np neutron induced fission - Объединенный...

NEW NEEDS, CHALLENGES, OPPORTUNITIES

237237NpNp

Neutron Induced Fission Neutron Induced Fission

ISINN-25, 22-26 May 2017, Dubna, Russia

Ivan N. Ruskov

http://www.free-powerpoint-templates-design.com/free-powerpoint-templates-design

http://www.free-powerpoint-templates-design.com/free-powerpoint-templates-design

A A short review of the short review of the activities activities in the field in the field

of of neutron induced fission is presented. neutron induced fission is presented.

Further Study of Further Study of NNeutron Induced Nuclear Fission eutron Induced Nuclear Fission

@ IREN @ IREN -- GNEIS GNEIS -- GELINA GELINA -- n_TOFn_TOF -- LANSCE LANSCE

is desirable, but….where?is desirable, but….where?

Introduction and motivation

237Np is a major component of spent nuclear fuel

Accurate knowledge of cross-section essential for waste transmutation and advanced nuclear reactor studies (fast reactors etc.)

However…

Significant discrepancies exist in data and in recent evaluations

Recent measurements have not clarified the situation

237Np(n,f) measurement @ n_TOF EAR-1 & EAR-2 (CERN-INTC-2015-007 / INTC-P-431) 49th INTC Meeting, CERN, February 11, 2015

There is an urgent need in basic nuclear

data for the fast and thermal reactor

systems in the GENERATION IV initiative

and accelerator-driven system (ADS)

technologies.

Scare database on fission resonance parametersScare database on fission resonance parameters

Is there (n, Is there (n, ggf) and its influence to the fission f) and its influence to the fission

fragment massfragment mass--energy distributions ?energy distributions ?

The nature of the coupling between I and II class The nature of the coupling between I and II class

states unclearstates unclear

Why the Why the 237237Np isotope is so important andNp isotope is so important and

interesting object of further study? interesting object of further study?

Is there and where is the resonance of IIIs there and where is the resonance of II--class ?class ?

Why the Why the 237237Np isotope is so important andNp isotope is so important and

interesting object of further study? interesting object of further study?

1. The 237Np isotope is accumulated in the reactor core.

One 1000 MW power reactor produces several

kilograms of Np per year.

2. The values of: T1/2(α) = 2.14x106 years;

σf(th) = 20 mb

3. The transmutation of Np becomes an important task of the fuel

cycle.

Neptunium, which is predominantly represented by the single isotope Np-237, is a significant contributor to long-term radiotoxicity, because of its very long half-life. However, Np-237 does not contribute significantly to decay heat output. Np-237 can be transmuted in both thermal and fast reactors by mixing it homogeneously with the nuclear fuel. Neptunium transmutation is less problematic in fuel manufacturing than americium or curium but nevertheless, managing radiological doses in fuel manufacturing remains challenging.

http://www.nnl.co.uk/media/1053/minor_actinide_transmutation_-_position_paper_-_final_for_web1.pdf

238238U U

(n,(n,gg))

236236U U 237237U U 237237NpNp 237237NpNp

235235U U

2.14х10 6 y

22..33 dd

23 23 minmin

66..7575 dd

239239U U 239239NpNp 239239NpNp

(n,(n,gg))

(n,(n,gg))

237237NpNp 237237NpNp 238238PuPu

84.74 y 2.382.38 dd

232388NpNp

(n,(n,gg)) = (140 = (140 30) b30) b

239239NpNp

240240NpNp

223939PuPu

240240PuPu

The The 237237Np resonance neutron fission/Np resonance neutron fission/capture cross sections and resonance capture cross sections and resonance parameters are important forparameters are important for

The The 237237Np resonance neutron fission/Np resonance neutron fission/capture cross sections and resonance capture cross sections and resonance parameters are important forparameters are important for

•• Modeling of the nuclear Modeling of the nuclear transmutation;transmutation;

•• Calculation of nuclear reactors;Calculation of nuclear reactors;

•• Neutron Metrology;Neutron Metrology;

•• Routine and Accident Dosimetry;Routine and Accident Dosimetry;

•• Radiation Dosimetry, Safety and Radiation Dosimetry, Safety and SecuritySecurity

•• Studying the shape of the Studying the shape of the fission barrier;fission barrier;

•• Searching levels in the II Searching levels in the II minimum of the potential minimum of the potential fission barrier.fission barrier.

