Diapositive 1

1
Site search to set two underground detectors at
Dnearlt500 m Dfar1.8 km around French Nuclear
Power Plants Thierry Lasserre CEA/Saclay Low
energy Neutrino Workshop University of Alabama,
Tuscaloosa May 1 2003
2
Optimal distance reactor-detector VS ?m2atm
2800 meters
1150 meters
1800 meters
15.5
Naive SK/K2K combination, 90 C.L
10
(R Ue30 R Ue30.2236) / R Ue30
Relative Rate Suppression
?m2atm 1.6 10-3 eV2 ?m2atm 2.5 10-3 eV2 ?m2atm
3.9 10-3 eV2
XXX
1.3
2.2
Distance (km)
CHOOZ
XXX (1.8 km)
CHOOZ(1.1km)
T. Lasserre
3
Comparison of Ue32 reactor projects
Dfar (km) P (GWth) Nevents per year Target Volume Proposed Target volume Kashiwasaki eq. Free protons Kashiwasaki eq. (events per year)
CHOOZ 1.0 8.2 13925 5 tons - -
Kr2Det 1.1 1.6 2245 50 tons 54.3 tons 4.13 1030 (24406)
Kashiwasaki 1.3 24.3 24418 5 tons 5.0 tons 3.78 1029
Diabolo Canyon 1.2 6.2 73118 50 tons 16.7 tons 1.27 1030 (24437)
Wolf Creek 1.2 3.1 36559 50 tons 33.4 tons 2.54 1030 (24437)
Paluel 1.8 16.5 34698 20 tons 14.0 tons 1.07 1030 (24207)
Cruas 1.8 11.7 24530 20 tons 20.0 tons 1.50 1030 (24437)
Penly 1.8 8.3 17339 20 tons 28.1 tons 2.14 1030 (24411)
Flamanville 1.8 8.3 17339 20 tons 28.1 tons 2.14 1030 (24411)

• Rates are given for the no-oscillation case
• Benchmark CHOOZ unloaded liquid scintillator
• 5 tons 3.78 1029 free protons
• d 0.854
• 13.3 free protons

4
Comparison of Ue32 reactor projects
Shape analysis
Rate analysis
14
14
5
Comparison of Ue32 reactor projects

• All projects compared with the same analysis
  framework same systematics, and statistics
  errors
• Rate Analysis ? Optimum baseline _at_1.8 km for
  ?matm2 2.5 10-3 eV2
• Shape Analysis ?Improve the constraint when the
  far detector is not at the optimum baseline
• ?BUT optimum baseline gives better constraint
• ?BUT optimum baseline is less sensitive to ?matm2
  

6
Forthcoming Ue32 constraints
Experiment sin2(2?13) Ue32 ?13 (deg) Ue32 constraint
CHOOZ lt0.14 lt0.036 lt11 -
MINOS lt0.06-? lt0.015 lt7.1 ?
ICARUS 5 years lt0.04-? lt0.010 lt5.8 2011 ?
OPERA 5 years lt0.06-? lt0.015 lt7.1 2011 ?
NUMI-OA 5 years lt0.006-0.015 lt0.0015 lt2.3 2012 ?
JHF2K 5 years lt0.006-0.015 lt0.0015 lt2.3 2011 ?
Kr2Det (Russia) lt0.016 lt0.004 lt4.6 ?
US proposals lt0.01 lt0.0025 lt2 ?
Kashiwasaki (Jp) lt0.026 lt0.0065 lt 3.3 ?
PALUEL/PENLY/FLAMANVILLE ? lt0.02 lt0.005 lt4.1 2010 ?
?sys 1

• When the C.L. are not given, upper limits
  correspond to 90 C.L
• ?m2atm 2.5 10-3 eV2 and sin2(2?atm) 1
• sin2(2?13) 4 Ue32 (1 -Ue32)
• Non exhaustive table

T. Lasserre
7
French Nuclear Power Plants
Flat and swampy
Flat topography H 0 meter
Nuclear plants embedded in chalk cliff Near and
Far sites candidates
Cavity at 700 m for the near site too far away
Close site OK ? Problem for the far site ?
Very flat topography, but a lots of space
Around La Loire Flat topography all around the
power plants (vut no detail check )
Small cliff at 2km from the reactors, but problem
to find the near site
Around Le Rhone Problem to find a near site
close to the river Near site swampy St Alban
Far site OK ?
Around La Garonne Flat topography
Cruas is interesting because the far site is well
shielded h300 m rocks
8
Nuclear Power Plants embedded with cliffs

• Goals Find Near _at_ lt500 m and Far _at_1.8 km
  underground detector sites
• Dig as less as possible to decrease cost
• We looked for hills or equivalent around French
  nuclear power plants
• Systematic search for underground site around
  the plants has not been done

• Far Site _at_1.8 km
• Dig Vertical shaft (Kashiwasaki) ?
• or
• Dig Horizontal gallery ?
• or
• Existing gallery !

