Farfield Monitoring of Rogue Nuclear Activity with an

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 December 16, 2005 Eugene H. Guillian / Neutrino Geophysics Conference 1

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

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

Detector Module Specifications 100 m (1) Required target mass > ≈ 1 Megaton 100 m 0 10 (2) Required exposure time ≈ 1 year (reactor) (10 -second burst for bomb) (3) Target material Water + 0. 2% Gd. Cl 3 Cheap GADZOOKS! Enable Antineutrino Detection Super-K with Gadolinium Eugene H. Guillian / Neutrino Geophysics December 16, 2005 J. F. Beacom & M. R. Vagins, Phys. Rev. Lett. 93, 171101 Conference (2004) 4 m

Detection Mechanism Inverse Beta Decay Prompt Event Cherenkov radiation ≈ 20µs Delayed Event n + Gd + g cascade Evis ≈ 3~8 Me. V December 16, 2005 Eugene H. Guillian / Neutrino Geophysics Conference 5

Neutrino Energy Spectrum GADZOOKS! Threshold • En > 3. 8 Me. V Kam. LAND Threshold • En > 3. 4 Me. V GADZOOKS! Efficiency 58% of entire spectrum (En > 1. 8 Me. V) 82% of Kam. LAND efficiency December 16, 2005 Eugene H. Guillian / Neutrino Geophysics Conference 6

A Very Basic Look at the Detector Hardware 100 m ~$120 Million @ $1000 per unit Photo-Sensor Requirement ≈ 120, 000 units (10 Super-Kamiokande) 0 m 100 m 10 Gadolinium ~$10 Million @ $3 / kg 2000 metric tons Cost? Water Purification 200 Super-Kamiokande’s capacity The cost of just one module looks to be easily about $500 Million! December 16, 2005 Eugene H. Guillian / Neutrino Geophysics Conference 7

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

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 December 16, 2005 Eugene H. Guillian / Neutrino Geophysics Conference 9

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

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

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

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

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

Rogue Activity Detection Strategy Input Output (1) Hypothesis “No rogue activity is taking place” Bi events expected in detector “i” Log-Likelihood Function (2) Observation Loglikelihood function value Ni events observed in detector “i” December 16, 2005 Eugene H. Guillian / Neutrino Geophysics Conference 15

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

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

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

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

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 December 16, 2005 Eugene H. Guillian / Neutrino Geophysics Conference 20

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

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

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

Map of Signal Strength Rogue Activity 2000 MWth December 16, 2005 Eugene H. Guillian / Neutrino Geophysics Conference 24

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

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

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

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

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

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 December 16, 2005 Eugene H. Guillian / Neutrino Geophysics Conference 30

P 99 Map for 5° Array MWth December 16, 2005 Eugene H. Guillian / Neutrino Geophysics Conference 31

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

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

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

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

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

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 December 16, 2005 Eugene H. Guillian / Neutrino Geophysics Conference 37

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

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

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

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

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

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 TWth Total commercial nuclear activity ≈ 1 TWth If a terawatt-level georeactor does exist, the background level for rogue activity monitoring increases significantly! December 16, 2005 Eugene H. Guillian / Neutrino Geophysics Conference 43

log 10 Background No Georeactor Ratio 3 TWth / No Georeactor log 10 Background 3 TWth Georeactor December 16, 2005 Eugene H. Guillian / Neutrino Geophysics Conference 44

Fission Bomb Monitoring Fission Bomb • Assume 100% detection efficiency for En > 1. 8 Me. V • Integrated over 10 sec. burst time The background from reactors is small (in most places) because of the 10 -second window December 16, 2005 Eugene H. Guillian / Neutrino Geophysics Conference 45

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: December 16, 2005 Eugene H. Guillian / Neutrino Geophysics Conference • 10 -Megaton 46 modules

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

“Y 99” for Bomb Monitoring kton TNT December 16, 2005 Eugene H. Guillian / Neutrino Geophysics Conference 48

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

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

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

Array Configurations Global Monitoring Regime Regional Monitoring Regime Want sensitivity to anywhere on Earth Want 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 Smaller Modules Will Do • 10 Megatons • 1 year exposure • 1 Megatons • 1 year exposure December 16, 2005 Eugene H. Guillian / Neutrino Geophysics Conference 52

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 (3) observation Use a statistical technique (minimum log-likelihood) to & expectation estimate the position & power of the rogue activity December 16, 2005 Eugene H. Guillian / Neutrino Geophysics Conference 53

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

Antineutrino Detection Rate for H 2 O + Gd. Cl 3 Detector Reactor • Assume 100% detection efficiency for En > 1. 8 Me. V Fission Bomb • Assume 100% detection efficiency for En > 1. 8 Me. V • Integrated over 10 sec. burst time December 16, 2005 Eugene H. Guillian / Neutrino Geophysics Conference 55

Antineutrino Detection Rate for H 2 O + Gd. Cl 3 Detectors Reactor • Assume 100% detection efficiency for En > 1. 8 Me. V Fission Bomb • Assume 100% detection efficiency for En > 1. 8 Me. V • Integrated over 10 sec. burst time December 16, 2005 Eugene H. Guillian / Neutrino Geophysics Conference 56

Background Processes Antineutrinos from sources other than the rogue reactor • Commercial nuclear reactors • Geo-neutrinos • Georeactor (possibly) Non-antineutrino background mimicking antineutrino events • Cosmic rays • Radioactivity in the detector • Require En > 3. 4 Me. V • Place detector at > 3 km depth under water • Fiducial volume cut + radon free environment December 16, 2005 Eugene H. Guillian / Neutrino Geophysics Conference 57

Antineutrino Detection with a H 2 O + Gd. Cl 3 Detector Inverse beta decay on target hydrogen nuclei ne + p n + e + ≈ 20 µs Delayed Event n + Gd Gd* Gd + g cascade Ecascade ≈ 3~8 Me. V Prompt Event Physics Threshold: En > 1. 8 Me. V Ee ≈ En – 1. 3 Me. V Detector Threshold: Ee > 2. 5 Me. V En > 3. 8 Me. V Eugene H. Guillian / Neutrino Geophysics December 16, 2005 by Gd @ 0. 2% concentration 90% neutron captured Conference 58

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

3. 5 The effect of commercial nuclear reactors on the detection sensitivity for a rogue nuclear reactor Assume that a rogue reactor with P = 250 MWth is operating just north of Hawaii Top: Middle: log 10 S log 10 B 7. 0 # events from rogue reactor # events from commercial reactors 1. 5 Bottom: • Detector target mass = 10 megatons • 1 year exposure • Detectors allowed only in oceans & large Eugene H. Guillian / Neutrino Geophysics December 16, 2005 lakes Conference • 100% detection efficiency 60

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

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