Generation and Transmutation Generation and Transmutation

of of 237237NpNp

223939PuPu

(n,g) = (140 30) b

(n,g) 237237NpNp 237237NpNp PuPu 238238PuPu

2.38 d

NpNp 232388NpNp

NpNp 239239NpNp

NpNp 240240NpNp

PuPu 223939PuPu

PuPu 240240PuPu

84.74 y

“Transmutation” branch:

- 2n + 2.7n = +0.7n

“Power reactor”

branch:

- 3n + 2.7n = - 0.3n

BowmanBowman--LisowskiLisowski idea Np to be used as a “generator” idea Np to be used as a “generator”

of neutrons during the transmutation process in of neutrons during the transmutation process in

highhigh--flux thermal reactors flux thermal reactors

Neutron balance:

That isotope 237Np could undergo neutron capture and furnish additional 239Pu. That is,

However, in a very high neutron flux, the intermediate nucleus 238Np could attain a high probability

of capturing a second neutron and fissioning before the beta decay could take place.

Thus, in principle, a high-flux transmutation scheme could achieve a higher fissioning rate

of various isotopes than a scheme that operates at ordinary thermal flux levels.

232377 NpNp + + 11nn 238 238 NpNp 232377 NpNp + + 11nn 238 238 NpNp

9393NpNp238238 oo--o nucleus:o nucleus:

< < DDII> ~ 0.5> ~ 0.5 –– 0.6 eV0.6 eV ::

big number of lowbig number of low--energy energy

resonances: n ~resonances: n ~ 100100

@@ ЕЕnn < 100 eV< 100 eV, , reached reached

for investigation with for investigation with

resonance neutron resonance neutron

spectroscopyspectroscopy

9393NpNp238238 oo--o nucleus:o nucleus:

< < DDII> ~ 0.5> ~ 0.5 –– 0.6 eV0.6 eV ::

big number of lowbig number of low--energy energy

resonances: n ~resonances: n ~ 100100

@@ ЕЕnn < 100 eV< 100 eV, , reached reached

for investigation with for investigation with

resonance neutron resonance neutron

spectroscopyspectroscopy

TT 1/21/2 = 2.14x10= 2.14x1066 yy

f f ~ ~ ((0.0.001 1 -- 1010)) bb

< < f f > > (7)(7) ~ 10~ 103 3 < < f f > > (5)(5)

Radiotoxic: MACRadiotoxic: MAC = 0= 0..03 03 BqBq/l/l

Migrates in mediaMigrates in media

AA ~ ~ 226.6.2 2 MBqMBq/g/g

TT 1/21/2 = 2.14x10= 2.14x1066 yy

f f ~ ~ ((0.0.001 1 -- 1010)) bb

< < f f > > (7)(7) ~ 10~ 103 3 < < f f > > (5)(5)

Radiotoxic: MACRadiotoxic: MAC = 0= 0..03 03 BqBq/l/l

Migrates in mediaMigrates in media

AA ~ ~ 226.6.2 2 MBqMBq/g/g

Decay half-live

Fission ClustersFission Clusters in in ff

N e u t r o n e n e r g y En , eV

The fission cross section 237Np multiplied by E1/2 as a function of the neutron energy below 500 eV.

A fine structure is seen in the first resonant cluster at energy of ~ 40 eV. At higher energies, the

experimental resolution smooths out the fine structure in clusters at 120 eV, 200 eV, and so on.

The average distance between clusters is ~ 50 eV.

Michaudon A., Symposium. on Nuclear Structure, Dubna, 1968, p. 483

f . E

n1/2

, b . e

V1/2

30

20

10

0

40

30

20

10

0 20 40 60 80 100 120 130 200 300 400 500

237237Np Np resonance neutronresonance neutron fission cross sectionfission cross section

Measured at:Measured at:

Underground Nuclear Burst Physics 8, Underground Nuclear Burst Physics 8, GGiacolletiiacolleti et al.et al. …..…..19721972

SaclaySaclay TOF spectrometer, TOF spectrometer, PlattardPlattard et alet al.………….……………………………1976…1976

LANL TOF spectrometer, M.S. Moore LANL TOF spectrometer, M.S. Moore et al.et al. ……………………………1984…1984

Kiyoto Lead Slowing down nKiyoto Lead Slowing down n--spectrometer, Kimura et al...spectrometer, Kimura et al...19921992

DubnaDubna IBRIBR--30 TOF, 30 TOF, DermendjievDermendjiev et al………..et al………...….…....1993, 19991993, 1999

KurchatovKurchatov Institute Lead cube, Institute Lead cube, GerasimovGerasimov et al………..et al………..….1997….1997

EXFOR nuclear data libraryEXFOR nuclear data library

94D4: Dermendzhiev, E., Ruskov, I., Zamyatnin, Yu.S., Gov

erdovskij, A.A.: Yad. Fiz. 57 (1994) 1362.

