Wednesday 2nd May 2001
National Physical Laboratory

Present:

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

There were 38 other members present from 23 establishments including:

AEA Technology (Harwell)		AEA Technology (Winfrith)
AEA Technology QSA (Harwell)		BAE Systems (Barrow-in-Furness)
BNFL Berkeley		BNFL Sellafield
Centronic, Croydon		DERA Rad. Prot. Service (Alverstoke)
DRaStaC (Aldermaston)		Guy's & St Thomas' Hospital Trust
HMS Sultan, Gosport		Johnson Controls (Dounreay)
Kingston University		National Physical Laboratory
National Rad. Prot. Board (Chilton)		NRPB Northern Centre, Leeds
Northern Ireland Rad. Prot. Service (Belfast)		Nycomed-Amersham
St Gobain Crystals and Detectors UK Ltd		Sherwood-Nutec Consultancy
UKAS (Feltham)		Velindre Hospital, Cardiff
Warship Support Agency, Foxhill

Thirteen more members, including some from a further five establishments, had sent apologies.

AGENDA ITEMS

Gamma-radiation Monitoring Comparison

Duncan McClure (NRPB, Chilton) reported on the meeting of the Working Group planning the fourth IRMF comparison of calibrations of gamma-ray dose-rate monitors. It had been decided that passive dosemeters were outside the remit of the WG and should not be included in the this exercise. The exercise would be a test of the ability of laboratories to routinely calibrate portable dose monitors. At least one of the instruments would require setting up by the individual participants. It had also been decided that no check source would be circulated because transportation of a radioactive source had introduced delays in previous exercises.

This time, the quantity to be reported would be ambient dose equivalent instead of air kerma. Participants would be requested to supply uncertainty budgets in order to stimulate participants to think about their uncertainties. The protocol would be circulated by e-mail.

The three instruments chosen for this exercise were the Electra with MC20 probe, the Minirad 1000 and the EPD Mk2. (Participants would be able to choose whether to calibrate the EPD on-phantom or off-phantom.) The calibrations would be in ²⁴¹Am, ¹³⁷Cs and ⁶⁰Co fields.

Participants would be allotted two weeks each to cover measurements and transportation. It was expected that the measurement phase would start in September 2001 and could last a year. Participating laboratories would be expected to report their results within a month of completing their measurements. The normal, agreed disclosure conditions would apply.

The desirability of holding a comparison concerned with X-ray energies was considered to be a separate issue, to be decided by IRMF. Tony Richards (Leeds) would discuss the issue with IPEM and report back to the next IRMF meeting.

Neutron Monitoring Comparison

Vic Lewis (NPL) reported on the meeting of the Working Group planning the third IRMF comparison of calibrations of neutron area survey monitors. After a review of the previous exercises, the nature, aims and justification of another comparison had been discussed and it was decided to continue the three-year cycle of comparisons. The third exercise would involve the circulation of different instrumentation from that used in the other exercises and would be extended to include accelerator-produced neutron fields.

The WG had agreed to use a Mark 7 NRM (spherical moderator) and an NM2 (cylindrical moderator). All participants except BNFL (Berkeley) would calibrate the two monitors in fields produced by ²⁴¹Am-Be and ²⁵²Cf sources; NPL and BNFL would calibrate the monitors in 2.7 MeV monoenergetic neutron fields.

Each participant would be assigned a calendar month and would be expected to report results to NPL within one month of completing the measurements. Any participant taking longer would be listed in the report. As previously, participants would be required to submit uncertainty budgets. There would be full disclosure of the identity of the results. It was hoped to finish the measurements by May 2002 and produce the report by October 2002.

Comparison of surface contamination monitoring

Clare Scott (NPL) reported that all fourteen original participants plus four who had been on the reserve list had completed their measurements and all but one had submitted results. The two meetings that had been held to discuss the data were very useful for resolving and explaining many of the issues arising. Analysis of the data was continuing at NPL.