Possibility to find a near site _at_ lt500 m
? Horizontal gallery
9
Flamanville site Location

• Flamanville is located in La Manche (50)
• Nuclear plant 2 PWR cores (1330 GWelec each)
• Nuclear power plant embedded in the Cliff
• (12 meter above see level)
• Cliff is 100 m high, composed of granits
• But Power plant constructed on a iron mine

10
Flamanville site 8.25 GWth (2 cores)
Flamanville
Type PWR
Cores 2
Net Power 2x1330/0.31 8.5 GWth
Coupling 1985-86
Discontinuation ?
Gross load factor (, in to 2000) 69.2, 84.5
Cumulated gross load factor (, up to 2000) 65.0, 66.8
Manufacter Framatome
Operator EDF
Distance (km) 1.8
Events /28 tons/y 24000
Flux weight () 99.91 (Paluel ? 8 events/y)
11
Flamanville site Far Detector
1.8 km
1.8 km
h-90 -150 meters Dielettesmine
0.5 km
h70 meters
12
Flamanville site Near Detector
100 m
500 m
13
Dielettes iron mines Preliminary

• German mine constructed in the nineteen
  century, closed on 1962
• The Flamanville power plant was constructed on
  the Dielettes iron mine
• The mine has two gold mines _at_90 meters and
  _at_150 meters but
• This is a sub-marine mine with galleries
  running perpendicular to the coast

• Problem is that the mine is presently drowned
  But the mine was already drowned and drained 10
  times ! Last time in 1950 it took 3 months and
  mines former president said it will take 8-10
  days nowadays There are still some dry area in
  the mine. There is also natural ventilation in
  the mine.
• 3 shafts (just plugged up with cement tile)
  still exist at the power plant ?
• Gallery size 6 meters wide and 2.5 meters high,
  possible to enlarge it.
• Near site could be just 150m below the nuclear
  plant. Far site would be in one of the gallery
  (plans to be received soon)

14
?
Flamanville site Far Detector
1.8 km
1.8 km
0.5 km
h70 meters
15
Penly site Location

• Penly is located in Normandie (more precisely in
  Seine-maritime, 76)
• Nuclear plant 2 PWR cores (1330 GWelec each)
• Nuclear power plant embedded in the Cliff
• (12 meter above see level)
• Cliff is 120 m high, composed of chalk
• (soft material)
• Nuclear plant is at the edge of a valley
  embedded in the chalk cliff. There might be some
  possibilities to excavate a near and a far
  detector cavity without digging to much, taking
  benefit of the excavation done in the 80ies for
  the power plant construction.
• Geology around the plant should be partially
  known water draining inside the soil already
  monitored

16
Penly site 8.25 GWth (2 cores)
Penly
Type PWR
Cores 2
Net Power 2x1330/0.31 8.5 GWth
Coupling 1990-92
Discontinuation ?
Gross load factor (, in to 2000) 70.7, 82.5
Cumulated gross load factor (, up to 2000) 71.5, 73.2
Manufacter Framatome
Operator EDF
Distance (km) 1.8
Events /28 tons/y 24000
Flux weight () 99.80 (Paluel ? 20 events/y)
17
Penly site Far Detector
1.8 km
0.5 km
h115 meters
18
Penly site Near Detector
500 m
100 m
500 m
19
Paluel site Generalities

• Paluel is located in Seine-Maritime (76),
  between Fecamp and Dieppe, close to the
  Veulette/mer holidays village.
• Nuclear plant 4 PWR cores (1330 GWelec each)
• Nuclear power plant embedded within the cliff
  that is 75 m high, made of chalk.
• Far site possibility to dig a gallery
  horizontally from La grande vallee (3 meter
  above see level) or with a -10 slope to go down
  to -75 m this would provide a shielding of 300
  m.w.e., but one needs probably to pump water.
• Near site excavated by digging a short
  horizontal gallery of a couple hundreds meter
  from the power plant site depth up to 100 meters
  (chalk).
• Geology water draining in the cliff partially
  known at the time of the central construction.

