Wednesday 15 November 2000
National Physical Laboratory

Present:

Chairman: Dr M R Sené, National Physical Laboratory
Secretary: Dr V E Lewis, National Physical Laboratory

There were 39 other members present from 25 establishments including:

AEA Technology (Harwell)		AEA Technology (Winfrith)
AEA Technology QSA (Harwell)		BAE Systems (Barrow-in-Furness)
BNFL Berkeley		BNFL Sellafield
Bristol General Hospital		Centronic, Croydon
DERA Rad. Prot. Service (Alverstoke)		DRaStaC (Aldermaston)
Guys & St Thomas Hospital Trust		Johnson Controls (Dounreay)
Kingston University		Leeds General Infirmary
Mainance International		Mini-Instruments
National Physical Laboratory		National Rad. Prot. Board (Chilton)
Northern Ireland Rad. Prot. Service (Belfast)		NE Technology
Nycomed-Amersham		RRPPS, Edgbaston
Sherwood-Nutec Consultancy		UKAS (Feltham)
Velindre Hospital, Cardiff

Six more members, including some from a further three establishments, had sent apologies.

MAIN AGENDA ITEMS

Comparison of calibrations of surface contamination monitoring

Clare Scott (NPL) reported that the participants’ measurements had started at the beginning of April and the last of the fourteen participants had nearly completed their measurements. Eight sets of results had been sent in so far and a limited analysis had been carried out.

Three instruments (DP6, LB122, EP15) were being circulated around the laboratories. Participants were encouraged to use as many reference sources as they had available. However, only data for ¹⁴C, ³³⁶Cl, ⁹⁰Sr, ²⁴¹Am were presented. The results to date, shown as percentage deviations from the means, were shown for each instrument/nuclide combination. The results of one participant had to be corrected on account of an obvious error.

There were five laboratories on the reserve list. In view of the length of time between this comparison and the previous exercise, and the value of having significantly more results for comparison, there was a general feeling that it would be sensible to include everything in one report. Any delay could be minimised by starting the initial analysis before all results had been submitted. It was very important that the reasons for problem data were found and published in the report so that lessons could be learned. The results from the first fourteen participants would be submitted to NPL by mid-December. This would provide sufficient material to indicate problems that had arisen and enable the analysis to begin. A meeting would be held to discuss the results in early January. In the meantime, the “reserves” would be contacted and the timetable for the next phase of measurements arranged.

Comparison of calibrations of gamma-ray dose-rate monitors

Vic Lewis (NPL) discussed the situation of the comparisons of calibrations of portable gamma-ray dose-rate monitors. The third exercise in the series had involved the circulation of four monitors around nineteen establishments. The overall accuracy had been satisfactory and calibrating facilities could meet the requirements of NPL Good Practice Guide 14. The consistency of the ²⁴¹Am results was not as good as would be expected from the estimated uncertainties. The treatment of uncertainties was inconsistent. The previous IRMF meeting had considered that a 3-year cycle was appropriate for comparisons.

The form that the next exercise should take was discussed. There were requests for getting involved more in operational dosimetry in realistic fields, for the use of different instrumentation from previous exercises and for the inclusion of personal dosemeters (passive and electronic). It was said that the analysis of comparisons based on passive personal dosemeters was extremely difficult, lengthy and inconclusive. An EPD had been successfully used in the second comparison and there would be no problem in getting one for the next exercise if required. The use of phantoms and having a measurement of H_p(10) was discussed.

The general feeling was that the next exercise needed to break new ground, although some elements of previous exercises could be repeated. There was also concern that the next exercise should not attempt to cover too much. There might be a need for running a separate exercise involving personal dosemeters only, say.

A working group would be set up to consider these matters and produce proposals for the next IRMF meeting in May 2001, with a view to starting measurements in August 2001.

Comparison of calibrations of neutron area survey monitors

Vic Lewis (NPL) described the two IRMF comparisons of calibrations of neutron area survey monitors. Both exercises had involved five participants, and were based on calibrations of two monitors in fields produced by ²⁴¹Am-Be and ²⁵²Cf sources. The report of the second exercise had concluded that the overall agreement and accuracy had been very satisfactory and had demonstrated that the calibrating facilities could meet the requirements of GPG 14. The treatment of uncertainties had been consistent.

The nature, aims and justification of a third comparison were discussed. The case for a three-year cycle for comparisons in this area, where the numbers were small, and the agreement and accuracies were so good, was questioned. It was also thought desirable to use different instrumentation and neutron fields from that used in the first two exercises. However, those that had been used were the ones most commonly calibrated by the participants for their customers. Also, the number of different models of neutron dosemeter was very limited. Their use in regular comparisons gave reassurance and was also valuable for UKAS accreditation purposes. A three-year cycle was adequate but a four-year gap was getting too much.

