Qweak Target Qweak Target MeetingMeeting

Greg Smith, Dave Meekins, Greg Smith, Dave Meekins, Mike Seely, Silviu CovrigMike Seely, Silviu Covrig

January, 2008January, 2008

• Design Questions• Signals/Feedthrus• Relief Stack

• Job Jars• Schedule• Safety/Relief Calculations

Top Plate Design Top Plate Design QuestionsQuestions

– Coolant standoffs• Length “cut to fit” by tgt grp• Interferences? Accessibility? Relative height?• Several sizes in use at Jlab, Bert needs your

guidance here

– Lifter EC position fixed– Electrical feedthrus

• Bert needs input asap (part goes out this week)• How many of what type?• HPH feedthru config (2 or 2*4?)• Spares

Top Plate LayoutTop Plate Layout

Coolant Coolant StandoffsStandoffs

TargetTargetSignalSignal

ss

From Inside Target Scattering Chamber:

Leads NameThermometer Cernox1 4 Tmi 1 quadThermometer Cernox2 4 Tmo 1 octal 1 quadThermometer Cernox3 4 T4Khxi 1 quadThermometer Cernox4 4 T4Khxo 1 octal 1 quadThermometer Cernox5 4 Tpi 1 quadThermometer Cernox6 4 Tpo 1 octal 1 quadThermometer Cernox7 4 T15Khxi 1 quadThermometer Cernox8 4 T15Khxo 1 octal 1 quad

Subtotal 32 4 octal 8 quad

Thermometer Solid tgt ladder Platinum 2Thermometer Thick Dummy Platinum 2Thermometer Thin Dummy Platinum 2 1 octalThermometer Phytron Platinum 2Thermometer Spare Dummy Platinum 2Thermometer Optics Target Platinum 2Thermometer Spare Platinum 2 1 octal

Subtotal 14 2 octal 0 0

Motor Phytron Motor 4 1 quad 15ALimit switch Phytron home 1Limit switch Phytron left 1Limit switch Phytron right 1Brake Phytron brake 2Readback Phytron encoder 3 1 octal

Subtotal 12 2 0 0

Motor Pump 3 1 quad 30A 1 quad 30AMotor Tachometer 2 1 dual 1 dualHeater Heat Tape 2 1 dual 30A 1 dual 30A

Subtotal 7 3 3

Heater HPH Top 2 1 2-pin 50A 1 2-pin 50AHeater HPH Bottom 2 1 2-pin 50A 1 2-pin 50A

Subtotal 4 2 2-pin 50A 2 2-pin 50A

Thermometer 4K Supply 4 1 quadThermometer 4K JT 4 1 octal 1 quadThermometer 4K Return 4 1 quadThermometer 15K Supply 4 1 octal 1 quadThermometer 15K JT 4 1 quadThermometer 15K Return 4 1 octal 1 quad

Subtotal 24 3 octal 6 quad

Grand Total 93 93 18 19

Scatt Chmbr Feedthru Loop Feedthru

Electrical FeedthroughsElectrical Feedthroughs

Target Group Purchases for the standard pivot targets:Flange Pin

Ceramaseal Diameter Diameter I_maxPart # Page Application Unit Price Quantity Total (inches) (inches) (A)9340-03-CF 8 conductor/small pin 23 1.33 0.032 210236-02-CF 10 conductor/large pin 25 Cernox 236.00$ 1.33 0.062 22044-02-A large pins 132 30.80$ 10/pkg 5 154.00$ accepts 0.062 1511911-02-X small pins 132 31.91$ 10/pkg accepts 0.050 1510287-01-CF 2 conductor, 30A 17 133.00$ 6 798.00$ 2.75 0.094 309545-02-CF 2 conductor, 30A 17 85.00$ 6 510.00$ 1.33 0.094 30

Items we may need for Qweak:

16705-01-CF 2 conductor, 150A 17 HPH 2.75 0.25 1508176-08-CF 4 conductor, 15A 18 Pump & Motors 1.33 0.05 15

EFT0541253 Lesker 4 pin, 75 A 3-25 HPH $284 2.75 0.25 75MCF1504M NorCal 4 pin, 56 A 95-186 HPH 2.75 0.25 56

Relief Plumbing Relief Plumbing QuestionsQuestions

– Fill line and separate return line• Opposite sides of pump

– Mike suggests very small fill line, has to go on suction side of pump

• Coaxial (sort of) to main 2 7/8” id vent– Ok? Thermal crosstalk a problem?

