planning and preparation approaches for non-nuclear waste ... · planning and preparation...

Planning and preparation approaches for

non-nuclear waste disposal

Lucia Sarchiapone

Laboratori Nazionali di Legnaro (Pd)

Istituto Nazionale di Fisica Nucleare – INFN

✉ [email protected]

☎ +39 049 8068 394

Outline

• Laboratori Nazionali di Legnaro

• The SPES Project

• Expected levels of radioactivity, studies:

– The irradiation target

– The shielding structure

• Approach for the disposal

2 NEA Workshop on the Management of Non-nuclear Radioactive Waste 3rd May, 2017

New building

area hosting the cyclotron and

the irradiation bunkers

NEA Workshop on the Management of Non-nuclear Radioactive Waste

3

Existing

acceleration line Linear accelerator ALPI

3rd May, 2017

Cyclotron ALPI

PIAVE

TANDEM

Protons,

40 MeV

200 mA

RIB: Sn-132+1,

I-135+1, …

up to 40 kV

according to

mass

RIB: Sn-132+n,

I-135+n, …

up to 40 kV

RIB: Sn-132+n,

I-135+n, 9

MeV/amu

4

Radioactive beams: 90Rb, 135I, 137Te, 138Xe, 94Kr, 132Sn, 134Sn

NEA Workshop on the Management of Non-nuclear Radioactive Waste 3rd May, 2017

The SPES Project (Selective Production of Exotic

Species)

5

name: p70

made by: Best Cyclotron

energy: 40-70 MeV

maximum current: 750 uA

particles: H-

special remarks: dual port


The Cyclotron

6

Developed by the SPES target group, www.lnl.infn.it/~spes_target/

7 UC2 disks

1 mm thick

Graphite

holder

Graphite

dump


The fissionable target

7

Ionization of the

radioactive beam

The type of source is related to

the final beam

beam effusion at work

A. Andrighetto NEA Workshop on the Management of Non-nuclear Radioactive Waste 3rd May, 2017

Target ISOL technique

The SPES target is made of 7 UCx disks, 4 cm diameter, 1

mm thickness (about 30 g uranium-238 content)

UCx disk

Graphite box

window

dumper

Proton beam

The irradiation cycle lasts 14 days, a total of 1021 protons on

target and a total of 1019 fissions are induced on the target

Flu

ka g

eom

etry

8 3rd May, 2017

The target: irradiation cycle and inventory

NEA Workshop on the Management of Non-nuclear Radioactive Waste


9

Ato

ms

per

pro

ton

production in target at 40 MeV

0 20 40 60 80 100 120 140

N

0

10

20

30

40

50

60

70

80

90

100

Z10

-11

10-10

10-9

10-8

10-7

10-6

10-5

10-4

10-3

10-2

10-1

ato

ms p

er

pro

ton

Production in target at 40 MeV proton energy

Number of neutrons N

Ato

mic

nu

mb

er Z

Mass number A

Ato

mic

ab

un

dan

ces

(ato

ms

per

20

0 u

A)

109

1010

1011

1012

60 80 100 120 140 160 180

ato

mic

ab

un

dan

ce

(a

tom

s p

er

20

0u

A)

mass number (A)

Direct fission from 40

MeV protons on UC2

FLUKA simulation

1013 fissions/sec

Total target activity after 2 weeks

irradiation 3.7 1013 Bq


• 14 days

• 1021 protons on target

• 1019 fissions/cycle

• About 1 kCi totally produced

in 1 cycle

70%

17%

10%

1% 2%

T1/2 < 1 hour

1 hour < T1/2 < 1 day

1 day < T1/2 < 1 month

1 month < T1/2 < 1 year

1 year < T1/2 < 10 years

T1/2 > 10 years

NEA Workshop on the Management of Non-nuclear Radioactive Waste 10 3rd May, 2017



The target: induced radioactivity

Bq

Small area to store the

irradiated targets before their

final destination as waste


The temporary storage design

Lead and steel box, as designed and realized

by the target group at LNL


Simulation set up

mSv/h

2800 3200 3600 4000 4400

X (cm)

-100

0

100

200

300

400

500

600

700

800

Y (

cm

)

10-2

10-1

1

10

102

103

104

105

106

107

< 50 mSv/h

Gamma dose rate from exhausted targets

• Once filled the rack, targets will shield each other: dose rate below 50 uSv/h

• A concrete wall 50 cm thick will reduce the dose rate by a factor 100

Ceiling

floor


RP consideration on temporary storage

p40MeV

200 mA

UC2

UC2 target (30 g) in the form of 7 thin disks.

