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The HB11 reaction doesn't produce neutron radiation. I've seen claims that there would be side reactions, generating neutron radiation totaling under 1% of the

The HB11 reaction doesn't produce neutron radiation. I've seen claims that there would be side reactions, generating neutron radiation totaling under 1% of the energy output, but the only source of that I can think of is if deuterium isn't removed from the hydrogen, and we could do that if necessary. It might not be, since neutrons from deuterium fusion are a lot less energetic than D-T neutrons. The energy output of HB11 consists of fast-moving alpha particles, which is good because that's the energy you capture, along with x-rays. None of this would activate reactor components. The waste product is non-radioactive helium.

Retric 7y ago
It’s not that simple. 1% of even 1MW is a lot of radiation so it comes down to what the walls are made of more than the total neutron flux. ITER style lithium blankets would be recycled for tritium without producing much net waste. Light water nuclear reactors have several feet of water to absorb fast neutrons, which makes a huge difference. The walls of this are a more open question.
- DennisP 7y ago
  So I looked it up, and found there actually are two side reactions from the primary fuels, no deuterium required. In a thermal plasma the resulting neutrons would carry less than 0.2% of the energy output. I don't know what the percentage would be for this reactor, since the fuel isn't a thermal plasma while fusion is happening. https://en.wikipedia.org/wiki/Aneutronic_fusion#Boron https://en.wikipedia.org/wiki/Aneutronic_fusion#Boron Neutron energy would be a bit under 3 MeV, comparable to fast fission neutrons but in much lower quantity for the power output. https://en.wikipedia.org/wiki/Neutron_temperature https://en.wikipedia.org/wiki/Neutron_temperature Interestingly, that page says the thermal neutrons in a conventional nuclear reactor are better at activating materials than fast neutrons. According to a presentation I saw by the leader of MIT's fusion program, the inner wall of a D-T tokamak would be activated by the neutrons, but would only need to be stored for a few decades. D-T releases 80% of its energy as 14 MeV neutrons. According to LPP, which is working on a different boron fusion design, a 20MW reactor would activate the walls with short-lived radiation, but it could be safely opened for maintenance after about twelve hours (iirc).

Retric 7y ago

It’s not that simple. 1% of even 1MW is a lot of radiation so it comes down to what the walls are made of more than the total neutron flux. ITER style lithium blankets would be recycled for tritium without producing much net waste. Light water nuclear reactors have several feet of water to absorb fast neutrons, which makes a huge difference. The walls of this are a more open question.

DennisP 7y ago
So I looked it up, and found there actually are two side reactions from the primary fuels, no deuterium required. In a thermal plasma the resulting neutrons would carry less than 0.2% of the energy output. I don't know what the percentage would be for this reactor, since the fuel isn't a thermal plasma while fusion is happening. https://en.wikipedia.org/wiki/Aneutronic_fusion#Boron https://en.wikipedia.org/wiki/Aneutronic_fusion#Boron Neutron energy would be a bit under 3 MeV, comparable to fast fission neutrons but in much lower quantity for the power output. https://en.wikipedia.org/wiki/Neutron_temperature https://en.wikipedia.org/wiki/Neutron_temperature Interestingly, that page says the thermal neutrons in a conventional nuclear reactor are better at activating materials than fast neutrons. According to a presentation I saw by the leader of MIT's fusion program, the inner wall of a D-T tokamak would be activated by the neutrons, but would only need to be stored for a few decades. D-T releases 80% of its energy as 14 MeV neutrons. According to LPP, which is working on a different boron fusion design, a 20MW reactor would activate the walls with short-lived radiation, but it could be safely opened for maintenance after about twelve hours (iirc).