20
Paluel site 16.55 GWth (4 cores)
Paluel
Type PWR
Cores 4
Net Power 4x1330/0.31 17 GWth
Coupling 1984-86
Discontinuation ?
Gross load factor (, in to 2000) 78.4, 84.8, 84.6, 72.3
Cumulated gross load factor (, up to 2000) 65.9, 65.6, 69.1,69.6
Manufacter Framatome
Operator EDF
Distance (km) 1.8
Events /14 tons/y 24000
Flux weight () 99.94 (Penly ? 5 events/y)
21
Paluel site Far Detector
1.8 km
0.5 km
h75 meters
h3 meters
22
Paluel site Near Detector
500 m
100 m
23
Reactor Geo-Neutrinos Background

• gt300 GWth European power plants included
• Rate 17/year/14t
• Rate lt 0.07 Paluel flux

• Geophysical anti-?e
• U, Th, K natural decay chains.
• From Earth ?Earth 80 mW/m2
• LEarth 40TW (104 nuclear plants !)
• Neutrinos from 238U, 232Th daughters
• Characteristic spectrum E? lt 2.4 MeV
• Measurement _at_ KamLAND BOREXINO
• Rate 0.5-3.6/year/14t
• lt 0.015 Paluel flux

24
Schematic view of the detector

• CTF like design
• Water Buffer
• Muon Veto
• Pure PXE scintillator
• - d 0.99 g/cm3
• - Pvapor1.4 10-5 kPa _at_20oC
• - Flash point 149 oC
• - High LY (no Gadolinium)
• - Stable
• - Excellent PSD
• - lt 10-17 gU/g
• - No fiducial volume
• PMTs coverage 30
• - 400 pe/MeV

20 tons
25
?e detection free of background
Anti-?e tag ?e p ? e n, 1.8 MeV
Threshold

• Prompt e, EP1-8 MeV, visible energy
• Delayed neutron capture on H, ED2.2 MeV
• Prompt(?/?) - Delayed(?/?) ? pulse shape
  discrimination

Time correlation ? ? 200?sec Space correlation
lt 1m3
Several kind of backgrounds

• Geophysical anti-?es
• Reactor anti-?es
• Background from radioactivity
• rocks, detector material, water shielding,
  scintillator)
• Background induced by cosmic rays
• radioactive nuclei produced in the detector
• neutrons induced by muons in detector rocks

Depend on depth
Goal error from background ltlt total systematic
error
26
Backgrounds from radioactivity
Based on estimation done for the HLMA project,
S.Schoenert, T.L, L.Oberauer, Astropart.Phys.
18 (2003) 565-579

• Correlated
• U-chain Radon daughters 214Bi-214Po decays with
  ? ? 237 ?sec ? mimick ? tag
• But (?-?) ? Pulse Shape Discrimination
• E?0.8 MeV (quenched) ? gt10? from Ed2.2 MeV (?
  5 _at_ 1MeV)
• Accidental bacc bp x bd x ? x Vcoincx Vdet
• Goal rate bacclt 1/year
• PMTs, concentrators (BOREXINO Scaling)
• Th-chain 208Tl line _at_2.6 MeV
• _at_BOREXINO activity (Th activity ? 103 Bq).
  RPMTsgt3.7 meters ? bacclt 1/year
• Water shield (MC simulation)
• U ? 10-12 g/g ,Th ? 10-12 g/g , K ? 10-10 g/g ?
  Rn ? 100 mBq/m³
• CTF ? U ? 10-14 g/g ,Th ? 10-14 g/g
• Trace impurities in liquid scintillator (MC
  simulation)

bp, bd specific prompt, delayed rate Vdet
detector volume 100m³ ? coincidence time
1ms Vcoinc coincidence volume 1m³
27
Muon Flux at Paluel
Is it possible to put a detector at relative
shallow depth ?
Hypothesis 1 h 150 m.w.e
Hypothesis 2 h 300 m.w.e

• Depth cliff high ? h75 meters
• ltdgt 2 g/cm3 ? 150 m.w.e
• ltEgt 29 GeV
• Muon flux ? ?150 1.4/m2/s
• ?150/ ?0 1.4 10-2
• ?150/ ?300 4.56
• Rate 13.1 ?/s (20 tons PXE)

