LLNL

A Sandia and Lawrence Livermore National Laboratories Joint Project

Nathaniel BowdenDetection Systems and AnalysisSandia National Laboratories, CA

Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company,for the United States Department of Energy under contract DE-AC04-94AL85000.

The Safeguards Detector at SONGS

LLNL

Design Principles

• Simple, inexpensive, robust– Rapid deployment– Use well known detection concepts/technology

• Antineutrino detection via inverse beta decay• Gd loaded scintillator• central target surrounded by various shielding layers

– Physically robust for reactor environment (e.g. steel scintillator vessels)

– Modular for manhole access• Do a relative measurement

– Use automatic calibration based on background lines to account for all time dependent variations

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Sandia/LLNL Antineutrino Detector

• Detector system is…– 0.64 ton Gd doped

liquid scintillator readout by 8x 8” PMT

– 6-sided water shield

– 5-sided active muon veto

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Cell Design

• Stainless tanks – no scintillator attack– Tank size determined by manhole size

• PMTs coupled to scintillator by acrylic plugs and mineral oil

• Light reflectors are argon filled PTFE bags (Bugey)

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Prototype deployment –San Onofre Nuclear Generating Station

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• Tendon gallery is ideal location– Rarely accessed for plant

operation– As close to reactor as you can

get while being outside containment

– Provides ~20 mwe overburden• 3.4 GWt => 1020 / s• In tendon gallery with ~1017 / s

per m2

• Around 4000 interactions expected per day

San Onofre Nuclear Generating StationUnit 2 Tendon Gallery

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Installation at SONGS

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Installation at SONGS

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Some results• Detector is ~ 10%

efficient

• Stability is difficult to maintain with only background lines for calibration

• Even so, reactor power excursions are clear; probably burnup too

Rea

ctor

Pow

er (

%)

-20

0

20

40

60

80

100

Date

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

Ant

ineu

trin

o co

unts

per

day

0

100

200

300

400

500

600

Predicted count rate using reported reactor power and burnup estimateReported reactor powerObserved Count rate, 7 day average

Reactor OutageReactor in Operation

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Background singles rate is high

• With hardware threshold at ~ 1.5 MeV, singles rate is ~500 Hz

• Analysis threshold is 3 MeV

Energy (MeV)0 2 4 6 8 10 12

Co

un

ts

1

10

100

1000

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Our detector is “all edge”

• A large fraction of the -rays from the Gd shower escape our detector, resulting in a broad delayed energy distribution

• Data Monte Carlo

Events/MeV

Delayed Energy (MeV)

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Lessons Learnt

• We need:– Better gamma shielding/cleaner material– More, and more uniform, light collection– Better calibration (background lines won’t be

enough, no sources possible?)• We would like

– Smaller footprint– Less flammable/aggressive scintillator– Smaller surface/volume ratio

• Leading to higher efficiency in a smaller volume, with excellent stability

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13 vs. nonproliferation?

• “State of the Art” vs. a detector that is “good enough”

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Conclusions

• Our very simple device has made interesting measurements and has been invaluable as a demonstration, but we can and must do better

• We are likely to begin a new detector development program this year, beginning by studying the use of steel shielding with shallow overburden

• It is important in our discussions to identify the necessary features to make nonproliferation detectors successful, but not too complex or expensive