fusione, tecnologie e presidio nucleare sezione ingegneria sperimentale iea workshop on t/pb16li...

Fusione, Tecnologie e Presidio NucleareSezione Ingegneria Sperimentale

IEA Workshop on T/Pb16Li Idaho Falls, 11-12/06/2007

Tritium extraction from Pb16Li

and He: EU experience and proposals

I. Ricapito, ENEA CR Brasimone, FPN-FISING



OBJECTIVE

To summarise the EU experience on tritium extraction from Pb16Li and

He for DEMO and Power Plant, presenting at the same time the

proposals to ITER for TBM tritium processing systems. Moreover

possible fields of collaboration are indicated.

Tritium extraction from Pb-16Li

Tritium extraction from He (TRPS; CPS)

Proposals for EU TBMs T-systems

TES/TRPS

CPS

Possible developments

OUTLINE



GAS LIQUID CONTACTORS

V GETTERS

BUBBLE COLUMN-PERMEATOR (SiC-SiCf)

spray columns

bubble columns

packed columns

plate columns

Tritium Extraction from Pb-16Li

Different technologies have been proposed and studied in EU




Most of the experimental activities on GL contactors were carried out on Melodie loop

MELODIE LOOP: PFD




Test n. LM flow-rate

(lh-1)

Ar flow-rate

(N lh-1)

PH2, in

(Pa)

(%)

1 80 -105 30 1300 -1400 10 -12

2 80 -105 60 1200 9 -11

3 50 - 65 60 1150 -1200 >14

800 mm height, 54 mm diameter, 673 K

Bubble columns: experimental results on Melodie loop

Results from Melodie loop on GL contactors




Test n. LM flow-rate

(lh-1)

Ar flow-rate

(N lh-1)

PH2,in

(Pa)

(%)

10 70-90 6 1200-1350 20-22

11 30-50 6 1000-1100 29-31

12 30-50 30 975-1000 29-31

13 30-50 6 450-475 23-25

14 30-50 6 220-230 23-25

800 mm height, 54 mm diameter, packing area: 750 m2/m3, T:673 K

Results from Melodie loop on GL contactors

Packed columns: experimental results on Melodie loop



Tritium Extraction from Pb16Li

G-L contactors, experimental results: summary

disappointing results were obtained by bubble columns because of the small G-L interface area: particularly, coalescence of gas bubble, already at low gas flow-rate, was claimed to be the main reason of the low efficiency

maximum extraction efficiency was nearly 0.3, achieved with packed columns (0.8 m in height)

the effect of hydrogen addition to the purge gas on the extraction efficiency was not studied

L/G molar ratio was not optimised




TES: V Getters

V was selected because of the high Sieverts’ constant for tritium and good compatibility with Pb-16Li

A deuterium gettering rate constant in the range 10-7 10-8 mol m-2 s-1 mbar-1/2 was experimentally determined, increasing with the temperature because of the increasing deuterium diffusivity in the LM boundary layer (controlling step in the mass transfer)

the system is more compact than G-L contactors for a given extraction efficiency

a cyclic operation is intrinsically necessary (two beds in parallel)




TES: bubble column- permeator

High extraction efficiency is claimed to be achievable with a very compact system, but experimental confirmation is necessary

tritium is recovered by two channels in parallel:

- a tritium flow from LM to ascending bubbles

- tritium permeation through 2D- SiCf/SiC with a sweep He

flow recovering permeated Q2 or by vacuum

Pb-16Li inlet

Pb-16Li outlet

He

He +Q2

He +Q2




column operative temperature: 623-723 K;

internal diameter of the column: 12.8 cm;

column height: 20-120 cm

specific surface of the filler: 350 m2/m3

mass flow rate of Pb-16Li: G 0.2-1.0 kg/s;

Segmented packed column

Ongoing activities on TRIEX loop at ENEA CR Brasimone

Aims: - study and optimisation of GL contactors (first phase)

- study and optimisation of alternative technologies (integrated bubble column-permeator) in the ambit of international collaboration