• ½” fill line. OK? Bigger? With a gusset.

– Pump geometry fixed to opposite leg as relief line.• Means return line attaches to upper corner opposite pump,

on output side of pump– So can’t ever use this to fill the target!– Pump differential pressure relative to ½” fill line

– Fill & return mainly tube, with short hose• Heater tape?

– Separate tap for vapor pressure bulb? Coaxial too?

Relief Relief DesignDesign

6” od relief bellows(3.5” id)

2 7/8” id cold relief

G10 spacer 300K sleeve

short flex hose to loop to accommodate horizontal motion (not shown)

to ballasttank

4K stand-

off

15K stand-

off

Coaxial Coaxial Fill LineFill Line

Fill: ½”

Return: 2 7/8” id

Up & DownUp & Down

Fill: ½”Return: 2 7/8” id

Broken Broken SymmetrySymmetry

Given: • Pump must be on opposite side as relief stack.• Fill line must be on inlet side of pump.• Heater will be on the leg opposite to the HX.

Question:• Which side of pump should HX be on? Suction side, as shown here? Or the other side?

Coarse ScheduleCoarse Schedule• Safety Review this spring• Test pump in LN2 late spring

– Must decide if we need to go commercial by August

• Assemble tgt this summer• Test tgt this fall in test lab with GHe• Neon test spring 2009• Install in Hall C fall 2009• LH2 test winter 2009-2010• Run for Qweak spring 2010-2012

Bert’s Design Job JarBert’s Design Job Jar– Transition between 2

scattering chambers• Needs pump, HX

geometry (fixes ht)

– SC window• Needed for Safety

review?

– SC ports• Where? How many?

– Motion mech’s– Relief stack– Cryostacks– New relief/vent

plumbing

– Top plate• Needs feedthru info

– 8” SS pipe– Bracket that fixes

the loop to the 8” pipe

– Loop basics– Qweak

Support/Storage tripod

– Support plate• HKS stand to SC

– Gas Panel schematic

Target Group Design Job Target Group Design Job JarJar

(with some help from GRS, SDC)(with some help from GRS, SDC)

– Cell– Cell manifolds– Cell positioner– Exit window

• >7” diam, .005” nipple

– Entrance window– Pump– HX– Dummy

target/ladder design?

• Bert/Dan?

– Gas Panel• Hall C techs?• GRS/SDC

– Loop details– Survey tools– Help on safety

document– Dump G0 D2

The Fast TrackThe Fast Track• Motion Mechanisms

built by March• Relief stack & top

plate built by March• Tripod by March• Pump prototype

– Build early spring, test by late spring

• Need 1 year if we have to go to BN

• HX could be ready in 3 weeks...

• Cell mechanical design by spring– Fabricate late

spring/early summer

• Heater by summer (MSU)

• Gas panel by summer• SC ready by fall

– Transition, ports

The Slow TrackThe Slow Track• Plate for HKS stand/Sample SC transition• SC window (a big job)• Cell positioner

– Need a wag though

• New Relief & Vent plumbing• Final exit & entrance windows

– Need something though (could be thick)

• Ballast tanks • New HX from cryo• Dummies• New HX for CHL return from cryo group

Dirty gas to CHL

HP HX:20 K 1 atm return

15K, 12 atm supply

T

CHL4.5K 3 atm

QW

Tgt

Hall C

NewHX

ESR

Oct., 2007, GRS

Sho

rt N

ew I

ns.

