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Radionuclide metrology

Objective

Specific Objectives

- To support European and other international metrology organisations in establishing 'International Equivalence' in radioactivity standards by co-operating with National Metrology Institutes (NMIs);

- To characterise and certify reference materials and other samples for their radioactive components for the use in governmental organisations, industry and medicine;

- To assist European and other international organisations and NMIs in establishing radioactivity standards used in research, industrial applications, nuclear medicine and radio-therapy;

- To do low level and ultra-low level radioactivity measurements on samples containing smallest amounts of radioactivity for safeguards, environment, medicine and industry;

- To measure radioactive decay data and participate in international radioactive decay data evaluation programmes - such data being the basis for accurate measurement applications;

- To improve existing measurement methods and to develop new methods for the accurate measurement of radioactivity.
Planned Deliverables

- Specific Deliverables to DGs

- Measure swipe samples for DG TREN (continuous on request);

- Complete 2nd batch of measurements of JCO, Japan, samples March 2002 (DG RELEX);

- Prepare an international measurement comparison for the REM (Radiation Environmental Monitoring) network (JRC-IES - DG ENV) which is expected for May
2002;

- Preparation of a work plan for and execution of IAEA CRM homogeneity tests.
If these materials arrive soon, we expect the work to be finished end of 2002.

- Deliverables as a result of the research;

- In primary standardisation work, to complete the CCRI/BIPM international comparison on 238Pu (February 2002 and organise a key-comparison on 65Zn, May
2002);

- Proceed in the production of the prototype of the World Primary Standard of Radioactivity (CCRI/BIPM) - 1st prototype ready by August 2002

- Complete the work on the NIST Shellfish CRM by May 2002;

- Providing ultra low-level radioactivity measurements upon request (e.g. swipe samples for DG TREN, metal samples from Tokaimura, Japan);

- Collaboration of European Low-level underground Laboratories (CELLAR);

- Working with NMis to perform key comparisons to achieve international equivalence in radioactivity measurements;

- Certify reference materials for their radioactive components;

- Participation in the working group on the evaluation of key-comparisons at the "Bureau International des Poids et Mesures / Comité Consultatif pour les Rayons Ionisants" (BIPM/CCRI).

Summary of deliverables made by: 31/12/2001

PRIMARY STANDARDISATION

204Tl BIPM

Solving the problems of a recent key-comparison of 204Tl organised by BIPM and is also used in nuclear medicine.
New sources were prepared for the self-absorption study in order to test and confirm the reproducibility of the results. The spatial activity distribution of the sources was measured with the new high-resolution fluorescence-imaging screen. Further computer simulations using EGS4 were performed to make the experimental and simulated self-absorption study complete. The previously found discrepancy between liquid scintillation counting and 4ƒàƒÒ measurements on solid sources was attributed to self-absorption effects and can be resolved through optimisation of the source drying process. This task has been completed.

237Np measurements EUROMET

Measurements on this ~2 million years half-life radio nuclide are of paramount importance for final waste repositories and environmental protection.
Data acquisition software and hardware (list mode) was tested for ƒÑƒ{ƒ× coincidence measurements and the experimental equipment was set up.

Source Drier

To improve the preparation of solid deposits on various substrates by accelerated drying of liquid deposits aiming at homogeneous distribution and minimised crystal sizes.
The patent application was sent to the US-Patent office and the final designs started. Special material (vespel) was delivered. The patent filing receipt for THIN LAYER PREPARATION FOR RADIONUCLIDE SOURCES arrived from the U.S. Patent and Trademark Office on 22 February 2001.The NPL has ordered a copy of the instrument.

