Status of Current Deployments by LLNL/SNLhanohano/post/AAP2012/... · Sandia National Laboratories...

Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a

wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy’s National

Nuclear Security Administration under contract DE-AC04-94AL85000

This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore

National Laboratory in part under Contract W-7405-Eng-48 and in part under Contract DE-AC52-07NA27344.

Status of Current Deployments by

LLNL/SNL

David Reyna Sandia National Laboratories, CA

Lawrence Livermore National Laboratory

David Reyna

A Novel Technology for Reactor Safeguards

Antineutrino Monitoring of Reactors provides independent measurements of Thermal Power and Fissile Inventory

Non-intrusive with NO connection to plant systems

Continuous Remote Monitoring

Highly tamper resistant

Potential Applications to Present and Future Safeguards

Independent Confirmation of Operator Declarations

Reduction in needed Inspector visits

Provide fissile content information for Next-Generation fuel cycles (MOX, Th, bulk process)


Recent IAEA interactions and

interest

IAEA convened an ad-hoc physicist/inspector working

group in Vienna in September 2011

Expressed interest by IAEA after 2008 expert’s

workshop in Vienna:

• Shipper-receiver differences,

• Bulk Process/ Online Refuel Reactor

Verification

• Research reactor power

• Safeguards by Design, Integrated Safeguards

• Aboveground Detection

David Reyna


CANDU and Bulk Process Reactors

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

David Reyna


May 2007: Visit to AECL Chalk River

Mar. 2008: PLGS shutdown; first CANDU6 to undergo full

refurbishment (e.g. all reactor tubes to be replaced); planned restart

late 2009

Early 2009: AECL provides introduction to PLGS Rx Physics group

April 2009: First visit to PLGS; enthusiastic reception

Sept. 2009: Approval letter for deployment with PLGS support ―after

unit is back at power‖

Oct. 2009: Meeting at PLGS: AECL, SNL, LLNL, NA-22

Jan. 2010: 15 month refurbishment delay officially announced

Oct. 2010: Second refurbishment delay announced: full return to

service in Fall 2012 (all new tubes to be removed and replaced)

Mar 2012: Approval received for site prep work

Sep 2012 : Data collection begins – TBD

• Materials are staged at PLGS awaiting installation

Timeline

David Reyna


Deployment Location

David Reyna

Distance:

~77 m from

reactor core

Overburden:

~18 m.w.e.


Detector Design

David Reyna

To compensate for reduced flux, target will be 4m3 of BC-525 (0.1% Gd);

• expect ~20% overall efficiency

• Per m2 of footprint, ~10x as efficient as SONGS1

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.


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.

n interaction rate *

efficiency = detection rate

~ 4000/day * 10% =

~ 400/day

~2000/day *20% =

~ 400/day

Comparison to previous experiment

David Reyna


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 completed

•Inner detector assembled, filled and tested at LLNL.

•Modular water shield constructed and installed.

•Full assembly test with shield and veto completed.

•DAQ software upgrade ongoing.

Detector Assembly/Testing

David Reyna


Detector Assembly/Testing

Shield Installation

Filling

Mineral Oil

Scintillator

David Reyna


Fully Assembled System

David Reyna


Reconstructed event position(Cf-252 source

data) Initial calibrations have been

performed with a Cf-252 and Th-

228 source located on the outer

edge of the buffer tank

Initial Data/Calibration

David Reyna

Neutron Capture Spectrum


Significantly

Improved:

1. Energy

Resolution

2. Gd g-ray

shower

containment

The energy

resolution

improvements

lead to a

potential

positron spectral

analysis

Performance Comparison:

Neutron Capture Response (data)

David Reyna


PLGS is currently completing a full refurbishment.

• For only the second (and likely last) time, it will have a fresh core load at

restart

We hoped to measure the initial evolution to an equilibrium core.

• Online refueling will begin at about FPD75

• The current delays suggest we may miss the heart of this burn-in

David Reyna

Expected Observation


CANDU Summary

Barring unforeseen problems, a deployment at a CANDU reactor is scheduled for later this year.

• This will be our first antineutrino measurement of a reactor under safeguards.

• This will be the first antineutrino measurement of a CANDU core

This measurement will provide insight into Bulk Process Reactor operations.

• We had hoped to get fresh startup, but may still measure some fuel evolution

This detector represents our best performing homogeneous design yet

David Reyna


Aboveground Challenge is all about

Backgrounds

Without overburden or passive shielding, a detector is exposed to: • High muon rates • Hadronic showers • Electromagnetic showers • Secondary particles produced by all of the above in the

detector and its surroundings

Most of detector size is passive shielding

• Active detector in SONGS 1 design was less than 6% of total volume

• A shield can reduce backgrounds in a simple and cost effective way

Belowground (only a few meters) many of these

cosmic backgrounds are significantly reduced • To date, even below ground detectors have required

additional passive shielding

With good detector design, the need for shielding may be reduced or eliminated entirely

• Conceivably, SONGS1 performance could be achieved with a 1m2 footprint

Particle Identification (PID) is a powerful tool

• Identify and reject fast neutrons and multi-neutron events

• Explicitly tag final state Positron and thermal neutron (capture)

David Reyna


David Reyna

Standard Detection of

Inverse Beta-decay

We use the same antineutrino detection technique used to first detect (anti)neutrinos:

ne + p g e+ + n

Standard detectors of gammas and neutrons are sufficient to find this correlated signature

