# Presentation: 933396

## Reactor Antineutrinos& Non Proliferation :

**Reactor Antineutrinos****& Non Proliferation :**

-  Nantes (SUBATECH) & SPhN CEA Saclay

- 1

-  Muriel Fallot
-  AAP Workshop – 26 sept. 06

** ****Experimental needs for a better knowledge of the antineutrino spectra from ****235****U, ****239,241****Pu, ****238****U**

## Outline

**Outline**

- 4

-  Muriel Fallot – 26 sept. 2006

-  Development of MURE simulation tool for scenario studies...

-  Previous measurements of antineutrino energy spectra

-  « Dissection » of antineutrino energy spectrum of 235U : FP contributions

- m

-  Interfacing MURE with nuclear databases and using an interface on the Beta-S code

-  Conclusions and outlooks

## MCNP Utility for Reactor Evolution

**M****CNP ****U****tility for ****R****eactor ****E****volution**

- Fission product proportions vary with the fuel burn-up and with time because of the wide range of half-lives involved.

- Aim = Simulation of the anti-neutrino spectrum built
- from the fission product spectra

- Need for « dynamical » calculation to simulate the evolution of fuel composition and the decay chains of the fission products

- 3

-  Muriel Fallot – 26 sept. 2006

- For proper translation from beta to antineutrinos: individual end-points and shapes

- MURE : O. Méplan et al. ENC Proceedings (2005)

**Simulation effort**

## Simulation effort

**Simulation effort**

- 2 – Folding with the detection cross-section

- 3 – Cumulative spectrum in energy of antineutrinos folded by the detection cross-section

- 4

**235****U ****239****Pu**

- Threshold : 1.804 MeV

- _Developments to obtain a precise calculation of the evolution with time of the antineutrino spectrum in order to have a generic tool for proliferation scenario studies (even for rapid changes)_

- Thèse de S. Cormon

- 1 – Simulated spectra of emitted antineutrinos from the fission of 239Pu and 235U using MURE :

- Preliminary results

- Preliminary results

-  Muriel Fallot – 26 sept. 2006

- Relevant observables ?

## Starting an experimental program...

** ****Integral ********spectra**** **measured by Schreckenbach et al. (at better than 2% until 8 MeV) & Hahn et al. @ILL 235U, 239,241Pu targets,
- but conversion : global fit including 30 arbitrary contributions: global shape uncertainty from 1.3%@3MeV to 9%@8MeV** **
** ****FP contributions :**** **measurements of Tengblad et al. 111 nuclei @ISOLDE  and OSIRIS
- don’t agree with the experimental integral spectra (important errors : 5% at 4MeV, 11% at 5MeV and 20% at 8MeV)** **
** ****Chooz and Bugey :**** **energy spectrum and flux** **in agreement with Scheckenbach et al. + Vogel et al., 1.9 % error on reactor e flux** **

**Starting an experimental program...**

** ****Theoretical approach**** ****:**** **Klapdor & Metzinger microscopic calc. of trans. matrix elements (PLB82 + PRL82), Vogel et al. for 238U

- Subatech – SPhN Saclay

- 5

-  Muriel Fallot – 26 sept. 2006

## Examinating the FP contributions

-  Tengblad et al. included 370 nuclides in his spectrum including 111 exp. spectra from short half-lives, but also 177 BR and end-points (spin/parity ?), 25 known -strengths and 67 extrapolated -strength !!!

- First step = build back the spectrum obtained  that time

- ENSDF : BR and endpoints, spin/parities when known !
- JEFF3.1 : BR and endpoints, spin/parities when known
- ENDF-B-VI : BR, endpoints, spin/parities + continuous spectra by Gross theory
- JEF2.2 : contains some of the spectra measured by Tengblad et al.

** **_**Beta Decay Theory to have the spectrum shape :**_

- Fermi Theory of Beta Decay:
-   -Assumes a Weak interaction at a point.
-                            = 2 | Vfi |2 (Ef) where Vfi =  f*VI dv
-                           and (Ef) = dn/dEf  - no.of states in interval dEf

_** **__**Need to read nuclear databases :**_

- 6

-  Muriel Fallot – 26 sept. 2006

## Beta Decay Theory

- 7

-  Muriel Fallot – 26 sept. 2006

**Beta Decay Theory**

**τ**

**N(Z,W)dW =g****2****/2********3**** x F(Z,W) x ********W(W****0****-W)****2**** x S****n****(W) dW**

- The shape of the spectrum goes like:

- Fermi Function

- Nuclear Matrix element

- Shape factor for allowed and nth forbidden transition

- Weak interaction coupling constant

- Momentum in mec2 units

- Total electron energy in mec2 units

- End point

## -decay and Classification of -spectra :

- 8

-  Muriel Fallot – 26 sept. 2006

******-decay and Classification of ********-spectra :**

-  « Shape factors » : emphasize the high energy region of the spectra compared with allowed spectra

| Classification | J |  | logft |
| --- | --- | --- | --- |
| Allowed | 0,1 (0+  0+) | No | 4-6 |
| 1st forbidden non-unique | 0,  1  | Yes | 6-10 |
| 1st forbidden unique |  2 | Yes | 7-10 |
| 2nd forbidden non-unique |  2 | No | 11-14 |
| 2nd forbidden unique |  3 | No | 14 |
| 3rd forbidden non-unique |  3 | Yes | 17-19 |
| 3rd forbidden unique |  4 | Yes | 18 |

-  The vast majority of -transition are classified as allowed type

-  Transition rate   = _0.693_ .