238Pu BIPM

To standardise the radioactivity concentration of a 238Pu solution (BIPM Key-Comparison).
The solution for the comparison arrived and planning for source preparation was performed with four measurement techniques selected. Two dilutions of the 238Pu mother solution were made and thin, open sources were prepared for the three different activity levels. Measurements started with three different techniques (liquid scintillation, low solid angle alpha counting and Large Pressurised Proportional Counter (LPPC)) and the fourth (CsI) is in preparation.
The liquid scintillation measurements showed a large scatter. A new batch of sources was prepared and the corresponding results show little variation. The Large Pressurised Proportional Counter (LPPC) measurements were repeated at a higher gas pressure (500kPa) and an upper limit for the correction factor for self-absorption of alpha particles in the foil was derived.
The low solid angle alpha measurements were performed with an updated version of the MKS MCA data acquisition software. For the computation of the solid angle, a new software program was written and improvements made resulting in excellent agreement of the results in two different geometries and also the variation amongst sources could be reduced.
4Ĉ-CsI(Tl) measurements were done on diluted sources. The results of all activity (Bq/g) measurements seem to agree well within a few tenths of percent. The variation among sources is higher than expected from the statistical uncertainty.

CHARACTERISATION OF REFERENCE MATERIALS

NIST Shellfish RM NIST, USA

This RM is required to test the performance of the analytical methods employed in surveying and monitoring radioactive materials in the sea.
The measurements of the actinide samples by alpha spectrometry were preformed and the data are being currently evaluated.

Milk powder and soil RMs IAEA

The IAEA will start a 3-year co-ordinated research project entitled Upgrading of Analytical Quality Control Services (AQCS) inter-comparison materials to reference materials with assigned property values traceable to the International System of Units.
The contract with IAEA was signed and the project plan was finalised. A time schedule and task distribution list was sent to the IAEA coordinator and the work will commence upon arrival of the samples.

ULTRA LOW LEVEL MEASUREMENTS

Radioprotection using passive neutron monitors IRMM

Radioprotection studies using highly sensitive passive neutron monitors at different locations at the IRMM site.
2 Ta- discs exposed to neutrons in the environment of the 150MeV linear accelerator (GELINA) were measured. Preliminary results of the Ta- discs show no extreme values for neutron flux. These values however may be very useful for benchmarking in the event of an "abnormal" operation. The complete decay scheme of Ta-182 was worked out and implemented in a MORTRAN code for modelling the experiment using the EGS4 code.

94Nb IRMM

Measurement of activation products in neutron irradiated Mo-samples in support to IRMM's neutron data measurements programme.
7 cubes were measured in HADES for the second time to establish the activity of all radio nuclides activated in the samples in the previous measurement ¡V the main constituent of interest being 94Nb. The measurements of 14 cubes (for a second time for better counting statistics) were completed and the spectra delivered. The Nb-94 activities were calculated and results were in agreement. On request to measure the remaining liquid solution from the sample, the measurements started are presently ongoing.

CELLAR (Collaboration of European Low-level underground Laboratories)
Merging European expertise in low-level measurements.
The collaboration agreement was signed by everyone (except MEL-IAEA for which a separate agreement is now being set up) on 31 August 2001.

Measurements of 60Co in metals activated by the JCO accident JCO, Japan
Ultra low-level gamma-ray spectrometry of metal pieces activated by neutrons from the JCO accident.
This task started in the first quarter of 2001. The first step to screen all the samples (spoons) to roughly ascertain sample activities (~ half a week measurement time) was completed. Data analysis and long measurements commenced in October and is presently ongoing.

Measurements of 210Pb in lung tissue of German U mine workers German Cancer Research Centre
Low-level measurements of 210Pb (daughter product of radon) in lung tissue allows to establish a correlation between incidences of lung cancer and exposure to radon gas.
This new task commenced in the third quarter of 2001. Three samples already arrived and measurements on one of the samples started.

WORK FOR INTERNATIONAL METROLOGY ORGANISATIONS

The Bq @ the basic level BIPM/CCRI

The development of the future World Primary Standard of Radioactivity.
The concept of the system has been developed. Tolerances for materials and dimensions of crucial parts were determined. Drawings of the prototype are produced and the major mechanical parts of the system are commissioned for machining.

