NPL – 6 November 2002

 

Attendees:		Rajesh Bhanot	BNFL
		Trevor Birkett	John Caunt Scientific
		Derek Brazer	AWE
		Peter Burgess	UKAEA
		Julian Dean	NPL
		Mike Dolan	AWE
		Stephen Domone	AWE
		James Forde-Johnston	Canberra-Harwell
		Rachel Golding	AWE
		Roger Jackson	Serco Assurance
		Simon Jerome	NPL
		Steven Judge	NPL (Chairman)
		Desmond MacMahon	NPL
		Fred Martin	BNFL
		Ian Mather	RCD-Lockinge
		Carole Neale	AWE
		Trevor Nicholls	Lab Impex Systems
		Thomas Nobes	BNFL
		Bob Otlet	RCD-Lockinge
		Chris Palmer	Lab Impex Systems
		Hilary Phillips	NPL
		Max Pottinger	BNFL
		Mark Rainbird	AWE
		Dale Robinson	BNFL
		David Ryden	Canberra-Harwell
		John Simpson	RWE Nukem
		Stephanie Vallet	Canberra-Harwell
		Eliot Williams	UKAEA
		Andrea Woodman	NPL
		Mike Woods	NPL
		Simon Woods	NPL (Secretary)
Apologies:		Phil Hurst	British Energy
		David Orr	NRPB

 

1. Introduction, Previous Minutes and Actions Arising

1.1 Steven Judge introduced himself as the new AMUG Chairman and described the changes that had taken place at NPL since the last meeting.

1.2 The previous minutes were accepted as a true record.

1.3 Action 1.1: Self absorption factors. Still no consistent approach to corrections. A comparative study is required. Action 2.1: Anybody with documents/references regarding self absorption factors to supply them to Simon Woods.

1.4 Action 1.2: Questionnaires. These will be handed out during the meeting.

1.5 Action 1.3: Flow rate measurements. There is still interest in this field. Action 2.2: NPL to arrange for a speaker from NEL on flow rate measurements for the next meeting.

1.6 Action 1.4: Website. This is in the process of being upgraded.

1.7 The revised AMUG Terms of Reference were accepted.

2. Invited Talk: ³H Air Monitor Calibration

2.1 Desmond MacMahon (NPL) presented a talk on ³H air monitor calibrations. A summary of the slides is attached to these minutes. Discussion followed.

2.1.1 The low uncertainty on the calibrations was queried. Equivalence measurements show that they are justified.

2.1.2 The measurement uncertainty should increase with each dilution. The figure shown was confirmed as 1% per dilution, with no sticking problems observed.

3. Invited Talk: Discrimination Against Radon and Thoron Background

3.1 David Ryden presented an invited talk on discrimination against Radon and Thoron background.

3.1.1 David concentrated on alpha backgrounds e.g. ²³⁹Pu where the small DAC leads to measurement problems.

3.1.2 There is a need for prompt and reliable warning of radionuclides present.

3.1.3 One particular problem - radon backgrounds are often 1000x the activity you need to measure, though radon itself is not the problem; it’s the particulate daughters.

3.1.4 Techniques to compensate include alpha spectrometry, alpha-beta pseudo coincidence, decay rate analysis and separation by aerosol size. Alpha spectrometry may be combined with the other techniques, but not all of the time e.g. Curium can only be detected by decay rate analysis.

3.1.5 David described the various means available for radon compensation but noted that the spectrum shape depends on the position of the filter relative to the detector.

3.1.6 The operation and the pros and cons of commercially available systems were discussed, particularly the data update period. The consensus was that the update period is acceptable for all major systems.

3.1.7 Calculating uncertainties for thoron/radon compensation is complex - some twenty pages of mathematics. It was noted that the aim of sampling is to reduce the systematic uncertainties.

4. Measurement Good Practice Guide: Air Monitoring

4.1 Max Pottinger gave an introduction to a proposed Measurement Good Practice Guide (GPG).

4.2 The meeting split into four breakout groups to discuss the aim and contents of the GPG.

4.3 These groups presented their deliberations and an overall AMUG consensus was obtained. The recommendations are attached to these minutes.

5. Any Other Business

5.1 It was suggested that NPL should develop expertise in radon/thoron compensation techniques and their effectiveness as this will aid industry. This will be discussed at the RMG programme formulation Focus Groups next April. Action 2.3: Max Pottinger to supply Steve Judge with case for developing expertise in radon/thoron compensation.

5.2 Tom Nobes described the RADNET data communication system developed at Los Alamos. This system has developed from the need to transfer data from multiple detectors/inputs to a central server at higher rates with improved reliability. This has now been achieved and may be of value to any user who has high measurement throughput rates. Details and history may be a complex issue to those with no networking background, but a fully integrated freeware package is now available. Further details may be obtained from Tom or directly from the Los Alamos website.

5.3 Max Pottinger updated the AMUG on ISO/IEC matters:

5.3.1 There is an international standard on effluent monitoring – ISO60761.

5.3.2 Draft standards for comment will be placed on the AMUG website.

5.3.3 IEC WG on ³H monitoring is on-going.

5.3.4 IEC WG on noble gas monitoring is on-going.

5.3.5 Next year an IEC WG on monitoring of particulates in air will begin work.

5.4 David Ryden described the confusion over the use of calibration sources with different diameters. Although many instruments use 25mm diameter filter papers, a 19mm reference source has sometimes been used (for historical reasons). If a 19 mm diameter reference source is used the change in efficiency must be considered.

6. Topics for the Next Meeting

• Flow rate measurements (NEL).
• Comparison of available standards in air monitoring.
• P-factors.

Simon Woods

Secretary AMUG

Summary of Actions

Action 2.1: Anybody with documents/references regarding self absorption factors to supply them to Simon Woods.

Action 2.2: NPL to arrange for a speaker from NEL on flow rate measurements for the next meeting.

Action 2.3: Max Pottinger to supply Steven Judge with case for developing expertise in radon/thoron compensation.