Upload
lydang
View
219
Download
3
Embed Size (px)
Citation preview
Welcome to the 4th meeting of the Airborne Radioactivity Monitoring Users Group
Steven JudgeAndrea Woodman
3000 BC
The "Royal Egyptian Cubit" was decreed to be equal to the length of the forearm … of the Pharaoh or King ruling at that time.
Agenda
• Minutes and matters arising• High Volume Particulate Sampling (Simon
Jerome, NPL)• Reducing avoidable deaths from radon in the UK
(Brian Ahern, Radon Council)• Good Practice Guide (Max Pottinger)• Breakout Groups• AOB• Meeting of GPG Working Group or Lab Tours
Commercial reference sources
• www.isotrak.de• www.analyticsinc.com• www.ipl.isotopeproducts.com/new_ipl_site• www.lea-cerca.com
Air monitor cards
• Isotrak only (as far as known)
• Anodised foils or sealed plastic
• Calibrated to ISO8769
• Customised to match equipment
Cartridges
• Mixed gamma emitters
• Homogeneously mixed with charcoal or zeolite
• Face loaded – sealed plastic foils
Simulated gas standards
• Low density foams, simulating a range of pressures (0.015gcm-3 to 0.20gcm-3)
• Available in many container types
• Isotrak, Analytics, IPL
Filter papers
• Anodized foil type
• Mylar membrane of various superficial densities (0.5, 0.85, 1.7 mgcm-2)
Mylar vs anodized foils
• www.analyticsinc.com/paper1.htm (and references therein)
• Real samples differ from reference materials –self-absorption, backing plates)
• The paper compares mylar coated sources to electroplated
Gas bottle standards
• Pressurised / unpressurised gas bottles
• Glass ampoules
• IPL/CERCA/Isotrak
Measurement of Airborne Radioactivity by the CTBTO
Simon Jerome, NPL
ARMUG, 9th November 2004
Event and date 2
What is the CTBTO?
• The Comprehensive Test Ban Treaty Organisation
• An international organization established by the States Signatories to the Comprehensive Test Ban Treaty on 19th November 1996
• Their main task is the establishment of the 337 facility International Monitoring System and the International Data Centre, and the development of operational manuals, including for on-site inspections.
Event and date 3
Aims of the CTBTO
• To detect, locate and identify nuclear weapons tests down to 1kTequivalent
• The data used to detect, locate and analyse events are processedimmediately, with the first automated products being released within two hours
• The data comprise lists of seismoacoustic events and radionuclides that have been detected by monitoring stations
• Analysts subsequently review these lists in order to prepare quality controlled bulletins
• Implications of getting it wrong are not good
Event and date 4
Monitoring Technologies
• The aim – what, where, when, how, who (but not why)• Seismological monitoring system – size, location and time of underground
tests• Hydroacoustic monitoring detects acoustic waves – size, location and
time of underwater tests• Infrasound network detects very low-frequency sound waves in the
atmosphere – size, location and time of atmospheric tests• Radionuclide network of 80 stations uses air samplers to detect
radioactive particles released from atmospheric explosions and vented from underground or under water explosions (the ‘smoking gun’).
