UCN&CN Physics and UCN&CN Physics and SourcesSources

S.S.--PetersburgPetersburg--Moscow, 1Moscow, 1--7 July 20077 July 2007

PelletizedPelletized Cold Cold Neutron Moderators for Neutron Moderators for

the IBRthe IBR--2M reactor2M reactor

Presented by Presented by

EvgenyEvgeny P. SHABALINP. SHABALIN

UCN&CN Physics and Sources UCN&CN Physics and Sources S.S.--PetersburgPetersburg--Moscow, 1Moscow, 1--7 July 7 July

20072007PelletizedPelletized Cold Cold

Neutron Moderators for Neutron Moderators for the IBRthe IBR--2M reactor 2M reactor

Presented by Presented by EvgenyEvgeny P. SHABALINP. SHABALIN

Coworkers:Coworkers:AnanievAnaniev V.D., V.D., BeliakovBeliakov АА..АА., ., KulaginKulagin E.N., E.N., KulikovKulikov S.A., S.A., KustovKustov A.A., A.A., ProkhorovProkhorov I. K., I. K., ShabalinShabalin DD..ЕЕ., ., FedorovFedorov A. N. A. N. -- ((JINRJINR))BusykinBusykin O. N., O. N., KazakovKazakov A.V. A.V. -- (C(CААHIHI))RomanovaRomanova N.Y., N.Y., TretiakovTretiakov II..ТТ..-- ((RDIPE)RDIPE)

ContentsContents

1.1. Solid Solid mesitylenemesitylene cold moderator, cold moderator, comparative performance of comparative performance of mesitylenemesityleneto methane.to methane.

2.2. Preparation and transport of solid Preparation and transport of solid mesitylenemesitylene balls . balls .

3.3. Current status of the Current status of the mesitylenemesitylene cold cold moderator project. moderator project.

Solid Solid mesitylenemesitylene as a cold as a cold moderatormoderator

Aromatic hydrocarbon 1,3,5 Aromatic hydrocarbon 1,3,5 –– trimethylbenzenetrimethylbenzene..Tm Tm –– melting point melting point

Benzene

Tm = 278 K

Toluene

Tm = 180 K

Mesitylene

Tm = 227 K

Mesitylene

Solid Solid mesitylenemesitylene as a cold as a cold moderatormoderator

Tm = 227 K

Mesitylene mm--xylenexylene

Tm = 225 KMixture with Mixture with mm--xylenexylene or or pseudocumenepseudocumene is of glassy is of glassy structure, and has good neutron structure, and has good neutron thermalizationthermalization property.property.

0 10 20 30 40 50 600

50

100

0

Energy transfer - ν [meV]

M:m-X = 3:1 volume solution Mesitylene (M) - crystal phase I m-xylene (m-X) - crystal phase

G(ν

)

Solid Solid mesitylenemesitylene cold moderatorcold moderator

00Density of Density of vibrationalvibrational states (by I. states (by I. NatkaniecNatkaniec) )

Solid Solid mesitylenemesitylene cold moderatorcold moderator

Density of states for methane and TMB mixtureDensity of states for methane and TMB mixture

0 50 100 1500

2

4

6

8

10

12

14

16

G(ν

) [a

.u.]

Neutron energy transfer - ν [meV]

methane - CH4

1,3,5:1,2,4-TMB = 3:2 volume solution

H2O:CH

3OH = 1:1 volume solution

T = 20K

NORM: number of H atoms = 1024 monitor counts = 106

Calculated neutron fluxes from methane (2) and Calculated neutron fluxes from methane (2) and mesitylenemesitylene (1) cold moderators(1) cold moderators

1E-3 0,01 0,1 1

1E-9

1E-8

1E-7

n/c

m^2

/eV

per

neu

tro

n o

f th

e so

urc

e

Energy, eV

1

2

1 - mesitylene 3 cm at T = 20K,

2 - methane 2 cm at T = 60K

Note: To avoid problems with hydrogen and burps, methane should Note: To avoid problems with hydrogen and burps, methane should be be used at T>used at T>60 60 КК and at fast neutron flux <and at fast neutron flux < 10**12 10**12 nn//смсм22//ss

RadiolyticRadiolytic hydrogen production:hydrogen production:

in solid methanein solid methane::6 106 10--77 mol/Jmol/J for absorbed dose for absorbed dose ≤≤ 1 kJ/g1 kJ/g;;3 103 10--77 mol/Jmol/J for absorbed dose >> 10 kJ/g.for absorbed dose >> 10 kJ/g.

in in mesitylenemesitylene::3.9 103.9 10--8 mol/J8 mol/J = 11.7 % of solid methane;= 11.7 % of solid methane;in in mesitylenemesitylene + toluene, 50 by 50 %+ toluene, 50 by 50 % ::

1.8 101.8 10--8 mol/J 8 mol/J *)*) = 5.5 % of methane.= 5.5 % of methane.

