Combined Alpha (5^th) and Gamma-ray (7^th) Spectrometry User’s Forum

Module 16 Lecture Theatre, NPL – 26 May 2005

Participants:		Simon Jerome	NPL (Chair)
		Arzu Arinc	NPL (Secretary)
		Ian Adsley	RWE NUKEM
		Roksareh Alavi	IAEA fellow
		Luc De Baerdemaeker	Canberra Harwell Ltd
		Nasser Baghini	Imperial College Reactor Centre
		Eleanor Bakhshandeiar	NPL
		Roger Benzing	Harwell Scientifics
		Keith Bradshaw	NNC Ltd
		Richard Brown	NPL
		Dominique Calmet	CEA
		Paula Chadwick	Durham University
		Sean Collins	NPL
		John Crookes	Nottingham Trent University
		Matthew Curtis	VLA
		Ashley Davies	AWE
		Tony Dell	VLA
		Julie Eccles	UKAS
		Jost Eikenberg	Paul Scherrer Institute
		Chris Gilligan	NPL
		Gavin MacGregor	VLA
		George Ham	HPA
		Arvic Harms	NPL
		Ed Holden	Ametek
		Steven Hutchins	AWE
		Kym Jarvis	Kingston University
		Gareth Johnson	AWE
		Pamela Jones	URENCO (Capenhurst) Ltd
		Steven Judge	NPL
		Sami Kafala	Imperial College Reactor Centre
		Richard Lukey	VLA
		Craig Maddigan	Ametek
		Maria Marouli	NPL Research Student
		Kareena McCrindle	Bil Solutions
		Ian McGregor	Rolls Royce
		Desmond MacMahon	NPL
		John McNamara	British Energy
		Susan Parry	Imperial College at Silwood Park
		Andy Pearce	NPL
		Lorna Proctor	RWE NUKEM
		Ben Sanderson	Bil Solutions
		Sarah Sheperd	URENCO (Capenhurst) Ltd
		John Simpson	RWE NUKEM
		Mathew Simpson	DSTL
		Erika Sjolund	British Nuclear Group
		Paul Smedley	CEFAS
		Ben Taylor	CEFAS
		Maggie Tunnicliff	NPL
		Karen Verrall	British Nuclear Group
		Jon Wardle	AWE
		Claire Watt	AWE
		David Watt	Canberra Harwell Ltd
		David Welham	HPA
		David Whithorn	AWE
		Mike Youngman	HPA
Apologies:		Nichola Chapman	Imperial College Reactor Centre
		Chris Dale	NNC
		Tony Dix	British Nuclear Group
		Andrew Frith	IRAS Limited
		Nick Harmon	RWE NUKEM
		Elizabeth Jones	University Hospital of Wales
		Piers de Lavsion	NPL
		Calum Powrie	Bil Solutions
		Tony Ware	Consultant
		Shiela Webb	Canberra Harwell Ltd

1. Chairman’s Welcome, Previous Minutes and Actions Arising

• Simon Jerome introduced himself and welcomed members to the third meeting.
• The minutes of the second meeting were accepted as a true record.
• Actions:

A6.1: Keynote speakers with, for example, talks about applications of nuclear spectroscopy in space. This meeting.

A6.2: Better balance between gamma/alpha/mass spectrometry. This meeting.

A6.3: More notice of meetings. The time scale seemed to be convenient for this meeting.

A11.1: Ian Adsley had sent Alan Nichols’ paper 'Decay of Th-234 and Daughter Pa-234m in Secular Equilibrium' to Steven Judge.
Action A1.1: Piers de Lavison to put paper onto the NSUF website.

• Simon Jerome described briefly the new organisational structure at NPL.
• Simon introduced Maggie Tunnicliff (radioactivity@npl.co.uk) as the first point of contact at NPL for any enquiries.

