A Sandia and Lawrence Livermore National Laboratories Joint Project

1
The Safeguards Detector at SONGS

• A Sandia and Lawrence Livermore National
  Laboratories Joint Project
• Nathaniel Bowden
• Detection Systems and Analysis
• Sandia 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.
2
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

3
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

4
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)

5
Prototype deployment San Onofre Nuclear
Generating Station
6
San Onofre Nuclear Generating StationUnit 2
Tendon Gallery

• 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 gt 1020 n / s
• In tendon gallery with 1017 n / s per m2
• Around 4000 interactions expected per day

7
Installation at SONGS
8
Installation at SONGS
9
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

10
Background singles rate is high

• With hardware threshold at 1.5 MeV, singles
  rate is 500 Hz
• Analysis threshold is 3 MeV

11
Our detector is all edge

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

Events/MeV

• Data
• Monte Carlo

Delayed Energy (MeV)
12
Lessons Learnt

• We need
• Better gamma shielding/cleaner material
• More, and more uniform, light collection
• Better calibration (background lines wont 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

13
q13 vs. nonproliferation?

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

14
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