Pressure of hydrogen on walls of a Pressure of hydrogen on walls of a moderator chamber. moderator chamber.

During annealing (or burping), gas of During annealing (or burping), gas of radiolyticradiolytic hydrogen hydrogen expands and builds up pressure inside of matrix and on expands and builds up pressure inside of matrix and on the walls of the chamber.the walls of the chamber.This pressure in solid methane was measured as high as This pressure in solid methane was measured as high as ~1 bar/hour as compared to that value for ~1 bar/hour as compared to that value for mesitylenemesitylene~0.1 bar/hour at the same absorbed dose rate.~0.1 bar/hour at the same absorbed dose rate.

Segment 7.5 Segment 7.5 мммм, , TirrTirr. = 11 h. = 11 h Segment 7.5 Segment 7.5 мммм, , TirrTirr. = 10.5 h. = 10.5 h

Spontaneous reaction of recombination of radicals in Spontaneous reaction of recombination of radicals in water ice sampleswater ice samples

No spontaneous reaction of recombination of radicals in No spontaneous reaction of recombination of radicals in mesitylenemesitylene samplessamples

СегментСегмент H=7.5H=7.5 мммм, , ВремяВремя облучоблуч. = 8 h, T = 20 K. = 8 h, T = 20 K

ПриПри облученииоблучении вв течениитечении 45 45 часовчасов припри ТТ=20=20КК нини спонтаннойспонтанной нинииндуцированнойиндуцированной реакцииреакции рекомбинациирекомбинации нене наблюдалосьнаблюдалось

Solid Solid mesitylenemesitylene cold moderatorcold moderator

Properties of Properties of mesitylenemesitylene::Density atDensity at 202000СС –– 0.86 0.86 gg//ccмм33, , atat 20 20 КК ~~1 1 gg/ / ccмм33

Heat capacity atHeat capacity at 20 20 КК -- 0.2 0.2 JJ//gg//KK, , atat 80 80 КК -- 0.6 0.6 JJ//gg//KK..Melting temperature and heat Melting temperature and heat –– 228 228 КК and and 100 100 JJ//ggVaporization temperature and heat at p=Vaporization temperature and heat at p=1 1 барбар ––437 437 КК and and 320320 JJ//ggThermal conductivity at Thermal conductivity at 2020КК-- 40 40 КК –– 0.2 0.2 WW//мм//KK

Concept of Concept of PelletizedPelletized

Cold Cold ModeratorModerator

1 – moderator chamber 2 – tube for charging of balls3 – ball dosing device 4 – ball production device 5 – heat exchanger6 – helium blower 7 – helium pipes of

the primary loop8 – used mesitylene bin9 - the secondary loop

Solid balls of the frozen mixture Solid balls of the frozen mixture of of mesitylenemesitylene and and mm--xylenexylene

Method of solid ball production Method of solid ball production is based on freezing of dropletsis based on freezing of droplets in liquid nitrogen. in liquid nitrogen. Diameter of the balls is 5 mmDiameter of the balls is 5 mm

Transportation of Transportation of mesitylenemesityleneballsballs

−−

⋅⋅−−⋅+−=dt

VVdCkg

dtdV gasball

ball

gasam

ball

gasball )()())(cos()(sin(

ρρ

ρρ

αα 1

+⋅−

⋅⋅⎟⎟⎠

⎞⎜⎜⎝

⎛⋅⋅− )(),,,Re,(, N

pipe

ballpipe

gas

gasballNgas

ballball

gas Csigndd

VVV

CVd

k Kωρ

ρ 2750

),,,Re),(,(, Kωρ

ρ

pipe

ballpipe

gas

gasball

gas

gasballDgas

ballball

gas

dd

VVV

signV

VVCV

d−−

⋅⋅⎟⎟⎠

⎞⎜⎜⎝

⎛⋅+ 2750

General equation for moving of a ball with gas General equation for moving of a ball with gas flow in the straight pipe is:flow in the straight pipe is:

Transportation of Transportation of mesitylenemesityleneballsballs

Averaged speed of gas is Averaged speed of gas is 8 8 m/sm/s; ; the speed of the ball the speed of the ball –– 3 3 m/sm/s ..