2. Invited talk: ‘Alpha spectrometry systems – A users perspective’ – George Ham, HPA

• George Ham began his talk by explaining the basics of radiochemistry.
• He outlined the aim of his talk: how to cope with real samples (low spectral quality) and the limitations of current analysis software.
• George gave a list of the necessary/ideal requirements for the system, the software and the data security.
• It was mentioned that one has to be careful as changing an input parameter in the software does not necessarily change the result of the analysis.
• Peak fitting and deconvolution is necessary when spectral interferences are present, but some difficulties have been found when using commercial software in this mode. Examples were given with Americium and Thorium spectra.
• George commented on the difficulty of defining the size of a region of interest for determining the activity of a contaminant and its impact on the calculation of the limit of detection.
• George concluded by saying that the commercial hardware and software were good, but not good enough to work with unsupervised.
• Following the talk, a comment was made that some commercial software was being released without being fully tested (this applied to gamma-spectrometry packages as well).
• The Canberra representative replied saying that there was a balance, that they tried to do the software tests and QA checks as well as possible and in compliance with relevant standards, but more time spend on QA implies more expensive software and long delays for updates.
• The method of validation and quality assurance of software was discussed. The general feedback was that the customer shouldn’t be the one that finds mistakes in the software.
• Steven Judge proposed to feedback what happens in the pharmaceutical area for validation of analytical instruments by putting a link on the website to the guidance for industry paper Q2B Validation of Analytical Procedures: Methodology. Action A2.1: Piers de Lavison to put link on the NSUF website.
  Of similar interest is the UKAS document LAB27 - Accreditation for Chemical Laboratories
• Desmond MacMahon pointed out that specialist laboratories in the area of alpha-spectrometry deconvolution (IRMM in Belgium and CIEMAT in Spain) will be at the ICRM conference held at Oxford in September.

3. Invited talk: ‘MIXMETER: a multiphase flow meter for subsea monitoring of oil wells’ – Susan Parry, Imperial College

• Susan started her talk by describing the benefits of the mixmeter device for monitoring the oil flow from subsea oil wells. The MIXMETER is cost effective, it reduces the weight of offshore structures by limiting the number of heavy devices and improves the management of oil reservoirs.
• Susan explained the difficulties encountered: an inhomogeneous system of water, gas and oil; the thick walls of the stainless steel pipes; the temperatures involved.
• The MIXMETER is a joint project in between various organisations and sponsors. The goals at the start in 1990 were to homogenise the flow, to evaluate the phase content with gamma rays and to measure the velocity of the flow.
• Susan explained the basics of the gamma ray attenuation metering and the need for two different gamma energies to determine the content of a system with three phases (oil, gas and water).
• The concept of the MIXMETER was described: the oil, water and gas passes through a mixing device which homogenises the liquid and then two sources (²⁴¹Am and ¹³⁷Cs) are used in cross correlation to determine the velocity of the flow by looking at the changes in the gas content.
• To improve the sensitivity of the system to the water and gas content, a thin window source was used for ¹³⁷Cs enabling the 33 keV X-ray to be measured as well as the 661 keV.
• The MIXMETER was tested at National Engineering Laboratory and was in very good agreements for the total liquid and oil fractions. The cross correlation was not successful due to the limitation on the measurement time. The new method was to use the pressure drop across the mixer, which was correlated with the velocity of the liquid. This worked very well.
• Susan mentioned that some further tests were carried out on land in Trecate and Humble.
• MIXMETER has patents in a large numbers of countries, including Brazil and Norway.
• Following the talk, a question was raised about the use of higher energy sources. Susan replied that this had not been tried.
• A comment was made about the fact that the device uses the photoelectric adsorption only.

4. Invited talk: ‘Revision of ISO Standard 10703 on the determination of the activity concentration of radionuclides by high resolution γ-ray spectrometry’ – Dominique Calmet, CEA, France

• Dominique Calmet began his talk with a brief presentation on the technical committee 147 on drinking water. The scope and the organisation of the ISO/TC 147 were described.
• Dominique then explained the various stages of the development of ISO standards from the proposal of the standard to the publication and re-revision of the international standard.
• A list of the Radioactivity Measurements Standard produced by TC 147 was displayed. The list included ISO 5667-3, ISO 9696, ISO 9697, ISO 9698 and ISO 10703.
• Dominique described ISO 10703, the aim of the standard, the procedures that it included and, as an example, showed the procedure for water samples with pH<2.
• Dominique explained how the systematic reviews of ISO 10703 and ISO 9696 were carried out. Only slight modifications to the original documents were required in both cases.
• Dominique highlighted that the publication of a new standard ISO 11929-7 on detection limits and decision threshold was affecting ISO 10703 as all the standards need to be coherent.
• Dominique concluded his talk by showing the EC Directive on Drinking Water Quality and stressed that the ISO 10703 standard should be used for water measurements.
• Dominique encouraged the audience to take part in the drafting of ISO standards.
• A question was raised about the existence of an accepted gross alpha measurement technique. Dominique replied that a draft was produced and that it would be sent for evaluation to different member countries. If accepted it will become a standard.
• A question was asked about the recommended levels of Ra-228 or Ra-226 omitted from the EC Directive on Drinking Water. Dominique answered that he agreed and couldn’t explain why the recommendations focused on levels of Po-210 and Pb-210.
• A comment was made about the fact that different methods were used to monitor gross alpha and gross beta content and that one needs to take account of the local knowledge.