Event and date 5
Network Locations
Event and date 6
Nuclear Weapon
• Initial fission reaction (20 kT - 239Pu)• Fuels second fission reaction (<500 kt 239Pu or 235U)• second fission reaction fuels fusion reaction (yield depends how much fuel
2H/3H in the form Li2H)• finally, fast neutrons induce addition fissions in the weapon containment
(yield depends on rest of weapon – 238U)• Fission products elements from Zinc to Terbium, all volatalised
Event and date 7
Fission Products
Thermal Fission yield s
0.001
1.001
2.001
3.001
4.001
5.001
6.001
7.001
8.001
9.001
65 70 7 5 8 0 85 9 0 9 5 10 0 1 05 1 1 0 1 1 5 1 20 1 25 13 0 13 5 14 0 1 4 5 1 5 0 15 5 1 60 1 6 5 1 7 0
Mass number
% ma
ss yie
ld
Pu -239U-235Pu-241
Event and date 8
Radioactivity remaining
Rad ioactivity after 10 days
1.00E+00
2.00E+15
4.00E+15
6.00E+15
8.00E+15
1.00E+16
1.20E+16
1.40E+16
65 70 75 80 85 90 95 100 105 110 115 120 125 130 135 140 145 150 155 160 165 170
Mass number
Activ
ity/B
q
Event and date 9
Radionuclide monitoring
• The radionuclide network of 80 stations uses air samplers to detect radioactive particles released from atmospheric explosions and vented from underground/underwater explosions
• Half of the stations in the radionuclide network also have the capacity to detect noble gases
• The relative abundance of different radionuclides in these samples can distinguish between materials produced by a nuclear reactor and a nuclear explosion
• The associated radionuclide laboratories are used to analyse samples that are suspected of containing radionuclide materials that may have been produced by a nuclear explosion
• The presence of specific radionuclides provides unambiguous evidence of a nuclear explosion
Event and date 10
Performance requirements
• For the network of radionuclide stations:90% probability of detection within 14 days of any event >1 kT
• Distinguish between nuclear explosion and:Radon (allow the sample to decay)Radioactive Xenon used in nuclear medicineEmissions from civil nuclear facilitiesCosmogenic radionuclides
• Based on the detection of 140Ba with a detection limit of 10 µBq/m3
• 1 kT = ~4×1012J = 1.3×1023 fissions = 5 PBq 140Ba• Trying to detect not very much at all of the device!
Event and date 11
Radionuclide monitoring stations
• Air flow: 500 m3/hour• Collection time: 24 hours• Decay time: ≤24 hours• Measurement time: ≥20 hours• Reporting time: ≤72 hours• Reporting frequency: Daily• Collection efficiency: ≥80% for 0.2 µm and ≥60% for 10 µm• Measurement: High resolution γ spectrometry, 88-1836 keV• Sensitivity: εγ >40% leading to 10-30 µBq/m3 for 140Ba• Data availability: ≥95%• Down time: ≤7 days in a row, ≤15 days per year
Event and date 12
Xenon monitoring stations
• Air flow: 0.4 m3/hour• Sample volume: 10 m3
• Collection time: ≤24 hours• Measurement time: ≤24 hours• Reporting time: ≤48 hours• Reporting frequency: Daily• Nuclides monitored: 131mXe, 133Xe, 133mXe and 135Xe• Measurement: β–γ coincidence counting or high resolution γ
spectrometry• Sensitivity: 1 mBq/m3 for 133Xe• Data availability: ≥95%• Down time: ≤7 days in a row, ≤15 days per year
Event and date 13
Supporting measurement
• Network of 16 radionuclide laboratories around the world• Provide more detailed analysis of filters if required
Key Nuclides:95Zr/95Nb – timing99Mo – timing106Ru – fuel132Te/132I – event 140Ba/140La – timing141Ce/144Ce – fuelPure α and β emitting fuel and casing activation products
Event and date 14
CTBTO Country Profile for the UK
Coordinates Location Type Treaty
Code Lat Lon
Eskdalemuir EKA Auxiliary Seismic Station AS104 55.3 -3.2
BIOT/Chagos Archipelago Hydroacoustic Station HA08 -7.3 72.4 Tristan da Cunha Hydroacoustic Station HA09 -37.2 -12.5 Tristan da Cunha Infrasound Station IS49 -37.0 -12.3 Ascension Infrasound Station IS50 -8.0 -14.3 Bermuda Infrasound Station IS51 32.0 -64.5 BIOT/Chagos Archipelago Infrasound Station IS52 -5.0 72.0
