1. December 16, 2005Eugene H. Guillian / Neutrino Geophysics Conference1 Far-field Monitoring of Rogue Nuclear Activity with an Array of Large Antineutrino Detectors Neutrino Geophysics Conference University of Hawaii, Manoa December 14-16, 2005 Eugene H. Guillian University of Hawaii, Manoa

2. December 16, 2005Eugene H. Guillian / Neutrino Geophysics Conference2 Rogue Nuclear Activity Two Types: Fission ReactorFission Bomb Purpose: Produce weapons- grade material Test to make sure bomb explodes Size: < ≈ 100 MW th 1 kton TNT Commercial Reactor ≈ 2500 MW th First Atomic Bombs 10-20 kton

3. December 16, 2005Eugene H. Guillian / Neutrino Geophysics Conference3 Characteristics of Rogue Nuclear Activity (1) Small compared to “normal” activities (2) Operated by a “hostile” regime Need large detector to compensate for small signalWon’t be allowed to monitor nearby (≈100 km) Signal decreases as 1 / distance 2

4. December 16, 2005Eugene H. Guillian / Neutrino Geophysics Conference4 Detector Module Specifications (1) Required target mass > ≈ 1 Megaton (2) Required exposure time ≈ 1year (reactor) (10-second burst for bomb) 100 m (3) Target material  Water + 0.2% GdCl 3 Cheap Enable Antineutrino Detection GADZOOKS! Super-K with Gadolinium J. F. Beacom & M. R. Vagins, Phys. Rev. Lett. 93, 171101 (2004)

5. December 16, 2005Eugene H. Guillian / Neutrino Geophysics Conference5 Detection Mechanism Inverse Beta Decay Delayed Event ≈ 20µs n + Gd  Gd +  cascade E vis ≈ 3~8 MeV Prompt Event Cherenkov radiation

6. December 16, 2005Eugene H. Guillian / Neutrino Geophysics Conference6 Neutrino Energy Spectrum GADZOOKS! Threshold E > 3.8 MeV KamLAND Threshold E > 3.4 MeV GADZOOKS! Efficiency 58% of entire spectrum (E > 1.8 MeV) 82% of KamLAND efficiency

7. December 16, 2005Eugene H. Guillian / Neutrino Geophysics Conference7 A Very Basic Look at the Detector Hardware 100 m Photo-Sensor Requirement ≈ 120,000 units (10  Super-Kamiokande) Gadolinium 2000 metric tons Water Purification 200  Super-Kamiokande’s capacity ~$120 Million @ $1000 per unit ~$10 Million @ $3 / kg Cost? The cost of just one module looks to be easily about $500 Million!

8. December 16, 2005Eugene H. Guillian / Neutrino Geophysics Conference8 Is a Megaton Module Outlandish? The linear dimensions are not that much larger than those of Super- Kamiokande Challenges Deep-Ocean environment Remote operations Mega-structure engineering

9. December 16, 2005Eugene H. Guillian / Neutrino Geophysics Conference9 Shielding from Cosmic Rays Super-Kamiokande Shielded by 1000 m of rock (equivalent to 2700 m of water) Mitsui Mining Co. property Super-Kamoikande (SNOLAB, Gran Sasso, Baksan, Homestake, IMB, etc.) would have cost too much if shielding had to be erected from scratch! For the megaton module array, we assume that cost of shielding on land is prohibitive. Ocean & Lake = Affordable Shielding

10. December 16, 2005Eugene H. Guillian / Neutrino Geophysics Conference10 Array Configurations Global 1.5°  5° 2.Equidistant 3.Coast-Hugging Regional North Korea ≈ 1000 modules 10 Megatons per module 1 year exposure Several modules 1 Megaton per module 1 year exposure

11. December 16, 2005Eugene H. Guillian / Neutrino Geophysics Conference11 Global Array 1 5º  5º Array Total of 1596 modules

12. December 16, 2005Eugene H. Guillian / Neutrino Geophysics Conference12 Global Array 2 Equidistant Array Total of 623 modules Minimum nearest- neighbor distance ≈ 600 km

13. December 16, 2005Eugene H. Guillian / Neutrino Geophysics Conference13 Global Array 3 Coast-hugging Array Total of 1482 modules Minimum nearest- neighbor distance ≈ 100 km Modules removed from coast line by ≈ 100 km

