sno+ scintillator purification and assay richard ford snolab lrt 20 10, sudbury, canada august 2 9,...

SNO+ scintillator purification and assay

Richard FordSNOLAB

LRT2010, Sudbury, CanadaAugust 29, 2010

Richard Ford (SNOLAB) LRT2010, Sudbury

The SNO+ Experiment

1000 tonnes D2O

Support Structure for 9500 PMTs

12 m Diameter Acrylic Vessel

1700 tonnes InnerShielding H2O

5300 tonnes Outer Shield H2O

Urylon Liner andRadon Seal

860 tonnes scintillator(LAB + 2g/L PPO)

Rope net anchored to the cavity floor

Scintillator purification


SNO+ Physics Program (2 phases)

Neutrino-less double beta decay (Nd loaded) Determine if neutrino is Dirac or Majoranna type Most sensitive measurement of absolute neutrino mass

Neutrino physics Solar neutrinos (pep, CNO) Geo antineutrinos Reactor antineutrinos Supernova neutrinos


ExistingSNO Facility

SNOLAB Excavation Phase I:Cube Hall and Ladder Lab

New personnelfacilities

SNO+detector

Water plant

Scintillatorpurification

Storage tanks

SNO+ in SNOLABSNOLAB Excavation Phase II:Cryopit cavity

Rail-car unloadingterminal

SNO+control room

Isolated 9’ ventilation raise to 6600L(Isolated vent path to surface)


Scintillator based on LAB

Linear alkylbenzene (LAB) identified as the liquid scintillator solvent: Chemical compatibility with acrylic High light yield High purity available Safe

Low toxicity High flash point 140°C Boiling point 278-314°C Environmentally safe Low solubility in water 0.041 mg/L

Inexpensive Suitable density = 0.86 g/cm3

Petresa Plant – Bécancour, QC


SNO+ signal and backgroundsZero-neutrino double beta with Nd56 kg of 150Nd and <mn> = 100 meV

3-year pep and CNO solar neutrino signals

- Backgrounds at Borexino levels: U and Th ~10-17 g/g, and K 10-18 g/g


Purification strategies: Multi-stage distillation

Initial LAB cleanup for high radio-purity and optical clarity Dual-stream PPO distillation for scintillator recirculation

Pre-purification of PPO concentrated solution N2 sparging, water extraction, and distillation

Pre-purification of Nd salt and TMHA pH controlled precipitation (self-scavenge) for Nd salt solution Thin-film evaporation of THMA

Steam/N2 stripping under vacuum Removes Rn, O2 and provides LAB humidity control

Water extraction (liquid-liquid extraction) Provides high-flow recirculation polishing stage Effective for ionic metals (K, Pb, Ra) and limited efficiency for Th and Po Stable for PPO and Nd-LAB solutions

Functional metal scavengers High-flow columns effective for Pb, Bi and Ra Can be regenerated with acid wash Processing and assay of the acid wash provides a method for radio-assay of scintillator


Production of Ra and Pb Spikes in LAB

Vacuum flaskP < 1 mBar

90 Bq 228Th evaporated on SS plate above LAB

Ra spike from 228ThIn vacuum 224Ra with 96 KeV recoilcan reach and implant into LAB. Flask cooled in dry ice to prevent condensation on source.

Peristalticair pump

Washing flaskwith LAB

228Th salt acid solution is absorbed by Dowex resin in a Teflon column

Pb spike from 228ThRadon emanation from the column is purged with air and through fine frit bubbled through LAB. Radon decays in LAB, with 212Pb recoiling into LAB.

Metals are not soluble in LAB, so we seek to produce “natural” radioactive spikes that are similar to the way that real contaminations will occur.


Laboratory LAB batch distillation tests

- Fractional batch distillation- 70 mTorr vacuum- 100°C- Improved UV transmission- Distillation effective for removal of heavy metals (Th, Pb, Po, Bi)


Dual-Stream Fractional Vacuum Distillation

Bottoms

Tower

Reboiler

CondenserReflux

LAB orScintillator

Vacuum pump

PPOsolution

Vac pump

Mix Scintillatoroutput

Kettle (LAB flashs and PPO boils)

55 Torr238°C

20 Torr242°C

Dual stream allows on-line distillation of scintillator (LAB + PPO).

Effectiveness depends on design (number of stages, reflux rate, bottoms concentration, vacuum level and stripping).


Borexino purification skids

Distillation tower

Reboiler

Condenser

The distillation tower is similarsize to that designed for SNO+.

SNO+ tower will be 32” dia x 15’ H.>99% removal efficiency for heavy metals at 20 LPM flow (1000kg/hr).


Liquid-liquid extraction purification(water extraction of solvent)

0 20 40 60 80 100

10-1

100

time, min

A, m

Bq

/mL

Output Activity of 224Ra in Water and LAB

WaterLAB

input LAB A0=14 mBq/mL

0 100 200 300 40010

-2

10-1

100

time, min

A, B

q/m

L

Output Activity of 212Pb in LAB and water

LABWater

input LAB A0 = 2.2 Bq/mL

• LLE efficiency of 212Pb removal from LAB is 87%.

• Tests with 224Ra show a high removal efficiency 98%.

• There is a lead component in LAB, irremovable by LLE.

• However, Pb and Ra removal efficiency is greatly reduced with Nd-loaded scintillator. Maybe the excess TMHA sequesters the Pb and Ra. Tests continue.