AWE Blacknest Chilton Radionuclide Laboratory RL15 TBD TBD
BIOT/Chagos Archipelago Radionuclide Station RN66 -7.0 72.0 St. Helena Radionuclide Station RN67 -16.0 -6.0 Tristan da Cunha Radionuclide Station RN68 -37.0 -12.3 Halley, Antarctica Radionuclide Station RN69 -76.0 -28.0
Event and date 15
Noble gas sampling
• Xenon is adsorbed on charcoal, purified and concentrated• Need to remove water and CO2
Interfere with adsorption of Xenon on charcoal• Radon needs to be removed
Variable concentrations, but much larger than radioactive XenonGas chromatography is used to separate Radon and Xenon
• Variable backgroundNuclear medicine (mainly 133Xe)Nuclear power
Event and date 16
Noble gas measurement
• 131mXe, 133Xe, 133mXe and 135Xe emit γ–rays and similar energy X–ray• Can use γ spectrometry to detect 133Xe (81 keV, 37%), 133mXe (233 keV,
10%) and 135Xe (250 keV, 90%)• 131mXe emits 30 keV X-rays, but no γ–rays; 133Xe, 133mXe and 135Xe also
emit X–rays at this energy• Use β–γ coincidence counting techniques to reduce background for 133Xe
and 135Xe• Use γ–β coincidence counting (gated on 30 keV X–ray) with an energy
resolving β detector to reduce background for 131mXe and 133mXe
Event and date 17
Noble gas interferences
• 131mXe, 133Xe, 133mXe and 135Xe can be present at ground level with activities of up to 100 mBq/m3 from nuclear power and from medical use
• Typically 3-10 mBq/m3 in the industrialiased regions of the northern hemisphere
• (133mXe:133Xe)reactor ~0.1 (133mXe:133Xe)weapon ~10• (135Xe:133Xe) reactor ~0.01 (135Xe:133Xe)weapon ~100
• Medically used 133Xe is practically pure• Activity ratios are more important than activity concentrations in this case:
(131mXe:133Xe:133mXe:135Xe)weapon ~ 1:104:105:107
Event and date 18
Particulate sampling
• Particulate activity is captured on organically based band filters of differing types
• Filter exposed for 24 hours• Allowed to decay for 24 hours
Radon daughter nuclides (mainly 212Pb) decay over this period, reducing interference with 140BaAll other major radon daughters decay to zero in 24 hours
• Measured for 24 hours• Data reported to IDC in Vienna
Event and date 19
Fission Products
Thermal Fission yield s
0.001
1.001
2.001
3.001
4.001
5.001
6.001
7.001
8.001
9.001
65 70 7 5 8 0 85 9 0 9 5 10 0 1 05 1 1 0 1 1 5 1 20 1 25 13 0 13 5 14 0 1 4 5 1 5 0 15 5 1 60 1 6 5 1 7 0
Mass number
% ma
ss yie
ld
Pu -239U-235Pu-241
Event and date 20
Particulate measurement
• Need for calibration standards• Filter standards prepared from solution standards• Detectors calibrated directly (88-1836) keV• Monte Carlo and other modelling techniques not used• Comparison exercises to verify quality of information supplied• CTBTO has very similar quality requirements to ISO 17025
Event and date 21
Comparison exercises
• 2000:22Na, 124Sb, 125Sb, 134Cs, 137Cs, 154Eu, 155Eu, 210PbActivity levels 5 – 250 Bq/filter
• 2001:91Y, 95Zr/95Nb, 99Mo, 99mTc, 103Ru , 106Ru, 132Te/132I, 137Cs, 140Ba/140La, 141Ce, 144Ce, 147NdActivity levels 5–75 Bq/filter
• 2002:91Y, 95Zr/95Nb, 99Mo, 99mTc, 103Ru , 106Ru, 127Sb, 132Te/132I, 137Cs, 140Ba/140La, 141Ce, 147Nd, 154Eu, 155EuActivity levels 0.1–10 Bq/filter
RADON
A VIEW FROM THE OTHER
END OF THE TELESCOPE
A presentation for and on behalf of
The Radon Council
by
Brian H Ahern (Chairman)
There is no getting away from the fact that radiation doses to the public from radon are more than a thousand times greater than those from the whole of the nuclear industry……
There is no surprise in this, except to the wishful thinkers. Itis now time for them to forget their daydreams. Radon is confirmed as the biggest radiation risk to the public by far.
