Wednesday 19^th November 2003
National Physical Laboratory

Present:

Chairman:		Martyn Sené		National Physical Laboratory
Secretary:		Clare Lee		National Physical Laboratory
		Nick Ardern		AWE
		Jen Barnes		Thermo Electron Corp, Beenham
		Graham Bass		National Physical Laboratory
		John Bennett		DERA RPS
		Reg Bosley		RWE NUKEM, Harwell
		Peter Burgess		UKAEA
		Wes Case		Amersham
		Robin Crosse		Thermo Electron
		Bill Croydon		Siemens Environmental Systems
		Lorrain Currivan		Radiological Protection Institute of Ireland
		Ian Dalton		BAE Systems Ltd
		Paul Deacon-Smith		St Thomas’s Hospital
		Geoff Druce		AWE, Aldermaston
		David Gallacher		St Thomas’s Hospital
		Andy Galpin		RWE Nukem
		Paola Hayes		HMS Sultan
		Steven Judge		National Physical Laboratory
		Vic Lewis		National Physical Laboratory
		Shaun Marriott		BAE Systems Ltd
		Bob Mason		Sherwood Nutec Consultancy
		Martin Palmer		National Physical Laboratory
		Mike Renouf		BNFL
		Tony Richards		Consultant, Leeds
		Keith Simmons		MDMSIPT
		John Simpson		RWE NUKEM, Winfrith
		Wyn Thomas		RPS, Velindre
		Eddie Veater		UKAS
		Jon Wardle		DRMS, AWE
		Nigel Watkins		National Physical Laboratory
		Andy Weeks		BNFL Instruments
		Tudor Williams		National Physical Laboratory
		Hayley Wilton		BNFL Instruments
		Mike Woods		IRMC

 

26.1  Welcome, announcements and apologies

On behalf of NPL, the Chairman welcomed members to the Twenty Sixth Meeting of IRMF.

The Chairman announced the tragic death of Simon Woods of NPL who had been known by many at the meeting and would be sadly missed.

Apologies had been received from –

Graham Beard		Mainance International Ltd
Denise Delahunty		RRPPS, Birmingham
Tim Dollery		Mainance International Ltd
Sharon Ely		NRPB
Norman Heffernan		RPS, Velindre Hospital
Don Mackenzie		Johnson Controls Ltd
Andy Main		Johnson Controls Ltd
Ray McConnell		BNFL
Sharan Packer		HSE
Max Pottinger		BNFL Instruments
Joanne Shaw		NRPB, Leeds
Graeme Taylor		National Physical Laboratory
David Walker		European Commission
Eliot Williams		UKAEA

 

26.2  Approval of Minutes of Twenty Fifth Meeting, 21 May 2003

Mike Renouf (BNFL) drew attention to two typographical errors in section 25.5 of the minutes. In each case ‘contiguous proportions’ should read ‘contiguous portions’.  The Secretary agreed to amend the meeting report featured on the IRMF website, full replacement minutes would not be distributed.  The Chairman approved the remainder of the minutes after it was agreed that they were an accurate record of the meeting.

26.3  Matters arising

Peter Burgess (UKAEA) reported that he’d received some information from Johnson Controls on the effect of cable length on the response of monitors. Johnson Controls had performed some work varying the cable length and had found that the response was affected by cable type rather than cable length. Jan McClure (NRPB) reported that they had varied the cable length of an EP15 from 6 m to 20 m and had observed no change in response. It was agreed that the Secretary should invite Don Mackenzie of Johnson Controls to present his findings at the next meeting.

The Chairman apologised to the members on behalf of himself and the Secretary for not having updated the IRMF catalogue of facilities.  Help from Martyn Sené’s PA had been secured so an update was expected soon.

26.4  Potential Comparison Exercise for X-Ray Qualities

Tony Richards (Leeds) reported he had approached IPEM about taking part in a comparison of X‑ray qualities, the IPEM were now discussing this. He asked the meeting to consider whether an exercise was really needed considering the effort involved in organising such an exercise. There was a long discussion of the series of qualities that could be included and the possibility of overlapping with UK hospitals. Jon Wardle (DRMS) reported that the HSE were organising a draft proficiency test for X-ray qualities so it would be useful for the IRMF to run a comparison exercise first. It was agreed by the meeting that such a comparison would be organised. Tony would approach the IPEM to determine the extent of their interest in participating and ascertain the appropriate contact person.  If the IPEM were not interested at the time of the next meeting, the IRMF would continue with the exercise anyway.