EXFOR 41165.

84A6: Auchampaugh, G.F., Moore, M.S., Moses, J.D., Nelson, R.

O., Extermann, R.C., Olsen, C.E.: Phys.

Rev. C 29 (1984) 174. EXFOR 12792.

81W2: Weston, L.W., Todd, J.H.: Nucl. Sci. Engin. 79 (

1981) 184.

84M4: Moore, M.S., Calabretta, Corvi, F., Weigmann, H

.: Phys. Rev. C 30 (1984) 214.

73K1: Keyworth, G.A., Lemley, J.R., Olsen,

C.E., Seibel, F.T., Dabbs, J.W.T., Hill, N.W.:

Phys. Rev. C 8, (1973) 2352. EXFOR 10532.

70G: Gavrilov, K.A., Kamaeva, K.K., Krajtor, S

.N., Pikelner, L.B.: At. Energ. 28 (1970) 362; S

ov. J. At Energ. (English Transl.) 28 (1970) 464

. EXFOR 40018.

84M5: Mughabghab, S.F.: Neutron Cross Sections, Vo l . 1 , Part

B. BNL, Acad. Press, N.Y. 1981. 76P2: Plattard, S., Blons, J., Paya, D.: Nucl. Sci. E

ngin. 61 (1976) 477. EXFOR 20448.

EXFOR nuclear data libraryEXFOR nuclear data library

www.cern.ch/n_TOF

nn__TTOFOF fissionfission detectorsdetectors

•Gas: Ar (90%) CF4 (10%)

•Gas pressure

•Electric field

•Gap pitch

: 720 mbar

: 600 V/cm

: 5 mm

•Electrode diameter : 12 cm

•Electrode thickness: 15 m (Al)

•Deposit thickness : 125 m/cm2

•Backing thickness : 100 m (Al)

•Window thickness : 125 m

•20x20 cm2

•Isobutane gas 7 mbar

•HV 500-600 V

•3 mm between electrodes

•1 anode (a few ns signal width)

•Electrode thickness : 1.5 m (Mylar+Al)

•Deposit thickness : 100-300 g/cm2

•Backing thickness : 0.1 m (Al)

• : 1.5 m (Mylar)

•Fission event identification: T2 in

coincidence with T1

Stefano Stefano MarroneMarrone DipartimentoDipartimento di di FisicaFisica and INFN, Bariand INFN, Bari 5th Workshop on Nuclear Astrophysics R5th Workshop on Nuclear Astrophysics RUSSBACH 3USSBACH 3--7March, 7March, 20082008

http://www.uni-mainz.de/Organisationen/vistars/talks_russbach2008/russbach2008_marrone.pdf

FICFIC PPACPPAC

http://www.cern.ch/n_TOF








http://indico.ictp.it/event/a07153/session/2/contribution/1/material/0/0.pdf


Capture 151Sm

204,206,207,208Pb, 209Bi

232Th

24,25,26Mg

90,91,92,94,96Zr, 93Zr

139La

186,187,188Os

233,234U

237Np,240Pu,243Am

Fission 233,234,235,236,238U

232Th

209Bi

237Np

nn_TOF_TOF experimentsexperiments

237Np(n,f)

Higher fission x-section in the sub-threshold region The n_TOF Collaboration

241,243Am, 245Cm

FICFIC--0 (2003)0 (2003)

Capture 151Sm

204,206,207,208Pb, 209Bi

232Th

24,25,26Mg

90,91,92,94,96Zr, 93Zr

139La

186,187,188Os

233,234U

237Np,240Pu,243Am

Fission 233,234,235,236,238U

232Th

209Bi

237Np

PPACs (2003)PPACs (2003) 237Np(n,f)

Higher fission x-section in the sub-threshold region The n_TOF Collaboration

241,243Am, 245Cm

nn_TOF experiments_TOF experiments

The n_TOF Collaboration

123 Scientists/ 39 Institutions

E. Dermendjiev et al. – Phys. At. Nucl. 57, 1362 (1994).

237Np (12.82 0.08)mg 235U (31.80 0.20)mg

Furman et al., 2003 En = 20 eV700 keV

90%Ar+10%CF4

600mbar=450.037Torr=6x104 Pa

ϕ40x30cm2

5mm/300V

Dt=2-3ns

The determination of

more accurate resonance parameters is possible.