Jon Miles – Excerpt from Radon Dreams - Environmental Radon Newsletter Winter 1998.
Radon is not only responsible for the highest domestic exposures to radiation, it also leads to the largest occupational doses. In some cases the doses are so high that if they arose from an accident in the nuclear industry a high profile prosecution would inevitably follow. Things are less easy when neither the individual concerned, the employer nor the enforcing agency are aware of the situation.
Gerry Kendall - Excerpt from editorial Journal of Radiological Protection.
COMPARATIVE ESTIMATES OF
ATTENDANCE AT MAJOR SPORTING INTERNATIONAL = 25,000+
WITH DEATHS IN THE UK OVER A 10 YEAR PERIOD
FROM RADON = 25,000
FROM PASSIVE SMOKING = 10,000
FROM ACCIDENTAL FIRES IN THE HOME = 3,000
FROM NEW VARIANT CJD = 150
WHY SUCH LITTLE INTEREST?
COULD IT BE THAT BECAUSE RADON IS NATURAL – THERE IS NO ONE TO BLAME?
OR THAT ANYTHING THAT UPSETS THE VALUATION OF A PROPERTY IS BAD
NEWS?
INTRODUCTION TO THE RADON COUNCIL
The Radon Council is a non-profit making self regulatory body.
It is NOT a trade association and was established 13 years ago as a Regulatory Body for the UK radon industry and consumers.
It came about in response to a request from a Parliamentary Select Committee Report on Indoor Environmental Pollution, for just such an organisation to provide regulation, in order to combat the “cowboy elements” that were beginning to enter the radon field.
Its primary objective is to protect the public and not industry.
Despite its origins the Council has rather surprisingly never received any funding from UK governmental or public agencies.
Functions of the Council
Maintain a Code of Good Practice.
Publish “The Radon Manual”.
Provide Training Courses, with examination.
Award of Certificate and CPD points to successful candidates.
Maintain an annual List of Contractors.
Radon Council Services.
Provide a telephone information service.
Provide and maintain a radon website in association with the Universities Radon Network.
www.radonhotline.org
Collaborate with ERRICCA and other International programmes.
www.euradoncouncil.com
Training Course ContentAn intensive whole day course which on completion is
eligible for CPD points.
Radon and Health risks.Detection methods.
Health and Safety Legislation.Radon remediation.
Radon in new-build: Sumps and Barriers.Environmental law. Lecturers’ Forum.
Personal study.Examination.
Main Radon Council Policy
Start to reduce the 2500 avoidable annual deaths in the UK.
Over time test all UK homes.
“To Test is Best”.
Adequate testing and remediation knowledge already in public domain.
Maintain and where necessary raise standards.
The Radon Council is concerned at the avoidable and tragic waste of 2,500 lives each year from radon. Despite numerous initiatives tried over the past decade, at substantial cost to the taxpayer, many people are still unaware of the danger.
The Radon Council is advocating a revision of national policy in order to eradicate this menace and start to reduce these unnecessary annual deaths, by the following means:-
1) Make a minor revision to CON 29 and to include radon in the proposed Home Information Packs (HIPS).
2) All homes both new and old should be required to furnish a valid and recent radon test certificate at the time of conveyancing.
3) Any homes found to have radon levels in excess of the current action level, should be remediated.
Over the past two years the Radon Council has had numerous telephone calls and some correspondence from puzzled consumers asking what a 1% or 3% possibility of there being radon in their home can mean.
The answer is quite frequently whether in ‘bad’ or ‘good’areas it means very little. Like drains, woodworm, dry rot or roof faults,
“To Test is Best”
is the only 100% reliable guide to any individual home and could be a lifesaver into the bargain.
THE LIFE YOU SAVE MIGHT BE YOUR OWN!
WHY SHOULD NEW HOMES BE TESTED?
Although new homes allegedly complying with Building
Regulations will frequently include a “radon membrane”
and some even a “radon sump”, experience shows that
unless these are specified and installed correctly, high
radon levels can still occur.