 Three instruments (DP6, LB122, EP15) had been circulated around the laboratories. Participants had to set up the DP6 from a “scrambled” setting, but this had presented no apparent problems. For each instrument preliminary results were presented for the radionuclides ³⁶Cl, ⁹⁰Sr, and ²⁴¹Am, expressed as percentage deviations from the means, with additional data for ¹⁴C with LB122 and EP15, and ²³⁸Pu for DP6. Where justified, some amending of obviously discrepant results had been carried out at the meetings. The ownership of results was disclosed for fourteen of the participants; the rest had chosen to remain anonymous. The spreads of the results varied considerably from one set of data to another. The reported uncertainties varied greatly; from virtually zero up to thirty and forty per cent.

In the coming months there would be further analysis, involving the recalculation of some participants’ data where excessive numbers of source positions had been used. Some data and some of the techniques used would be discussed with participants. Further trends in the results would be sought, possibly relating to the method of source calibration or the effect of the EHT setting for the DP6 or in the ±+² setting for the DP6.

Additional investigations were envisaged to quantify “edge effects” for the LB122, to compare the use of scaling for detector area with the use of the contiguous portions method for the LB122 and to determine if contiguous portions measurements are appropriate for the DP6.

Good Practice Guide 30, Practical Radiation Monitoring

Mike Woods (NPL) described GPG 30 as a consensus of good practice in practical radiation monitoring. The GPG was intended as a less statutory document than GPG 14 and GPG 29. It was designed to be as user-friendly as possible and aimed at users and supervisors. Alan Edwards (DraStaC) emphasised that the guide was aimed at the small user rather than big companies who already had a good deal of experience in-house.

Sections ranged from defining the problem and gathering information, deciding the strategy for monitoring and choosing the appropriate type of instrument, monitoring techniques and the interpretation of results. There were appendices on detector strengths and weaknesses, typical record sheets and estimation of surface activity, and worked examples on monitoring strategies in hospitals and nuclear laboratories. It did not cover air-borne contamination.

Mike Renouf (BNFL, Sellafield) commented that the previous GPGs were more metrology-based, but GPG 30 came more into the operations area, and there would be pressure for large operators such as BNFL to follow the guide even if it was not statutory. Therefore such organisations should be represented on the Working Group. It was pointed out that large organisations were not fully represented in IRMF itself.

The WG would meet next in July and it would make sure that the consultative document goes out to members of the IRMF at least, with an instruction to pass it on to anyone who could comment. It was hoped that publication would be in late summer or early autumn.

Good Practice Guide 29, The Examination, Testing and Calibration of Installed Radiological Protection Instrumentation

 

Max Pottinger (BNFL, Berkeley) reported that fifteen sets of comments on the consultative draft had been received. A number of exclusions and changes had been made in recent months. It had been decided to exclude air monitoring; the general consensus was that this merited a separate guide produced by its own specialist working group. The GPG would specifically exclude neutron monitoring instrumentation; this was partly justified by the international move towards the practice of removing the detector heads and taking them away for calibration. Criticality instrumentation was also excluded.

(Provision of a GPG covering air monitoring will be included in the next NMS Programme on Ionising Radiation Metrology. The NMS Air Monitoring Club would oversee its production.)

Among the changes was re-testing after repair being introduced as a specific part of the testing regime. The weekly test requirement was changed to routine testing. After some discussion on the requirement for alarms to be tested at 50% above threshold (this is a subtle variation on what is specified by GPG 14) it was decided to review this outside the meeting. Table 1 had been simplified with the incorporation of both main types of surface contamination monitoring in a single section. Many changes had been made to ensure consistency with the text. The definitions of Qualified Person and Employer had been firmed up at the request of HSE. The definition of Test House had a reference to accreditation.

It was aimed to have publication by the end of August 2001.

