Safety And Power Multiplication Aspects Of Mirror Fusion-Fission Hybrids

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Safety And Power Multiplication Aspects Of
Mirror Fusion-Fission Hybrids

• K. Noack1, O. Ågren1, J. Källne1, A. Hagnestål1,
  V. E. Moiseenko2
• 1Uppsala University, Ångström Laboratory,
  Division of Electricity,
• Box 534, SE 751 21 Uppsala, Sweden
• 2Institute of Plasma Physics, National Science
  Center Kharkiv Institute of Physics and
  Technology, Akademichna st. 1, 61108 Kharkiv,
  Ukraine

• Articel Annals of Nuclear Energy 38, 578 (2011)

FUNFI workshop, Varenna, Italy, September 12-15,
2011
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2/17

• CONTENT
• Present Neutronic Model
• Safety Considerations
• Discussion and Conclusions

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1. Present Neutronic Model
3/17
? Modified radial structure
4
1. Present Neutronic Model
4/17
? Standard axial dependence of the neutron source
? Length of the core 25 m !
5
1. Present Neutronic Model
5/17
? Reactivity effect of the Reactivity modulator
(RM)
Calculation model 2 B4C-annuli at the outer
core surface at both ends Thickness 1
cm, height 2.5 m Boron is 90 enriched in 10B
? Reactivity range 4000 pcm (10-5)
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1. Present Neutronic Model
6/17
? Disadvantage Advantages

• Disadvantage
• Reactor technology has no experience with such
  long systems.

• Advantages
• Highly efficient utilization of the neutron
  source.
• First wall problem is considerably mitigated.
• The shielding of the magnetic coils is a fission
  shielding problem.
• The vertical installation could enable natural
  circulation of the LBE-coolant.
• See talk O12 of H. Anglart, this workshop.
• The long system implies a small leakage and
  hence a relatively small effect of the
  thermo-structural expansion.
• Low average fission power density of 76 W/cm3
  and low average linear pin power of 80 W/cm.
• Low radial peaking factor of 1.15 and of 1.30
  over the whole core.

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2. Safety Considerations
7/17
? Steady-state power amplification

• Demand The generation of the fission power must
  be manageable in any case to prevent the system
  from damage!

? The blanket must remain sub-critical in any
case!
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2. Safety Considerations
8/17
? Temperature feedback effects at start-up
switch-off
Calculation model Fuel 400 K ?? 1100 K
LBE, structure 400 K ?? 900 K
? Expected maximal total temperature effect for
start-up/switch-off (or loss of plasma)
?/800 pcm
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2. Safety Considerations
9/17
? Coolant void effects - Voided radial areas
within the core
Calculation model LBE-voided radial core
areas (cm) 1 115 lt r lt 122 2 113 lt r lt
124 3 111 lt r lt 126 4 entire
core 5 buffercoreexpansion zone
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2. Safety Considerations
10/17
? Coolant void effects - Loss of LBE-coolant
Calculation model vertically installed
hybrid united volume of buffer, core, exp.
zone different LBE-levels
? Loss of the LBE-coolant results in a negative
reactivity effect!
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2. Safety Considerations
11/17
? Reactivity effects of water in the coolant loop
and in the vacuum chamber
Cases 1 H2O within the core 2 H2O within
core, buffer, exp. zone 3 H2O within buffer,
exp. zone 4 H2O within the vacuum chamber
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2. Safety Considerations
12/17
? ?-Effect of the axial distribution of the
neutron source
Calculation model Deformations of the axial
dependence.
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13/17
2. Safety Considerations
? Axial dependence of the specific fission
heating
hfis(z) Fission heating per source neutron
emitted at z
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3. Discussion and Conclusions
14/17
? With regard to the blanket (A keff0.95, B
keff0.97)

• Response to changes of Pfus.
• To reduce thermal shocks the Pfis should
  respond gradually.
• In this respect, option B is not worse than A!

• Response to inadvertant insertion of
  ()-reactivity.
• Worst case
• Inflow of cold LBE Ejection of the
  inserted RM
• 800 pcm ? Restriction 1000 pcm
• Then, even B is in deep sub-criticality!

• Responses to start-up and switch-off at the
  beginning of the cycle.
• Start-up (?800 pcm)
• ? Withdrawal of the RM to meet the nominal
  criticality in the operation state.
• Switch-off (800 pcm)
• ? Insertion of the RM to fulfill keff 0.95
  (0.97).
• No safety relevant disadvantage of option B
  compared to A!

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3. Discussion and Conclusions
15/17
? With regard to the blanket (A keff0.95, B
keff0.97)

• Response to unprotected transients.
• Incidence Driver cannot be shut off on demand.
• ?T- increase ? insertion of (?)-reactivity
• ?T-increase is slowed down.
• In this respect, option B is more
  advantageous than A!

• ? Further reduction of the PAF by completely
  inserting the RM.
• In this respect, option B is more
  advantageous than A!
• Our position
• The shut-off of the driver definitely takes
  place after a minimal delay!
• ? Quantitative estimates of possible core damage
  need
• dynamic calculations!

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3. Discussion and Conclusions
16/17
? With regard to the blanket (A keff0.95, B
keff0.97)

• Response to filling the LBE-coolant loop with
  water
• Incidence For example, intended misuse.
• ? Negative effects, provided that buffer, core
  and exp. zone
• form a united volume!
• No safety relevant difference between both
  hybrid options!

• Comparison of the hybrid options A and B
• ? The study revealed that option B does not
  exhibit substantial disadvantages with regard to
  safety!

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3. Discussion and Conclusions
17/17
? With regard to the mirror driver

1. Minimal value as low as possible lt Pfus lt
   definite maximal value.

1. The driver must be equipped with several
   redundant, quick shut-off techniques.

1. Pfus should be supplied gradually tunable and
   stable.

• If Pfus is fluctuating, the frequencies should be
  clearly
• above 10 Hz.

1. The probability of plasma collapses must be
   minimal.

• The neutron source should have the axial peaks at
  stable positions.
• In case of fluctuations, the frequency range
  should be clearly above 10 Hz.

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Thank you for your attention!