An estate at Higham Ferrers in east Northampton, where the probability of radon is said to be in the 3% - 10% band was tested.
Results showed that 35% of the properties were over the action level.
Even though they were classified as only requiring secondary protection.
Environmental Management and Health Vol 11. No 4. Year 2000
The following survey conducted by University College
Northampton and Northampton General Hospital
illustrates the problem.
© UCN 2004
A Study of the Efficacy of Radon Proof Membranes
Prof A.Denman, Prof P.Phillips, and Dr R.Crockett
© UCN 2004
Introduction• Since 1992, New Houses in UK Radon Affected Areas must be
built with radon protection. In affected areas, this takes the form of a radon proof membrane as the damp proof course, sometimes with the addition of a sump or additional air bricks.
• Minimum specification is 300 µm polythene sheet, extending over the cavity wall. (BRE Document, BR211)
• UK practise does not require a radon test in such new homes, andthe developers rarely have an effective procedure that informs buyers that the area is radon affected, or that radon preventative measures have been taken.
© UCN 2004
Study Area• The UK Action Level for domestic properties is
200 Bq m-3
Brixworth (NN6 9..) is in Northamptonshire, in an area where 17.7 % of houses have been found to be over the action level.
444 new houses have been built in Brixworth, on a large development with three main builders, since 1992.
© UCN 2004
Measurements• The NRPB Measurement Protocol uses two track etch
detectors placed for three months – one in the bedroom, one in the main living area
• The weighted average of these two measurements is seasonally corrected, and compared to the Action Level
• This methodology was adopted for this study, with an exposure time of 90 ± 2 days.
• 100 Householders in new houses were offered a free radon tests. 63 returned detectors, of which 3 were spoiled, leaving 60 usable results.
© UCN 2004
Study Results•The results have a log-normal distribution
•Showing that sample is not biased•6 houses (10 %) over Action Level•Our recent DEFRA-funded study showed that the equivocal range for 3 month track etch detectors is 112 to 356 Bq m-3
•Above 356 – definitely abnormal•Below 112 – definitely OK•Between 112 and 356 – result should be repeated
•14 houses in equivocal range (23.3 %)•1 (1.7 %) definitely abnormal
© UCN 2004
Analysis
• If the membrane works then all results should be below the Action Level
• It is not possible to have a direct comparison to a control group
• However, NRPB showed that 17.7 % existing houses in the local area (Brixworth and some adjoining villages) were over the Action Level
• Thus the membrane provides inadequate protection in over 50 % of cases.
© UCN 2004
Irish Study• A similar study was conducted by Synnott et al
in two areas in Ireland• Legislation require a BBA Accredited
Membrane • Results were similar
• 11/90 (12 %) in an area where 27 % of existing homes were over Action Level
• 9/44 (20 %) in an area where 45 % over AL
A Survey of the Impact of Amending Building Regulations on RadonConcentrations in Irish Homes, H.Synnott, D.Pollard, P.A.Colgan, and D.Fenton, Proceedings of IRPA11 Congress, 2004
© UCN 2004
Conclusions• The pilot study suggests that radon-proof membranes used
in UK new homes do not always provide adequate radon protection
• The results are similar to an Irish study• The likely cause is damage to the membrane during building
• There is currently no requirement to test new houses in the UK
• This study indicates that it is essential to make radon measurements in new houses, in order to identify those where the membrane provides inadequate protection
RADON TESTING FOR EXISTING HOMES.
The need to test existing (or old) homes is obvious.
The size of the existing housing stock determines that these properties will result in by far the largest number of homes found to be affected by high levels of radon.
It has been suggested that because radon levels can be affected by life-style then in the absence of a radon test certificate the purchaser should move in and test after occupancy. Any buildings found to have high levels could then be remediated and the cost presumably clawed back from the vendor.
WOULD YOU BUY A SECOND HAND MOTOR CAR ON THE SAME BASIS?