It was hoped that the next comparison would also link up under a Euromet project with similar, national exercises being held in France and other European countries. Accelerator-produced neutron fields could also be included in the next exercise. The situation regarding personal dosimetry for neutron radiation was briefly discussed. A working group would be set up to consider these matters and produce proposals for the next IRMF meeting in May 2001 with a view to starting measurements in August 2001.

Good Practice Guide on Practical Radiation Monitoring (GPG30)

Alan Edwards (DraStaC, Aldermaston) reported that the guide was written in a straight-forward manner suitable for non-experts. The guide dealt with portable monitors used for alpha-, beta-, and gamma-surface contamination monitoring and beta, gamma and neutron dose rate monitoring. The title had not been finalised.

There would be six sections on -

• definition of the problem - assessing the aim of the monitoring;
• information gathering - available records, history of facility, etc,
• selecting instruments;
• monitoring strategies - training for surveyors, plan of work;
• monitoring techniques - how to get readings and what to record;
• interpretation - expressing data as meaningful radiation quantities.

It was intended to give examples of the assessment of problems.

After the next meeting of the working group in December, the document would go to a technical author provided by NPL who would translate it into a user-friendly format. It was hoped that this guide and GPG29 described below would be ready for the annual meeting of the SRP in April 2001 which was going to look at radiation monitoring.

Good Practice Guide on The Testing and Calibration of Installed Radiological Protection Instrumentation (GPG29)

Max Pottinger (BNFL, Berkeley) reported on the progress made by the working group. The guide covered installed gamma monitors and contamination monitors (including frisking, hand & foot, clothing and exit monitors). The GPG included appendices on setting up alarms on contamination monitors, workplace testing of gamma monitors (concentrating on jig design), directional dependence of gamma monitors and test radionuclides for different workplaces.

A formal draft had been circulated to all parties thought to have an interest inviting comments. It was planned to review the comments by the end of January and perhaps have a further meeting of the working group, with a view to publishing by March 2001.

Good Practice Guide on The Testing, Calibration and Use of Equipment for Radiometric Non-Destructive Assay

 

This GPG had been initiated at the request of the Nuclear Installations Inspectorate who funded the setting up of a working group that was chaired by Paul McClelland (UKAEA, Dounreay) with Vic Lewis (NPL) as secretary. The working group had representation from manufacturers of NDA equipment, users of such equipment at licensed sites and regulatory bodies. The secretariat was provided by NPL and supported by establishments across the nuclear industry as well as HSE. The GPG aimed to produce guidance and quality assurance for radiometric NDA equipment used in the nuclear fuel cycle, in particular that used for the detection of fissile material. This would cover equipment and techniques used for criticality control, safeguards, accountancy and waste assay. These ranged from gamma spectroscopy to active interrogation, and included piece monitors, drum monitors and crate monitors.

Future Good Practice Guides

Max Pottinger (BNFL, Berkeley) listed the equipment that was not covered by GPG14 and GPG29. This included electronic dosemeters, air samplers, air monitors (including stack monitors) and laboratory counting equipment associated with air monitoring results. The tests that needed to be covered in guidance on air sampling were listed. Guidance on counting systems would cover checks on a/b response, background, gas flow, plateau, high activity source and low energy betas.

An addendum to GPG14 covering electronic dosemeters had been suggested originally but the matter had been left unresolved. There was a discussion ensued on what was appropriate for routine checks, the need for overload tests, the form of energy tests and whether H_p(10) or H*(10) should be used. There was some disagreement over whether requirements would vary if it were a legal dosemeter. Other issues included the need for a periodic linearity test, the angle to be used for an angular response test, the use of a phantom and whether an H_p(0.07) test should be carried out as a first or a periodic test. The discussions highlighted the fact that there was only limited national guidance on the calibration of passive dosemeters. This information may need to be reviewed against any future testing requirements for an electronic dosemeter.

Martyn Sené said the production of two GPGs would be in the next NMS Programme. A demand for a GPG on air monitoring was expected from the Air Monitoring Users Forum. At the next IRMF meeting members should be prepared to decide on what other guide would be needed. Any member with a strong suggestion should let the Secretary know beforehand.

Working Party on Uncertainties in Radiological Measurements

Vic Lewis (NPL) reported that examples of uncertainty budgets had been produced for surface contamination, source calibration, neutron calibration and X-ray and gamma-ray dosimetry by the Working Party. Detailed explanations of derivations of the components had been drafted for each example. There was probably enough material in the contributions, but some needed to be finalised. All needed to be put into a uniform format and reviewed.