14. December 16, 2005Eugene H. Guillian / Neutrino Geophysics Conference14 Regional Array North Korea Choose locations based on sensitivity map (red dots are candidate module positions) 250 MW th fission reactor deep inside of North Korea Background from commercial nuclear reactors

15. December 16, 2005Eugene H. Guillian / Neutrino Geophysics Conference15 Rogue Activity Detection Strategy Log-Likelihood Function InputOutput (1)Hypothesis (2)Observation Log-likelihood function value “No rogue activity is taking place”  B i events expected in detector “ i ” N i events observed in detector “ i ”

16. December 16, 2005Eugene H. Guillian / Neutrino Geophysics Conference16 Scenario 1: No Rogue Activity Log-Likelihood Function InputOutput (1)Hypothesis (2)Observation Large value Hypothesis agrees with Observation! (most of the time…)

17. December 16, 2005Eugene H. Guillian / Neutrino Geophysics Conference17 Scenario 2: Small Rogue Activity Log-Likelihood Function InputOutput (1)Hypothesis (2)Observation Slightly biased to lower values (but can’t distinguish from null hypothesis) Hypothesis maybe agrees with Observation, but maybe not!

18. December 16, 2005Eugene H. Guillian / Neutrino Geophysics Conference18 Scenario 3: Large Rogue Activity Log-Likelihood Function InputOutput (1)Hypothesis (2)Observation Biased to lower values Hypothesis dis agrees with Observation! Confidently reject null hypothesis

19. December 16, 2005Eugene H. Guillian / Neutrino Geophysics Conference19 Likelihood Distribution for Scenario 1 The value varies from measurement to measurement because of statistical variation The distribution is known a priori 1% False Positive If value < threshold, ALARM!

20. December 16, 2005Eugene H. Guillian / Neutrino Geophysics Conference20 Likelihood Distribution for Scenario 2 If the rogue power is small, the bias is too small Large overlap with null distribution False negative happens too often

21. December 16, 2005Eugene H. Guillian / Neutrino Geophysics Conference21 Likelihood Distribution for Scenario 3 Define a quantity called “P 99 ” P 99 = the power above which the chance of false negative is < 1%

22. December 16, 2005Eugene H. Guillian / Neutrino Geophysics Conference22 Illustration of the Detection Strategy If no rogue activity takes place, module 1, 2, & 3 detects B 1, B 2, and B 3 events The size of the excess goes as: Power / Distance 2 With rogue activity, module 1, 2, and 3 sees an extra S 1, S 2, and S 3 events

23. December 16, 2005Eugene H. Guillian / Neutrino Geophysics Conference23 B = # background events S = # signal events Signal Strength = statistical uncertainty Signal Strength S S

24. December 16, 2005Eugene H. Guillian / Neutrino Geophysics Conference24 Map of Signal Strength Rogue Activity 2000 MW th

25. December 16, 2005Eugene H. Guillian / Neutrino Geophysics Conference25 Equidistant Detector Array Configuration 10 Megaton per module 1 year exposure

26. December 16, 2005Eugene H. Guillian / Neutrino Geophysics Conference26 Detectors with Signal Strength > 3

27. December 16, 2005Eugene H. Guillian / Neutrino Geophysics Conference27 Detectors with Signal Strength > 2

28. December 16, 2005Eugene H. Guillian / Neutrino Geophysics Conference28 Detectors with Signal Strength > 1

29. December 16, 2005Eugene H. Guillian / Neutrino Geophysics Conference29 Signatures of Rogue Activity (1)Log-likelihood function is below threshold (2)Cluster of near-by detectors with significant excess

30. December 16, 2005Eugene H. Guillian / Neutrino Geophysics Conference30 Global Array Performance For each array configuration, make a map of P 99 Procedure for making map: 1.Vary the rogue reactor position 2.At each location, determine P 99

31. December 16, 2005Eugene H. Guillian / Neutrino Geophysics Conference31 P 99 Map for 5°  5° Array MW th

32. December 16, 2005Eugene H. Guillian / Neutrino Geophysics Conference32 P 99 Map for Equidistant Array Scaled to 1596 Modules MW th

33. December 16, 2005Eugene H. Guillian / Neutrino Geophysics Conference33 P 99 Map for Coast-hugging Array Scaled to 1596 Modules MW th

