Transcript Anti-Neutrino Detection, Earth Reactor

“Georeactor” Detection with
Gigaton Antineutrino
Detectors
Neutrinos and Arms Control Workshop
February 5, 2004
Eugene Guillian
University of Hawaii
Finding Hidden Nuclear
Reactors
 The focus of this conference is on
detecting hidden man-made nuclear
reactors
 But there may be a natural nuclear
reactor hidden in the Earth‘s core!
The “Georeactor” Model
 An unorthodox model
 Chief proponent: J.M.Herndon
 The model
 A fuel breeder fission reactor in the Earth‘s
sub-core
 Size: ~4 miles radius
 Power: 3-10 TW
Man-made vs. Geo
 Man-made:
 (~500 reactors) x (~2 GW) = 1 TW
 Georeactor:
 3-10 TW
If a georeactor exists, it will be the
dominant source of antineutrinos!
Outline of Presentation
1. Georeactor detection strategy
2. Describe the georeactor model
3. Can a georeactor be detected with
KamLAND?
4. What minimum conditions are necessary
to detect a georeactor?
Strategy for Georeactor
Detection
 If a georeactor does not exist…
• From commercial power plants
• Depends on the net power output
• Rate corrected to 100% livetime & efficiency
• Assume no neutrino oscillation
• Corrected to 100% livetime & efficiency
• Neutrino oscillation effect included
Slope = average neutrino oscillation
survival probability
2f = Spread
<R> = Average
f = Spread
Rmax = (1+f)<R>
Rmin = (1-f)<R>
<R> = Average
Y-inercept = Georeactor Rate
0
Strategy for Georeactor
Detection
 If a georeactor does exist…
10 TW georeactor
Nonzero Y-intercept
(0.0742 events/day @ 10 TW)
Georeactor Detection
Strategy
 Plot observed rate against expected
background rate
 Fit line through data
 Y-intercept = georeactor rate
The Georeactor Model
 What we can all agree on:
1. The Earth is made of the same stuff as
meteorites
2. In its earliest stages, the Earth was molten
3. The Earth gradually cooled, leaving all but
the outer core in solid form
Melting a Rock
 Very high temperature:
 All of rock in liquid form
 Lower temperature:
 Slag solidifies
 Alloys and opaque minerals still in liquid
form
 Slag floats
Apply This Observation to the
Earth
Very Hot!
All Liquid
Apply This Observation to the
Earth
Cooler
Slag solidifies,
Floats to surface
Fission Fuel Trapped by
Slag?
 Actinides (U, Th, etc.) are lithophile (or
oxiphile)
 If given a chance, they combine with slag
 Slag rises to surface as the Earth cools
 Fission fuel found in the Earth‘s crust and
mantle, not in the core
 Therefore, a georeactor cannot form!
Fission Fuel Trapped by
Slag?
 Actinides (U, Th, etc.) are lithophile (or
oxiphile)
 If given a chance, they combine with slag
 Slag rises to surface as the Earth cools
 Fission fuel found in the Earth‘s crust and
mantle, not in the core
 Therefore, a georeactor cannot form!
If there is enough oxygen
If There Were Insufficient
Oxygen
 Some of the U, Th will be in alloy and
sulfide form
 These sink as the Earth cools
 Elements with largest atomic number
should sink most
 Therefore, fission fuel should sink to the
center of the Earth
 Georeactor can form!
How Can One Tell if the Earth
Is Oxygen Poor or Not?
 Slag has high oxygen content
 Alloys and opaque minerals have low
oxygen content
 Alloy/Slag mass ratio
 Strong correlation with oxygen content in a
meteorite
Oxygen Level of the Earth
Less
Slag
Enstatite Chrondite
Meteorite Data
Alloy
Slag
More
Slag
Ordinary Chrondite
Low
Oxygen Content
High
Oxygen Level of the Earth
Less
Slag
Alloy
Slag
Free
actinides
Actinides
trapped in
slag
More
Slag
Low
Oxygen Content
High
Oxygen Level of the Earth
Less
Slag
Alloy = Core
Slag
Mantle
Alloy
Slag
More
Slag
Low
Oxygen Content
High
Oxygen Level of the Earth
Less
Slag
Core/Mantle ratio
from seismic data
Alloy
Slag
More
Slag
Low
Oxygen Content
High
Measuring the Earth‘s
Oxidation Level
 Equate the following:
 Core
 alloy & opaque minerals
 Mantle + Crust  silicates
 Obtain Earth‘s mass ratio from density profile
measured with seismic data
 Compare with corresponding ratio in meteorites.