Good Practice Guide on The Treatment of Uncertainty in Radiological Measurement

Vic Lewis (NPL) reported that over the past few years the Working Group concerned had produced several examples of uncertainty budgets, along with discussion of the components, for various types of radiological measurement such as radioactive source measurement, surface contamination monitoring, neutron area monitoring and photon dosimetry. The purpose was to produce a document on uncertainty that would augment the existing guidance in the UKAS publication M3003. Mike Woods had collated and reviewed the work before the previous IRMF meeting. Several IRMF members had sent in their uncertainty budgets for therapy-level and protection-level photon dosimetry since that meeting.

At the previous IRMF meeting it had been decided that it would be appropriate to produce the guidance document as a GPG. The gathered material had since been put into a more consistent format for a GPG. This involved some more review and revision because uncertainty budgets were evolving all the time. The GPG was slowly taking shape but progress was slow due to other commitments. A first draft of the Introduction, which was a brief summary of the principles contained in M3003, had been completed. Two of the four radiological sections were almost ready and a third was being drafted. It was intended to circulate a first draft to members of the WG before the next IRMF meeting.

Good Practice Guide 34, The Testing, Calibration and Use of Equipment for Radiometric Non-Destructive Assay

Vic Lewis (NPL) reported on this initiative to help standardise best practice and 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. The GPG would contain sections on the methods used, their limitations, calibration, uncertainties, performance demonstration, routine and maintenance testing and other aspects of quality assurance.

The IRMF was not involved directly with this GPG. The Working Group had representation from the manufacturers of NDA equipment, users of such equipment at licensed sites and regulatory authorities. It had met twice. The individual sections had been produced and peer reviewed. They were now being put together as the first draft of the GPG, which would be reviewed by the WG in July. It was intended to produce a consultation document by the end of the year for trial throughout the industry during year 2002. A final version would be published at the end of 2002. It was also intended to review the GPG after a further five-year period.

This GPG had been initiated at the request of the Nuclear Installations Inspectorate and was sponsored by HSE and key stakeholders (AWE, BNFL, UKAEA and the Environment Agency through NNC). The DTI did not provide any funding but would hold the Intellectual Property Rights on behalf of the user community, as it does for all NPL GPGs.

Issues concerning Good Practice Guides

Consultation

The issue of ensuring adequate consultation by the user community was discussed. The final draft of a GPG should be put out to a wide audience about six months before the intended publication date. This had worked well in the case of GPG 29. The two extremes were to trust the working group exclusively or to put the draft document out to the whole user community. In the case of GPG 14 the latter course had proved to be too lengthy because of the volume of changes (many trivial) requested. Members urged that a balanced approach, between the two extremes, should be taken. A very strict timetable must be adopted for the consultation process in order to avoid undue delay. It was necessary that everyone could have opportunity to have a say; there should be reasonable time between drafting and publication for consultation.

Review

It was suggested that, because of the increasing influence of GPGs both in the UK and abroad, there should be a review and maintenance policy for GPGs along the lines of those for international standards.

Possible issues to be discussed in the case of GPG 14 included -

• Current legislation needed to be referred to.
• A decision should be taken on whether to include environmental monitors.
• The low-energy alpha contamination test should be considered.
• Methods for defining the response of a contamination monitor should be reviewed.
• Inclusion of electronic personal dosemeters should be re-considered.
• The inclusion of floor monitors should be considered.
• Type testing should be removed.

Price

In response to the question of whether members of the user community should pay for GPGs, Martyn Sené agreed that it seemed inappropriate that the user community should be charged for copies after it had put a lot of effort into their drafting. However, GPG 14 had not been funded in the same way as those being written at present. Although HSE had made a contribution, a major part of the cost had been borne by NPL without DTI support. The price of GPG 14 covered this cost as well as those of printing and distribution.

The costs for producing high-quality, hard copies of the forthcoming GPGs would still have to be covered by the price, because, if these were issued free of charge, many more would be ordered at greater cost to NPL. The NPL would investigate making GPGs downloadable from the NPL website. The matter would be raised also with DTI, who funded NPL’s role. Several members commented that £25 was not a huge price to pay for glossy copies.