Line

20K

Ret

urn

Line

WR

Lin

e

15K

S

upp

ly 1

2 a

tm

Lin

e

20K

Ret

urn

Line

House Helium Line (300K Supply)

20K, 50 psia LH2 Loop

20K, 3 atm return

300K 4 atm supply

5K, 1 atm return

4K, 3 atm supply

Hall C Moller

HMS *warm*

Qweak Gas

Panel

H2 Ballast Tank

H2 vent

LP HX:20 K

2.5 atmReturn

Warm return

4K 3

atm

Su

pply

Lin

e

Relief Calculation Relief Calculation StrategyStrategy

• Follow “Hydrogen Safety Assessment Document” written by Mike Seely for the Jlab LH2/LD2 targets in 2004

• Reproduce those calculations:– Get Mike Seely to agree with results– Compare to actual performance

• Use the resulting tested and certified template to design & calculate Qweak relief in 3 scenarios:1.Design for a sudden LOV incident2.Design for a cell rupture3.Worst case accident: inventory dumps into Hall C

(1/2 done)

Basic ReliefBasic Relief

Ballast TankRelief Line

Outside World

Inside Hall C

Outside Vent

3) Cell & Window Rupture

into Hall C

Scattering Chamber

2) Cell Rupture

1) LOV,No

Ruptures

Sudden LOVSudden LOV• Assume target cell remains intact

– LH2 boils rapidly and relieves to ballast tank– No gas gets into vent header (relief valves remain closed)

• Can occur if:– A scattering chamber window breaks– A pump fails– A valve to atmosphere inadvertently opened

• Will be deliberately tested (with Neon)• Want to calculate: Maximum pressure rise• Assumptions:

– External plumbing is 300K (worst case)

– Internal plumbing stays at 80K (worst case is 300K)

– Superinsulation (worst case is no superinsulation)XX

Hall A Hall C G0 QweakTarget warm:Storage volume 1000 1000 2500 6000 gallonsStorage volume (1 atm) 3785 3785 9463 22710 litersStorage (warm) pressure 48 40 33 75 psiaStorage temp 25 25 25 25 CVolume of H2 in hall when tank is 1 atm 7855 5968 10792 85342 STP litersMass of H2 in hall when tank is 1 atm 701 533 964 7620 gramsVolume of H2 in tank at storage pressure 11322 9435 19460 106147 STP litersMass of H2 in tank at storage pressure 1011 842 1738 9477 grams

Target cold:Operating (cold) pressure 22 22 24 45 psiaSTP volume in cold tgt 6133 4246 5307 42459 STP litersMass of H2 in cold tgt 548 379 474 3791 gramsLH2 density 0.072 0.072 0.072 0.072 g/cm^3Liquid volume 7.6 5.3 6.6 52.7 liquid liters

remaining ballast volume 5189 5189 14153 63688 STP litersLH2/ballast pressure 22 22 24 45 psia

Ballast InventoriesBallast Inventories

More Storage?More Storage?

Assumes:• 45 psia Poperating

• 52 liters LH2

Drop Pop Pstorage drops

• More storage doesn’t really help that much:– Doubling Vstorage only reduces Pstorage ~20%

• because Poperating is so high

– Puts more gas into hall in event of an accident

Existing: 2 2500 gal tanks

1 1000 gal tank

BaseliningBaselining

Sudden warmup, Hall C tgt, Nov. 13, 2007:

Pressure

Temperature

• Observed ΔP=1.6 psi• Calculated ΔP=2.6 psi

– Conservative assumptions

• Sudden LOV• 300K external relief

lines• 80K internal relief lines

• Observed Δt~5 min• Calculated Δt=2 min

ΔP

Pstorage

Pretty reasonable agreement!

