Transcript γ IRRADIATION IN TRIGA mk.2 REACTOR Klemen Ambrožič

𝛾 IRRADIATION
IN TRIGA mk.2
REACTOR
Klemen Ambrožič
Review of a hypothetical 𝛾 ray irradiation
chamber
Mentor: Dr. SNOJ Luka
OVERVIEW
• Irradiation chamber goals.
• Nuclear decay modes.
• Nuclei activation by neutron radiation (n,𝛾).
– Branching ratio.
• Neutron flux spectrum at the TRIGA mk. 2 reactor
ports.
• Application of reactor spectrum on nuclei activation
and decay.
• Energy, released by 𝛾 emmision.
• Calculation conclusion
• TLD dosimeters
• Plans for the future
Irradiation chamber goals
• Heavy 𝛾 exposure:
• Medical equipment sterilization.
• Plant seeds mutation.
• 𝛾 ray exposure testing (satellites, particle accelerator
detectors).
• Minimal or none neutron exposure:
• Causes discoloration in plastic and structural damage.
• Solution: Neutron activated 𝛾 source, moved
from neutron field.
Nuclear decay modes
• Decay law:
𝑑𝑁𝑖
𝑑𝑡
= −𝜆𝑖 𝑁𝑖
– 𝛼 decay: 𝐴𝑍𝑋𝑖 →
𝐴−4
𝑍−2𝑋𝑓
Heavy nuclei
+ 42𝐻𝑒
– 𝛽 decay:
• 𝛽 − : 𝐴𝑍𝑋𝑖 →
𝐴
𝑍+1𝑋𝑓
+ 𝑒 − + 𝜐𝑒
Neutron rich nuclei
• 𝛽 + : 𝐴𝑍𝑋𝑖 →
–𝛾
𝐴
𝑍−1𝑋𝑓
+ 𝑒 + + 𝜐𝑒
Proton rich nuclei
decay: 𝐴𝑍𝑋 ∗ 𝑖 → 𝐴𝑍𝑋𝑓 + 𝛾
Spin change to base state,
short decay times
• Activity: 𝐴𝑖 =
𝑑𝑁𝑖
𝑑𝑡
=𝜆𝑖 𝑁𝑖
Fig. 1: Table of isotopes and decays
𝛾 decay
𝑚1
Fig. 2: 𝛾 decay scheme for products of 116
after 𝛽 decay.
49𝐼𝑛
Nuclei activation by neutron radiation
(n,𝛾)
•
𝐴
𝑍𝑋𝑖
+ 10𝑛 →
𝐴+1
𝑍𝑋𝑓
• Reaction rate:
𝑑 𝐴+1
𝑍𝑛𝑓
(𝐸) = 𝐴𝑍𝑛𝑖 ∙ 𝜎𝐴 (𝐸) ∙ 𝜙(𝐸)
𝑑𝑡
𝜎𝐴 (𝐸): microscopic cross-section for absorption [barn=10−24 𝑐𝑚2 ]
Branching ratio can be given directly in 𝜎𝐴 (𝐸) or 𝜎𝐴 (𝐸) ∙ 𝜇𝑎
1
𝜙(𝐸): neutron flux [ 2 ]
𝑐𝑚 𝑠
1
n: nuclei density [ 3 ]
𝑐𝑚
𝑛∙𝑀
• 𝑚=
, 𝑁 = 𝑛 ∙ 𝑉, 𝑛
𝑁𝐴
=
𝜌∙𝑁𝐴
𝑀
Nuclei activation by neutron radiation
(n,𝛾)
𝜎𝐴 (𝐸) for 𝑛, 𝛾 reaction on 115𝐼𝑛. Product: 116𝐼𝑛𝑚1
Fig. 3: Absorption cross section 𝜎𝐴 (𝐸) for 𝑛, 𝛾 reaction on 115𝐼𝑛.
