Etude et impact du bruit de fond corrélé pour la mesure de l'angle ...

64 3. The Double Chooz experiment
tel-00821629, version 1 - 11 May 2013
(a) Reference spectra
Figure 3.17: Reference ¯⌫ e spectra from [65, 75] and related uncertainties.
measured in [84]. The ¯⌫ e energy is related to the positron energy by:
E e + = 1 2
s
m 2 n 4m p
✓ 2 m 2 e
2m p
+ E ⌫
◆
(b) Comparison to ILL
m n
!
Figure 7.36: New reference anti-neutrino spectra. See text for details.
(3.7)
where m p and m n are the masses of the proton and the neutron respectively
and = m n m p .
3.5.6 Fission rates
The fission rates ↵ k evolve in time depending from the reactors thermal
power and the evolution of the fuel assemblies. The thermal power for a
given fission is relatively insensitive to the specific fuel composition since
the mean energy released per fission167di↵ers by less than 6 % among the
di↵erent isotopes. However the detected number of ¯⌫ e directly depend from
the di↵erent spectra of the isotopes. For such reason an accurate modelling
of the evolution of the reactor core has been developed.
Two complementary simulation codes have been used to model the reactor
cores evolution, MURE and DRAGON [72, 70]. MURE is a Monte Carlo
code which use a statistical approach to solve the neutron transport equation
in a 3-D reactor core. DRAGON uses a deterministic approach to solve,
with some approximations, the neutron transport equation in a 2-D core.
The performance of the codes are compared against each other and validated
against data from the Takahama-3 reactor [67].