26.5  Surface Contamination Monitoring Comparison

Clare Lee (NPL) reported that the protocol used in the second surface contamination comparison exercise would be amended slightly and adopted for the current (third) exercise.  Participants would be allocated two weeks in which to perform their measurements and transport the equipment to the next organisation; since a check source would not be circulated, the transport was expected to be more straight forward than in the previous exercise.  A spare week would be incorporated into the timetable after every three organisations to allow for any repairs needed to the instrumentation and absorb any minor slippage in the timetable. Participation would be limited to 15 organisations to ensure the measurement phase of the exercise would be completed by the end of September 2004. The Working Group would meet to discuss the results of the exercise and if necessary enter discussions with any organisations reporting discrepant results. The Working Group would present the findings of the exercise to the IRMF meeting in November 2004 and a full report would be published after that. 

The instruments chosen for the exercise were the EP15 (for comparison with results of previous exercises), a Mini 44B and the DP8 plus Electra (to assess the use of the contiguous portions technique). Participants would be asked to calibrate the 44B with as many photon reference sources as were available to them but using ⁵⁵Fe, ¹²⁹I and ⁵⁷Co as a minimum. Cobalt-57 had been added after discussion with a number of medical physicists; it was considered relevant because its energy was the closest of the ISO series to that of ^99mTc, the most widely used medical radionuclide. Andy Weeks (BNFL Instruments) asked why the 44B had been selected for the exercise and reported that he’d experienced problems with it when using ⁵⁵Fe. Duncan McClure (NRPB) commented that the response of the 44B to ⁵⁵Fe could be used as an excellent indicator of the onset of crystal failure.  John Bennett (DRPS) confirmed that this, and the fact it was popular, were the reasons for including the instrument in the exercise.

Registration forms to participate in the exercise were available at the meeting and participation would be allocated on a ‘first come first served basis’. Options regarding the disclosure of results were included on the registration form and decisions on this could not be reversed once the exercise was underway; this was in accordance with the IRMF policy on disclosure (reaffirmed at the last IRMF meeting).

Mike Woods (IRMC) asked if the laboratories accredited by UKAS to perform surface contamination monitor calibrations would be given priority for participation. Clare Lee responded that they would not however she did not expect the 15 places would be taken before the UKAS labs had chance to register.

26.6  Discussion of Gamma and Neutron Monitoring Comparisons

Vic Lewis (NPL) describedthe current policy of running each of these exercises on a three-year cycle. As the measurement phases of both of the last exercises had begun in September 2001, it would be necessary to establish Working Groups for the next exercises at this meeting (if the 3 year cycle were to be maintained). However Vic proposed that the start of the next two exercises was staggered to make them more manageable, Duncan McClure agreed with this.  Vic also stated that the Neutron Metrology Group at NPL would prefer to delay the start of the neutron exercise by six months. After some discussion the meeting was in agreement that the gamma monitoring exercise should begin now and the neutron monitoring exercise would begin in six months time. Eddie Veater (UKAS) confirmed that this would not be a problem for UKAS.

To this end, a Working Group for the gamma monitoring exercise was elected; the members were Graham Bass (NPL) forming the secretariat, John Bennett (DRPS), John Simpson (RWE Nukem), Duncan McClure (NRPB) and Jon Wardle (DRMS).

Jon Wardle (DRMS) asked if EPDs would be included in this exercise. Various arguments were made for and against their inclusion however it was decided that the Working Group should discuss the issues and make the final decision.

26.7  Discussion of Potential Good Practice Guide on ADS Instruments and EPDs

The Chairman reminded members of a discussion at the last meeting about the possible production of a Good Practice Guide on ADS Instruments and EPDs. At that meeting, several members expressed agreement that there was a need for this guidance so it was decided that consideration would be given to proposing such a guide be included in the next NMS programme. However, following that meeting reservations were expressed about the need for such a guide.  The Chairman therefore invited further discussion of this topic.

Mike Renouf (BNFL) stated that the few existing Approved Dosimetry Services have a significant amount of documentation already covering their instrumentation so a GPG would not be needed for personal air samplers.  He felt however that there was little existing guidance for EPDs and consideration should be given to either producing a separate Guide for these or their inclusion in a future version of GPG14. John Bennett (DRPS) echoed these views and was keen to see some guidance for EPDs.

Andy Weeks (BNFL Instruments) spoke as the head of an ADS that uses electronic and passive dosimetry. He said that HSE recommend the use the old NAMAS PCS docs despite them not being supported by UKAS so there was a gap in the guidance.  However he didn’t think this was an issue for the IRMF as it was mainly to do with Passive Dosimetry. With regard to electronic dosimetry there are several different types of dosemeter available, it was his opinion that there was a definite need for Guidance within GPG14 or separately if the topic proved to be big enough alone.  ADS should not be included.