Averaged speed of gas is 10Averaged speed of gas is 10m/sm/s; ; the ball is stopped .the ball is stopped .

By computer simulation of gas flow with a separate ball inside cylindrical tube, characteristics of hydrodynamics and forces onto a ball was calculated

( )0122

222

Cv

vfv

vbSv

Dd

vvCS

vF

gasgas

gasgas

gas

gasgasgasX ⋅⎟

⎟⎠

⎞⎜⎜⎝

⎛⋅+⋅−⋅⋅=⎟

⎟⎠

⎞⎜⎜⎝

⎛⋅⋅= )(Re,, ρρ

mg

FfrictFgasX

Transportation of Transportation of mesitylenemesitylene balls balls Simplified, analytically soluble equation for transport of a Simplified, analytically soluble equation for transport of a

ball in the straight pipe is:ball in the straight pipe is:

2(sin( ) cos( )) 0,75 ( ,Regas ball gasgas X pipe

ball ball gas

V VdV g k V Cdt d V

ρα α

ρ−⎛ ⎞

= − + + ⋅ ⋅ ⋅⎜ ⎟⎝ ⎠

where factor where factor АА<1 is weakly depend on Re and<1 is weakly depend on Re and ddballball/d/dpipepipe , , and and СС(0) (0) is a drag force factor for the stopped ball. is a drag force factor for the stopped ball.

vv22gasgas((11--Av/vAv/vgasgas)C(0))C(0)

It is clear that it’s possible to simulate mesitylene beads transport by 80 K helium gas with transportation of glass beads of the same size with flow of room temperature nitrogen due to equality of the complex in the brackets.

0 10 20 30t [sec]

0

2

4

6

8

10

Vball

Omega=Vball/Rball

k=0.1

k=0.05

Transportation of ideal solid balls

Speed of a ball (d=5 mm) moving Speed of a ball (d=5 mm) moving in a straight pipe (d=17 mm) with in a straight pipe (d=17 mm) with gas flow 11 gas flow 11 m/sm/s versus time . versus time .

Black curves Black curves –– sliding of the ball sliding of the ball with friction factors with friction factors k=0.05k=0.05 and and k=0.1k=0.1; ; the blue curve –– rolling of rolling of the ball. the ball.

Magenta –– analytic analytic calculation for calculation for k=0.05k=0.05

Computer hydrodynamic Computer hydrodynamic model:model:

Experiment versus theory:Experiment versus theory:Calculated values of the drag coefficient agree

well with the experimental values in the range 0-50% of the speed of gas flow, Showing rolling character of a ball motion

BUTBUT……....

““Acceleration Acceleration versus versus speedspeed””ofof a ball a ball at 11 at 11 m/sm/s gas gas

velocity.velocity.Red Red and and black black

symbols symbols ––experiment, experiment,

green green –– theory for theory for rolling of ideal ball rolling of ideal ball along a pipe with along a pipe with

ideally smooth ideally smooth walls. walls.

Vo

α

Vl

L=Vl t

VL =0.88 Vl

Kinetic energy of the ball dissipates due to friction forces: F L = (2 mVo /t) · k· (VL t) = ·m V2 sin 2α ·k

ΔE/E = - m V2 sin 2α ·k/ (m V2/2) = - 2 sin 2α ·k At α=1/6 and к=0.33 ΔE/E = - 0.217

Pieso-electric transducers fasten to the tube showed that fast moving balls start to bounce and lose their velocity

Clip Clip 8.02.07 8.02.07 P2080008cP2080008cam2am2

Scheme of the IBRScheme of the IBR--2 (left) and IBR2 (left) and IBR--2M reactors2M reactors(green marks moderator area)

IBR-2M is more compact, 1.7 gain in flux

Lay-out of the moderator complex and vertical section of the moderators at the central direction

1.1. Chamber of Chamber of the cold the cold moderatormoderator

2.2. Light water Light water prepre--moderator; moderator;

3.3. Flat water Flat water reflector reflector

4.4. Outer border of Outer border of the reactor; the reactor;

No 4,5,6,1,9 No 4,5,6,1,9 ––numbers of numbers of neutron neutron beams.beams.

