W. T. Shmayda, N. P. Redden, R. F. EarleyUniversity of RochesterLaboratory for Laser Energetics

Enhancing Gas Chromatography Performance

1

Tritium Focus Group-SandiaAlbuquerque, NM

22–25 October 2018

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• Thermal conductivity and tritium monitor detector measurements are complementary and predict similar atom fractions in H/D/T mixtures within 1%

• Miniaturization of the pressure sensing detector and the effluent isolation valve will reduce DT injection quantities for assay by 60%

• LLE has analyzed two of the three inactive gas samples provided by Sandia National Laboratories as part of the round robin exercise to compare assay results across the complex

Outline/Summary

Filling cryogenic targets in the permeation cell is a multistep process

G6218r

5

DT High-Pressure System (DTHPS) Glovebox

Tertiary containment

Syringe pump

Cryostat

FTS Glovebox

To tritium removal system

TFS Glovebox

USB 2 Assay

USB 1

DTHPScondensation

tube

High-pressure

guage Permeation cell

Condensationtube

P/Ddiffuser

TFS: Tritium Fill StationUSB: uranium storage bedFTS: Fill/Transfer Station

The lighter isotopic species concentrate whilepressurizing the permeator in the Tritium Fill Station

E25066c

6

Medium-pressuresystem

High-pressuresystem

T/D = 1.62

T/D = 1.60T/D = 1.62

PermeatorDiaphragmcompressor

TFS

T/D = 2.33

Composition in %: H/D/T

Variation in T/D downstream of the TFS = 1.2%

Gas chromatography uses iron-doped alumina at 77 K to separate the hydrogen isotopologues

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Minimum aliquot size: 80 nLError:

– systematic 1.2% – relative (peak to peak) <0.5% – reproducibility <0.2%

Fe-dopedMS 5 ÅLN2

Helium

Helium

MS 5 Å80°C

NeonTCD

Sample

Vacuum

Neon

P

TM

TCD

MS: molecular sieve TM: tritium monitor TCD: thermal conductivity detector

The assaying process requires four steps; first step: evacuate the injection volume

E26599c

4

Fe-dopedMS 5 ÅLN2

Helium

Helium

MS 5 Å80°C

NeonTCD

SampleVacuum

Neon

P

TM

TCD

To effluent capture

To effluent capture

Pump

Fe-dopedMS 5 ÅLN2

Helium

Helium

MS 5 Å80°C

NeonTCD

SampleVacuum

Neon

P

TM

TCD

To effluent capture

To effluent capture

Pump

Second step: charge the loop with a predefined aliquot of gas

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Minimum aliquot size: 80 nL

VacuumTo effluent capture

Pump

Fe-dopedMS 5 ÅLN2

Helium

Helium

MS 5 Å80°C

NeonTCD

Sample

Neon

P

TM

TCD

To effluent capture

Third step: inject the aliquot into the separation column and detection circuit

E26599e

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Fourth step: sample analysis

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00.0

2.5

5.0

7.5

2 4Time (min)

O2 CH4

COSign

al (m

V)

6 8

Fe-dopedMS 5 ÅLN2

Helium

Helium

MS 5 Å80°C

NeonTCD

Sample

Vacuum

Neon

P

TM

TCD

To effluent capture

To effluent capture

0

3

6

9

Sig

nal

(V)

Time (min)0 20 40

50% T91% T

T2

HTDT

Time (min)0

0

1

2

20

H2T2

HT

HD

5.45% H60.62% D33.93% T

40

Det

ecto

r sig

nal (n

V)

60

D2 DT

The 4-cm3 tritium monitor and thermal conductivity agree within 1% over all T/D ratios

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1.04

1.03

1.02

1.01

1.00

0.99

0.98

0.97

0.960 10 20 30 40 50 60 70 80 90 100Tritium fraction from thermal conductivity detector

TCD error: !1.5%

Triti

um m

onito

r/the

rmal

con

duct

ivity

The minimum aliquot required for analysis by the TM is 0.01 nL.The gas inventory of a typical target is ~20 nL!