5. Invited talk: ’Latest Results from the High Energy Stereoscopic System (HESS) γ-ray telescopes’ – Paula Chadwick, Durham University

• Paula began her talk by explaining the basics of the imaging atmospheric Cerenkov technique. For energies of 20 GeV and above, the Cerenkov light produced by the interaction of the γ-ray in the upper atmosphere is detected by a large 10-metre mirror.
• Paula explained that the background in γ-ray astronomy was high due to creation of Cerenkov light by the cosmic rays as well. But fortunately it is possible to distinguish them: the Cerenkov light produced by cosmic rays is isotropic and has a different spatial distribution to the light distribution produced by γ-rays.
• Paula pointed out that the ability to find astronomical sources with ground-based techniques is much better than with space-based techniques. Paula added that the HESS telescopes were directional instruments with an accuracy better than 0.1°.
• The important features of the technique were stated: effective area of telescopes, energy threshold of instrument, no measurements possible during full moon and cloudy weather.
• Then Paula described the characteristics of the HESS telescopes and displayed the list of the partners involved in the project.
• Paula highlighted the improvement in sensitivity of the HESS by a factor of 10 to 100 compared to previous telescopes and displayed pictures of pulsars taken by the HESS.
• Paula explained the problems and mysteries encountered by astronomers in trying to interpret the cosmic ray spectrum. (The main issue was to prove that protons could be accelerated in Super Nova Remnants).
• Paula showed some results of measurements:
  1. System with a pulsar in orbit around a star
  2. Source of γ-rays from the Galactic Centre
  3. Emission from Active Galactic Nuclei
• Paula finished her talk with the plans for the future HESS. The plans are to build a single 28 m diameter telescope with a lower detection threshold.
• Following the talk, a question was raised about what was the most distant object that could be observed. Paula replied that one couldn’t see to enormous distance with this technique due to pair creation in the background.
• A question was asked about the kind of PMT used. Paula replied that they were standard PMTs as the Cerenkov light after going through the atmosphere had a wavelength of 400nm.

6. Invited talk: ‘Elements and Isotopes: has ICP-MS delivered all it promised?’ – Kym Jarvis, Kingston University

• Kym gave an outline of her talk. She would start at the beginning of the ICP-MS technique, would follow its evolution and would finish with what the technique can offer now.
•  Kym described the requirements expected at the start of the project in 1971 for the new mass spectrometer.
• The landmarks in the development were (in 1974) the use of DC plasma to ionise the elements, which was then replaced by the Inductively Coupled Plasma. That led to the first commercial instrument in 1983.
• Kym displayed pictures of various instruments created (Vertical ICP, ‘Angel Plasma’, Prototype ICP-MS…)
• Kym explained how the ICP-MS worked, showed pictures of the components of the instrument and gave the features of the ICP-MS.
• Kym pointed out that the precision on isotope ratio measurement was much better than the precision on a single isotope. Two issues affecting the precision were discussed: matrix effect on isotope ratio and deposition of material inside the sampling cone.
• The development of multi-collector ICP-MS gave the ability to make extremely precise measurements.
• Kym concluded that ICP-MS delivered more than it promised at the start and that the development of the multi-collector system had opened a window on many new applications.
• Following the talk, a question was raised about the possibility of summing of elements as observed in γ-spectrometry. Kym replied that the Oxygen, Argon, Nitrogen and Hydrogen contained in the plasma chamber were combined with the element of interest and with each other and also appearing in the spectrum. Kym added that for heavier elements (above Sn) the analysis is almost interference free.
• A question was asked as to whether the multi-collector ICP-MS could replace the thermal ionisation mass spectrometer (TIMS) as the instrument of choice in the applications discussed. Kym answered that the multi-collector ICP-MS was not yet used at the limit of its capability. She added that she couldn’t tell if it would replace TIMS, but that it had a very good chance of taking lot of the work from TIMS.
• A comment was made about the presence of a detection limit for the element Fluorine in some of the tables. Kym replied that this was certainly showing the over-optimism of the manufacturer at the beginning, she continued by saying that it was not possible to ionise Fluorine and Helium due to their high ionisation potential in comparison to Argon.
• A question was asked about the possibility of ICP-MS achieving the same levels of sensitivity as TIMS. Kym mentioned that there was one type of ICP-MS, which is a magnetic sector instrument with a single collector that was very sensitive. Measurements of Pu and Am in soils have shown the very high sensitivity of this equipment.

