Antineutrino monitoring of burning mixed oxide plutonium fuels

Background: Antineutrino monitoring of reactors is an enhanced nuclear safeguard that is being explored by several international groups. A key question is whether such a scheme could be used to verify the destruction of plutonium loaded in a reactor as mixed oxide (MOX) fuel.

Purpose: To explore the effectiveness of antineutrino monitoring for the purposes of nuclear accountability and safeguarding of MOX plutonium, we examine the magnitude and temporal variation in the antineutrino signals expected for different loadings of MOX fuels.

Methods: Reactor burn simulations are carried out for four different MOX fuel loadings and the antineutrino signals as a function of fuel burnup are computed and compared.

Results: The antineutrino signals from reactor-grade and weapons-grade MOX are shown to be distinct from those from burning low enriched uranium, and this signal difference increases as the MOX plutonium fraction of the reactor core increases.

Conclusion: Antineutrino monitoring could be used to verify the destruction of plutonium in reactors, although verifying the grade of the plutonium being burned is found to be more challenging.

Figure 1

Fission fraction for ${}^{235,238}$U and ${}^{239,241}$Pu as a function of burn-up for pure MOX fuels. Panel (a) is for RG and (b) for WG plutonium. The two grades of Pu are distinguished by the relative importance of ${}^{239}$Pu and ${}^{241}$Pu.

Figure 2

Fission fraction for ${}^{235,238}$U and ${}^{239,241}$Pu as a function of burn-up for 33.3$\%$ MOX and 66.7$\%$ LEU. Panel (a) is RG and (b) WG plutonium.

Figure 3

The effective antineutrino detection cross section per fission for each fuel type. For 100$\%$ MOX the effective cross sections increase with the burn, while for all loading with significant LEU they decrease with the burn.

Figure 4

(a) The antineutrino signal relative to that at the start of the burn. (b) The ratio of the antineutrino signal for MOX fuels relative to that for fresh LEU.