The Secretary was asked to draft a procedure document to be considered for the next meeting. This would cover the setting up of the working group, drafting and peer review of the various versions, consultation by the user community and the review process. The GPGs produced by NPL would be looked at to see if IRMF could adopt a commonality of approach.

Instrumentation Issues

International standards

Max Pottinger reported on the redrafting of the contamination standard IEC 60325. This covered type testing of alpha-beta contamination sources but did not include floor monitors or gamma-contamination monitoring. The BSI had prompted IEC to produce two new international standards. The first, dealing with gamma contamination monitoring would probably be drafted by BNFL, hopefully with strong input from IRMF. This would be relevant to decommissioning projects and in hospitals. It could include the derivation of response of a gamma monitor, discussions on derivation of P-factors and the question of activity per unit area or unit mass, and the characteristics of typical probes.

It was expected that the UK would also play a significant role in drafting the second new standard that would cover air particulate monitoring.

Some members voiced their concern about the inadequate communication concerning things that were happening on the international standards scene and also on the lack of knowledge of GPGs both inside and outside the UK user community. It was felt that information could be given at IRMF meetings; some members were on the standards committees.

Draft HSE documents

Peter Burgess (NRPB) described two draft documents being circulated by HSE. The main purpose of the first document (of four pages) was to give to inspectors to enable them to say whether appropriate instruments were being used. The document did not conflict with GPG30.

The second, more detailed and much longer, document was aimed more at qualified persons and went through the pros and cons of each instrument in a lot of technical detail. It had been written by Peter, who had consulted various experts on any contentious points as and when necessary. When finalised, this would be freely-available on the NRPB website as NRPB R326. There would also be copies to buy.

Members involved in de-commissioning were recommended to have a look at the document MARSSIM on the EPA (US DoE) website. Reference: NUREG-1575 or EPA402-R-57-016.

Repair of tritium monitors

John Simpson (AEA, Winfrith) asked if there was anyone on the UK who could carry out the major servicing and maintenance of tritium monitors. At present these had to be sent to the US and they often took a very long time to be returned.

Field testing of radiological protection instruments

John Simpson commented on the administrative problems in the sending of relatively small radioactive sources between sites. He quoted an example of the vast amount of effort involved within the UKAEA in the case of a small mixed source including 700 Bq of ²⁴¹Am to be carried around for use in testing instruments in the field. If constraints on the use of sources became such that people became reluctant to test RP instrumentation, safety could be compromised. Members agreed that there was a problem of the paperwork involved in the transportation of small sources and it was suggested that there should be a de minimus level. There was also the aspect of private car insurance. It was thought that the regulation was too concerned with demonstrating control of radioactive material rather than ensuring safety of use.

National Measurement System Programme for Ionising Radiation Metrology

Martyn Sené (NPL) gave an update on the next three-year NMS Programme for Ionising Radiation Metrology, funded by DTI, starting in October 2001. A final programme document, taking all comments into account, had been submitted to DTI and appraised by the NMS Policy Unit with the aid of external experts. It had next to get ministerial approval.

Over the next few months, details of the programme would be widely publicised. The main points included maintenance of all existing primary standards and calibration services. The major facilities would be maintained with the exception of the SAMES accelerator that provided 14 MeV neutron standards. These would be transferred to the ASP facility at AWE.

Most of the programme would still be carried out at NPL; this was recommended by the MAC Working Group that advised DTI and also the vast majority of respondents. A number of projects would be competitively tendered in due course – hopefully within six months.