This work is in progress with SAMMY code.

The n_TOF Collaboration

122 Scientists/ 39 Institutions

FIG. 6. (Color online) 237Np fission resonances around 40 eV.

n TOF data are shown in comparison with the ENDF/B-VI.8, ENDF/B-VII.0, and JEND

L-3.3 evaluations. We have also included data from Furman et al. [41],

Auchampaugh et al. [42], and Plattard [43].

Paradela et al.,

5

14.8 MeV14.8 MeV

Comparison of Comparison of n_TOFn_TOF 237237Np fission cross section, relative to Np fission cross section, relative to 235235UU

Physical Review C 82, 034601 (2010)

DOI: 10.1103/PhysRevC.82.034601

Argonne Fast neutron Generator laboratory

(1 to 10 MeV )

GNEISS neutron source in Gatchina

Los Alamos Neutron Science

Center (0.1 to 200 MeV)

Tovesson’s measurement the cross section has been normalized

to the ENDF/B-VI nuclear data at 14.8 MeV because the amount

of target material was not known with the desired precision.

Paradela et al., 2010 Neutron

-induced fission cross section

of Np measured at the CERN

n_TOF facility

Paradela et al., 2010,

CERN n-TOF (0.7 eV - 1 GeV)

Fig. 6. The data on 237Np(Fig. 6. The data on 237Np(n,fn,f) from the PPAC detector are systematically higher) from the PPAC detector are systematically higher than previous measurements by about 7% above 1 MeV, than previous measurements by about 7% above 1 MeV, but are not confirmed by more recent n TOF results. but are not confirmed by more recent n TOF results.

A. Tsinganis et al., The fission programme at the CERN n TOF facility, THEORY-3, 2014

Physics Procedia 64 ( 2015 ) 130 – 139, doi: 10.1016/j.phpro.2015.04.017

Neutron-induced fission cross-section of 237Np obtained with two different detection systems

49th Meeting of the INTC CERN, February 11, 2015

L. Audouin1, E. Berthoumieux2, Y. Chen1, N. Colonna3, M. Diakaki2, I. Durán4, F. Gunsing2, J. Heyse5, M. Kokkoris6, C. Paradela5, P. Schillebeeckx5, A. Stamatopoulos6, D. Tarrio4,7, L. Tassan-Got1, A. Tsinganis6, R. Vlastou6

and the n_TOF Collaboration

1) Institute de Physique Nucleáire d'Orsay, CNRS, France 2) Commissariat à l’Énergie Atomique (CEA) Saclay - Irfu, Gif-sur-Yvette, France

3) Istituto Nazionale di Fisica Nucleare (INFN), Bari, Italy 4) Universidad de Santiago de Compostela, Spain

5) European Commission JRC, Institute for Reference Materials and Measurements, Geel, Belgium 6) National Technical University of Athens (NTUA), Greece

7) University of Uppsala, Sweden

Spokespersons: L. Tassan-Got (IPN Orsay), A. Tsinganis (NTUA)

Technical Coordinator: O. Aberle (CERN)

https://indico.cern.ch/event/369115/contributions/874338/attachments/734390/1007567/Np237_INTC.pdf

https://indico.cern.ch/event/369115/contributions/874338/attachments/734390/1007567/Np237_INTC.pdf

237Np(n,f) cross-section: present status


Significant discrepancies ~6-8% exist in data above the fission threshold

Recent evaluations (ENDF/B.VII.1, JENDL-4.0) are also discrepant within a few percent in the same region

n_TOF results obtained with PPACs (EAR-1) systematically higher than other measurements in fission plateau

Other n_TOF dataset (with FIC detector) more in agreement with previous measurements

Singularity of n_TOF PPAC results not conclusive…

…because apparent agreement between previous measurements is partly due to arbitrary normalizations: ENDF/B-VII adjusted to Tovesson !

Tovesson normalised to ENDF/B-VI at 14 MeV due to unknown sample content !