 Oxygen Content of the Earth:
 Same as meteorite with same mass ratio as the
Earth‘s
Evidence for Oxygen-poor
Earth
The Earth
Seems to be
Oxygen-poor!
Herndon, J.M. (1996) Proc. Natl. Acad. Sci. USA 93, 646-648.
3He
Evidence for Georeactor
 Fission reactors produce 3H
 3H decays to 3He (half life ~ 12 years)
3He
Measurements
 In air:
 RA = 3He/4He = 1.4 x 10-6
 From deep Earth:
 R ≈ 8 x RA
 Elevated deep Earth levels difficult to
explain
 Primordial 3He and “Just-so” dilution
scenarios
 A georeactor naturally produces 3He…
… and Just the Right Amount!
SCALE Reactor Simulator
(Oak Ridge)
Deep Earth Measurement
(mean and spread)
Fig. 1, J.M.Herndon,
Proc. Nat. Acad. Sci.
USA, Mar. 18, 2003
(3047)
Other Phenomena
 Georeactor as a fluctuating energy
source for geomagnetism
 3 of the 4 gas giants radiate twice as
much heat as they receive
 Oklo natural fission reactor (remnant)
Can a Georeactor Be
Detected with KamLAND?
 KamLAND
 A 0.4 kton antineutrino detector
 Currently, the largest such detector in the
world
 2-parameter fit
 Slope (constrained)
 Y-intercept (unconstrained)
Can a Georeactor Be
Detected with KamLAND?
 KamLAND
 A 0.4 kton antineutrino detector
 Currently, the largest such detector in the
world
 2-parameter fit
Solar neutrino
 Slope (constrained) experiments
 Y-intercept (unconstrained)
Can a Georeactor Be
Detected with KamLAND?
 KamLAND
 A 0.4 kton antineutrino detector
 Currently, the largest such detector in the
world
 2-parameter fit
 Slope (constrained)
 Y-intercept (unconstrained)
Georeactor Rate
Measuring the Georeactor
Rate with KamLAND
Slope constrained by
solar neutrino
measurements
Georeactor
rate
Slope ≈ 0.75 ± 0.15
Large Background
S/B ≈ 1/3 ~ 1/8
Background
Signal
Slope Uncertainty
Best fit
1s uncertainty in solar neutrino
oscillation parameters (Dm2, sin22q)
(rough estimate)
Can a Georeactor be
Detected?
 Use Error Ellipse to answer this question
Ellipse Equation
Ellipse Equation
Distance of measured
rate from true value
Measured georeactor
ne rate
(y-intercept)
True georeactor
ne rate
Ellipse Equation
Distance of measured
slope from best estimate
Mueasured slope
Best estimate of slope
(from solar n experiments)
Ellipse Equation
Correlation between slope
and rate measurements
Ellipse Equation
Confidence level
of fit result
Ellipse Equation
Ellipse Parameters
They determine the size of the ellipse
Ellipse Equation
Ellipse Parameters
Parameters
depend on
Rg
Georeactor rate
T
Exposure time
<R>
Average background rate
f
Spread in background rate
sm
Slope uncertainty
Ellipse Parameters
<R> = average background rate
f = fractional spread of background rate
T = Exposure time
Rg = georeactor rate
sm = oscillation probability uncertainty
m0 = 0.75
Error Ellipse for KamLAND,
3 Years






<R> ≈ 0.62 events/day
f ≈ 16% (i.e. RMS(R)/<R> = 0.16)
T = 3 years (12% down time fraction not included)
Rg = 0.0742 events/day (10 TW georeactor)
sm = 0.15 (slope uncertainty from solar n meas.)
m0 = 0.75 (slope = avg. surv. prob.)
KamLAND, 3 Years
KamLAND, How Many Years?
40 years for
90% confidence level!
