Optimisation of Noble Gas Installation Locations using Meteorological Criteria

Ian Hoffman, Jing Yi, Kurt Ungar Radiation Protection Bureau of Health Canada, Ottawa, ON Canada

Dov Bensimon, Réal D’Amours, René Sevranckx, Richard Hogue, Jean-Philippe Gauthier Canadian Meteorological Centre, Dorval, QC

Paul Eslinger, Derek Haas, Harry Miley, Brian Schrom Pacific Northwest National Laboratory

Paul Saey University of Vienna

Introduction Many improvements in knowledge since the original network was

designed in 1998 1.  Improvements in calculation capacity and methodology, coupled

with a long history of station specific ATM models, and experimental observations

2.  Better knowledge of background sources and their surprising strength (20% of the source term from 1 kt explosion) and their impact on analysis interpretation

3.  More knowledge of state-of-the-art NG analysers and their development potential

A new assessment of the network design could provide benefits in monitoring capability.

Goals of Study

Determine optimal sites for the NG systems that have yet to begin the installation process through a consideration of 2 criteria: 1.  Globally balanced detection capability accomplished by using a

figure of merit (FOM) to assess IMS locations 2.  Ability to discriminate radioxenon emitters and their impact on

potential explosion observations

We use the INGE results collected to date to inform design, and give special consideration to the tropics - station placement and equipment deployed

Improve the knowledge the NG network generates by considering alternate IMS sites for construction of NG systems (background knowledge and coverage)

Figure of Merit – Global Coverage

We use a constant source term with all NG systems having a detection threshold of 0.3 mBq/m3 (133Xe) and the ECMWF SRS files to count detections in excess of MDC.

FOM = Sum of all detected explosions at a grid point Sum of all detected explosions at the best grid point

The FOM denominator is the maximum number of detections at a single grid point (1°x1°) in the 39 station network

CTBT/PC-7 Network Coverage

133Xe Annual (2009 data) – MDC 0.3 mBq/m3

• Tropics are less covered than other regions, overall sensitivity is generally good

• Worst areas can be ~1000x less sensitive than the best areas

Improved MDC Network

39 Station Network Annual (2009 data) – 0.06 mBq/m3

PC-7 network

Full Network - MDC 0.06 mBq/m3

Planned network

5-10 times better sensitivity than normal in mid/polar latitudes regions while equatorial area is typically 5-10x worse than the best performance of 39 station network

Background Sources

We account for the impact of background sources on network performance by:

•  Assigning a source term to all planned and operating facilities and “score” MA detections (105 maximum score/coordinate)

•  “Score” is a linear normalised value that is summed for all stations/nuclear facilities –  0.06 mBq/m3 (score 0.02) to 3 mBq/m3 (score 1) –  Values greater than 3 mBq/m3 are considered 1 (quantified

accurately ± 10% or better)

Country Facility Type Name Daily source (Bq/m3)

Argentina Separations CNEA Ezeiza 1.00E+10

Australia Separations Lucas Heights - ANSTO 1.10E+12

South Africa Separations Pelindaba - NECSA 1.30E+13

Canada Separations NRU Chalk River 1.60E+13

Belgium Separations Fleurus - IRE 4.60E+12

Netherlands Separations Petten - Covidien 2.50E+09

S. Korea Separations Hanaro 1.6E+12

Power Reactor

All other global sites having Power Reactors(190 sites or 400+ reactors) 1.00E+09 per reactor

133Xe Background Sources

Note: the 7 facilities were considered the major xenon sources in the world

• CRL and Fleurus are the dominant detected background sources

• Power and research reactors are generally not significant – only 5 stations were sensitive to “Others”

• Hanaro was added as potential MI site

• 45 IMS locations are sensitive to background sources

• Planned network has 19 of the 45 locations sensitive to background sources

CAP15 CAP17 DEP33 FRP28 ISP34 MRP43 MNP45 RN41 RN53 SEP63 USP72 USP74 USP75

CAP17 DEP33 FRP28 ISP34 NOP49 RN41 RN53 RUP54 RUP56 RUP59 RUP61 SEP63 ARP01

AUP08 AUP10 FRP29 FRP30 GBP66 GBP67 RN12 RN25 RN62 TZP64

AUP04 AUP06 NZP46 NZP47

JPP37 JPP38 PHP52 RN20 RN22 RUP58 RUP60 USP78

Optimised Background Network

We now construct a network optimised for global coverage (40 most sensitive stations) and any remaining stations sensitive to background sources (17 stations). Total Network is then 57 stations

57 Station Network Annual (2009 data) – 0.06 mBq/m3

Remaining Noble Gas Systems

There are five sites remaining in original network design that have not begun the installation process

•  What detection sensitivity and background assessment improvements could be made if their locations were altered?

•  What happens if we move the Antarctic system to a new location?

One Proposal for Alternate NG IMS Sites for Remaining Systems to be Installed

Planned Site Alternate Site Reason RN62 (South Africa) JPP37 (Japan) Best for potential

Hanaro MI operation RN69 (Antarctica) CLP18 (Chile) “Almost” Antarctica

RN48 (Niger) TZP64 (Tanzania) Best for discounting Pelindaba

RN25 (Ethiopia) RN39 (Kiribati) Coverage for “hole” in Pacific

RN36 (Iran) is unchanged to help with equatorial coverage

Modified Network PC-7 network

Conclusions

1.  This FOM approach is capable of providing guidance on IMS site selection to derive maximum benefit from NG network •  Discrimination of background and potential background sources

from observations is necessary and can be improved with careful site selection

•  Equatorial coverage (areas of low sensitivity) can be improved 2.  52 day integration gives a reasonable network – However the

data presented here represents an average for a particular year: •  On a daily basis we would select a different 40 stations depending on annual/

season/climate shifts. The best 40 stations fluctuates. •  Examining other years may provide further insight into the variability of the optimal

network.

Conclusions

3.  The Antarctic system could be installed elsewhere with negligible impact using this FOM approach.

4.  Equatorial coverage can only be gained by installing systems in the tropics

5.  More stations are needed in locations to assess background sources contributions for the verification mission •  Only 6 big background sources have any meaningful impact •  More stations are useful to provide balanced global

coverage and understand background