Qweak Heat xfer Qweak Heat xfer CoefficientsCoefficients

Prep work: Calculate some coefficients of heat transfer:

D 0.0762 m D = diameter, characteristic dimension of the system. Taken to be the cell diameterT_w 77 K Temp at the Wall, fixed to 77K by N2 condensation.P_tgt 45 psia Operating pressureT_l 24.86 K 24.72 Temp of the liquid: 24.86 K is the boiling temp at 45 psiaT_f 50.93 K Temp of the film (film boiling), assumed to be the mean of the wall and liquid temperatures

dT 52.14 K DT = Tw - Tl

mu_f 2.54E-06 Pa-s Viscosity at: 50.93 K and 45.0 psiak_f 0.03991 W/(mK) Thermal Conductivity at: 50.93 K and 45.0 psiarho_l 64.88 kg/m^3 Density of the liquid at: 24.86 K and 45.0 psiarho_f 1.5146 kg/m^3 Density at: 50.93 K and 45.0 psiadeltarho_f 63.37 kg/m^3 liquid-film density differenceC_pf 1.09E+04 J/(kgK) Specific Heat at: 50.93 K and 45.0 psiasigma 1.20E-03 N/m Liquid surface tension at: 24.86 K and 45.0 psialambda 4.08E+05 J/kg heat of vaporization (liquid-vapor enthalpy difference at same T&P)lambda' 8.85E+05 J/kg 0.00137

0.0182 0.19303 0.007h 274.8 W/(m^2 K) coefficient of heat xferhdT 14327.2 W/m^2 heat flux for film boiling H2.

Also will be taken as the heat flux for UNINSULATED surfaces.

k_SS 8 W/(mK) thermal conductivity for SS in, eg, the HXt_SS 0.134 m SS thickness of eg, the HXh_SS 59.7 W/(m^2 K) heat transfer coefficient for SS, ie the conductance per unit area

k_SI 0.02 W/(mK) thermal conductivity for superinsulationt_SI 0.007 m thickness of 25 layers of superinsulation (7 mm)heff_ins 2.8 W/(m^2 K) Effective heat xfer coeff for insulated surfacesheff_insdT 791.8 W/m^2 Effective heat flux for INSULATED surfaces

HeaHeat t

LoaLoad d

frofrom m

HeaHeat t

Flux Flux and and Area Area

Surface Area Calculations:

Hall C machined cell (helicoflex gasket)

W/diam (cm) length (cm) Area (cm^2)4.85 18 uninsulated upstream window

18 254 uninsulated downstream window35 1278 insulated area of conical frustum cell

10 35 700 insulated rectangular input manifold, top & bottom faces10 2.54 51 insulated rectangular input manifold, upstream & downstream faces10 35 700 insulated rectangular output manifold, top & bottom faces10 2.54 51 insulated rectangular output manifold, upstream & downstream faces

26.162 60.452 4969 insulated one HX26.162 insulated HX diameter

7.62 insulated loop diameter16.764 2033 insulated two conical HX transition pieces

7.62 93.98 2250 insulated straight pipe as long as a HX7.62 30.48 730 insulated flex hose, 1' long7.62 17.95 430 insulated 2 45 degree elbows7.62 15.24 365 insulated 6" straight leg7.62 17.95 430 insulated 6" straight leg7.62 17.95 430 insulated pump inlet7.62 17.95 430 insulated pump outlet7.62 15.24 365 insulated 6" straight leg7.62 15.24 365 insulated 6" long bellows, 3" dia7.62 15.24 365 insulated 6" straight leg7.62 17.95 430 insulated 90 degree elbow7.62 30.48 730 insulated tee for H2 I/O7.62 15.24 365 insulated 6" straight leg7.62 15.24 365 insulated 6" straight leg7.62 17.95 430 insulated 2 45 degree elbows7.62 30.48 730 insulated flex hose, 1' long

A_ins 18988.0 18988.0 cm^2 Total insulated surface areaA_unins 272.9 272.9 cm^2 Total uninsulated surface area

Q_tot 1894.5 1894.5 W Total power or heat loadmdot 4.6 4.6 g/s mass evolution rate = heat load / heat of vaporizationH2 mass in tgt 3791.0 gTime to recover 13.6 minutes

First: Study consequences of a sudden loss of IV. H2 relieves back into ballast tank. What is P_max?

Not that different from the Hall C standard pivot

target!