Geoff Druce (AWE) added that he felt strongly that Personal Air Samplers should not be included and GPG14 would be a suitable location for EPDs.  Duncan McClure (NRPB) and Peter Burgess (UKAEA) also believed it was important for clear guidance on EPDs.

The Chairman suggested that the forthcoming review of GPG14 could be an opportunity for EPDs to be considered for inclusion.

26.8  Review of Good Practice Guide 14

Clare Lee (NPL) informed the members that GPG14 was due to be reviewed during 2004.  At the last meeting, John Bennett had volunteered to assist with this however more help would be beneficial, in particular from someone with expertise of PIDs. Peter Burgess (UKAEA), Geoff Druce (AWE), Jan McClure (NRPB) and John Simpson (RWE Nukem) volunteered.  In addition, Max Pottinger (BNFL Instruments) and David Thomas (NPL) were proposed by Andy Weeks and Vic Lewis respectively. The working group was given two tasks, the first being to review the existing GPG14 and the second to produce guidance for PIDs (the guidance for PIDs may or may not be located within GPG14).

Mike Woods (IRMC) asked Clare if she had received any feedback on GPG14 and if a dossier of problems already existed. Clare responded that she had received very little feedback and the only area of contention was the contiguous portions technique. Mike stated that he’d be very worried to see GPG14 amended unless there was something significant to be changed and PIDS guidance could be published as a separate document.

Clare outlined her plans to produce a web based form for direct electronic submission of comments to her. She offered to contact those who had purchased copies of GPG14 to inform them that a revision was underway and publicise the comments form, however Peter Burgess felt this was unnecessary considering the effort that would be involved. Clare stated that the aim was to receive as much feedback on the Guide as possible and asked members to mention the review to relevant colleagues.

It was agreed that the deadline for submission of comments would be the end of March 2004, allowing the working group to meet before the next IRMF meeting when they would report back to the members.

Secreatry’s note: the comments submission form is available from the IRMF website http://www.npl.co.uk/irmf/

26.9  Discussion of Good Practice Guide 30

Clare Lee (NPL) reported that she had received some feedback on GPG30, part of which is reproduced below:

“I have just received and read my copy of GPG30 "Practical Radiation Monitoring", the content of which will be of considerable use to me and others who regularly train laboratory staff in monitoring techniques.  We shall recommend GPG30 as a point of reference to all our lab trainees.”

The remainder of the feedback had raised two potential problems with GPG30. The first of these had concerned the definition of efficiency provided on pages 35 and 36 of GPG30 – it was not possible for efficiency to be dimensionless (as stated) and be the reciprocal of the calibration factor (which was not dimensionless). The second had related to Equation 2 defined in Appendix 3 and the example calculation in Appendix 6 – there was inconsistency in the use of activity and activity per unit area.

Clare reported that she had reviewed these issues and was in agreement with the feedback.  In addition, she had also been concerned about the definition of the P-factor (Appendix 3.1) conflicting with that in GPG14 (page 35). Mike Woods (IRMC) had made further suggestions.

Clare had communicated these issues to the authors of GPG30 and as a result there would be an open discussion meeting held after the main IRMF meeting; all members would be welcome.

26.10  NMS Programme Formulation

Martyn Sené (NPL) described the National Measurement System (NMS), its purpose, function and general content. Formulation of the next ionising radiation programme for October 2004 to September 2007 began in April 2003 and was ongoing. PA Consulting had been contracted by the DTI to determine the trends and drivers for ionising radiation measurements in the UK. Representatives had attended the last IRMF meeting and PA consulting had now presented the findings of their study at an orientation meeting. Following this was a period of consultation where NPL asked users of ionising radiation what their present and future needs were. Based on this, NPL formulated a draft programme of projects, which had recently been presented to the Measurement Advisory Committee Working Group (MACWG, a committee of experts in radiation measurement appointed by DTI). After further refinement, a draft for public consultation would be put in the public domain in January 2004 for anyone to comment; IRMF members would be invited to comment by DTI. The programme would be finalised in June 2004 and would start in October 2004.