• Depth cliff 75 m ? h150 meters
• ltdgt 2 g/cm3 ? 300 m.w.e
• ltEgt 50 GeV
• Muon flux ? ?300 0.31/m2/s
• ?300/ ?0 3.1 10-3
• ?300/ ?300 1.
• Rate 2.9 ?/s (20 tons PXE)
• Depth of CHOOZ ? 3 corr. evt. /day
• (just rescaling CHOOZ meas. to PALUEL size)

Hypothesis Near detector _at_250-500 m ?
?(?)near-250/500m/ ? (?) far-1.8km 50-13 _at_50
meters depth (?100 3.1/m2/s) ?
?(?)near-100mwe / ? (?) far-300mwe 10 ltEgt 12
GeV
?(?)near-100mwe / ? (?) far-150mwe 2
(S/N)near-250m-100mwe ? ---------------------
gt1 (S/N)far-1800m-300mwe
28
Muon induced production of radioactive isotope

• Background Production of radioactive nuclei on
  12C in the scintillator
• NA54 Isotope production on 12C target _at_SPS/CERN,
  ? beam _at_100/190 GeV ? ?(E) ? E0.73 (T. Hagner et.
  al.)

Isotope T1/2 Emax (MeV) Rate (day-1) 150 mwe Rate (day-1) 300 mwe Type
?- 12B 0.02 s 13.4 - - Uncorrelated
?- 11Be 13.80 s 11.5 lt 13 lt 4 Uncorrelated
?- 11Li 0.09 s 20.8 - - Correlated
?- 9Li 0.18 s 13.6 11?2 4?0.6 (/2) Correlated
?- 8Li 0.84 s 16.0 21?8 7?3 Uncorrelated
?- 8He 0.12 s 10.6 11?2 4?0.6 (/2) Correlated
?- 6He 0.81 s 3.5 86?9 28?3 Uncorrelated
?, EC 11C 20.38 m 0.96 4850?310 1600 ?100 Uncorrelated
?, EC 10C 19.30 s 1.9 620?80 200?26 Uncorrelated
?, EC 9C 0.13 s 16.0 26?8 9?3 Uncorrelated
?, EC 8B 0.77 s 13.7 38?8 13?3 Uncorrelated
?, EC 7Be 53.3 d 0.48 1230?120 400?40 Uncorrelated

• Rates are given for the Paluel case
• 1.07 1030 free protons
• PXE scintillator d 0.99 ? 20 tons detector
• PXE scintillator C16H18 ? 0.951 1030 12C
• Depth 2 hypotheses considered 1) 150 mwe 2)
  300 mwe

29
Muon induced production of radioactive isotope

• Single Rate (uncorrelated)
• Dominated by 11C
• Rate(Paluel, 20t PXE) 4850/day _at_150 m.w.e
  (1600/day _at_300 m.w.e )
• ? bacc lt 1/year
• ? Needs position reconstruction _at_150 m.w.e (OK
  at 300 m.w.e)
• Correlated events
• ?-n cascade, ?few 100ms - Only 8He, 9Li, 11Li
  (instable isotopes)
• Rate(Paluel, 20t PXE) 10/day _at_150 m.w.e
  (4/day _at_300 m.w.e)
• But could be efficiently tagged ? ? - n
  - ? - n
• lt
  ------ gt
• 
  200 ?s
• lt ------------ gt
• 0.12-0.18 s
• lt ------ gt
• 200?s

30
? induced background neutrons
Background tag ? ? n? p recoil? space-time
coincidence ? n capture

• ? in water shielding, PXE
• _at_CTF 0.3 n/day/ton (LNGS, 3600 mwe, 1.16
  ?/h/m2)
• Scaling Paluel_at_150 mwe ? 220 n/day/ton (h1
  150 mwe, 5000 ?/h/m2)
• Scaling Paluel_at_300 mwe ? 73 n/day/ton (h2 300
  mwe, 1100 ?/h/m2)
• ? Muon preceding a neutron to be recognized with
  a loss lt 1.5(4.5)/105 events to have less than
  0.1 of this background ? ? track used for
  discrimination
• ? Level achieved in KamLAND ?
• ? in surrounding rocks
• From high energetic shower developing in the
  rocks (up to GeV) From (?,n) reactions (few MeV)
  ? Thick water buffer
• No ? track used for discrimination
• _at_LNGS 25/m2/year (Hadronic cascade generated by
  muons in the rock)
• ? Scaling at Paluel (150 m.w.e) 7.105/year
  (3 times less _at_300 m.w.e)
• Challenge ? overall reduction factor 2-7x105.
• Water shielding to be optimized PSD plastic
  scint. panels surrounding detector ?
• CHALLENGE at this shallow depth