november 10, 2011 lownu 2011workshop.kias.re.kr/lownu11/?download=y11m11d08_us... · possible...

LLNL-PRES-511475

This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under contract DE-AC52-07NA27344. Lawrence Livermore National Security, LLC

November 10, 2011 LowNu 2011

Lawrence Livermore National Laboratory LLNL-PRES-511475

Sandia National Laboratories

Antineutrino Monitoring provides independent and quantitative measurements of:

Reactor Thermal Power Reactor Fissile Inventory

These measurements are:

Non-intrusive – no connection to plant systems Remote, Unattended, and Continuous Highly tamper resistant

Antineutrino Monitoring may allow:

Independent confirmation of power history and initial and final fissile inventory declarations

This may prove useful in Next-Generation fuel cycles: Regaining Continuity of Knowledge in bulk process reactors Confirming initial fissile load in MOX or Th fuel cycles

This technique is only feasible for critical systems - it cannot monitor spent fuel or fuel processing facilities.



Reines and Cowan, 1956: • First to detect antineutrinos using a

reactor source and a liquid scintillator detector

Three decades of neutrino oscillation studies have provided: • A mature technology base • A quantitative understanding of

reactors as an antineutrino source

0.2

0.4

0.6

0.8

1

1.2

1.4

0

101 102 103

Distance to reactor (m)

ILL

Savannah River

Bugey

Rovno

Goesgen

Krasnoyarsk

Palo Verde

Chooz

KamLAND

Nobs/Nexp

104 105


Sandia National Laboratories 4

• Several antineutrinos are produced by each fission:

• Antineutrinos cannot be shielded, and “small” detectors have useful interaction rates, e.g. for 0.64 ton detector:

• 25 m from 3 GW core: ~4000 interactions/day

• 5 m from 100 MW core: ~3000 interactions/day

thPN

• Antineutrino emission rate and energy spectrum are sensitive to the isotopic composition of the core

• Due to difference in emissions from fissions of different isotopes



Can verify declared operation by comparison of measured antineutrino evolution to prediction

Example: PWR Equilibrium Fuel Cycle




Example: On-Load Reactor in Equilibrium Fuel State




Example: Full MOX core

Fis

sio

n F

rac

tio

ns

MOX Simulation: Anna Hayes, LANL

Rela

tive A

nti

neu

trin

o R

ate

(%

) 110

100

90

0.8

0.6

0.4

0.2

0



The LLNL–SNL antineutrino detector “SONGS1”



Reacto

r P

ow

er

(%)

0

20

40

60

80

100

Date

06/2005 10/2005 02/2006 06/2006 10/2006

Dete

cte

d

can

did

ate

s p

er

day

0

100

200

300

400

500

Predicted rate

Reported power

Observed rate, 30 day average

Fuel Cycle n+1RefuelingOutage

Fuel Cycle n

Re

ac

tor P

ow

er (%

)

See: J. Appl. Phys. 105, 064902 (2009)



“The American group has done the first practical demonstration, and its detector is promising, because it is not much bigger than other systems the IAEA currently deploys at reactors.” — Julian Whichello

IAEA Novel Technologies Group representative, quoted in IEEE Spectrum article, April ‘08

“Ad-hoc” Physicist/Inspector Working Group convened in Sept. 2011

Interest in:

• Shipper-receiver differences,

• Bulk Process/ Online Refuel Reactor Verification

• Research reactor power

• Safeguards by Design, Integrated Safeguards

• Aboveground Detection



Group Country Technology Application

SNL/LBL USA Coherent Scat. PPC Ge

Compact

LLNL USA Coherent Scat. Dual Phase Argon

Compact

Nucifer France Liquid Scint., Comprehensive engineering

Research Reactor, Power Reactor, “industrialized”

Angra Brazil Gd doped Water Cerenkov

Aboveground/ Portable

Tohoku Univ. Japan Liquid Scint. Aboveground/Research Reactor

PANDA Japan Segmented Plastic Aboveground/ Portable

Niigata Univ. Japan Gd-doped Plastic Non-flammable

U. Hawaii USA Fast Liquid Scint. “Time cube”

Directional detection

“Mars” UK Inhomogeneous Organic/Inorganic 6Li

Background rejection



Aboveground, Mobile System - Focus on Background Rejection

Verification of Core and Assembly Level Fissile Declarations – Quantify Sensitivity

On-Load Reactor Deployment

Optimization of Homogenous Scintillator Detector



The daily movement of fuel bundles at a CANDU plant presents a safeguards challenge - item accountancy remains a primary strategy

Close analogue to future Bulk Process Reactors

Item accountancy is not possible on the “continuous” or finely divided fuel of a BPR – a Bulk Materials Accountancy approach will be necessary.