Positron

• Immediate

• 1- 8 MeV (incl 511 keV gs)

Neutron

• Thermalization then capture

• Delayed capture (t = 30-100 ms)

n

ne p

511 keV

511 keV e+

Gd, Li, …

t ~ 30 ms

prompt signal + n capture on Gd

Switch to Lithium-6 yields good detection efficiency for compact detectors


David Reyna

Segmented Scintillator Detector

Individual Segments contain organic scintillator with ZnS:Ag/6LiF screens on outer surface

• 4 cells with plastic or liquid scintillator

Use of ZnS:Ag with 6LiF allows identification of neutron capture

• ZnS:Ag is sensitive to alpha from n-capture on Li

• Very slow scintillator time constant (~100ns) allows pulse shape discrimination to separate n-capture from γ events

With Liquid Scintillator, proton recoils are also easily identified

• Allows a comparison to test need for additional rejection

Ultimate design would be for 16 or 64 cells but this 4-cell prototype was sufficient for first testing


David Reyna

Particle Identification (PID)

Positron Identification through Topology

Positrons are rare in nature

• Deposit most of their kinetic energy very quickly through standard ionization losses

Positrons will annihilate into two back-to-back 511 keV gammas

• Very distinctive signature

• Gammas will travel ~2-5‖ through most scintillators

en

e+

n

Liquid or Plastic

scintillator

Neutron identification through Pulse Shape Discrimination (PSD)

Liquid Cell Plastic Cell


David Reyna

Aboveground Deployment at SONGS


David Reyna

Aboveground Performance

Detector Performance looks stable

• Detector efficiencies look reasonable

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

Very encouraged by technology

performance

• Operational Difficulties prevented

measurement of reactor transition

• Tested operation outside of the

shield and saw only minimal

increase in detected background

rates

Only Neutron PID

1,830 ev/day

Max PID info

23 ev/day

No PID

225,200 ev/day


PID = Simple Analysis

Signal Background

David Reyna

Independent measure of uncorrelated backgrounds allows simple subtraction

Automated energy calibration

using naturally occurring

Potassium and

Thorium endpoints


David Reyna

Preliminary Results of

Aboveground Data (events/day)

Event Definition

Shielded operation (30 days) Unshielded Operation (20 days)

Correlated Un-

correlated

Subtracted

Signal Correlated

Un-

correlated

Subtracted

Signal

1) Using only neutron PID 1118 8 368 5 750 9 15930 32 13835 30 2095 44

2) Neutron + positron PID 119.1 2.6 28.7 1.3 90.4 2.9 1371 9 1168 9 203 13

Event

Def.

Antineutrino Rate

Expectation from MC

1) 18

2) 6

Measured Errors on Subtracted Signal are already

below expected antineutrino signal

• Prototype 4-Cell array is still highly inefficient

Unshielded Operation Shows Promise

• Uncorrelated rates increase by x 40

• Correlated only goes up by x 2—3

• Motivation for subsequent testing


Segmented Scintillator

Belowground Deployment

Re-packaged 4-cell prototype for optimal deployment • Total system (detector, electronics, HV,

computer) fits within a single rack • Shipped fully assembled (no assembly required)

Deployed below ground, without shield or muon veto • Fully operational within 2 hours of being

placed at location

Stable operation since January 2012 at SONGS • Began data taking during a reactor

refueling outage

• Reactor turn-on delayed until December 2012 (or later)


Detector Performance Belowground

David Reyna

Expected Signal (~40 ev/day) is larger

than error on background (~7ev/day)

Robust/Continuous unattended operation for several months

Automated calibration/analysis

shows stable performance Neutron Candidates

Positron Candidates

Selected Event Candidates


David Reyna

Road to a Full System

We believe that a larger version of this detector would demonstrate worthwhile reactor antineutrino sensitivity

Size would depend on desired sensitivity

Without a shield, this is a compact detector system

• Up to 9 cells could fit within the existing rack

• 64-cells could still be contained within a single square meter footprint

16-Cell Array 64-Cell Array

Increase for

Event Def.

1

Increase for

Event Def. 2

Increase for

Event Def. 1

Increase for

Event Def. 2

Increase in Mass x 4 x 4 x 16 x 16

Neutron Capture Efficiency x 2 x 2 x 2.5 x 2.5

Positron Detection Efficiency no change x 1.8 no change x 2

Total Signal Increase x 8 x 14 x 40 x 80

Total Background Increase x 4 x 4 x 16 x 16

Improvement in S/B x 4 x 7 x 10 x 20


David Reyna

Conclusion

Previously demonstrated short and long

term relative monitoring of power operational

status, and fissile content in reactors

Very encouraged by performance of

Segmented Scintillator prototype • This project aims to expand the range of utility by

reducing the overall footprint and enabling deployment

in high-background or unshielded locations

• Demonstrated rejection of backgrounds of 3+ orders of

magnitude even without an external shield

• Reasonable efficiencies have been achieved even with a

small 4-cell detector

• Increase to a 16 or 64 cell system would show marked

improvement

Looking forward to deployment at a CANDU

reactor scheduled for late 2012. • First deployment at bulk process reactor

• First deployment at reactor currently under safeguards

Status of Current Deployments by LLNL/SNLhanohano/post/AAP2012/... · Sandia National Laboratories...

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