n_ToF Target #3 - Design of N2

and moderator cooling stations

F. Dragoni - EN-CV29.05.2019

Summary

• User’s Requirements - EDMS2068190

• Technical Solution - EDMS2068336

• Integration

• Occupational H&SE

Design Review

• IEDR (15.05.2018)

• PRR - Question 13:

• Is the design and progresses on the design of the N2 cooling and moderator(s) station adapted to cope with the operational requirements of the new spallation target?

• Is there any major improvement that would need to be implemented before the tendering phase?

User’s Requirements – EDMS2068190

• 3 cooling circuits in total:

• Housed in existing CV technical room

• n+1 redundancy on chillers and moderators pumps

• HEPA and active carbon filtration on nitrogen

• Filters in dynamic confinement

• Pipework to RP monitoring chambers

Cooling

requirements Unit Target circuit

Horizontal

moderator

Vertical

moderator

Cooling media [-] Nitrogen gas –

≥99.995 %

Demineralised or

Borated Water

Demineralised or

Borated Water

Supply temperature [°C] 20 ± 2 20 ± 2 20 ± 2

Cooling power [W] 2600 200 200

Flow rate [m3/h] 780 (Nm3/h) 0.70 0.70

Maximum pressure at

equipment inlet [bar] 0.4 2.5 2.5

Technical solution: EDMS2068336

Existing moderator circuit

Chilled

water

circuit

Target N2

cooling circuit

Air extractor

Dynamic confinement extractorN2 generator

New moderator circuit

Chilled water - N2 generator - Electricity• Chilled water circuit renewal:

• 2 x 30 kW Chillers – n+1 redundancy

• Independent temperature control on each circuit

• Serves both moderators and target cooling circuits

• N2 generator

• Serviced and modified to supply up to 1 Nm3/h N2 -purity > 99.995%

• Keep cooling circuit in overpressure to avoid in-leaks and external contamination

• Power and control cubicles moved outside Controlled Area

Chilled water circuit – N2 generator: Integration

Foreseen downtime for preventive maintenance:

• Chillers – max 1 week/year;

• N2 generator – max 2 days/year;

• Electrical cubicles – max 2 days/year

Standard technology across CV (except for N2

generator)

1. Aligned with target

operational requirements

2. No technical

modifications needed

before procurement

Power and

Control cubicles

Chiller #1

Chiller #2

N2 Generator

Chilled water pipework

to heat exchangers

Nitrogen

filling line

Target N2 Cooling Circuit

• Designed to work up to 1000 Nm3/h at ∆P = 285 mbar(G)

• 4 modes of operation: (1) BEAM, (2) FLUSH (3) ACCESS (4) CLEANING

• N2 supply kept at T = 20 °C via water cooled tubular heat exchanger

• Bypass to allow for system testing – when target not installed

• Instrumentation: PT (3x); PI (3x); TT (3x); FT (1x).

(1) BEAM Mode - Blower ON

75 °C

20 °C

20 °C

30 °C30 °C

T

A

R

G

E

T

Low pressure

point: 50 mbar(G)

N2 Generator

1000 Nm3/h

Target N2 Cooling Circuit

• Circuit dilution via N2 gas flush to target area (manually actuated)

• New purge pipework to TT2 tunnel

• Finally exhaust to the atmosphere via existing TT2 tunnel extraction

• Differential pressure continuously monitor via transmitter

T

A

R

G

E

T

(2) FLUSH Mode – Blower OFFTo Tunnel

N2 Generator1 Nm3/h

Target N2 Cooling Circuit

T

A

R

G

E

T

(3) ACCESS Mode – Blower OFF

N2 Generator

Circuit kept under

inert atmosphere

(4) CLEANING Mode - Blower ON

32 °C

20 °C

20 °C

20 °C

T

A

R

G

E

T

N2 Generator

400 Nm3/h20 °C

N2 cooling station: Modelling

• 1D – Steady-state and Transient analysis of

whole cooling circuit including : blower, heat

exchanger, filter (clean/clogged)

• Study quantities at any point in the circuit

2200 rpm

Shaft speed

Flow rate

Pressure

Blower curves

Surge

2950 rpm

2950 rpm

2200 rpm System

curve

Blower: technical selection

• 22 kW motor - Magnetic motor/shaft coupling

• Pressure and leak tested at 700 mbar(G) - 2 x

Pmax - Measured leak rate: << 5 L/h

• Improve bearing selection – no need for

lubrication change every 2 years at 75 °C

outlet temperature

Characteristic curve

Magnetic coupling• Foreseen downtime for preventive

maintenance: max 2 weeks/year;

• Tests on similar model confirmed that leak

rates is well below RP threshold

1. Aligned with target

operational requirements

2. No technical

modifications needed

before procurement

Filters: technical selectionA. NUCLEAR GRADE AIR TIGHT ENCLOSURE• Fully welded Stainless Steel - Bag In/Bag Out (BIBO)

• Class 3 (EN ISO 10648) Max leak rate < 0.005 Nm3/h

• Leak tested @ 400 and 570 mbar(g)

• Max working P = + 400 mbar(g)/ -200 mbar(g)

• Pressure tested (integrity) – 570 mbar(g)

• Instrumentation: Differential Pressure Switch on each filter

B. FILTERS

• HEPA Filter - for spallation and erosion products• Supply and return lines• Efficiency > 99.98% up to 200 °C

