half-life is 1.6 x 107 years. Accelerator Mass Spectrometry (AMS) provides a highly sensitive and accurate technique for analyzing very small quantities of 36Cl and 129I. The techniques describing the measurement of radio-nuclides via AMS are described in Elmore et al. (1986).

The primary objective of this study is to provide 36Cl and 129I isotope data pertinent to a hydrologic experiment in the vicinity of Yucca Mountain.

This procedure applies to PRIME Lab personnel who use this procedure to provide data for site characterization for customer organizations.

Organization

The organizational structure for the Purdue Rare Isotope Measurement Laboratory (PRIME Lab) as it relates to analytical work consists of the PRIME Lab Director and Associate Director, the PRIME Lab QA/data analyst, and the PRIME Lab staff. The Associate Director is responsible for the implementation of the specified QA and technical requirements applicable to analyses of customer samples.

Personnel Qualification and Training

Personnel handling samples and operating the AMS will be trained in the applicable QA requirements prior to performing quality-affecting activities. Personnel also will have the appropriate technical training, education, and experience required by their position descriptions. Documentation of job requirements, education, training, and experience are maintained by the PRIME Lab.

The PRIME Lab associate director is responsible for verifying that all personnel are qualified to perform the quality affecting work.

Implementing Documents

All quality affecting work shall be performed in accordance with this QA requirements document. The PRIME Lab Associate Director is responsible for ensuring the technical accuracy of all documents pertaining to this document. He is also responsible for approval of technical procedures and the Quality Assurance Requirements Document. Implementing documents shall contain the following information: 1) sample chain of custody; 2) sample loading procedures; 3) procedures pertaining to the isotopic analysis determination; 4) quantitative or qualitative acceptance criteria sufficient for determining that the activities were satisfactorily accomplished, including quality verification and hold points; 5) prerequisites, limits, precautions, process parameters, and environmental conditions; 6) and methods for demonstration that the work was performed as required.

Document Control

The technical procedures will have unique identifiers that include the revision level. The PRIME Lab associate director is responsible for ensuring that the latest approved technical procedures and QA requirements document are distributed to appropriate personnel.

Control of Measuring and Test Equipment

The accelerator mass spectrometer is the only instrument requiring calibration. It is to be calibrated by the operator for each run as specified in the current version of technical procedure titled Tuning the Beam for AMS.

No special handling, storage, and/or shipping is required. All materials and equipment shall be as per listed manufacturer or equivalent.

6.1 Sample Preparation
Completed prior to use of this procedure

6.2 Mass Spectrometry
Accelerator mass spectrometer: a HVEC Model FN
Commercial grade Cs for the sputter source
Aluminum and copper target holders
NIST 4422L
NIST 4943
NIST SRM 3230 Iodine - 129 Isotopic Standard (Low Level) 

Software

Software utilized by PRIME Lab for quality affecting activities is an integral part of the AMS analysis. The software is URSULA (current version). URSULA is validated using NIST standards as part of the mass spectrometer calibration. URSULA data reduction process is also validated during the calibration. Software changes are not approved for use until validated with a NIST standard

Samples

Sample control is performed in accordance with the current version of PRIME technical procedure titled Sample Chain of Custody. Samples will be prepared by the submitting organization and identified in accordance with the procedure titled General Loading Procedures. Samples entering the AMS laboratory must be clearly and uniquely labeled, and accompanying documentation must be provided to the satisfaction of the QA analyst before processing can proceed. For samples that are not accompanied by satisfactory documentation the QA analyst will notify the submitting organization of the problem and will make note of the submitting organization's response.

All samples are to be discarded after they have been removed from the mass spectrometer.

Methods

The general principles of AMS techniques are described by Elmore et al. (1987).

9.1 Mass Spectrometry

36Cl: Isotopic analysis of chlorine will be done on the HVEC Model FN Accelerator mass spectrometer. The AgCl samples are loaded in copper target holders. A wheel is composed of up to 50 samples. Samples are to be clearly identified by the submitter. Negative Cl ion beams are generated by a Cs sputter ion source. Beams of 35Cl, 36Cl, and 37Cl ions are sequentially selected for injection into a tandem electrostatic accelerator operating at ~ 8.0MV. A carbon foil stripper in the accelerator voltage terminal is used to strip the ions to positive charge status and to break up molecules. Ions emerging from the accelerator are mass-analyzed with a 90-degree magnet and stable Cl ions are detected in a Faraday cup. 36Cl ions are selected using a second magnetic analysis stage and an electrostatic filter, and are detected and distinguished from any remaining contaminants in a multi-anode gas ionization detector. Isotopic measurements are carried out by determining 36Cl/Cl ratios and by normalizing the results from unknowns to those for the primary standards [c.f. Sharma et al. (1990)].

