Doses from cosmic radiation received by members of the public during high altitude expeditions sold by UK companies. Bob Kerr, April 2014

Transcription

1 Doses from cosmic radiation received by members of the public during high altitude expeditions sold by UK companies Bob Kerr, April 2014

2 Introduction Cosmic radiation facts High altitude expeditions Relevant radiation protection legislation Measurement of doses received by members of the public on Everest Conclusions

3 Cosmic radiation basics Source: RadiationSources InterplanetarySpace.jpg

4 Cosmic radiation measured at sea level Dose rate in microsieverts per hour Good northern lights display

5 Solar cycle sunspot numbers Source:

6 Cosmic radiation intensity variation Latitude variation Solar cycle variation Source: RP140 Cosmic Radiation Exposure of Aircraft Crew

7 Cosmic radiation variation Cosmic radiation dose rates vary with altitude

8 Cosmic radiation exposure Plane cruising altitude range High altitude peaks

9 Doses received during expeditions Components of public dose: Doses received during air travel to/from mountain Doses received when on the ground at altitude

10 Doses received during expeditions Doses received on expeditions are influenced by: Latitude of mountain Altitude of mountain Time spent at altitude Solar cycle Solar flares Coronal mass ejections Are the dose rates experienced significant?

11 Cosmic radiation dose rate estimate Dose rates can be estimated using calculators

12 High altitude Everest is 29,035 or 8,848 m high Everest grows by 0.25 or 6.4 mm per year

13 Summit of Everest Dose is measurement in jet stream most of the year Wind can blow at over 200 mph Temperature Text can be down to below 60 C ( 80 F) Text 2

14 Cosmic radiation dose rate estimate No one spends long per trip up at extreme high altitude, but do these cosmic radiation doses matter for legislative compliance and are they significant?

15 Cosmic radiation regulation IRR99 applies to: Any practice Work involving production, processing, handling, use, holding, storage, transport or disposal of radioactive substances Operation of electrical equipment emitting ionising radiation Any work carried out in an atmosphere containing radon 222 gas where. Any work (other than above) with any radioactive substance containing naturally occurring radionuclides.

16 Cosmic radiation regulation IRR99 applies to: Any practice Work involving production, processing, handling, use, holding, storage, transport or disposal of radioactive substances Operation of electrical equipment emitting ionising radiation Any work carried out in an atmosphere containing radon 222 gas where. Any work (other than above) with any radioactive substance containing naturally occurring radionuclides.

17 Cosmic radiation regulation As IRR99 doesn t apply, no need to worry about regulation 11 (dose limitation) IRR99 guidance states : Exposures received as a result of natural background radiation at normal levels are not considered in determining compliance with dose limits. What is normal?

18 Cosmic radiation regulation Plane cruising altitude range High altitude peaks Air Navigation Order 2009

19 Cosmic radiation regulation Air Navigation Order 2009: Protection of air crew from cosmic radiation Keeping and production of records of exposure to cosmic radiation (if likely to be > 1 millisv/yr) Inform the workers of the health risks their work involves Doses to be ALARA during pregnancy (and <1 millisv) Excludes passengers

20 Cosmic radiation regulation Plane cruising altitude range Ground level High altitude peaks 96/29/Euratom Article 2 does not apply to cosmic radiation prevailing at ground level.

21 Everest climb dose estimate Dose assessment needs to include: Dose received during air travel to/from mountain plus dose received when on the ground at altitude minus dose received if stayed at home in UK Calculated dose (microsv) Dose estimate for climbing Everest is ~ 1 millisv alba.com/images/irpa13poster.pdf

22 Everest climb dose measurement Cosmic radiation doses received by members of the public whilst on high altitude expeditions are excluded from UK legislative requirements. Radiation doses of Everest climbers never previously measured. In the pre monsoon season of 2013 this was undertaken.

23 Everest climb dose measurement Parameters to consider: Radiation field to be measured Weight of detectors Operational range of batteries in detectors Recharging of detector batteries Operation of detectors LCD screens Detector operating temperatures Contingency in measurements

24 Everest climb dose measurement Radiation field to be measured Source:

25 Everest climb dose measurement Weight of detectors Detectors

26 Everest climb dose measurement Operating range of batteries in detectors: NiCd and NiMH = down to about 5 C Silver oxide = down to about 10 C Alkaline = down to about 15 C (Output drops rapidly below room temperature) Lithium ion = down to about 40 C (Output drops slowly as the temperature drops) Source:

27 Everest climb dose measurement Recharging of detector batteries?

28 Everest climb dose measurement Operation of detectors Require minimal operator interaction to avoid frostbite

29 Everest climb dose measurement LCD Screens: 10 C to +60 C standard operating range Typical maximum altitude specification 10,000 to 12,000 feet (3,050m to 3,660m) Source: Failure Mechanisms in Electronic Products at High Altitudes, Blattau et al.