Who would wish to buy a second-hand motor car, that might have a latent defect, on the understanding that it could be corrected later if the purchaser’s style of driving caused it tomaterialise.
The Radon Council is totally opposed to this suggestion and advocates the policy of testing all properties at the time of conveyancing. In this way a purchaser will know what they are buying.
TO TEST IS BETTER THAN A GUESS
It is argued by some that meaningful tests cannot be conducted at the time of conveyancing.
This is not the case. Reliable and internationally accepted testing methods for measuring radon already exist, providing the correctinterpretation is placed on the results.
These can be as short as 7 days which is a timescale that does not delay the conveyancing process, or as long as 3 months, a test that can be conducted in many cases well ahead of the sale.
It is important to appreciate that all essential techniques for testing and carrying out adequate radon remediation work are already in the public domain. The Radon Council publishes an annual list of approved contractors, well able to provide services or undertake this work.
Ultimately all properties should be included. This not only means NEW and EXISTING HOMES, but SCHOOLS, HOSPITALS, and WORKPLACES as well.
We operate stricter gas protection regimes against landfill and brownfield gases, which are less dangerous, than we do against a known killer.
LIST OF CONTRACTORS….
The Radon Council publishes an annual list of contractors who have reached an acceptable level of competence and have demonstrated a knowledge of building techniques.
Every entrant has to sign a written contract with this Council and follow a Code of Conduct as well as produce evidence of valid Liability Insurance.
A RECENT COMPLAINT
This is not always the case with contractors who have not received adequate training. The Radon Council has recently received a complaint from a private householder about work carried out by an “approved contractor”.
The example showed a disregard for the IEE Wiring Regulations, undermined the fabric of the building and caused an electrical fault when it rained.
This contractor has not attended a Radon Council training course and does not appear on the Radon Council’s list of contractors.
COMPLAINTS PROCEDURE
As part of its Duty of Care the Radon Council has a complaints procedure.
A Disciplinary Group comprising a chartered chemist, a chartered engineer, a master builder and a legal advisor are available to investigate any complaints received by the Council concerning anyone appearing on our published list.
A few cases have already been considered over the past years and resulted in a successful conclusion for the consumer.
Unfortunately the contractor responsible for the work described in the previous example is not known to the Radon Council and as such we are unable to mediate directly.
The Future
The Radon Council is of the opinion that only when these recommendations have been adopted will a start be made to reduce the unacceptable annual waste of life from radon.
National Good Practice Guide: Airborne Radioactive Particulate in the WorkplaceMax PottingerBNFL Instruments
Page 25665
History to Date
Meeting Feb 2003Scope the document Broad Test Categories
First WG Draft May 2003Review Meeting Sep 2003Second WG Draft May 2004Review Meeting July 2004Abridged Document issued to ARMUG Nov 2004
Page 35665
Revised Content
Abridged document agreedScopeContains summary tables of test required
Removed sectionsSource constructionAppendices: leakage, uncertainties, alarm settingsAddenda may be added later
Final details of testing to complete
Page 45665
Types of Equipment
Airborne Particulate MonitorsNormally some alpha spectrometry
Airborne Particulate samplersDust samplers
Laboratory Counting Equipment
Page 55665
Periodic Tests - Air Samplers
Parameter CheckPump TestFlow rate accuracyLow flow alarm Low differential pressure alarm
Flow Rate Leakage - TBFU
Page 65665
Periodic Tests - Air Monitors
All air sampler testsResponse testBackgroundActivity Alarm Detection Efficiency
Nuclides recommended by manufacturer
Page 75665
TBFU - Air monitors
All Periodic TestsEnergy Response
cover energies encountered in the workplaceCross Response
Check beta rejection by alpha channelGamma compensationOver Range Test
Geiger only monitors
Page 85665
Periodic Tests - Lab Equipment
Parameter checkResponse TestBackgroundActivity alarm testDetection efficiencyEnergy Response - TBFUCross Response - TBFULinearity - TBFU
Page 95665
The Future
Aim for 3rd WG Draft in early 2005
Submission to ARMUG 2005
Additional reference information added in later years