The work had originally been conceived as a replacement to the UKAS document NIS 0825 (which had been withdrawn by UKAS about five years previously), supplementing NIS 3003 (now M 3003). Alternatively, it might now be more appropriate to produce it as an NPL GPG, thus expediting its publication. Used in conjunction with M 3003, a GPG would be acceptable to UKAS for the purpose of accreditation.

NMS Programme for Ionising Radiation Metrology

Martyn Sené (NPL) gave an update on the present NMS Programme for Ionising Radiation Metrology, funded by DTI. A course in reference dosimetry (mainly for radiotherapy) was planned for 4, 5 June 2001 and a workshop on uncertainties in radiochemical analysis for sometime in the first half of 2001. In response to demands from the user community, DTI had approved the setting up of the Air Monitoring Users Forum and the Liquid Scintillation Users Forum, both of which would hold their first meetings before October 2001. A calibration service for tritium-in-air and tritiated water vapour had just been launched.

Formulation of the next programme, starting in October 2001, was underway. NPL staff were producing a draft programme document that was based on input from five focus group meetings held for different technical areas, the user community, NPL staff and the MAC Working Group that advised DTI. The draft programme would be produced and put on the DTI website early in 2001 for consultation. A final programme document, taking into account all comments, would be submitted to DTI in May 2001 and the content would be decided.

There were three technical themes covering Dosimetry, Radioactivity and Neutrons. There was general support for all existing standards held at NPL and elsewhere (at AWE) and support for all existing calibration services. The significant changes in legislation in recent years would affect the programme. The increase in remediation, decommissioning and environmental monitoring had led to demands for more realistic reference materials. There was increased emphasis on demonstrating the equivalence of national standards. Other issues of increasing importance included realistic neutron fields, cosmic ray dosimetry and neutron spectrometry. There was a plan to replace the NPL linac (used for industrial dosimetry as well as for radiotherapy). It was possible that the SAMES accelerator facility would close and 14 MeV neutron standards would be provided using the ASP facility.

A fourth theme, Technology Transfer, ensured that the benefits are disseminated to the user community through promotional activities, user groups, the organisation of comparisons, the provision of workshops and training courses, the production of guidance documents and by work on national and international committees. As a result of the increased demand from the user community for advice, training and fora such as the IRMF, there would be more funding for this theme. As well as the need for new clubs, there were requests for existing ones to have annual meetings. The DTI would be asked to fund NPL staff to advise on and shadow measurements being made at users facilities. Training provided by NPL staff would be integrated into courses run by medical physics departments and universities.

Private Finance Initiative at the National Physical Laboratory

Martyn Sené (NPL) reported on the re-building of NPL. Most of the facilities of the Centre for Ionising Radiation Metrology, and their associated services, would “decant” into Module 6 of the new building in March 2001. This would contain the radioactivity work and services, the X-ray facilities for therapy, diagnostic, mammographic and protection-level air kerma calibrations and the industrial-level dosimetry facility. Stocks of materials were being built up to minimise disruption of the radioactivity standards services. The therapy and protection-level calibration services would run as close to the scheduled times as possible.

The new ⁶⁰Co facility was occupied in July 2000. The ⁶⁰Co protection-level calibration period was just starting. The therapy-level facility service would start in December. The existing Linac Building was not being replaced. The neutron accelerator facilities would stay put, but the manganese bath facility would be moving into the neutron building.

Faraday partnership

Duncan McClure (NRPB, Chilton) said that NRPB were involved with industry, end-users and some research establishments in an application for a Faraday partnership. This was a means of obtaining government funding for research aimed at producing a specific end-product that end-users want. The application was targeted at new and novel radiation monitoring instrumentation for decommissioning and remediation type of work. If the application were successful, the work would start in about a year. The programme could last three years or so and could be worth £2 - 3 million. Anyone interested in becoming involved in any capacity should contact him.

IRMF Catalogue of Calibration and Testing Facilities

The Secretary reported that no amendments had been received although some entries needed updating; he would get in touch with all the facilities represented shortly. Over the past ten months there had been over 400 hits on the introduction and index pages of the version maintained on the IRMF Website. Individual page entries had averaged about thirty hits each. Members were asked to report any changes to enable the Catalogue to be kept up-to-date.

Next Meeting

The next meeting will take place on Wednesday 2 May 2001.

Vic Lewis
Secretary, IRMF
Centre for Ionising Radiation Metrology
National Physical Laboratory
Teddington
Middx TW11 0LW

The above report is a summary of the minutes of the meeting. The minutes have been sent to all members attending the meeting and to those who had previously expressed an interest in the activities of the IRMF.

Anyone with an interest in the metrology of ionising radiation who wishes to attend or learn more about IRMF meetings and activities should contact the Secretary at the above address.

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