Loss of Continuity of Knowledge over the core contents would be difficult to recover



Quantity SONGS 1

CANDU

estimates

Reactor thermal power 3.4 GW 2.2 GW

Core distance ~25 m ~77 m

Relative Flux 1.00 0.08

Detector active mass 0.64 tons 3.6 tons

Deployed Footprint 6 m2 10 m2

Overburden ~25 m.w.e. ~ 18 m.w.e.

interaction rate *

efficiency = detection rate

~ 4000/day * 10% =

~ 400/day

~2000/day *20% =

~ 400/day



Scintillator level Filling

Buffer tank: Mineral Oil

Inner Tank: Gd-doped Scintillator 10” PMT

LED Calibration device

•Inner tank and Buffer tank fully constructed

•Inner detector electronics and DAQ software completed.

•Inner detector assembled, filled and tested at LLNL.

•Modular water shield construction underway.

•Full assembly and testing with shield and veto this winter.



Much Improved:

1. Energy Resolution

2. Gd g-ray shower containment



PLGS is currently being refurbished. For only the second (and likely last) time, it will have a fresh core load at restart

Online refueling will begin at about FPD75; we expect to observe the evolution of the fuel burnup to the equilibrium condition.



All previous antineutrino detectors have operated under at least several 10s of meters of “overburden”, to shield out background generating cosmic rays

• If operated aboveground, our SONGS1 detector would see 100-1000 times higher background

Clearly, removing the need for cosmic ray attenuating overburden would allow for much great flexibility in:

• deployment location

• deployment mode (e.g. in ISO container)



n

n deposits energy

g ~ 8 MeV

Gd t ~ 30 ms

n Gd

t ~ 30 ms n Gd

Cosmogenic Neutron Background:

n

e p

511 keV

511 keV e+

Gd, Li, etc

t ~ 30 ms

Positron

• Immediate

• 1- 8 MeV (incl 511 keV gs)

Neutron

• Delayed (t = 28 ms for Gd)



We have developed two methods to attempt Aboveground Antineutrino Detection:

Method Background reduction

Advantages Disadvantages

Water Cerenkov (Gd doped)

Reduces background via insensitivity to proton recoils

Simple, non-combustible, non-flammable, inexpensive detection medium.

Low Cerenkov light yield Ineffective against multiple neutron background

Advanced Scintillator

Identify signal and/or background via segmentation and Pulse Shape Discrimination

In principle, can reject all backgrounds

Complex detector geometry may be inefficient Materials may be expensive



To support reactor deployments of both detector technologies, we have built a shield inside a 20ft container:



This device exhibits clear sensitivity to neutron captures

A very high rate of multiple neutron captures was observed

• After muon veto and neutron multiplicity cuts, observe ~ 40,000 events/day

Expected antineutrino signal ~ 400/day

Conclusion: This technology overwhelmed by multiple neutron background, aboveground

Correlated events

Vs

Uncorrelated events



Use 6Li:ZnS coupled to plastic scintillator to identify neutron captures:

• Reduce random and multiple neutron backgrounds

• Use topography to reject some neutron recoil backgrounds

4 segments deployed (35 liter volume), but many equipment problems during reactor outage period.

e

e+

n

Liquid or Plastic scintillator



Detector efficiencies

• N-capture efficiency of 18%

• Positron efficiency 2—87%

Background rates are reasonable for a possible observation of reactor transition

• 2 – 4 orders of magnitude rejection

• 2 methods of analysis agree

Based on expected νe signal, expect 3 sigma detection in 4 – 6 weeks

• Expect 1 – 37 ev/day

Very encouraged by technology performance

Only Neutron PID 1,830 ev/day

Max PID info 23 ev/day

No PID 225,200 ev/day



Reines and Cowan, 1956: • First to detect antineutrinos using a

reactor source and a liquid scintillator detector

Three decades of neutrino oscillation studies have provided: • A mature technology base • A quantitative understanding of

reactors as an antineutrino source

0.2

0.4

0.6

0.8

1

1.2

1.4

0

101 102 103

Distance to reactor (m)

ILL

Savannah River

Bugey

Rovno

Goesgen

Krasnoyarsk

Palo Verde

Chooz

KamLAND

Nobs/Nexp

104 105

?