Martyn highlighted some of the proposed projects from the MACWG draft programme that were relevant for radiation protection; these included,

• Maintenance of all existing standards
• International comparisons of standards
• Maintenance of existing calibration services
• Maintenance and improvement of existing facilities
• Knowledge transfer, user groups and national comparison exercises
• Production of Measurement Good Practice Guides
• Extension of protection level calibration service to include ²²⁶Ra
• Production of more cost effective photon emitting surface contamination standards
• Various improvements to services for measurement of large area reference sources
• Investigation into the response of surface contamination monitors including derivation of P-factors
• Study of radon compensation techniques
• Study of techniques for production of realistic standards for air monitoring systems
• Extension of the range of monoenergetic neutron fluences (8 keV to beyond 15 MeV)
• Assessment of workplace neutron spectra to test personal dosemeters
• Investigation of photon doses in standard neutron fields
• Investigation of neutron doses around radiotherapy sets
• Solar flare watch project
• Participation in the development of codes of practice for decommissioning

Members were also encouraged to comment on the public consultation document in 2004. A good level of interest and support was vital to shape the future work and to demonstrate to DTI that the work was of relevance.

Secretary’s notes: the draft ionising radiation programme can be found at http://www.npl.co.uk/ionrad/nms/formulation/

Martyn Sené’s presentation can be viewed from the IRMF website at http://www.npl.co.uk/irmf/

26.11  Any Other Business

(a)  Critical Review of Procedures – A Near Miss

Peter Burgess (UKAEA) shared the experience of a ‘near miss’ that had occurred at UKAEA with the members present.  Although discharge authorisation levels were not reached and there had been no regulatory consequences, Peter felt others could learn from their situation.

It had involved Harwell 3230 instruments used for detection of beta emitters in air.  The instruments had been tested regularly using ⁹⁰Sr/⁹⁰Y sources with a typical detection efficiency of 26% quoted by the manufacturers.  However the sources were found to have a forward peaked emission due to the excessive depth of the active layer, this resulted in a much higher efficiency being obtained for the test source than would have been the case with a real source.  New sources were designed and purchased and the efficiency of the system was reduced to 15%.  The manufacturers issued a statement about the changes but for some reason this did not trigger an update in UKAEAs procedures (possibly due to changes in staff and loss of continuity).

Staff at UKAEA did not immediately spot the error due to a mistake in the procedure (where a 2p to 4p correction was made twice when calculating the efficiency) resulting in reasonable agreement with the previous 26% efficiency of the system.  This overestimated detection efficiency was then incorrectly assumed to apply to real sources and was used to set the alarm level of the system.

Fortunately it was routine practice at UKAEA for the filter papers to be counted retrospectively using a different method and there had never been an over-alarm event.  Peters message to the IRMF was:

• Be suspicious of anything you inherit;
• Use new staff to review procedures - they don’t know the “right” answer;
• And 2π to 4π is always an opportunity for confusion.

(b)  How to Sell New Instruments to the Workforce

Peter Burgess (UKAEA) described an MSc project being performed by Paddy Copeland of RWE Nukem. The responses of a selection of good quality, well calibrated, gamma dose rate instruments to complicated dose situations were compared with a view to purchasing new instrumentation.  A field trial was conducted using an RO-10 ion chamber, a Mini 1000RA (steel GM detector) and a Mini 1000RLA (end window compensated GM).  While the instrument responses showed general agreement, there were some situations where the responses varied by a factor of 3.  Reasons for the observed discrepancies included: inverse square law effects close to sources; very non-uniform fields giving uneven detector irradiation and low energy radiation at shallow angles.

Peter hoped this work would be published at some point.  The IRMF members agreed that this would be very useful information.

(c)  The Inclusion of Conversion Factor Uncertainties on UKAS Certificates

Andy Weeks (BNFL Instruments) raised the issue of reporting uncertainties on UKAS calibration certificates.  The current requirement was to quote the uncertainty on the radiation field in terms of air kerma. At a recent UKAS visit Andy had been directed to ISO 4037 section 4.1.2 which states that uncertainties associated with conversions to dose equivalent should be 2% for BNFL Intsruments’ particular situation (tables of values for other circumstances are provided in the ISO document).  Andy had found this to contradict GPG49 which states errors in conversion co-efficients should not be included in uncertainty budgets for calibrations certificates.  Andy’s personal view was that these uncertainties should not be included until GPG49 could be reviewed and clarification sought from the authors of ISO 4037.

Eddie Veater (UKAS) said that ISO 4037 took precedence over GPG49 however there was alot of merit to the argument not to quote this uncertainty and there did appear to be ambiguity in the standard.  To address this, Eddie requested the IRMF prepares an argument for submission to the ISO working group.

Mike Woods (IRMC) said that when comparing monitor responses with type test data (which includes a conversion factor) for the purpose of compliance testing, it would be wrong to include this uncertainty because it is not involved with the process of measurement.  He was worried that ISO 4037 contained no justification as to where the uncertainty values originated.  As a compromise position, he suggested that this uncertainty could be excluded from the overall uncertainty as long as a statement was made to the effect that an additional uncertainty associated with the conversion factor had not been included.  This would not result in a non-compliance as all uncertainties would have been examined and presented to customer, it is not a requirement to combine them all.