- t1/2

- We introduce ft1/2  Const./ |Mfi|2

## « BESTIOLE » package : interface by D. Lhuillier (CEA/SPhN) on BETA-S code from Oak Ridge*

- 9

-  Muriel Fallot – 26 sept. 2006

**« BESTIOLE » package : interface by D. Lhuillier (CEA/SPhN) on BETA-S code from Oak Ridge***

-  _Allowed, 1st, 2nd and 3rd forbidden unique _transitions are explicitly represented

-  _1st forbidden non-unique :_ shape factor S1(W) independent of energy = idem as allowed transitions

-  _2nd and 3rd forbidden non-unique_ : original approximation = assumed to have an allowed shape

- Modified to take the 1st and 2nd forbidden unique shape instead

-  Reads ENSDF Branching ratios, End-points and spin/parities

- *Report COG-96-33-I RC-1564

## Results

- 10

-  Muriel Fallot – 26 sept. 2006

**Results**

- Tengblad et al. 1 year of irradiation
- Compared with BESTIOLE for ~950 nuclei with cumulative yields

- Tengblad et al. 20min. of irradiation
- Compared with MURE 20min. evolution
- using the spectra from BESTIOLE

_**No Condition**_**:**
**~950 nuclei in ENSDF databasis**

-  Large discrepancy at high energy when take into account more nuclei than Tengblad et al.,
-  MURE = in good agreement up to 4 MeV,
-   More influence of the other nuclei in MURE than with cumulative yields : influence of the short half-lives greater in 20min than at equilibrium

- 235U

## Results

- 11

-  Muriel Fallot – 26 sept. 2006

**Results**

- Tengblad et al. 1 year of irradiation
- Compared with BESTIOLE and 75 exp. spectra among the 111 mesured by Tengblad et al. for ~950 nuclei with cumulative yields

- Tengblad et al. 20min. of irradiation
- Compared with MURE 20min. evolution
- for BESTIOLE and 75 exp. spectra

_**No Condition**_**:**
**~950 nuclei in ENSDF databasis**

- 235U

## Towards a better understanding of antineutrino spectra:

-  Astroparticle physics : future neutrino experiments (relic Supernovae...)  spectrum never measured beyond 8 MeV

-  Double-Chooz phase 1: when only far detector,
- => better precision on the reactor e spectrum very useful

-  Nuclear structure (exotic nuclei), nuclear astrophysics for the most exotic ones...

-  Double-Chooz phase 2: best measurement of reactor e spectrum and flux ~  >105 evts/y

- 12

-  Muriel Fallot –26 sept. 2006

-  Nuclear reactor physics and safety (decay heat calc.)
-     /future (Gen. IV) reactors (decay heat + -delayed n)

**Towards a better understanding of antineutrino spectra:**

**n-rich fission products beta decay**

## ZAN

- 13

- Strong common points with measurements for reactor decay heat calculation in nuclear reactors

-  Muriel Fallot – 26 sept. 2006

-  Data required-cross-sections, fission yields, decay half-lives, mean beta  and gamma energies, neutron capture cross-sections and uncertainties in these data.

- The problem of measuring the β - feeding (if no delayed part.emission)

- - **? **

- ZAN

- Z+1AN-1

- γ

- γ

- γ2

- γ1

-  We use our Ge detectors to construct the decay scheme
-  From the γ-balance we extract the β -feeding

- Low efficiency of Ge detectors at high energy => Pandemonium effect = displacement of the -strength (overestimation of high energies)

- From W. Gelletly et al.

##  Test experiment @ Institut Laue-Langevin High Flux Reactor (Grenoble) last summer : 

-  Test experiment @ Institut Laue-Langevin High Flux Reactor (Grenoble) last summer :

- Focal point

- Refocussing magnet

- Electric condenser

- Dipole magnet

- Target

- LOHENGRIN Spectrometer : A/q

-  1 HPGe clover

-  25.8mm Silicon detector

-  Target 235U(6mg)

- spectra measurements for A=90, 94 :
-  beta singles +  coincidences

- Test of the simulation of the evolution of beta spectra from isobaric chains A=90,94

- 14

-  Muriel Fallot – 26 sept. 2006

- Analysis on  going..., PhD thesis of S. Cormon

-  Measure integral  spectrum from fast 238U fission : theoretical calculation from Vogel et al. (89), error  10%, gives  8% of PWR reactor antineutrinos

## Conclusions and outlooks

- 15

-  Muriel Fallot – 26 sept. 2006

**Conclusions and outlooks**

-  Possible origins of discrepancies between previous measurements :
-       - lack of short half-life nuclei
-       - highly forbidden transitions more important at high energy
-       - Pandemonium effect in nuclear data basis ?
-  Comparison between ENSDF and ENDF, JEFF...
-  Theoretical point of view : Gross Theory for - decay, Microscopic models ?
-  Isolate the most pertinent nuclei to be measured (forbidden non-unique transitions) that influence the spectrum shape (especially high energy part)
-  Proposal to use the ALTO facility, GANIL...  238U beta spectrum ?
- + Moscow-Kurchatov initiative...