Energy: 40 MeV Irradiation period: 20 years

Current: 200 mA Working load: 5000 hours/year

• target 2 m distant from the

wall surface;

• shielding wall 360 cm wide;

• cylindrical activation sample

“cut” in the wall, radius 3 cm,

zero degree parallel to the

beam direction


Irradiation process – the shielding

Elemental composition of concrete (r=2.3 g/cm3) used for the

shielding of the target hall:

• Hydrogen underestimated

(conservative assumption –

neutron slowing down

effect);

• Eu and Co important

because of their long half

lives;

• Iron percentage does not

include that due to the

reinforcement rods.

Reinforcement is obtained with a stainless steel grid, with rods of radius 1

cm, spaced by 10 cm.

Element Atomic

Fraction

Weight

Fraction

Hydrogen 0.1047 0.55%

Oxygen 0.584 48.91%

Magnesium 0.0157 2.0%

Aluminum 0.0317 4.48%

Silicon 0.2115 31.1%

Calcium 0.0479 10.05%

Iron 0.01 2.92%

Europium 3.7 10-8 0.294 ppm

Cobalt 0.826 10-6 2.55 ppm


Shielding Material

Neutron fluence

p40MeV

200 mA

UC2

cm

-2 p

er

pro

ton


Reactions of neutrons

with nuclei in the

shielding:

Thermal neutrons (E

< 1 eV)

High energy neutrons

(E > 20 MeV)


Neutron energy

Some long lived

radionuclides are

produced by high energy

neutrons (54Mn, 22Na)

54Mn 54Fe (n,p) 55Mn (n,2n)

22Na 23Na (n,2n)


Neutron energy and radioactive species

Some radionuclides

produced by thermal

neutrons: the activity

concentration as a function

of the depth in concrete

resembles that of thermal

flux.

46Sc 45Sc (n,g)

59Fe 58Fe (n,g)

60Co 59Co (n,g)

152Eu 151Eu (n,g)


Neutron energy and radioactive species

Following the irradiation of the

concrete structure by secondary

neutrons, nuclei de-excite by the

emission of energetic g-rays;

Table:

Radionuclides with T1/2 > 1 month.

The more energetic

g emitters have been included.

Nuclide Half life

g-ray energy

(keV)

152Eu 13.5 y

121.78

…

1408.01

60Co 5.27 y

1173.24

1332.5

59Fe 44.5 d

1099.22

1291.56

56Co 77.27 d

…

846.7

1238.0

54Mn 312.12 d 834.83

46Sc 83.79 d

889.25

1120.51

26Al 7.4 105 y

1808.0

1129.0

22Na 2.602 y 1274.54


Radioactive species in concrete

Nuclide Half life

Activity

(Bq/g)

152Eu 13.5 y 232.7

60Co 5.27 y 172.7

59Fe 44.5 d 137.8

55Fe 2.73 y 1.2 104

54Mn 312.12 d 1.5 103

45Ca 162.61 d 1.0 104

26Al 7.4 105 y 216.0

22Na 2.602 y 223.0

3H 12.33 y 1.4 103

Long lived radionuclides in a sample

20 cm deep from the surface, at the

end of the irradiation period (20

years).

6% of the overall activity is due to

nuclides with half life longer than 1

year.

The nuclides specified in the table are

found in the concrete sample.

In the rods some of these nuclides can

be found (species produced by

irradiation of iron, 60Co, 59Fe, 55Fe, 54Mn) with higher concentrations.


Radioactive species in concrete

Activation and cooling

Activity concentration rapidly

decays as the depth increases in

the first 20-30 cm.

Symbols represent the activity

concentration in the rods,

while lines represent the same

quantity in concrete.

As a representative value, 1Bq/g

is obtained after 20 years of

cooling time in the outer part 185

cm thick.


Conclusions

• LNL host particles’ accelerators for research in

nuclear physics

• New projects and high power involved push for

consideration of waste production and planning for

disposal

• Necessary to start the study before civil construction

starts, in order to plan places and techniques for future

disposal.


3rd May, 2017 NEA Workshop on the Management of Non-nuclear Radioactive Waste 25

Thank you for your attention

• L. Sarchiapone

• Laboratori Nazionali di Legnaro (Pd)

• Istituto Nazionale di Fisica Nucleare – INFN

• ✉ [email protected]

• ☎ +39 049 8068 394

mailto:[email protected]

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