Forthcoming Events

The following meetings and courses were announced:

• First meeting of NMS Liquid Scintillation Users Forum on 5 September 2001 at NPL
  (contact: John Makepeace, tel: 020 8943 6480)
• First meeting of NMS Air Monitoring Group on 20 September 2001 at NPL
  (contact: John Makepeace, tel: 020 8943 6480)
• Tenth meeting of NMS Neutron Users Club on 25 September 2001 at NPL
  (Contact: Peter Kolkowski, tel: 020 8943 6855)
• Course on uncertainties in radiochemical analysis to be arranged for September 2001 at NPL.
  (Contact: Mike Woods, tel: 020 8943 6425)
• Nuclear Instrumentation Calibration Course to run from 19 November to 7 December 2001 at HMS Sultan.
  (Contact: Jon Taylor on 02392 546051)

Private Finance Initiative at NPL

Martyn Sené (NPL) reported on the effect of the re-building of NPL on the measurement and calibration services offered by the Centre for Ionising Radiation Metrology.

The new ⁶⁰Co facility was fully operational for both the air kerma absorbed dose protection- and environmental-level calibrations and for therapy-level calibrations. The new main building would house other X-ray sets and facilities, the high-level ⁶⁰Co irradiator for industrial dosimetry and all radioactivity work. The next environmental–level gamma-radiation calibration period would be July 2001. The next protection-level calibration period would be as expected in the autumn of 2001. The next diagnostic-level and mammographic-level calibration service would start in November. The next therapy-level calibration period would in the winter.

Most of the radioactivity services had been suspended from 1 May until the end of July. Orders would still be accepted in the meantime, but delivery would be unlikely until September. The radioactive gas standards services would be suspended for four weeks in August/September. Environmental radioactivity standards would continue to be issued from stocks.

Details of the disruption to services will also be set out in the latest Ionising Radiation News, to be distributed in May. Anyone with a particular query about the availability of any NPL service should contact Martyn Sené (0208 943 7028) or Brian Chapman (0208 943 6708).

Change of Secretary

The Chairman announced that Clare Scott would succeed Vic Lewis as Secretary from 1 October 2001. Vic Lewis had held the post for the past five years, covering eleven meetings.

IRMF Catalogue of Calibration and Testing Facilities

The Secretary had asked the contact persons of twenty three facilities for updates to their entries on the version maintained on the IRMF Website (www.npl.co.uk/irmf/). Fifteen had responded and, as a result, about half of the entries for the UKAS-accredited and non UKAS-accredited laboratories had been updated (a total of 35 out of 70). NPL had a further fifteen entries to be updated later in 2001. Members were asked to inform the Secretary of any changes to enable their entries in the Catalogue to be kept up-to-date.

Next Meeting

The next meeting will take place on Wednesday 7 November 2001.

Discussion of the IRMF’s Terms of Reference will be an agenda item at the next meeting. Members are asked to consider what changes, if any, should be made. A copy is attached to these minutes. Written comments before the meeting should be sent to the Secretary.

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 or on vic.lewis@npl.co.uk 

Ionising Radiations Metrology Forum - IRMF

TERMS OF REFERENCE

Aims

The Forum shall aim to facilitate both the exchange of information about available UK calibration and testing facilities and the efficient use of those facilities by those required to comply with the requirements of current ionising radiation regulations and associated codes of practice. It shall represent members' interests in discussions and correspondence with expert bodies, including those responsible for regulations and for forming standards.

Activities

The Forum shall:

- encourage, by all means which shall be deemed appropriate and practical including proficiency testing, good practice in measurement, including traceability to national standards,

- hold regular meetings to discuss matters of common interest relating to calibration and measurement, including national and international specification standards,

- maintain and disseminate a register of UK calibration and testing facilities and services.

Membership

Members shall be representatives of UK establishments or organisations actively involved in calibration or measurements in the field of ionising radiation and radionuclide metrology, together with representatives of manufacturers of instruments and artefacts pertaining to such measurements.

Management

The Forum shall be managed by NPL, assisted by advisory committees drawn from and established according to the wishes of the members. Those responsible for the management of the IRMF shall take due account of views of the members. NPL shall provide the Chairman and Secretary of the IRMF.

Fees

There shall be no annual subscription but NPL shall reserve the right to make a charge for organising meetings, producing reports and providing services.

Liability

Neither NPL nor the IRMF nor any member thereof shall be responsible for any consequence arising from the activities of the IRMF.

Revised March 1991

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