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shimwell committed Jun 18, 2024
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192 changes: 188 additions & 4 deletions 2_nuclear_data.md
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Expand Up @@ -269,6 +269,26 @@ Q values of fusion fuel reactions

---

## Energy of neutrons from DT fuel

<div class="columns" style="font-size: 30px;">
<div>

- A DT plasma has several fusion reactions.
- DT is the most likely reaction.
- DD and TT reactions also occur with lower probabilities.
- All reactions and emit different energy neutrons.

</div>
<div>

![](images/dd_tt_dt.png)

</div>
<div>

---

## Microscopic Cross Section

<div class="columns" style="font-size: 30px;">
Expand Down Expand Up @@ -348,15 +368,52 @@ Reactions have characteristics

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# Experimental data
## Angular distribution

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- The scattering angle varies depending on the energy of the incident neutron
- Low energy neutrons have isotropic scattering (even probability in all directions)
- High energy neutrons are more likely to have a low deflection angle and are forwards bias.

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![](images/angle_energy_cross_section.png)

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## Energy distribution

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Availability of experimental data varies for different reactions and different isotopes.
- There is also data on neutrons released in reactions such as (n,2n).
- The (n,2n) reaction is a threshold reaction and requires energy.
- No run away chain reaction possible.

</div>
<div>

![](images/angle_energy_be9.png)

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---

Typically the experimental data is then interpreted to create evaluation libraries, such as ENDF, JEFF, JENDL, CENDL.
# Experimental data

<div class="columns" style="font-size: 30px;">
<div>

- Availability of experimental data varies for different reactions and different isotopes.

- Typically the experimental data is then interpreted to create evaluation libraries, such as ENDF, JEFF, JENDL, CENDL.


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Expand All @@ -383,4 +440,131 @@ There are several groups that produce and distribute nuclear data
- FENDL 3.2b 🌐 191 neutron
- CENDL 3.2 🇨🇳 272 neutron

---
---

# Path length

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<div >

- Path length = 1 / $\Sigma_{T}$
- A 14MeV neutron will lose energy via scattering interactions
- As the neutron energy decreases the path length also decreases
- Path length at thermal energy is more constant

![](images/neutron-scatter.png)
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![](https://s3.amazonaws.com/media-p.slid.es/uploads/1162849/images/9184302/water_path_length.jpg)

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# Energy loss

The average logarithmic energy decrement (or loss) per collision ($\xi$) is related to the atomic mass ($A$) of the nucleus

<div style='text-align: center;'>

$\xi = 1+ \frac{(A-1)^2}{2A} ln \frac{(A-1)}{(A+1)}$

</div>

<table style="width:100%">
<tr>
<th></th>
<th>Hydrogen</th>
<th>Deuterium</th>
<th>Beryllium</th>
<th>Carbon</th>
<th>Uranium</th>
</tr>
<tr>
<td>Mass of nucleus</td>
<td>1</td>
<td>2</td>
<td>9</td>
<td>12</td>
<td>238</td>
</tr>
<tr>
<td>Energy decrement</td>
<td>1</td>
<td>0.7261</td>
<td>0.2078</td>
<td>0.1589</td>
<td>0.0084</td>
</tr>
</table>

---

## Why lithium

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- Lithium has a particularly high cross section for tritium production
- Li6 has a very high cross section at low neutron energies
- Li7 has a reasonable cross section at high neutron energies
- Other reaction channels are relativity low
- Often alloyed with Si or other elements to improve material properties (e.g. flammability)

</div>
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![](images/all_tritium_multi.png)

* Elements up to Iron plotted
</div>
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---

## Why beryllium

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- Beryllium has the lowest threshold energy for any isotope with a n,2n reaction.
- This means even low energy 3MeV neutrons can undergo (n,2n) reactions.
- Often alloyed with Ti or other elements to improve material properties (e.g. swelling due to retention)
- Lead is also a popular choice for a neutron multiplier

</div>
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![](images/all_neutron_multi.png)
* Elements up to Iron plotted

</div>
<div>

---

## Other materials


## Tungsten

- High atomic number = good gamma attenuation

- High neutron capture resonances = good neutron attenuation

## Water

- High hydrogen content = excellent neutron moderator

## Helium 4

- Low interaction cross sections and low density = transparent to neutrons and gammas


---

## Neutron spectra through materials

16 changes: 1 addition & 15 deletions 3_prompt_response.md
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Expand Up @@ -94,9 +94,7 @@ style: |

# Neutron wall example

TODO image of plasma
TODO image of tokamak
TODO plot of wall loading vs angle
Note to self draw tokamak with wall loading vs angle

- Significant poloidal variation of neutron wall loading occur in toroidal magnetic confinement fusion reactors
- Details in model behind the FW not needed for NWL calculation!
Expand All @@ -112,18 +110,6 @@ TODO plot of wall loading vs angle
- Total heating is used for sizing cooling systems
- Nuclear energy multiplication (Mn) is ratio of energy deposited by neutrons and gamma photons in the reactor to neutron energy incident on FW

TODO making into a table
Fusion power
1GW

Neutron power
0.8GW

Heating deposited
1.1GW

Neutron multiplication
1.1

---

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71 changes: 12 additions & 59 deletions 4_delayed_response.md
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Expand Up @@ -68,78 +68,31 @@ style: |
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<div>

- activation
- activity build up and decay (shark fin)
- emission spectra
- shut down dose
- waste
- decay heat vs time
- Activation
- Activity build up and decay (shark fin)
- Emission spectra
- Shut down dose
- Waste
- Decay heat vs time

</div>
<div>

- analysis needed to lift or cool components
- activated coolant
- impact of burn up
- Analysis needed to lift or cool components
- Activated coolant
- Impact of burn up
- TBR
- shielding
- pulsed irradiation / constant irradiation
- Shielding
- Pulsed irradiation / constant irradiation

</div>
<div>

---

# Activation of materials

Neutron induced reactions lead to unstable radioactive products.

<h1>https://www.w3schools.com/graphics/svg_line.asp</h1>
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<text x="5" y="15" fill="red">I love SVG!</text>

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<!-- slide from neutronics workshop isotope chart with arrows -->

---

# Build up, saturation and decay

---

# Activation reactions


![bg 50%](images/reaction-directions.png)

---
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