Relief Relief DesignDesign

6” od relief bellows(3.5” id)

2 7/8” id cold relief

G10 spacer 300K sleeve

short flex hose to loop to accommodate horizontal motion (not shown)

to ballasttank

4K stand-

off

15K stand-

off

Qweak LOV Qweak LOV ΔΔPP

Relief calculationsmdot 4.6 g/s mass flow used in the relief calculatios

Internal ExternalT 77 300 KP 5.10 5.10 atm storage pressure when tgt is warm (maximum pressure)rho 1.62 0.417 kg/m^3 densitymu 3.50E-06 8.96E-06 Pa-s viscosity

L or # od wall thick id Area vel hydraulic dP dP(ft) (in) (in) (in) tube, hose, what (m^2) (m/s) N_RE 4f or k diam(m) (psi) (% of Tot)10 2 0.0625 1.875 tube (internal) 1.78E-03 1.6 3.55E+04 0.016 0.04763 0.00 0%2 2 0.0625 1.875 hose 1.78E-03 1.6 3.55E+04 0.016 0.04763 0.00 0%2 1.875 elbows (internal) 1.6 0.9 0.00 0%

20 1 hose 5.07E-04 22.0 2.60E+04 0.072 0.76 43%45 1 0.05 0.9 tube 4.10E-04 27.2 2.89E+04 0.024 0.32 18%4 elbows 27.2 0.9 0.08 5%1 ball valve 20 SCFM 27.2 5 0.11 6%1 check valve Circle Seal 269B6PP 27.2 2 0.04 3%

150 2 0.05 1.9 pipe 1.83E-03 6.1 1.37E+04 0.027 0.03 2%13 elbows 6.1 0.9 0.01 1%9 1 hose 5.07E-04 22.0 2.60E+04 0.072 0.34 19%1 ball valve 22.0 5 0.07 4%

Total 1.77 100%

P_ballast 75.00 psiP_peak 76.77 psi

Ballast tank storage pressurePeak pressure=ballast storage pressure+pressure drop

fittingsfor (K) v P

and pipe and tubehose,for (L/D) v(4f) P

vD/N

A/m v

221

221

RE

D

D

Completely reasonable! ~Same as for existing Hall C tgt

With the plumbing that exists in the Hall right now.Using existing ballast tanks. 45 psia operating P.

Superinsulation on loop except at windows. 52 liters LH2.

Relief PathRelief Path

Question: relief lines have a goofy bottleneck where they connect to the ballast tank: looks like 2” to 1” to 2”.

Sudden LOV ResultsSudden LOV Results

Note: 75 psia storage pressure, 100 psia reliefs on ballast tanks: ΔPmax = 25 psi

Conclusion: With minor mods to existing Hall C plumbing, we can withstand a sudden LOV even if all SI is blown away!

Relief PlumbingRelief Plumbing

• Tie into existing 2” relief lines to ballast tank here, with 40’ of new 2” line to the Qweak target (replacing existing 1” lines).

Sudden LOV SummarySudden LOV Summary

• Ballast: 2 G0 + 1 Hall C tank looks OK– Adding a 3rd “G0 tank” may be desirable

• To handle most realistic case, do not need to do anything

• To handle worst case, need to:– Replace 1st 20’ of 1” hose with 2” or 3”

hose– Replace next 45’ of 1” tube with 2” tube– Put both 150’ 2” lines back to tanks in ||

Cell RuptureCell Rupture• Assume target cell ruptures

– LH2 inventory dumps into scattering chamber• Scattering chamber windows remain intact

– It boils rapidly and expands • Must handle entire gas inventory until ballast tank reaches 1

atm• Reality: not hard to keep ballast gas outside hall

• Can occur if:– Relief line back to ballast tank becomes blocked– Structural failure of cell

• Will not be directly tested, – but all components must be tested to 1.5* Pmax

expected in a sudden LOV incident• Want to calculate: Scattering Chamber ΔP

– Note: no downstream beamline gate valve

Qweak cell Qweak cell rupturerupture

NEXT Part: Cell breaks, dumping LH2 into SC. SC windows stay intact. What is SC dP?