Tritium Extraction from He purge (TRPS)

TRPS is the process downstream a GL based TES

TRPS feed stream depends on the GL contactor design specification

SG

CPS

P

ISS

TES

Q2

Pb-16Li

H2

TRPS

He+Q2+ imp. Q2

WGS

impuritiesHe Q2

HCS

to stack

to fuelling

H2O, H2




Tritium Removal from Purge Gas: TRPS

VPSA (Vacuum Pressure Swing Adsorption)

TSA (Thermal Swing Adsorption)

PdAg Permeator battery

Candidate Processes




Process steps

a) Feed pressurisation (all valves closed except V1)

b) Adsorption at 77 K and 1-2 MPa (all valves closed except V1, V3)

c) Co-current blow-down (all valves closed except V2, V4)

d) H2 addition (all valves closed except V6)

e) Co-current evacuation (all valves closed except V2, V5)

Q2 to ISS

H2

He+Q2

pure He to TES

Adsorption column

V1

V6

V3

V2

V4

V5

VP

To Imp. Processing

VPSA process




Alternative to VPSA is a cryogenic TSA process. For this application TSA is

operated at 77 K in adsorption phase, while the regeneration of the adsorbent

beds takes place under counter-current He stream at RT or under vacuum,

depending on the bed dimensions.

Recovered Q2, concentrated in the He regeneration stream, is then processed by

Q2 permeators (Pd-Ag)

TSA process




Pd-Ag Permeators (solution proposed for DEMO)

Cooler

Blanket

Permeator 5

Water to WGSR

O2 recirculator

O2 addition

Blanket

to HISS

VacuumPump

VacuumPump

VacuumPump

VacuumPump

Permeator 4 Permeator 3 Permeator 2 Permeator 1

In the last reactor-permeator HT partial pressure in the shell side is virtually zero by oxygen addition




Considerations on TRPS

TSA is more technologically mature than VPSA, especially when operated at

cryogenic temperature, because of the simplicity of the regeneration phase

in TSA tritium inventory is higher than in VPSA: in VPSA configuration, the

adsorbent beds are much more compact than in TSA

Pd-Ag permeators require large surface area and pumping power because of

the low differential Q2 partial pressure (driving force)



Tritium Extraction from He purge (CPS)

About CPS…

CPS is the most critical tritium system in HCLL blanket (DEMO or Power Plant) because of:

- large feed flow-rate to be processed: in the worst

conditions (PRF=1, low LM flow-rate) it exceeds 10 % of

the total coolant flow-rate, which is unacceptable

- relatively small Q2 concentration in the feed stream

- presence of Q2O and impurities at very low partial

pressure (range of Pa)




LM flow-rate (kg/s) 800 1600 1600

PRF 10 10 10

TES efficiency 80% 80% 60%

CPS efficiency 95% 95% 90%

T_perm. rate (g/d) 12.3 4.8 9.0

Average T conc. in LM (mol m-3) 2.3x10-2 1.2x10-2 1.8x10-2

CPS feed flow-rate (Nm3/h) 2.1x106 8.2x105 1.6x106

Fraction of the coolant flow-rate 2.7% 1.1% 2.1%

Possible Working Points




OUT

Q2O

impurities to WGDS

oxidizer (Cu2O-CuO)

700-750 K

ADSORBERS 2

He

RHE

He + Q2 + Q2O + imp.

IN

CT

H2O + H2

CPS: possible configuration for DEMO/Power Plant (possibly to be tested in ITER)



Each TBM will have a Tritium Extraction System (TES) to extract

the small amount of tritium generated

Each TBM will have a Coolant Purification System (CPS) for the

extraction of tritium permeated into coolant

Processing of tritium within the Tritium Plant

could be carried out, alternatively, through:

the Tokamak Exhaust Processing System

with the subsequent tritium recovery by the Isotope Separation

System

or the Vent Detritiation System

with subsequent tritium removal / recovery by Water Detritiation

System and, in series, Isotope Separation System

General Statements




TBMISS

CPS

TES TRPS

He purge gas

HCS

to SDS

TEPQ2

WDSA/VDS

Integration of TES/CPS in the ITER Fuel Cycle




For the EU TBMs (HCLL and HCPB), the tritium extraction from

He purge could be accomplished by two diferent systems for

the low duty and high duty DT phase, respectively

In view of ITER

Low duty: isolated pulses, low amount of Q2 to be extracted

High duty: sequence of standard pulses (back to back pulse series) or long pulses