129I: The mass spectrometric techniques for the measurement of the 129I /127I ratio are similar as those described for 36Cl. Iodine is loaded into aluminum cathodes as AgI. Prior to loading the AgI is mixed with an equal volume of Nb, which serves as a binder material. It is important that the AgI be thoroughly dry before loading into the cathodes. If moisture is observed in the AgI the material must be dried further, sending notification of the sample submitter. Iodine is run with much lower terminal voltage than Cl, ~ 2-3 MV.

Setup and tuning of the analytical equipment is carried out only by staff who have been specifically trained and approved. Generation of an ion beam is started after vacuum has reached 5 X 10-6 torr or better. Measurements are undertaken only when the analyst in charge is satisfied that the hardware and software are operating normally, and after measurements on blanks have established that no ion source contamination is present. Operating normally is indicated by consistent readings on several targets containing primary standards and by measurements yielding a correct ratio between primary and secondary standard. If these conditions are not met, then run is suspended until the necessary cleaning or repairs have been carried out. The tuning procedures are described in the procedure for beam tuning.

9.2 Operational Controls
Operational checks are performed following the steps outlined in the procedure titled Sample Wheel Change. In addition to these checks, the mass spectrometer is checked at least every 8 samples by the analysis of a laboratory standard or standards.

These operational checks of the mass spectrometry laboratory shall incorporate components that measure and/or regulate vacuum, accelerating voltage, and ion-beam current. If the results of these operational checks are not within acceptable limits mass spectrometer operations are suspended until the problem(s) is (are) identified and rectified. After these checks have been made, an entry will be made in the logbook to indicate that the system is operating normally or that the system has been shut down because of a problem.

Calibration

All calibrations shall be performed and documented in the output files from URSULA. Unless otherwise indicated, the following calibrations are performed by the AMS operator.

10.1 Mass Spectrometer: The mass spectrometer is calibrated independently of the laboratory by analyzing the NIST standards.

10.2 Calibration Documentation: Mass spectrometer calibrations are documented in the mass spectrometer logbook. If appropriate, calibration documentation shall be sent to submitters of samples.

Limitations and assumptions

Mass spectrometers are complex systems having many components. Electronic problems will commonly manifest itself as beam instability such as drift or instability in the isotopic ratios measured on a single target during the course of the analysis. If such a failure occurs the instrument will be shut down pending resolution of the problem by trained personnel. There are no unconstrained assumptions in the laboratory procedures that have not been experimentally tested during the long-term operation of the facility.

Verification and hold points

Data will not be released from the laboratory until all samples of a given set have been examined for internal coherence and data reductions have been cross-checked by a qualified PRIME Lab staff member.

Acceptance criteria

All measurements are quantitative. Adherence to these tolerances will be demonstrated by the replicate analyses of NIST-certified standard samples. NIST-traceable standards, and of unknowns. The submitter will specify the precision for each sample submitted.

Quality assurance records

Quality assurance records shall include documents that support the completion of the tasks as outlined in this document. These include position descriptions, training records, personnel qualification records, and data as specified in the current version of this technical procedure. The PRIME Lab QA/data analyst is responsible for maintaining QA records for up to three years. The records produced under this procedure shall be prepared and stored in duplicate on site or with one copy on site and a duplicate sent to the sample submitter for storage.

14.1 Data Records: The basic completed analytical data sets obtained will consist of isotopic ratios for each sample and blanks. This data will be sent to the submitter and stored on site.

14.2 Supporting Information: Mass spectrometer logbooks shall record, at a minimum, sample numbers, dates analyzed, and instrument operator. If a notebook or logbook contains data, a statement will be noted in the book documenting which information is data. As appropriate, the documentation containing the information shall be sent to the submitter.

Corrective Actions

The PRIME Lab data/QA analyst is responsible for promptly notifying the customer of any corrective actions impacting their results. This notification includes reporting the violation of an implementing document, such that the collection, preparation, and/or analysis of samples could have been adversely affected.

Deficiency Reporting/Corrective Actions 

16.1 Deficiencies are defined as materials or measurements deemed unsuitable for publication in technical reports.

16.2 Any anomalous behavior of the AMS system or of a particular sample that might adversely affect results (ion source faults or other hardware problems, etc.) will be noted in the logbook by the operator during the run.

16.3 During the data analysis, the database analyst will determine whether any problems are sufficiently severe as to render the data for a given sample unreliable. The reasons for the poorer quality of the data will be noted in writing in the report to the submitter.

16.4 If the data for a given sample is considered reliable, but of significantly lower-than-normal quality, (e.g., the results, have larger-than-normal standard deviation), results will be provided for that sample. The reasons for the poorer quality of the data will be noted in writing in the report to the submitter.

16.5 The submitter will be contacted to determine how to correct any such deficiencies. Depending on the circumstances, this might involve measuring another sample aliquot, carrying out additional background checks, etc. 

Revision No. Effective Date Description of Revision
0 Jan. 15, 2004 Initial Issue
1 Jan. 17, 2006 In corporation of 129I
2 Jan. 3, 2007 Change the date format for PDF

Marc W. Caffee, Driector of PRIME Lab