Counter-current water extraction

Water purification(integrated with the SNO high-purity RO system)

Scintillatorinput

Scintillatoroutput

Packed column

50 psig80°C


KARR® and SCHEIBEL® are registered trademarks of Koch-Glitsch, LP.

SCHEIBEL® Column for liquid-liquid extraction

SNO+ column is 30” dia x 23’ H.Flow 150 LPM, with 4 equilibrium stages.

www.modularprocess.com


Gas stripping

Vacuum pumpto vapour recovery and vent header

Scintillatoroutput

Scintillatorinput

N2

Steam generator

Packed column 150 Torr100°C

SNO+ column is 24” dia x 24’ H. Flow 150 LPM.- 95% Rn removal eff.- 99% O2 removal eff.


QuadraPureTM Metal Scavenger

- QuadrapureTM metal scavengers are functionalized macro-porous polystyrene-based resin beads (~500 um) for extraction of metal contaminants.- In flow tests with spikes, high extraction efficiencies are obtained even at high flow rates, up to 150 bed volumes per hour (depends also on column dimensions).- Beads can be stripped with HCL acid and regenerated with methanol.


SNO+ columns 6” dia x 200” H.Six columns for flow 150 LPM.

SNO+ scavenger columns


- delayed coincidence liquid scintillation counter

SecondaryConcentration

Elution

~ 800 Tonnes LAB Scintillator

QuadraPure scavenger columns

100 L 0.1M HCl

100 ml 0.25M EDTA (pH 10)

30.0 g Dowex 5WX8 resin

HTiO co-precipitation

1.5 ml conc. HCl

Extraction

Counting

Sur

face

labo

rato

ryU

nder

grou

nd p

lant

MeOH regeneration

Ada

pted

fro

m S

NO

tec

hnol

ogy

Method for radio-assay of scintillator


Scintillator plants Status: The plants have been designed and a process hazard review has been completed. The columns, vessels, HXs, and equipment is specified and currently being quoted for fabricated.


Specifications Materials – SS316, Teflon, glass, acrylic Pressure – max pressure of any pump + 50% (so that burst disk is not

close to operating range) ~ 150psi. Temperature – 350°C (just over BP at 18psi) Surface preparations and cleanliness – Electropolished. Final cleaning

to Mil spec 1241 class 50. Oxygen service specification generally okay Leak tightness – 10-9 mbar.L/sec fittings, 10-8 for vessels. Pumps, valves and fittings:

- 1”-2” SS electro-polished tubing, fusion welded- VCR fittings (<=1”)- Metal gaskets (eg. Helicoflex) for >1”- O-rings Teflon Encapsulated Viton (TEV)- Diaphragm or bellows valves for leak tightness- Mag-drive pumps

Insulation to TSSA and INCO standard for underground Codes (electrical CSA, pressure vessel TSSA, …)


SNO+ Process Interconnection System

SNO+ Operating Modes• LAB receiving and purification• PPO concentrate mix and purification• Nd(RCOO)3 concentrate loading and purification• Scintillator Mixing, stripping, and filling the AV• On-line purification and assay (SNO+ Nd phase)• Removal of Nd(RCOO)3 • On-line purification and assay (SNO+ SN phase)• Unloading AV and shipping LAB


AV Fill (PPO from storage)


Conclusions SNO+ will requires extremely low levels of high-energy beta and gamma-ray background

activities from 214Bi, 212Bi, and 210Bi, all from the 238U and 232Th chains, and also 40K.

We have investigated LAB scintillator purification methods for the purpose of designing the SNO+ purification and loading/unloading plants.

We have developed methods to make “natural” spikes of 212Pb and 224Ra using recoil implantation techniques from a 228Th source, for the purpose of testing purification methods.

Distillation is a well known reliable technique for the initial purification of the LAB and PPO, however the flow rate is low due to the size and heat and cooling requirements. We have designed the SNO+ plant “dual-stream” so that the scintillator can be distilled and remixed in recirculation mode.

Water liquid-liquid extraction is effective for ionic metals (K, Pb, Ra), and will will a good method for high-flow “polishing” recirculation of the scintillator. It is stable with Nd-LAB, but maybe not very effective due to TMHA.

Functional method scavengers are effective in high-flow columns for removal of Pb and Ra (and maybe Th and Po). More testing to show stability with Nd-LAB is on-going. The functional groups can be stripped and regenerated, with recovery and processing of the acid providing a radio-purity assay method.

The SNO+ purification and liquid handling plants have been designed partly on the basis of these tests, and partly on the basis of column efficiency silulations and the experience of Borexino.


IX

Filter & deaeorateZeolite

NewH2O RO

PrimaryRO

SNO+ H2O Simplified Process Flow Block Diagram

HTiOUV254

185

HX-01

HX-02

VE-0210-Tonne

INCO water

Jan-08: New water plant additions to provide AV fill and recirculation

P-15

P-11

PDG

F-06

New RO commissioned 2006

SNO+ Cavity

Softener

sno+ scintillator purification and assay richard ford snolab lrt 20 10, sudbury, canada august 2 9,...

Documents

richard ford snolab

sudbury scintillator

scintillator slide

sno scintillator purification

tonnes scintillator

snolab snolab excavation

assay richard ford snolab

sudbury sno signal