TES in the low-duty DT phase (isolated standard pulses)

For the low duty DT phase, a simple “Tritium Measurement System” (TMS) could be used as TES.

TMS (FZK concept)

is based on a Zn reducing reactor, followed by a U getter bed

it has to be equipped by suitable tritium accounting system (on line or in the tritium building)

has to be placed close to the TBM (port cell)

requires a space approximately 2.3x1.3x1.5 m (LxWxH) for both HCPB and HCLL TBMs

TMS




TES-HCPB: properties

Feed flow-rate (Nm3/h) 8

Temperature (K) 723

Pressure (Pa) 1000

HT molar fraction (vppm) 3.9

H2 molar fraction (vppm) 1070

HTO molar fraction (vppm) 0.13

H2O molar fraction (vppm) 3.9


TRS-HCLL: inlet gas properties

Feed flow-rate (Nm3/h) 0.23

Temperature (K) 673

Pressure (Pa) 1000

HT molar fraction (vppm) 21

H2 molar fraction (vppm) 1000

HTO molar fraction (vppm) -

H2O molar fraction (vppm) -

EU TBMs: gas stream to be processed by TES/TRPS

HCPB-TBM HCLL-TBM



TES/TRPS

For the high duty DT phase (back to back pulse series and long pulses), different

alternatives could be envisaged. One of them is here proposed which is, in principle:

- able to recover Q2 with a good efficiency (90%) and in a wide range;

- able to distinguish between HTO and HT generated in the breeder;- DEMO relevant

A candidate process consists, essentially, of two in series TSA systems, the

first one operated at RT in adsorption phase for Q2O removal and the second

one at LN2 temperature for Q2 removal.

In this process the main components are:- a cooler to cool down the He stream from the TBM outlet (450°C) up to RT

- a TSA for Q2O removal operated at RT in adsorption phase (for HCPB-TBM)

- a pre-cooler to cool down the dry He stream close to LN2 temperature

- a TSA for Q2 removal operated at LN temperature in adsorption phase

- a heater to bring the pure He stream to RT

- a blower to circulate the He stream into HCPB-TBM




parameter Q2O TSA Q2 TSA

Temperature in adsorption phase 298 78

Total mass flow-rate (g/s) 0.4 (8 Nm3/h) 0.4 (Nm3/h)

Duration of adsorption phase (FPh)* 36 6

Temperature in regeneration phase (K) 573, He purge RT, vacuum

Duration of heating + regeneration phase (h) 6 6

He flow-rate for regeneration (Nl/h) 150 -

Column length (cm) 50 60

Column internal diameter (cm) 20 20

Adsorbent material (pellet 1/16”) Silica-gel Zeolite 5 A

Max tritium inventory in HTO form (Ci) 45 (31 mg) -

Max Q2O inventory (g) in Q2O-TSA 0.92 -

Mean Q2O molar fraction in regenerating He (%) 0.12 -

Max tritium inventory in HT form (Ci) - 225 (31 mg)

Max Q2 inventory (g) - 4.6

TES/TRPSProperties of the Q2O-TSA and Q2-TSA

Analytical instrumentation consists of:

- n. 7 ionization chambers, located in different points of the circuit. Their measurement range is 1E3÷1E6 Bq/ml- n. 3 H2 detectors, with a range of 1E-3÷1E0 % in He- n. 2 hygrometers, located in the regeneration loop of Q2O-TSA; measurement range -60÷+10 °C (d.p.)-n. 1 gas-chromatograph, with a measurement

range of the impurities as 1E-1÷1E2 vppm

TES-HCPB


TRPS-HCLL



CPS-HCPB: INLET GAS

Feed flow-rate (Nm3/h) 7.0

Temperature (K) 773

Pressure (MPa) 8

H2 partial pressure in the feed stream (Pa) 1000

H2O partial pressure in the feed stream (Pa) 30

T molar fraction, HT-HTO (vppm) 3.7e-2

Impurities (CO2, N2, CQ4, O2) 10


EU TBMs: gas stream to be processed by CPS

CPS-HCLL: INLET GAS

Feed flow-rate (Nm3/h) 42

Temperature (K) 773

Pressure (MPa) 8

H2 partial pressure in the feed stream (Pa) 1000

H2O partial pressure in the feed stream (Pa) 30

T molar fraction, HT-HTO (vppm) 3.7e-2

Impurities (CO2, N2, CQ4, O2) 10



CPS /1

The proposed CPS for HCPB-TBM is a three stage process, derived from the DEMO conceptual design:

1) oxidation of Q2 and to Q2O and CO to CO2 by means of an oxidising

reactor (Cu2O-CuO) operated at 280 °C;

2) removal of Q2O by a room temperature PTSA (Pressure Temperature

Swing Adsorption);

3) removal of the impurities by a cryogenic PTSA




parameter Q2O-PTSA IMP-PTSA

Temperature in adsorption phase 298 78

Mass flow-rate in adsorption phase (g/s) 0.35 (7.0 Nm3/h) 0.09 (1.75 Nm3/h)

Pressure in adsorption phase (MPa) 8 8

Duration of adsorption phase (h) 3 3

Temperature in regeneration phase (K) 573 373

Flow-rate in regeneration phase (Nl/h) 90 50

Pressure in regeneration phase (MPa) 0.2 0.2

Duration of heating + regeneration phase (h) 3 3

Column length (cm) 110 50

Internal Column diameter (cm) 17 15

Adsorbent material (pellets, 1/16”) Silica-gel Zeolite 13X

Max tritium inventory in HTO form (Ci) 1.0 (0.7 mg) -

Max Q2O inventory (g) in Q2O-TSA 2.2 -

Mean Q2O molar fraction in regenerating He (%) 0.12 -

CPS /2

Analytical instrumentation consists of:- n. 4 ionization chambers, operated in the range 1E2÷1E4 Bq/ml- n. 3 hygrometers, with a measure range -80÷0 °C (d.p.)- n. 1 gas-chromatograph with detectable range of impurities 1E-1÷1E2 vppm

Size: 4.5x1.8x2.8 m (LxWxH)

close to HCS compressor (TWCS vault)

HCPB-CPS_PFD CPS-HCPB_3D




Although many experiments were done in the past years on Melodie

loop at CEA, experimental and modelling activities on the optimisation

of tritium extraction systems from LLE need to be continued.

An extensive experimental campaign is foreseen in TRIEX loop on GL

contactors, particularly for packed columns, with the aim to optimise

them with respect to different operating parameters: G/L, H2 content in

the stripping gas, hydrodynamics.

TRIEX loop is available to test other tritium extraction technologies

for their study and optimisation (e.g.: permeators and coupled bubble

columns/permeator)

Possible developments /1

Tritium Extraction from PbLi



Technologies of tritium extraction from He have been identified for both tritium extraction from the purge gas (TRPS) and coolant purification systems (CPS) but no related experimental campaigns have been carried out so far.

Adsorption technologies are potentially attractive for such applications but experiments on lab scale

adsorption multicomponent equilibria on different microporous materials under relevant

pressure, temperature and gas composition;

adsorption kinetics

and on pilot plants appear necessary taking into account the demanding performance and the very unusual feed stream properties.

Modelling of the system is the next step activity, useful also to refine the sizing of TES/TRPS and CPS for ITER

Possible developments /2

Tritium Extraction from He

fusione, tecnologie e presidio nucleare sezione ingegneria sperimentale iea workshop on t/pb16li...

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