Scattering Chamber Relief Path Evaluation

BP_diam 2 ftBP_length 12 ftV_BP 1067.5 litersV_LH2 52.65 litersSC1 diam 3.25 ft density at 22 psia and 21.7 K is 69.07 kg/cm^3 56.2SC1 height 4.14 ft density at 14.7 psia and 21.7 K is 1.229 kg/cm^3SC2 width 2.67 ft density at 45 psia and 24.7 K is 64.89 kg/cm^3 61.6SC2 length 3.00 ft density at 14.7 psia and 24.7 K is 1.054 kg/cm^3SC2 height 5.53 ftV_SC 2224.8 litersV_tot 3292.4

factor 62 If the volume of the scattering chamber is more than 52 times the total liquid inventory then the liquid can boil to form cold vapor

62*V_LH2 3264.4 without the pressure in the scattering chamber exceeding 1 atmosphere. actual factor 63 The venting process will then be relatively slow as the cold vapor warms up.safety margin 1.01 ( rho1(22 psia, 21.7K) / rho2(14.7psia, 21.7K)~56)

X(kg)=rho1*V1=rho2*V2So V2/V1=rho1/rho2, where V1 is tgt volume, V2 is SC volume.( rho1(45 psia, 24.7K) / rho2(14.7psia, 24.7K)~62)

SC vol 3292.4 litersH2 mass 3790.96 gdens 0.00115144 g/cm^3T 23.05 K

Scattering Chamber volumecould add beam pipe volume here, or not.

temp corresponding to 1 atm, and that density.

Scattering chamber volumemass of H2 in target.density of that H2 mass in SC volume at 1 atm, when SC relief opens

The SC relief opens at 1 atm. What temp does the vapor have then?

This is the temp the gas has when the SC relief opens.Determined from looking at a table of T vs rho at 1 atm

beam pipe diam open to scattering chamber even in a LOV incidentbeam pipe length open to scattering chamber even in a LOV incidentbeam pipe volume open to scattering chamber even in a LOV incident

Need some extra (beam pipe) volume to slow it down.

(we have it: no gate valve!)

Heat xfer rateHeat xfer rateNeed H2 properties at the initial temperature the relief opens at, determined above to be

22.9 K1 atm

300 K

mu 1.21E-06 Pa-sN_PR 7.27E-01k 0.0191 W/mKCp 11.494 J/gKbeta 0.04366812 K^-1

Vertical surface:D 2.95 m height of SC, or diameter of the base and the lidN_GR 2.08E+15N_RA 1.51E+15N_UL 3215.1h 20.8 W/m^2Karea 3.922 m^2ha 81.7 W/K

Base:D 0.99 m height of SC, or diameter of the base and the lidN_GR 7.90E+13N_RA 5.74E+13N_UL 1486.5h 28.7 W/m^2Karea 0.771 m^2ha 22.1 W/K

Lid:D 0.99 m height of SC, or diameter of the base and the lidN_GR 7.90E+13N_RA 5.74E+13N_UL 743.3h 14.3 W/m^2Karea 0.771 m^2ha 11.0 W/K

Q_tot 31,830 WTdot 0.73 K/sVdot 105.02 liters/s Rate of volume expansion.

inverse of starting temp

wall temperature

Total power transferred to the gasRate that the gas warms up

Comes from fact that 1/V dV/dt = 1/T dT/dt, ie dV/dt=V/T dT/dt

Prandtl numberFunction of the

scattering chamber geometry (and initial

conditions)

Still have to include heat transferred to gas

from beam pipe volume. Makes things

worse.

Assume chamber walls stay at 300K. What rate will heat be transferred to the H2 vapor?

Make use of these correlations:

D is the characteristic dimension;the height for the vertical surface and the diameter for the base and lid.

surface ertical v

N

0.4921

0.670N 0.68 N

94169

PR

1/4RA

UL //

gas. idealan for 1/T and T)D - (Tg

N

NN N :where

lid 0.27N N

base 0.54N N

2

3S

GR

PRGRRA

1/4RAUL

1/4RAUL

Now assume that escaping gas is warm (300K) and at 1 atm over most of the vent pipe

Properties of H2 gas at 1 atm & 300K:

rho 0.0882 kg/m^3mu 8.958E-06 Pa-s

d_vent 2.00 inA_vent 0.00202683 m^2mdot 0.01 kg/sv_vent 51.82 m/sN_RE 25,912.47 f 0.03