Sample

Vacuum

Neon

PDiaphragm

MKSbaratrongauge

Hand weld Microweld

Microweld

0.125

Hand weld

SS-4-VCR-1

Hand weld

6LV-4-VCR-3S-4TB7

SS-4BK-TW-1Cwith Cu STEM

60% of the gas delivered to the gas chromatograph is not used for analysis

E28002

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Injection loop volume: 1.5 mLPressure transducer andisolation valve volume: ~2.24 mLVolume injected for assay: 3.74 mL (4.84 Ci)

Selector valvePressuretransducer

Backup 4B safetyisolation valve

0Pressure (Torr)

200 400 600 800 10000

20

40

60

80

Volta

ge (m

VDC)

Voltage (mVDC) = 0.0762 P(Torr) –2.369R2 = 0.9997

The volume of the pressure detector and isolation valve assembly has been miniaturized ~200 fold

E28003

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Injection loop volume: 1.5 mLPressure transducer andisolation valve volume: <10 nLVolume injected for assay: ~1.5 mL (1.9 Ci)

Tritium interacts with stainless steel to generate CH4 and CO

E26600a

11

Impurity growth rateVessel ID CH4 CO677 21.2 14.3624 1.9 6.0

* Time after filling the sample vessel

00

30

60

90

120

150

2Time (min)

Sig

nal

(m

V/s

cc)

4

544 ppm 307 ppm265 ppm

60 ppmCO CO390 ppm

64 ppm169 ppm33 ppm

Vessel ID 677 Vessel ID 625

6 8 00

30

60

90

120

150

2Time (min)

4 6 8

51 h*601 h

66 h*602 h

CH4 CH4

0

2

1

3

Pro

tiu

m c

on

cen

trat

ion

in f

uel

(%)

0 600

Duration since purifying fuel (days)

1200

H2O

H2O

H2O

H2O

H2O

H2O

H2O

H2O

H2OHO

HO

Evacuated

Absorbedwater layer

Bulkmetal

Baked

Tritiumconditioned

HOH

M

M

M

M

M

HH

H

H

HO

HO

HO

HO

HO

HO

HO

H2O

H2O

HTOTO

HO

TO

TO

HOHTO

HM

M

M

M

M

HH

H

H

TM

M

M

M

M

HT

H

T

Assay vessel1.88 %/mo

Permeation cell

Contamination caused by

sample vessel

“D” and “T” exchange with adsorbed water layers on the inner surfaces of the sample vessel and the process loop

E26601b

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• Direct measurement of the protium content in a gas contained in unconditioned vessels leads to 300% errors in the protium fraction

LLE is participating in the national lab round robin gas-analysis exercise

E28004

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SampleID Composition Nominal

mixture (%)Measured

valueRSD*(%)

1 H2 35 42.95 0.11HD – 3.01 0.80D2 65 54.04 0.05H/D 53.8 80.02 0.16

3 H2 20 30.02 0.02HD – 44.30 0.06D2 20 25.50 0.01H/D 1 1.10 0.06

* Relative standard deviation

The isotopologue ‘HD’ dominates the H2/D2 spectrum in the Mass Cal Gas sample

2525 202015 1510 105 5

300

150

10

5

Time (min)Time (min)

Sign

al (m

V) H2

H2

D2

D2

HD

HD

Sample #1 (H2/D2) Sample #3 (Mass Cal Gas)

Need to run a calibration gas to confirm the locations of the non-hydrogenic species

1

0.5

Sign

al (V)

642Time (min)

H2

N2

CH4COorAr

This column can not identify CO2

Composition of Mass Cal Gas• H2• D2• N2• Ar• CH4• CO2

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Outline/Summary

• Thermal conductivity and tritium monitor detector measurements are complementary and predict similar atom fractions in H/D/T mixtures within 1%

• Miniaturization of the pressure sensing detector and the effluent isolation valve will reduce DT injection quantities for assay by 60%

• LLE has analyzed two of the three inactive gas samples provided by Sandia National Laboratories as part of the round robin exercise to compare assay results across the complex