34. December 16, 2005Eugene H. Guillian / Neutrino Geophysics Conference34 5º  5º Equidistant Coast-Hugging P 99 Summary LocationP 99 In Water< 100 MW th W/in several 100 km of coast Several 100 MW th Deep in continent Up to 2000 MW th

35. December 16, 2005Eugene H. Guillian / Neutrino Geophysics Conference35 Regional Monitoring Example: A rogue reactor in North Korea Signal Background Signal Strength About the Plots Signal Rogue power = 250 MW th Detector mass = 1 Megaton Exposure = 1 year Background Commercial nuclear reactors 1 Megaton 1 year

36. December 16, 2005Eugene H. Guillian / Neutrino Geophysics Conference36 Detector Locations 23 candidate locations based on map of sensitivity

37. December 16, 2005Eugene H. Guillian / Neutrino Geophysics Conference37 Performance of Various Array Configurations Consider configurations with 2, 3, and 4 detector modules For each configuration, determine: P 99 Probable location of rogue reactor

38. December 16, 2005Eugene H. Guillian / Neutrino Geophysics Conference38 Two Modules 95% Confidence 99% Confidence P 99 = 250 MW th Confidence = probability that rogue activity is taking place inside of band  2 saturates above 20 in the map

39. December 16, 2005Eugene H. Guillian / Neutrino Geophysics Conference39 Two Modules 95% Confidence 99% Confidence P 99 = 120 MW th

40. December 16, 2005Eugene H. Guillian / Neutrino Geophysics Conference40 Three Modules 95% Confidence 99% Confidence P 99 = 626 MW th

41. December 16, 2005Eugene H. Guillian / Neutrino Geophysics Conference41 Four Modules 95% Confidence 99% Confidence P 99 = 336 MW th

42. December 16, 2005Eugene H. Guillian / Neutrino Geophysics Conference42 Four Modules 95% Confidence 99% Confidence P 99 = 502 MW th

43. December 16, 2005Eugene H. Guillian / Neutrino Geophysics Conference43 What if a Georeactor Exists? The Georeactor Hypothesis: Unorthodox, but surprising things can happen…. If it does exist, its power is likely to be 1-10 TW th Total commercial nuclear activity ≈ 1 TW th If a terawatt-level georeactor does exist, the background level for rogue activity monitoring increases significantly!

44. December 16, 2005Eugene H. Guillian / Neutrino Geophysics Conference44 log 10 Background No Georeactor log 10 Background 3 TW th Georeactor Ratio 3 TW th / No Georeactor

45. December 16, 2005Eugene H. Guillian / Neutrino Geophysics Conference45 Fission Bomb Monitoring Fission Bomb Assume 100% detection efficiency for E n > 1.8 MeV Integrated over 10 sec. burst time The background from reactors is small (in most places) because of the 10-second window

46. December 16, 2005Eugene H. Guillian / Neutrino Geophysics Conference46 log 10 (signal) from 1-kiloton bomb just north of Hawaii log 10 (background) from commercial reactors log 10 (S/sqrt(S+B)) For all three plots: 10-Megaton modules 10-second exposure

47. December 16, 2005Eugene H. Guillian / Neutrino Geophysics Conference47 log 10 (background) from commercial reactors + 3 TW th georeactor

48. December 16, 2005Eugene H. Guillian / Neutrino Geophysics Conference48 “Y99” for Bomb Monitoring kton TNT

49. December 16, 2005Eugene H. Guillian / Neutrino Geophysics Conference49 Conclusions Untargeted global monitoring requires a very large array ≈ 1000 modules 10-Megaton per module 1-year exposure time A targeted regional monitoring regime looks credible Several modules 1-Megaton per module 1-year exposure time P 99 ≈ 100 MW th and localization within 100 km are attainable if: 1.At least one module is placed at about 100 km from the rogue activity 2.At least three modules are placed strategically at greater distances The existence of a terawatt-level georeactor increases the background level significantly This must be established before-hand Experiments like Hano Hano are crucial Obstacles toward realizing far-field monitoring Cost (several  $100 million per module) Lack of experience with deep-ocean environment In Summary: Targeted regional monitoring can deter rogue activity at a realistic level at a cost of several billion dollars The detector technology is mostly well- established Uncertainty with deep-ocean environment New developments in photo-detector technology would help greatly

50. December 16, 2005Eugene H. Guillian / Neutrino Geophysics Conference50 Appendix

51. December 16, 2005Eugene H. Guillian / Neutrino Geophysics Conference51 Cosmic Ray Background Like bullets! Occasionally they destroy atomic nuclei Unstable nucleiSometimes indistinguishable from antineutrinos!