Effect of Background Spread
Reducing the Background
Level
Slope Uncertainty
Improvements
Detector Size
Gigaton Detector
1 Gigaton = 2,500,000
Gigaton Detector
Go ~ 2.5 km along axis!
Summary of Results
 Georeactor will NOT be observed with
KamLAND
 Large spread in background rate helps
 Low background level
  Georeactor detectable with small detector
Summary of Results
 Slope uncertainty
 Improved knowledge helps somewhat
 A ~102 increase in detector size allows
georeactor detection
 1 Gigaton = 2.5 million x KamLAND
Most antineutrinos detected by a
gigaton detector will be from the
georeactor!
Event Rate @ Gigaton
Detector
 0.0742 events/day
 0.4 kton
 10 TW
x 2,500,000
≈ 200,000 events/day
Expected rate from man-made reactors: 20,000 ev/day
Caveat
 In this analysis, information from the
antineutrino energy spectrum was not
used.
 Therefore the statement that KamLAND
cannot say anything meaningful about a
georeactor is premature
 Setting 90% limit may be possible
 Positive identification, however, is
impossible
Conclusion
 An array of gigaton detectors whose
primary aim is arms control will definitely
allow the detection of a georeactor (if it
exists)
 The detection of a georeactor will have
giant repercussions on our understanding
of planet formation and geophysics
Evidence for Oxygen-poor
Earth (2)
 If we accept that the Earth was made from
molten meteorites, the following mass
ratios must hold
Mass(core)
Mass(alloys, opaque minerals)
=
Mass(mantle)
Mass(slag)
Using density
profile from
seismic data
Meteorite data
Evidence for Oxygen-poor
Earth (3)
The Earth
Seems to be
Oxygen-poor!
Herndon, J.M. (1996) Proc. Natl. Acad. Sci. USA 93, 646-648.
Earth‘s Interior from
Two Models
3He/4He
from the Georeactor Model
SCALE Reactor Simulator
(Oak Ridge)
Deep Earth Measurement
(mean and spread)
Fig. 1, J.M.Herndon,
Proc. Nat. Acad. Sci.
USA, Mar. 18, 2003
(3047)
Detection Strategy
Background
(commercial nuclear
reactors)
Slope =
average oscillation
survival probability
Signal (georeactor)
Detection Strategy
Slope constrained by
solar neutrino
measurements
Georeactor
rate
Slope ≈ 0.75 ± 0.15
Slope Uncertainty
Best fit
1s uncertainty in solar neutrino
oscillation parameters (Dm2, sin22q)
(rough estimate)
Slope Uncertainty
Measuring the Georeactor
Power
 Fit a line through data:
 observed vs. expected rate
xi = expected ne rate
yi = observed ne rate
si = stat. err. yi
i = bin index
b = georeactor rate
m = commercial reactor ne
avg. survival probability
m0 = best estimate from
solar n experiments
sm = estimated uncertainty
Measuring the Georeactor
Power
 Fit a line through data:
 observed vs. expected rate
xi = expected ne rate
yi = observed ne rate
si = stat. err. yi
i = bin index
Measure this
b = georeactor rate
m = commercial reactor ne
avg. survival probability
m0 = best estimate from
solar n experiments
sm = estimated uncertainty
Line Fit to Data
What Conditions are Necessary
to Detect a 10 TW Georeactor?
 Detector size
 Signal and background scale by the same factor
 Exposure time
 Overall increase in statistics
 Slope (average survival probability)
 Uncertainty that is independent of exposure time
 Improvement over time with more/better solar n
measurements
 Commercial reactor background
 Spread in background level
Error Contour Formula
Error Contour Formula
<R> = average background rate
f = fractional spread of background rate
T = Exposure time
Rg = georeactor rate
sm = oscillation probability uncertainty
m0 = 0.75
KamLAND, 3 Years
KamLAND, How Many Years?
Summary of Results
 Improved knowledge of neutrino oscillation
parameters help, but not enough to allow
KamLAND to detect a georeactor
 A x100 increase in detector size will
allow 99% detection of a 10TW
georeactor, even under high
background conditions as in KamLAND
 Don‘t need to go all the way to a gigaton
(x2000), although it will allow a comfortable
margin