300K

water

20K

No4

No 5

No 6

2

4

3

No 1

No 9

1

CombiCombi--moderator at the central direction of moderator at the central direction of the IBRthe IBR--2M reactor, plan view2M reactor, plan view

Neutron moderator for beams #2, 3Neutron moderator for beams #2, 3

MesityleneMesitylene pelletizedpelletizedmoderator chambermoderator chamber

Water Water premoderatorpremoderator

Drained Drained chamberchamber

1E-3 0,01 0,1 1

1E11

1E12

1E13

ch2 ch5 ch8

n/eV

/sr/

cm^2

/sec

Energy, eV

-- beam 8beam 8

-- beam beam 22

-- beam 5beam 5

Differential flux density at the surface of the three moderators

-8 -6 -4 -2 0 2 4 6 8

-8

-6

-4

-2

0

2

4

6

8

Hig

ht, c

m

ch5, E<5 meV

n/cm̂ 2/sec

Width, cm

2,000E11

2,625E11

3,250E11

3,875E11

4,500E11

5,125E11

5,750E11

6,375E11

7,000E11

Scalar neutron flux distribution at the surface of the cold moderator

a) – thermal neutrons, b) – cold neutrons

-8 -6 -4 -2 0 2 4 6 8

-8

-6

-4

-2

0

2

4

6

8

ch5, E<0,025 eV

n/cm̂ 2/sec

Width, cm

Hig

ht, c

m

4,800E12

5,150E12

5,500E12

5,850E12

6,200E12

6,550E12

6,900E12

7,250E12

7,600E12

aa bb

Intense sources Intense sources for research on extracted neutron for research on extracted neutron

beamsbeams

~ 12~ 12 ÷÷ 15152828(preference (preference --due to bigdue to bigmoderator moderator

area and area and low pulselow pulsefrequency )frequency )

~ 3~ 3~ 1~ 1(in 200 (in 200 μμs,s,100 cm100 cm22) )

Cold neutrons per pulse: Ф∙S / f

1012

(long wavelengths)

~ 3 ~ 3 ÷÷ 441.01.0~ 0~ 0..665050Cold neutron flux (Ф), 2π equivalent,

н/с/см2 , 1012

1.41.4 ÷÷ 22220.0.04046060Thermal power, MW

SNS 2007-2010

ИБР-2МISIS(second

target)

Grenoble

Present status of the Complex oPresent status of the Complex oModerators for the IBRModerators for the IBR--2M2M

At engineering plant At engineering plant ““HeliummashHeliummash”” , manufacturing of , manufacturing of the new refrigerator facility KGUthe new refrigerator facility KGU--700/15 is finished.700/15 is finished.

Fabrication of systems for manufacturing, charging andFabrication of systems for manufacturing, charging and discharging of discharging of mesitylenemesitylene beads are in progress at the beads are in progress at the Lab. Neutron Physics of JINRLab. Neutron Physics of JINR. . In RDIPE a preliminary design of the moderators In RDIPE a preliminary design of the moderators complex for the IBRcomplex for the IBR--2M2M is accomplished.is accomplished.

CCryogenicryogenic pipelinespipelines fromfrom the the cryogeniccryogenic facility KGUfacility KGU--700700/15/15 upup toto the moderators are in fabrication.the moderators are in fabrication.

With Cold Moderator With Cold Moderator -- toward North Pole! toward North Pole!

Conveying of ballsConveying of balls

Velocity of balls along transport pipe to the Velocity of balls along transport pipe to the moderator chamber at moderator chamber at 5 5 mm//s gas velocity s gas velocity (project) (project)

Filling the chamber without deflector (left) and with the Filling the chamber without deflector (left) and with the deflector of an optimized size and inclination (right) deflector of an optimized size and inclination (right)

Present status of the Complex of Present status of the Complex of Moderators for the IBRModerators for the IBR--2M2M

Theory of transportation of balls by gas flow in Theory of transportation of balls by gas flow in a pipe along a path of complicated shape is a pipe along a path of complicated shape is derived; experimental confirmation is in derived; experimental confirmation is in progress. progress.

Method of solid ball mass production is developed; Method of solid ball mass production is developed; ball generator is designed and fabricatedball generator is designed and fabricated..Design of a ball dosing machine to enter them machine to enter them into the transport pipe is worked out; into the transport pipe is worked out; techniques was previously confirmed with a techniques was previously confirmed with a mockmock--up. up.

aaexpexp =0.83=0.83--0.238 v0.238 v

aatheortheor=0.78=0.78--0.21v0.21v

Транспорт шариков – обработка опытовпри скорости газа 5 м/с

Differential flux density at the direction

of the beam # 7 at 4.5 m off the source

Differential flux density at beam 7 direction

1E-3 0.01 0.1 1

1E8

1E9

1E10

1E11

n/cm

^2/e

V/s

ec

Energy, eV