Vent Path:

L or # od wall thick id Area vel hydraulic dP(ft) (in) (in) (in) tube, hose, what (m^2) (m/s) N_RE 4f or k diam(m) (psi)

140 2 pipe 2.03E-03 51.8 2.59E+04 0.03 0.0508 0.437 elbows (internal) 51.8 0.9 0.119 2 hose 2.03E-03 51.8 2.59E+04 0.03 0.0508 0.08

Total dP 0.62

Pressure drop across a check valve:

CV C_v 51T 300 KP 15 psiVdot 105.02 liters/srho(air) 1.2011 kg/m^3sg 0.073dP 0.098 psi

P_CV 2 psiPtot 2.62 psig

pressure setting of the check valve (pressure it takes to open it)Total (Over-)Pressure expected in the scattering chamber

vent pipe diametervent pipe areamassflowvelocity of gas thru vent pipe

friction coefficient

volume flow thru the check valve

specific gravity of the gas relative to airPressure drop across the check valve

C_V for a 259B16PP 2" Check Valvetemp to evaluate the dP forpressure to evaluate the dP for

fittingsfor (K) v P

and pipe and tubehose,for (L/D) v(4f) P

vD/N

A/m v

221

221

RE

D

D

ResulResultt

Existing!

Vent PathVent Path

• Scatt. Chmbr vents thru burst disk

& relief valve in ||

• Can use same plumbing for Qweak

2” vent line

Vent PathVent Path Existing 2” Vent Line

Eight 4” penetrationsto outside

Dome penetration

Vent Stack

Cell Rupture ResultsCell Rupture Results

• Must add some beam pipe volume– Allows liquid to boil away without increasing

pressure inside scattering chamber– No space for a downstream gate valve anyway

• Calculation assumes 52 liters LH2• Existing 2” vent plumbing is adequate!

– More penetrations are available

• SC ΔP(Qweak) < ΔP(Standard Hall C tgt)• Caveat: have not treated beam pipe volume

yet...– Additional dump volumes possible in principle

Worst Case AccidentWorst Case Accident

• Simultaneous failure of Scattering Chamber windows AND Cell rupture– Very unlikely, but

• Projectile from outside could penetrate both in principle

• Cell rupture could potentially puncture SC windows

– Have to assume H2 inventory gets into Hall C• until ballast tank reaches 1 atm

– Even though this can be prevented with good design

More on Gas InventoriesMore on Gas InventoriesHall A Hall C G0 Qweak

Hall C volume 2.60E+07 litersHall C floor area 1598.245 m^2liquid liters/9.8 m^2 of floor area 0.05 0.03 0.04 0.32

Must be less than 4 l/9.8 m^2 of area to satisfy NFPA article 45 Class D fire hazard

ODH: % O2 in hall if tank goes to 1 atm: 20.99 21.00 20.99 20.93(Must be > 19.5%)

Note: One B-sized H2 cylinder 2.00E+03 litersNote: One A sized gas cylinder is 6.80E+03 liters

Note: Forklifts are powered by propane cylinders onsite that contain 33 lbs of propane. With an equivalency factor of

0.35 this corresponds to 5.24 kg of H2

A H2 combustion wave requires 10.4m to reach significant overpressure.A spherical volume 10.4 m in diameter is 588977.4 litersH2 to fill this volume at 4% concentration is 23559.1 litersSafety factor 3.00 3.95 2.18 0.28

Note: Target cell safety factor is 1.5 times maximum pressureexpected in a worst case (SLOIV) incident.

Options in worst case Options in worst case scenarioscenario

• Let it go (current solution):– no roof on tgt shield cave– vacuum interlock top plate electronics

• lifter, heater, JTs, etc.

– rely on Hall volume, dome vent

• Or, in addition (cuz of P wave problem):– Provide large vent hood over tgt top plate– “dryer plumbing” to 2’ φ Hall penetration– possibly also kick (explosion proof) vent

fan on with vacuum interlock

Finished