Product: 116𝐼𝑛𝑚1 an 116𝐼𝑛 . BR at low energies: 79%
Neutron flux spectrum in TRIGA mk.2
irradiation ports
Fig. 4: Top view of TRIGA mk. 2 reactor scheme at IJS (Jeraj, Ravnik, 1999)
Neutron flux spectrum in TRIGA mk.2
irradiation ports
Radial piercing thruport
Neutron flux at core full power (250kW), core 189, MCNP calculated
𝜙𝑡ℎ 1
𝑐𝑚2 𝑠
3,440 ∙ 1012
𝜙𝑡ℎ : 𝐸 < 0,625𝑒𝑉,
𝜙𝑒𝑝 1
𝑐𝑚2 𝑠
1,440 ∙ 1012
𝜙𝑒𝑝
𝜙𝑓 1
𝑐𝑚2 𝑠
1,138 ∙ 1012
: 0,625eV < E < 0,1MeV,
𝜙𝑡𝑜𝑡 1
𝑐𝑚2 𝑠
6,018 ∙ 1012
𝜙𝑓 : E > 0,1MeV
Fig. 5: flux spectrum in Radial piercing thruport, normalised to the corresponding value at 1eV.
Neutron flux spectrum in TRIGA mk.2
irradiation ports
Radial beam port
Neutron flux at core full power (250kW), core 189, MCNP calculated
𝜙𝑡ℎ 1
𝑐𝑚2 𝑠
2,834 ∙ 1011
𝜙𝑡ℎ : 𝐸 < 0,625𝑒𝑉,
𝜙𝑒𝑝 1
𝑐𝑚2 𝑠
4,147 ∙ 1010
𝜙𝑒𝑝
𝜙𝑓 1
𝑐𝑚2 𝑠
1,522 ∙ 1010
: 0,625eV < E < 0,1MeV,
𝜙𝑡𝑜𝑡 1
𝑐𝑚2 𝑠
3,400 ∙ 1011
𝜙𝑓 : E > 0,1MeV
Fig. 6: flux spectrum in Radial beam port, normalised to the corresponding value at 1eV.
Application of reactor spectrum on
nuclei activation and decay
• Equations:
𝑑 𝐴+1
𝑍𝑛𝑓
𝑑𝑡
𝐸 = 𝐴𝑍𝑛𝑖 ∙ 𝜎𝐴,𝑖 𝐸 ∙ 𝜙 𝐸 − 𝜆𝑓 𝐴+1𝑍𝑛𝑓
• Solutions:
– Neutron irradiation, 𝐴+1𝑍𝑛 𝑡𝑖𝑟𝑟 = 0 =
𝐴+1
𝑍 𝑛𝑓
𝑡𝑖𝑟𝑟 =
1
𝜆𝑓
∙ 𝜙 ∙ 𝜎𝐴,𝑖
𝐴+1
𝑍 𝑛0 :
∙ 𝐴𝑍𝑛𝑖 ∙ 1 − 𝑒 −𝜆𝑓∙𝑡𝑖𝑟𝑟 − 𝐴+1𝑍𝑛0 ∙ 𝑒 −𝜆𝑓∙𝑡𝑖𝑟𝑟
– Decay , 𝐴+1𝑍𝑛 𝑡𝑑 = 0 = 𝐴+1𝑍𝑛𝑓 𝑡𝑖𝑟𝑟 :
𝐴+1
𝑍 𝑛𝑓
𝑡 =
𝐴+1
𝑍 𝑛𝑓
𝑡𝑖𝑟𝑟 ∙ 𝑒 −𝜆𝑓 ∙𝑡𝑑
• Meeting the goals: maximum 𝜎𝐴,𝑖 (E) and 𝜙 𝐸
Application of reactor spectrum on
nuclei activation and decay
• Irradiation port candidate: Radial piercing thruport:
– Not in contact with primary containment
– Highest neutron flux 𝜙
• Irradiation material candidate: 115
49𝐼𝑛 :
– Orders of magnitude larger 𝜎𝐴 (𝐸) at low E, than any other material
1
𝑠
– Short enough decay half time (54min) : relatively large 𝜆𝑓 (2,13 ∙ 10−4 )
– Large density (7,31 𝑔
𝑐𝑚3)
• Rule of thumb apriximations for calculations:
– Neutron flux 𝜙~𝜙𝑡ℎ
[3,440 ∙ 1012 1
– 𝜎𝐴 (𝐸)~ 𝜎𝐴 (𝐸𝑡ℎ )~ 𝜎𝐴 (𝐸300𝐾 )
𝑐𝑚2 𝑠]
[161𝑏𝑎𝑟𝑛]
Application of reactor spectrum on
nuclei activation and decay
• For n~nmax99% saturation during irradiation
𝑡𝑠𝑎𝑡,99% ~2 ∙ 104 𝑠
• Estimated uncertainties:
– 𝜎 = 161𝑏𝑎𝑟𝑛 1 ± 0.3
Due to aproximation and 10% due to uncerainties from nuclear data.