Reactor Baseline Core Detector DL/L (FWHM)

Power Flux

/m2/s

ILL 10m Ø 0.4m x 0.2m (HEU)

Ø 1mx1m ~8% 58 MWth ~1x1016

Bugey3 15m Ø 2.5 x 2.5m 1mx1m ~30% 2800 MWth ~2x1017

SONGS 24m Ø 3m x 2m Ø 1mx2m ~10% 3400 MWth ~1x1017



(sin2(2q) =0.165, Dm2 =2.4 eV2)

SONGS

Bugey

ILL

Experiments at appropriate small and large reactors would be complementary, efficiently probing different Dm2 regions and measuring flux/spectra from different core compositions



Our proposal is to to perform a relatively rapid and inexpensive experimental measurement at SONGS

—High statistics flux and spectrum measurement from a single Pressurized Water Reactor (PWR)

—Direct sterile oscillation sensitivity via spectra distortion

SCRAAM detector:

• 1.5 ton active mass -> 4,000 /day @ 40% eff.

• Partial gamma catcher

• Double ended optical readout, 10% resolution at 1MeV



150 days, sin2(2q) =0.165, Dm2 =0.15 eV2

1.5% bin-to-bin systematic, 8/1 Signal/Background



150 days, sin2(2q) =0.165, Dm2 =0.60 eV2




150 days, sin2(2q) =0.165, Dm2 =1.2 eV2




150 days, sin2(2q) =0.165, Dm2 =2.4 eV2




150 days, sin2(2q) =0.165, Dm2 =4.8eV2




150 days, 99% C.L.

1.5% Energy scale error, 8/1 Signal/Background



150 days, 99% C.L.

4% Normalization, 1.5% Energy scale error, 8/1 Signal/Background


Sandia National Laboratories 38

Advanced Test Reactor at Idaho National Lab

Unique “serpentine” 1.2m HEU core, ~150MWth

Convenient 60 day on, 30 day off cycle

Potential below grade deployment locations near core

At 12m baseline, spread similar to that at SONGS



Practical, demonstrated antineutrino detector designs can provide continuous, non-intrusive, unattended measurements suitable for reactor safeguards regimes

We continue to quantify the sensitivity of these measurements to reactor fissile content, both at core and assembly level

Online refueled and Bulk Process Reactors present distinct safeguards challenges – antineutrino detection could provide a unique capability to track the core loading of these types

Aboveground operation is a great challenge – one that we have not fully achieved, but we have developed a promising technology

Measurements with appropriate reactor core –detector geometries can probe the Reactor Anomaly via spectral distortion



40



30mwe

High Flux: ~1017 /m2/s

130-180m to other reactor

Gallery is annular – unfortunately no

possibility to vary baseline



Daily and weekly averaging allows relative power tracking

See: J. Appl. Phys. 103, 074905 (2008)

Results: Short term monitoring of operational status and power

Daily: 8% Relative uncertainty

Weekly: 3% Relative uncertainty

Re

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r P

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er

(%)

-20

0

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Date

02/28/05 03/07/05 03/14/05 03/21/05 03/28/05

Co

un

ts p

er

Da

y

0

150

300

450

600

Predicted rate

Reported power

Observation, 24hr avg.

Reacto

r Po

wer (%

)



Inner Tank: Gd-doped Scintillator

Buffer tank: Mineral Oil Muon Veto

Water Shield

4m3 BC-525 target (0.1% Gd)

Double ended readout using 24x10” R7081 PMTs

• Acrylic windows, sealed via PTFE encapsulated o-rings

Optical coupling and hydrostatic support via mineral oil

Shielding from 6 interlocking water tanks (0.5m) and 2.5cm Borated Poly.

5cm thick muon veto on 5 sides.



Reconstructed event position(Cf-252 source data)

Initial calibrations have been

performed with a Cf-252 and Th-

228Thsource located on the outer

edge of the buffer tank



Whole Detector Inner portion Middle portion Outer portion

The full absorption Gd capture energy (~8 MeV) can be observed by restricting

events to the inner portion of the detector.

november 10, 2011 lownu 2011workshop.kias.re.kr/lownu11/?download=y11m11d08_us... · possible...

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