• Active Carbon Filter – for trapping volatile compounds• Return line only• Impregnated as per RP requirements• Each carbon batch tested by external lab• Working temperature up to 80 °C

ISO 10648-2

• After installation in-situ efficiency

measurement by accredited company

Guaranteed efficiency on filters

• Filter change needs : 0.5 day

1. Aligned with target

operational requirements

2. Technical selection

confirmed

Heat exchanger: technical selection

• 30 kW Water cooled Shell and tube heat exchanger

• DN200 flanged process connections

• Max working pressure (gas side): 500 mbar (g)

• Low pressure drop: 35 mbar at 1000 Nm3/h

• Possible future option: Double tube exchanger

Chilled

water IN

Chilled

water OUT

N2 gas

IN

N2 gas

OUT

• Pressure drop monitor (Tube and Shell side)

• Virtually maintenance free

• Stainless steel construction

1. Aligned with target

operational requirements

2. Technical selection

confirmed

• Consolidation of existing skid

• New skid similar to existing one

• Instrumentation: PT/PI, TT, FT, PDT, DPT, CT, FT, FS

Moderator skids

• Retain possibility to swap borated and demi water

• Replace motor VSDs• New expansion vessel,

• New heat exchanger• New distribution pipework• New ion-exchange cartridges

• Foreseen downtime for preventive

maintenance: max 1 week/year;

• Years of operational experience from target #2

1. Aligned with target

operational requirements

2. No technical

modifications needed

before procurement

CV technical room: Integration

Moderator

skids

Blower

Heat

Exchanger

Air tight filter

casing: HEPA + AC

Controlled

Area

Sealed AreaAir tight filter

casing: HEPA

Sealed area: extraction

• Civil works designed by EN-EA

• Door for personnel access

• Roof opening for material access

• Extraction circuit independent from nitrogen purge pipe

• 90 m3/h extraction flow rate to achieve -20 Pa

• Class D ductwork that connects to existing ductwork to tunnel

• Instrumentation:

• Differential pressure switches on each filter (UBAY)

• Differential pressure between sealed area and ISR8 (UBA6)

T

U

N

N

E

L

Sealed area: filters

• INLET

• Grill with damper

• OUTLET

• F7 Filter ePM1 50-75%

• HEPA filter in airtight casing

• Efficiency > 99.98

• Working P = ±2000 Pa

T

U

N

N

E

L

RP monitoring pipework

• Monitoring via CD 10 chambers

installed next to N2 generator

• Particulate filter

• 4 couples of pipework to RP

CD10 chambers

• 1 branch before HEPA/AC filter

• 1 branch after HEPA + AC filter

• 1 branch inside CV technical room

• 1 branch on dynamic confinement

duct

Cooling station: Air Extractor

• Purpose: extract excess heat from cooling station room

• Main heat load: Blower – 5kW according to manufacturer

• Extraction flow rate

• Assuming 25 °C room temperature and extraction at 35 °C

• Minimum 1500 m3/h

Cooling station: Occupational noise

• 3 main noise sources: (1) Blower/Motor; (2) Moderator Pump/Motor;

(3) Extractor fan Combined Lp-1m = 84. dB(A)

• 85 dB(A) – 8-hour exposure limit set by European Directives/ CERN

safety code A8

• Max Lp > 80 dB(A)

Earplug dispenser,

signalisation and training

REQUIRED

• Max Lp < 85 dB(A)

Collective protective

measure (noise dampening

at walls, blower noise

attenuator) NOT required

< 84 dB(A)

70 dB(A)

54 dB(A)

Max noise

70 dB(A)

Cooling station: Oxygen Deficiency Hazard• Max N2 release volume: 2 m3 at 1.6 bar (1.35 bar – max nominal value)

• Case #1: Cooling station room

• HSE estimated a O2 concentration 20.47% > 18%

• No ODH risk in this room

• Case #2: sealed enclosure

• HSE estimated a minimum sealing area volume to avoid ODH risk: 28.4 m3

• If volume smaller

portable ODH monitor;

signalisation, leave door

open during intervention

• Current volume (not

considering occupation

factor): 33 m3 in

theory no ODH risk

Sealed

area

Cooling

station room

Future option: gas analysis

• Gas analysis system• Gas continuous analysis at pressures 100

mbar to 2 bar (abs)

• Quadruple mass spectrometer

• Soft ionisation (no spectral fragmentation)

• Mass range: 300 amu

• Detection limit: 5 ppb (triple filter)

• Multi-stream sampling(option)

• Particulate analysis• Filter upstream gas analyser

• Periodic laboratory analysis on filtered

particulate

• Chemical composition

• Particle size distribution

Hiden HPR-20 R&D

Q&A?

SCK-CEN Visit

• SCK-CEN has unique experience in studying release and filtration of

spallation products from Pb/Bi alloy. Their studies focus on Polonium (Po)

• SCK-CEN studies show:

• Polonium - Po

• Po release rate at T< 400 °C complex phenomenon dependent on

many factors (temperature, Pb oxidation, reducing atmosphere, etc)

• Volatile Po will adhere to stainless steel surface at T < 400 °C

• Active carbon filter are efficient No Po could be detected after filters

• Gadolinium – Gd

• Gd is Lanthanide Strong affinity with O2 (similar behaviour to Lu)

• Tends to forms oxides even at few ppm Solid state – NOT volatile