– 𝜙 = 3,440 ∙ 1012 1
𝑐𝑚2 𝑠
1 ± 0.1
Due to aproximation and 7% accuracy from power detemination
Calculation results
Graph of 116
49𝑛 𝑡
4
Fig. 6: Graph of 116
49𝑛 𝑡 , irradiation time: 2 ∙ 10 𝑠. Blue graph is calculated with given data,
yellow and purple graph take into account uncertainties.
Calculation results
Log graph of 116
49𝑛 𝑡
4
Fig. 7: Log graph of 116
49𝑛 𝑡 , irradiation time: 2 ∙ 10 𝑠. Blue graph is calculated with given data,
yellow and purple graph take into account uncertainties.
Energy, released by 𝛾 emmision
• Branching ratios
• For each 𝛽 decay we
get ~2.50𝑀𝑒𝑉 in 𝛾
rays
• Calculate specific
activity 𝑎 =
𝑑𝑛
1
𝑑𝑡 𝑠∙𝑐𝑚3
Energy, released by 𝛾 emmision
Fig. 7: Graph of 𝑝𝛾 𝑡 specific radiation power, irradiation time: 2 ∙ 104 𝑠. Blue graph is calculated
with given data, yellow and purple graph take into account uncertainties.
Calculation conclusion
• High flux density for 𝛾 particles.
– Ideal for testing, sterilization
• Relativly short saturation times
– Radiation times can be shorter to suite our needs
• Rule of thumb-> large uncertainties, but have
general idea ( order of magnitude)
TLDs
•
•
•
•
Thermoluminescent dosimeters
Lithium fluoride, calcium fluoride
Gamma rays- material ionization
Free electrons captured in crystal
imperfections
• Heat the crystal-> releasing trapped electrons
• Released light counted using photomultiplier
Plans for the future
• Smaller uncertainties (estimated 10%, under development)
– Exact calculation of 𝜙 and 𝜎 across all energies.
– Exact consideration of 𝜙 and 𝜎 measurement
uncertainties.
• MCNP simulations ( 115
49𝐼𝑛 effect on flux density)
(to do)
• FISPACT( dose rate simulation program) (to do)
• Large dose rate detector (TLD, scinilation
detectors) (under development)
• Design plan, decommission plan, material
acquisition (upper stages must be resolved first)
• Working aplication (upper stages must be resolved first)
Literature
•
•
•
•
•
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•
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Luka Snoj, Gašper Žerovnik, Andrej Trkov: Computational analysis of irradiation facilities
at the JSI TRIGA reactor
https://www-nds.iaea.org/exfor/endf.htm (14.11.2013)
http://www.inl.gov/gammaray/catalogs/pdf/gecat.pdf (14.11.2013)
http://www.oecd-nea.org/tools/abstract/detail/NEA-1564/ (14.11.2013)
http://www.ncnr.nist.gov/resources/n-lengths/ (14.11.2013)
http://www.ndted.org/EducationResources/CommunityCollege/RadiationSafety/radiation_safety_equi
pment/thermoluminescent.htm (19.11.2013)
Frank Herbert Attix: Introduction to Radiological Physics and radiation dosimetry, WileyVCH Verlag GmbH& Co. KGaA, ISBN-13: 978-0-471-01146-0
James J. Dudersradt, Louis J. Hamilton: Nuclear Reactor Analysis, Department Of
Nuclear Engineering, The University Of Michigan, John Wiley & Sons, ISBN: 0-47122363-8
Ronald Allen Knief: Nuclear Engineering: Theory and Practice of Commercial Nuclear
Power, Tylor & Francis, ISBN-13: 978-1560320890
George I. Bell, Samuel Glasstone :Nuclear Reactor Theory, Van Nostrand Reinhold
Inc.,U.S. (December 1970), ISBN-13: 978-0442206840