30 Everest climb dose measurement Detector operating temperatures /06/ /03/ /04/ /04/ /05/ /05/ Temperature (degrees Celsius)

31 Everest climb dose measurement Contingency in measurements

32 Everest climb dose measurement Detectors selected Mirion Technologies Instadose v2 Direct Ion Storage Device Set to automatically record accrued dose every 2 hours

33 Everest climb dose measurement Detectors selected Tracerco T404 Personal Electronic Dosemeter Single Energy Compensated Geiger Müller Tube Able to extract minute by minute readings after use Able to extract data infield Field rechargeable Up to 300 hours operation 20 C to +50 C operating range.

34 Everest climb dose measurement Detectors selected Kromek GR 1 gamma ray spectrometer Not used above 17,000 due to limitations of netbook (LCD failure) 1 cm 3 CZT detector Only 60g

35 Everest climb dose measurement 80 Counts in 600 seconds Using Kromek GR 1 gamma ray spectrometer, no major difference in gamma energy intensities seen between 5,000 ft and 17,000 ft Gamma spectrometer energy (kev) Kathmandu Base Camp

36 Everest climb dose measurement Instadose v2 prototype measured data 1 detector stayed in Scotland (background) 2 detectors stayed at base camp 2 detectors went to the summit of Everest Instadose v2 was in development the units used were not hermetically sealed.

37 Accrued Dose (microsieverts) Everest climb dose measurement Instadose v2 measured data Everest summit

38 Dose rate (microsieverts per hour) Everest climb dose measurement Instadose v2 measured data Everest summit Negative dose rates?

39 Everest climb dose measurement Instadose v2 prototype measured data Results affected by temperature Affected by pressure? Radiation measurements on all detectors would have experienced a varying cosmic radiation field

40 Everest climb dose measurement Tracerco T404 PED measured data 2 detectors went to Everest Each one cycled between being the unit in use and swapping over to be recharged

41 Everest climb dose measurement

42 Everest climb dose measurement International flights

43 Everest climb dose measurement Acclimatisation trek Flight Lukla to KTM

44 Everest climb dose measurement Transit into Tibet Everest Base Camp

45 Everest climb dose measurement Advanced Base Camp

46 Everest climb dose measurement Everest summit push

47 Everest climb dose measurement Return to KTM

48 Everest climb dose measurement Base Camp measurements as expected

49 Everest climb dose measurement Advanced Base Camp measurements lower than predicted

50 Everest climb dose measurement All of this time spent above north col

51 Everest climb dose measurement T404 dose delta = 400 microsv

52 Everest climb dose measurement Contributors to cosmic radiation dose at altitude

53 Everest climb dose measurement T404 measured ~400 microsv as expedition dose. If assume the T404 detected everything except neutrons and if assume an average altitude of 5,500m then 5 / 9 ths of dose comes from unassessed neutron dose so we can determine a total dose value.

54 Climbing Everest Dose gives a estimates member of the UK public about 1 millisv of cosmic radiation Text dose. Text 2

55 Need to keep dose in perspective 1 millisv carries a risk of 1 in ~10,000 of dying per year. High altitude environments are dangerous.

56 Number of deaths on Everest Need to keep dose in perspective Year Source: Himalayan Database and

57 Need to keep dose in perspective 100% Death rate on Everest per successful summit 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% Year Source: Himalayan Database and

58 Need to keep dose in perspective 1 in 28* risk of death on Everest per summiteer. Causes of death on Everest: * = risk at end of 2013.

59 High altitude expeditions 7 summits

60 High altitude expeditions 7 summits By 2011, 348 people had climbed the 7 summits Some were mountain guides who were occupationally exposed to cosmic radiations Many were members of the public who had paid to climb them

61 High altitude expeditions 7 summits Ian McKeever climbed the 7 summits in less than 6 months. Source:

62 High altitude expeditions 7 summits Climbing the 7 summits results in about 2.2 millisv of dose. alba.com/images/irpa13poster.pdf

63 Conclusions Members of the public are receiving significant cosmic radiation doses (>1 millisv) during high altitude expeditions sold by UK companies. Most unaware of cosmic radiation exposure. All are aware of other more serious threats to life in these environments. Expedition companies should consider providing information to clients on this additional hazard as a duty of care. No current, or foreseeable regulations, have been breached by exposing these members of the public.

64 Acknowledgements

65 Thanks for listening Questions? alba.com alba.com