Eddie agreed this proposal would be acceptable in the interim until clarification could be obtained from ISO.  Provided there were no initiatives on international basis, Eddie was happy that a compliance statement that uncertainty had not been taken into account would be satisfactory.  Eddie agreed to write to all UKAS accredited laboratories to make this clear.

John Simpson, Peter Burgess and Tony Richards, as members of the NCE2 committee, agreed to raise this with ISO on behalf of  the IRMF.

Secretary’s note: at the time of issuing these minutes, Eddie Veater was reviewing the ISO standards.

(d) Minimum Detectable Activities for Radiation Protection Instruments

John Bennett (DRPS) said Health Physicists had asked him if MDAs existed for contamination monitors.  He had obtained some data from an American website and discussed this with Peter Burgess (UKAEA) who doubted the validity of the data.  John asked if other members of the forum had needed this information for clearance monitoring.

It was Peters opinion that this was a challenge for the senses, rather than for radiation detection as it was about identifying contamination rather than quantify it.  When monitoring for alpha emitters it is relatively easy as the background count rate is low but for beta emitters where the background could be 10 cps, one would normally notice a doubling in count rate. 

Poala Hayes (HMS Sultan) said their monitors had been given action levels above which contamination was to be reported.  Peter said it depended how the action level had been derived, where it had been set and how it compared with the regulatory levels for clearance.  The acceptable levels for alpha contamination are on limit of what can be detected, this makes decision on whether an artefact is clean very difficult, however the consequences could be great if court action resulted from materials incorrectly certified contamination free.

Martyn Sené suggested the HSE or Environment Agency might want to set up a collaborative project to look at the social psychology as well as the radiation measurement aspects of this.  Mike Woods advised that this should be considered practically rather than academically.  Steven Judge commented that a NUREG document contains data on the human factors of surface contamination monitoring and said he would provide a reference for it.  Tony Richards pointed out there is also a relevant international standard that is about to be published.

Secretary’s note:  the documents referenced above are as follows.

NUREG-1507. Minimum Detectable Concentrations With Typical Radiation Survey Instruments for Various Contaminants and Field Conditions. Washington DC: Nuclear Regulatory Commission. December 1997.

ISO 11929 Determination of the Lower Limits of Detection and Decision Threshold for Ionising Radiation Measurements and is produced in eight parts. Parts 1-4 have already been published parts 5-8 will be published in the near future.

(e)  Instrumentation Knowledge of RPAs

Duncan McClure (NRPB) asked if other organisations had found that RPAs generally had little experience of instrumentation.  Peter Burgess and Tony Richards said they had found this widely; others were in agreement. Duncan went on to announce a course on instrumentation to be held at NRPB 3 – 5 February 2004.

(f)  Instrument Capabilities

Geoff Druce (AWE) offered to present their findings on matching instrument capabilities to practical requirements at the next meeting.  The Chairman accepted this offer.

26.12  Next Meeting

The next meeting will be held on Wednesday 26 May 2004 in the Module 16 conference facility.
As usual, the meeting will commence at 10.30 am, with coffee served from 10.00 am.

Clare Lee
Secretary, IRMF
Centre for Acoustics and Ionising Radiation
National Physical Laboratory

ACTIONS

Secretary
Invite Don Mackenzie (Johnson Controls) to present his work on the effect of varying cable length on monitor response.

Secretary
Provide information to Martyn Sené’s PA for her to update the IRMF catalogue.

Tony Richards
Determine the appropriate IPEM contact person to discuss a comparison of X-ray energies (radiation protection special interest group?). Determine the extent of their interest to participate in this exercise and report back to the next IRMF meeting.

Secretary
Invite Sharan Packer from HSE to the next meeting.

Eddie Veater
Write to UKAS labs about compromise position for uncertainties in conversion factors on calibration certificates.

John Simpson, Peter Burgess and Tony Richards
Seek clarification via the NCE2 committee of the use of and origin of uncertainties for conversion factors stated in ISO 4037, in particular their confidence level and whether they should be included in overall uncertainties quoted on certificates for the calibration of instruments.

All members
Review the draft Ionising Radiation programme when it becomes available and submit comments.

Members representing calibration facilities
Send additions and amendments for IRMF Catalogue to the Secretary.

All members
Inform the Secretary of suggestions for presentations on technical topics for the next IRMF meeting before the end of April 2004.

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