29 October 1999

National Physical Laboratory

 

Attendees:	David Anstee		Harwell Instruments
	John Barton		Birkbeck College
	Roger Benzing		Imperial College
	Peter Danyluk		AWE Aldermaston
	Paul Davison		EG&G Instruments
	Piers de Lavison		NPL
	Tony Dell		VLA
	Will Evans		University Hospital of Wales
	Jim Fitzgerald		J F Computing
	Gordon Gilmore		Nuclear Training Services
	Matt Harker		AWE Aldermaston
	Jon Hartley		Somerset Scientific Services
	Trevor Hatt		EG&G Instruments
	Elizabeth Howie		British Energy, Hunterston
	M Islip		Millennium Inorganic Chemicals
	Simon Jerome		NPL
	Satwant Johal		NPL
	Steven Judge		AEA Technology QSA
	David Lambert		VLA
	John Lees		BNFL, Berkeley
	Andrea Lewis		NNC (WQCL, Winfrith)
	John Makepeace		NPL (Chairman)
	Fiona Miller		UKAEA, Dounreay
	Dagmara Modna		NPL
	Alan Nichols		AEA Technology, Harwell
	Andy Pearce		NPL
	Martin Phillips		BNFL, Berkeley
	Paul Rabaiotti		University Hospital of Wales
	Martin Rushby		AWE Aldermaston
	Bob Sharrock		URENCO
	Matthew Simpson		DERA
	Robin Treadwell		AWE Aldermaston
	Stephanie Vallet		Harwell Instruments
	Steve Waters		MRC.CU, Hammersmith
	Sandra Williams		British Energy, Hartlepool
	Simon Woods		NPL (Secretary)
	Mike Youngman		NRPB

1. Chairman’s opening remarks

The Chairman welcomed those present. He reported that NMSPU funding only covers two meetings of the GSUF. The question of a third meeting within the current NMSPU programme (1998 - 2001) would be raised at the end of the forum.

2. GSUF Terms of Reference

These had been referred to NPL’s Commercial Department, who had advised that the section referring to liability should be expanded. This had been done and an amended version sent to all members of the GSUF. No comments had been received and the meeting accepted the Terms of Reference as amended. These are attached.

3. Minutes of the 1^st meeting - 14 October 1998

These were accepted without correction.

4. Matters arising from the minutes

(Numbering refers to minutes of 14 October 1998)

3.6 Simon Woods: Confirm wording of Terms of Reference with NPL legal experts.

Completed. See 2 above.

4.1 Ian Adsley: Investigate use of AEAT decay data.

The new Radiochemical Manual (TRM) is now available on CD-ROM. AEAT are willing to commercially supply the decay data on CD, but are looking for funding. Both Harwell Instruments and EG&G commented that they would be interested if there was enough demand.

The question of formatting and automatic download from CD_ROM into gamma-ray spectrometry software packages was raised. The data belongs to AEAT and they should agree a format readable by all manufacturers.

Action 2.1: Simon Woods/Ian Adsley to discuss with interested parties to agree a suitable format.

Mistakes in/queries on the data in TRM have been passed onto the authors. It is planned to produce an addendum. Simon Woods gave a presentation summarising the comments received. Copies of the transparencies will be placed on the GSUF website.

It was suggested that daughter/parent relationships could be incorporated into data for non unity equilibrium for transfer to manufacturer’s software.

4.3 All: Inform Simon Woods of Millennium Compliance problems for dissemination to other forum members.

No comments received. Action continues.

Action 2.1: All to inform Simon Woods of any Millenium Compliance problems experienced for dissemination.

4.4 All: Inform Simon Woods of peak fitting problems for dissemination to other forum members.

No comments received.

6.5 Simon Woods: Investigate and quantify problems with calibrations sources.

Despite the concerns expressed by the GSUF, no feedback has been received from users which has been taken as indicative of low demand. Hence no further action is proposed.

6.6 Simon Woods: Devise and distribute intercomparison questionnaire.

Action stands.

Action 2.2: NPL (Simon Woods) to devise and distribute a questionnaire on user requirements for intercomparisons.

5. GSUF Subgroups

The three subgroups initiated at the previous GSUF, Low Energy Measurements, Field and Mobile Measurements and Minimum Detectable Activities, all met during 13 and 14 September. Simon Woods presented summaries of each of the subgroup meetings, the transparencies of which will be made available on the GSUF website.