7. Invited talk: ‘Chemical separation and source preparation for α-spectrometry’ – Jost Eikenberg, PSI, Switzerland

• Jost started his talk by introducing the Paul Scherrer Institute (PSI) and the activities of the radioanalytical laboratory. He continued by explaining the basics of α-spectrometry.
• Jost displayed a list of the most common chemical separation methods and explained in more detail the chromatographic method: theory, property of extraction resins, definition of capacity factor, list of the important organic extractants and some examples.
• The procedures used at PSI were given for three cases:
  1. Analysis of actinides in waste water
  2. U and Th in geological material
  3. Pu and Am in environmental samples
• Jost described the various methods for preparation of planar counting sources and detailed the electro-deposition and spontaneous deposition methods.
• Jost pointed out that the detection limit was lower with α-spectrometry than with γ-spectrometry or Rn-emanation technique.
• Jost concluded that extraction chromatographic procedures were useful for separation of pure α- and β-particle emitting nuclides and that electro-deposition was giving excellent α-peak resolution.
• Following the talk, Jost was asked if he had done any work on  micro-precipitation. He replied that he never tried it, but thought that the spectra quality and resolution were not as good as electro-deposition.
• A comment was made about electro–deposition method giving better resolution and being more consistent than micro-precipitation method.
• A question was asked about what was happening to the Uranium present in the water when deposition of Ra onto MnO₂ coated plastic disc. Jost replied that the Uranium should not get adsorbed onto the disc. He was asked if any test had been carried out to check the adsorption. Jost answered that although the Uranium content in the water they analyse is 10 times higher than the Ra content, they’ve never observed a Uranium peak.

8. Manufacture presentations: α-spectrometry analysis software

8.1 Luc De Baerdemaeker (Canberra)

• Luc introduced the next generation of α-spectrometry software: Apex-Alpha. Luc commented that Apex-Alpha is based on Genie-2000 software, but is highly focused on data-management.
• Luc explained the key features of the software: centralised management, ease of access to the data, professional database and tools, compatibility with Genie hardware and software, automatic calibrations, interactive data review, quality assurance automation, security and event log.
• The possibility of associating the γ and α report from the same source with Apex was pointed out.
• Luc mentioned that up to 100 chambers could be controlled from a single CPU.
• Luc finished his talk by displaying a couple of screenshots from Apex-Alpha.
• Following the talk, a question was raised concerning the method of validation of the QA, as it was theoretical only or if it had a practical validation as well. Luc replied that the first stage of validation was regarding the software consistency and internal programming mistakes. The second stage comes when the programming is finished, and is linked with the robustness of the software. Luc pointed out that at the moment, the software was being tested as in a real situation with 48 ‘input machines’ running.
• A question was asked about the possibility of using some old Genie 2000 files with Apex-Alpha. Luc confirmed that one could use old files: certificate, calibration and library files.

8.2 Craig Maddigan (Ametek)

• Craig introduced the new AlphaVision-5.3 software from Ametek.
• The software is compatible with Windows 2000 and Windows XP Professional.
• Craig described the major advantages of the new software: ease of calibration, flexibility of QA/QC, ease of batching and customisable reporting.
• He explained the flexibilities of the software: compatibility with Ortec equipment and with Canberra 5701 as well, count period can be set up by time, MDA or ROI, add more time without recounting, interim analysis is possible. Craig gave a list of the most useful options available.
• Craig ended his talk by pointing out the quality of the support available at Ametek and the ease of speaking to technical experts. Craig reminded the audience of the existence of training courses for AlphaVision or Alpha Spec.

9. Any Other Business

• Arvic Harms presented briefly the next NPL Environmental Comparison Exercise. Arvic gave the provisional timetable, described the different types of samples available and commented on the changes in the organisation of the exercise.
• Desmond MacMahon presented a brief talk on nuclear decay data. The Decay Data Evaluation Project (DDEP) is the source that is recommended to use by NPL. For radioisotopes not yet present in the DDEP, it is recommended to use the Evaluated Structure Nuclear Data File (ENSDF).
• Keith Bradshaw enquired about the publication of the updated TecDoc 619. Desmond replied that the report was practically complete and that the publication was eminent.

Forthcoming events

• Julian Dean announced that NPL was holding a Workshop on Metrology Decommissioning and Site Clearance on the 30^th of June 2005.
• Simon Jerome announced that the next International Conference on Radionuclide Metrology (ICRM) would be held at Oxford University from the 5^th to the 9^th of September 2005.

10. Date of the Next Meeting

Provisionally Tuesday 23^rd of May 2006.

Arzu Arinc,

Secretary, NSUF