Key-Comparison Working Group of the CIPM/CCRI (II) BIPM/CCRI

Evaluating KCRVs for the Appendix B of the CIPM MRA
At the February 2001 meeting of the BIPM, discussions on how to evaluate the more than 60 CCRI key-comparisons and determination of the KCRVs (Key-Comparison-Reference-Value) were held and rules were prepared for agreement by the CCRI. The Evaluation of SIR WG and the WG on International Equivalence were combined into one WG ¡V the Key-Comparison WG. At the CCRI (II) meeting in May 2001, the rules and tables of KCRVs were adopted. A Meeting of the WG in December 2001 will decide on the possible inclusion of the key-comparisons of the regional metrology organisations (RMOs) and on bi-lateral comparisons of the past ¡V one of them on 46Sc, organised by the IRMM.

Appendix C of the MRA (CIPM/BIPM ¡V EUROMET) Mutual Recognition Arrangement

To co-ordinate the set-up of the tables for the Appendix C of the Mutual Recognition of national measurement standards and of calibration certificates issued by national metrology institutes ¡V MRA for ionising radiation.
The Euromet Rapporteurs met in January 2001 in Vienna where mainly MRA issues were discussed. A Euromet CP meeting in February took place at SMU, Bratislava. There, new projects were launched and about 1800 CMCs were reviewed. The annual Euromet meeting at METAS was held in Bern in May. About 60 CMCs of IRMM were accepted for the MRA database at the BIPM. The final review of the RAD CMCs at IRMM in co-operation with BNM-LNHB and NMi was carried out.

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Output Indicators and Impact

A Memorandum of Understanding for the creation of VERMI - the Virtual European Radio nuclide Laboratory with IRMM as the Centre of Gravity will be signed in 2002. VERMI will become the Reference Point in the European Research Area for radionuclide metrology. In collaboration with JRC-IES and with direct support of DG ENV, a service of reference measurements and organisation of inter-comparisons for REM (Radiation Environmental Monitoring) system will be developed. BIPM/CCRI Key-comparisons on 238Pu, 65Zn will be carried out / organised. The first prototype of the World Primary Standard of Radioactivity will be operable.
Summary of the project

The present state of metrology in international trade and for European competitiveness has highlighted a great need for so called 'key comparisons' for the establishment of 'International Equivalence' of radioactivity standards. Reference materials need to be characterised and certified for their radioactive components and radioactivity measurements need to be of the highest level of accuracy. Ultra-low level radioactivity measurements are also becoming increasingly important especially in the fields of environmental safeguards, medicine and the semiconductor industry.

These criteria are fulfilled by providing:

- Support to metrology organisations in establishing 'International Equivalence' in radioactivity standards used in research, medical applications, environment and industry;

- Radioactive decay data measurements;

- Ultra-low level radioactivity measurements for the detection of traces of radioactive matter (in the underground laboratory).

Rationale

Metrological measurements of radioactivity and the characterisation of the corresponding radio-nuclides are indispensable for a reliable assessment of radioactivity in environmental samples, in contaminated food and for medical diagnosis and treatment. The importance of Radio-nuclide Metrology is even more exemplified since the signing of the Mutual Recognition Arrangement between NMIs -spectrometry facilities at IRMM have been developed and fine tuned and today this laboratory belongs to one of the leading reference laboratories globally for the certification of primary radioactivity standards. In conjunction with the underground laboratory HADES (223m below the ground level), IRMM's measurement capability in the area of radionuclide metrology is unique and needed to support EU policies with respect to nuclear issues (including IRMM on behalf of the European Commission) under the auspices of the CIPM.

Funding Scheme

JRC - Joint Research Centre research

Coordinator

Institute for Reference Materials and Measurements
Address
Retieseweg
B-2440 Geel
Belgium