5.1 Low energy measurements

Measurement problems within this area, particularly those associated with attenuation effects, were identified and discussed. It was felt that the best way to progress this topic would be via a questionnaire to identify the extent of the problems and the level of support available to address these problems.

Action 2.3: NPL (Simon Woods) to devise and distribute questionnaire to determine problems with low energy gamma-ray measurements.

5.2 Field and mobile measurements

There is no regulatory guidance on sampling and measurement procedures. It was recognised that this was not an area that the GSUF could tackle in isolation; there is a need to consult with bodies such as EA and NII. It was concluded that NPL, on behalf of the GSUF, should seek a meeting with interested parties. However, this recommendation was superseded by the matter being raised by representatives from DERA on the Inter Industry Group on Contaminated Land and Site Clearance. This group agreed that Dr Adrian Coyle, Head of Waste Management, BNFL, would contact the GSUF Chairman to clarify the relationship between GSUF interests and IIG recommendations.

Gordon Gilmore commented that models exist within the chemical field for sampling confidence; could these not be applied? It was generally felt that guidance should come from the regulators e.g. American Standards exist. The IIG is trying to standardise the regulatory bodies and are meeting monthly to attempt to progress this area. Communications (from the IIG) are awaited.

5.3 Minimum detectable activities

There is widespread confusion as to what is meant by MDA and how to calculate meaningful values. Gordon Gilmore, an established expert in this area, presented his views on how to tackle the issues in this field, defining Critical Limit, Maximum Activity and Limit of Detection (MDA). Formulisms for these quantities, based on those of Currie and adopting a 95% confidence level, may be found in the attached transparencies of the subgroup report. Usage was recommended as

1) Peak detected (above critical limit) - give result.

2) Peak not detected (below critical limit) - give maximum activity.

3) Characterisation of a system - give limit of detection.

Extensive MDA discussions may be found on Gordon Gilmore’s web site at http://www.nucleartraining.co.uk/mda.html

The level of confidence used was queried. Gordon Gilmore replied that a change of confidence level will change the numbers but not the principles behind the recommendations.

It was noted that different software packages calculate “MDA” differently, hence yielding different answers. Also, MDAs need to account for other factors such as sample matrix.

When quoting values for MDAs, they should be accompanied by a statement of the method used and the confidence level. Standardisation of the methodology is the goal so that customers with little statistical knowledge wont be confused. Members at the forum should assess the proposals, in particular the potential impact on their organisation e.g. through higher reported levels, and report.

Action 2.4: All to send any comments on the subgroup proposals to Simon Woods by the end of December.

Once substantial comments have been received, the subgroup may reconvene to discuss progression of this topic.

6. Invited talk

“Decay Data - Source Libraries” - Alan Nichols, AEA Technology, Harwell.

Described the methodology of the internationally recognised decay data files and the data contained therein. The transparencies will be made available on the GSUF website.

7. User discussions

7.1 User meetings with manufacturers

The GSUF thought it worthwhile if meetings with the main manufacturer’s could be arranged, in the same way as for the ASUF, to look at the direction of future products and, in particular, the policy and responsibility towards maintaining data libraries. The representatives of the manufacturers present, agreed that, in principle, this was a good idea, but requested that more specific and targeted details be provided to them prior to any such meeting.

Action 2.5: NPL (Simon Woods) to gauge amount of interest in proposed meetings, which manufacturers to target and identify topics for discussion.

7.2 ²²⁶Ra

Simon Woods noted that the evaluated value of the 186 keV gamma-ray transition following the decay of ²²⁶Ra is 0.0328(3), based on a level scheme balance. However, experimental values range from 0.032 to 0.039 (ENSDF 0.0359(6)) with a user preferred value circa 0.0354. Considering the importance of this nuclide in some measurements, this 9% discrepancy should be resolved.

Action 2.6: All to submit any data they may have on this transition to Simon Woods.

8. Concluding discussions

8.1 Future meetings

As noted by the Chairman at the start of the meeting, NMSPU only provide funding for two meetings within a three year period. Users present felt that annual meetings would be preferable.

Action 2.7: NPL (John Makepeace) to investigate the possible funding of a third meeting of the GSUF within the current NMSPU Ionising Radiation programme.

 

8.2 Communications

Those present were reminded that Simon Woods has electronic distribution lists covering members of the GSUF (and ASUF). If users had any information they wished to be disseminated or any topics that they wished to be aired, they should mail the information to Simon Woods (simon.woods@npl.co.uk) who will forward it to GSUF members on the e-mail listings.

Simon Woods

Secretary GSUF