52. December 16, 2005Eugene H. Guillian / Neutrino Geophysics Conference52 Array Configurations Global Monitoring RegimeRegional Monitoring Regime Want sensitivity to anywhere on EarthWant sensitivity to a well-defined region Can’t optimize module positioning Module positions can be optimized because of prior knowledge of likely locations Larger Modules Required 10 Megatons 1 year exposure Smaller Modules Will Do 1 Megatons 1 year exposure

53. December 16, 2005Eugene H. Guillian / Neutrino Geophysics Conference53 Rogue Activity Detection Strategy (1) Assume that no rogue activity is taking place (2) If this assumption is incorrect AND if the rogue activity is sufficiently large, there would be a discrepancy between observation & expectation (3) Use a statistical technique (minimum log-likelihood) to estimate the position & power of the rogue activity

54. December 16, 2005Eugene H. Guillian / Neutrino Geophysics Conference54 Seeing the Rogue Activity Above Random Fluctuations Observed Number of Events Background only Observed Number of Events Small Signal + Background Random Statistical Fluctuation Large Signal + Background

55. December 16, 2005Eugene H. Guillian / Neutrino Geophysics Conference55 Antineutrino Detection Rate for H 2 O + GdCl 3 Detector Reactor Assume 100% detection efficiency for E n > 1.8 MeV Fission Bomb Assume 100% detection efficiency for E n > 1.8 MeV Integrated over 10 sec. burst time

56. December 16, 2005Eugene H. Guillian / Neutrino Geophysics Conference56 Antineutrino Detection Rate for H 2 O + GdCl 3 Detectors Reactor Assume 100% detection efficiency for E n > 1.8 MeV Fission Bomb Assume 100% detection efficiency for E n > 1.8 MeV Integrated over 10 sec. burst time

57. December 16, 2005Eugene H. Guillian / Neutrino Geophysics Conference57 Background Processes Antineutrinos from sources other than the rogue reactor Non-antineutrino background mimicking antineutrino events Commercial nuclear reactors Geo-neutrinos Georeactor (possibly) Cosmic rays Radioactivity in the detector Require E n > 3.4 MeV Place detector at > 3 km depth under water Fiducial volume cut + radon free environment

58. December 16, 2005Eugene H. Guillian / Neutrino Geophysics Conference58 Antineutrino Detection with a H 2 O + GdCl 3 Detector Inverse beta decay on target hydrogen nuclei n e + p  n + e + Prompt Event Delayed Event E n > 1.8 MeV E e ≈ E n – 1.3 MeV Detector Threshold:  E e > 2.5 MeV E n > 3.8 MeV Physics Threshold: ≈ 20 µs n + Gd  Gd* E cascade ≈ 3~8 MeV Gd + g cascade 90% neutron captured by Gd @ 0.2% concentration

59. December 16, 2005Eugene H. Guillian / Neutrino Geophysics Conference59 Commercial Nuclear Reactors 433 reactors Total thermal power ≈ 1 TW

60. December 16, 2005Eugene H. Guillian / Neutrino Geophysics Conference60 The effect of commercial nuclear reactors on the detection sensitivity for a rogue nuclear reactor Assume that a rogue reactor with P = 250 MW th is operating just north of Hawaii Top: Middle: Bottom: log 10 S log 10 B # events from rogue reactor # events from commercial reactors 3.5 7.0 1.5 Detector target mass = 10 megatons 1 year exposure Detectors allowed only in oceans & large lakes 100% detection efficiency S, B, and S/sqrt(S+B)

61. December 16, 2005Eugene H. Guillian / Neutrino Geophysics Conference61 Possible Detector Locations 23 Locations based on S/sqrt(S+B) log 10 (S) log 10 (B) Map of S, B, and S/sqrt(S+B) for 1 megaton target exposed for 1 year

62. December 16, 2005Eugene H. Guillian / Neutrino Geophysics Conference62 If a Geo-Reactor Exists… If it does exist, its power is expected to be 1 ~ 10 TW th, 3 TW th being the most favored value. The total power from all commercial reactors world-wide ≈ 1 TW th In most locations around the world, antineutrinos from a georeactor would outnumber those from commercial reactors 3 TW th Georeactor