ENDF/B.VI adjusted to Lisowski !

Lisowski normalised to Meadows above few MeV due to unknown sample content !

(Courtesy M. Diakaki,

CEA)

Fission fragment angular distributions


The PPAC setup can also provide data on fission fragment angular distributions (FFAD)

FFAD data important to:

Theoretical study of fission, BUT...

...also for the more reliable determination of detection efficiency, improving accuracy of measured cross-sections

The effect is important even for the PPAC configuration

FFAD data for 237Np is scarce above 10 MeV and very uncertain around 14 MeV

As done previously with 232Th, this measurement can extend the energy range and accuracy of experimental data

237Np(n,f) cross-section: present status


Recent experiments with monoenergetic neutron beams have not resolved this discrepancy Results with Micromegas detectors at 4.5-5.3 MeV (Athens, “Demokritos” van de Graaf) lie

between evaluations and n_TOF data

Results for 237Np(n,f), obtained during the 240,242Pu(n,f) measurement at IRMM van de Graaf, show better agreement with n_TOF data (and better reproduction of Pu evaluations using these values) between 0.5-3 MeV

P. Salvador-

Castineira,

PhD Thesis (2014)

M. Diakaki et al.,

Eur. Phys. J. A (2013)

49: 62

Introduction and motivation Benchmark experiments lend additional support to n_TOF data

Enriched Np sphere inside enriched 235U shells (LANL)

Benchmark experiment of Np fission rate under 252Cf neutron field also favours n_TOF data

Based on available data, a final conclusion cannot be drawn An important open question in the field

Measurements with different techniques (TOF, monoenergetic beams) and detectors are necessary to isolate systematic uncertainties and improve accuracy of evaluated cross-section New measurements to be performed at IRMM and n_TOF (pending INTC approval)


For New Measurements

M. M. DiakakiDiakaki et al. et al. ((n_TOFn_TOF Collaboration),Collaboration),

NeutronNeutron--induced fission cross section of induced fission cross section of 237237Np in the Np in the keVkeV to MeV range to MeV range

at the CERN at the CERN n_TOFn_TOF facility, Phys. Rev. C 93, 034614 facility, Phys. Rev. C 93, 034614 –– Published 17 March 2016Published 17 March 2016

FIG. 6. The 237Np(n,f ) cross section,

shown with 50 bins /decade, in the

neutron energy range

100 keV to 1.5 MeV.

The error bars correspond to the

statistical uncertainties.

The relative statistical uncertainty

did not exceed 3% above 500 keV.

The present results are compared to

the latest experimental data of

Paradela [3] (obtained from the

same facility) and to the

evaluations ENDF/B-VII.1 [23],

JEFF 3.2 [25], and JENDL 4.0 [24].

DOI: https://doi.org/10.1103/PhysRevC.93.034614

https://doi.org/10.1103/PhysRevC.93.034614

WP7:WP7: SupportSupport toto NeutronsNeutrons ForFor ScienceScience andand thethe

ShortShort PathPath n_TOFn_TOF experimentalexperimental areaarea (EAR2)(EAR2)

CHANDA

General Meeting and Governing board

CIEMAT Oct 17-18, 2016

[email protected]

http://www.chanda-nd.eu/system/files/docs/03-CHANDA%20WP7%20Vlachoudis%20Report%20Oct%202016.pdf

mailto:[email protected]

DeDesigsignn ooff EAREAR22

~ 200 m

Protons

~ 20 m

Target

EAR2

EAR1

Collimator

Magnet

Dump

Two experimental areas (EAR):

[email protected]

• Horizontal flight path:

EAR1 at 182.5 m

• Vertical flight path:

EAR2 at 18.2 m

Both beam lines have: • 1st collimator:

halo cleaning + first beam shaping.

• Filter station.

• Sweeping magnet.

• 2nd collimator: beam shaping.

Two experimental areas running in parallel.


















• PAC 4-2: Measurement of the 237Np(n,f) reaction cross-section at the

CERN n_TOF facility EAR-2 using a Micromegas detector system

• Dates: 20.09.2016 … still running

• Hours: Requested: 504, Endorsed: 200, Delivered 700 (estimated)

EExxppereriimemenntsts SStattatusus:: PPreresseenntt

First analyzed fission events from 237Np: Target and detector preparation:

[email protected]


















n_TOF Report

DanielaDaniela MacinaMacina

n_TOF Run

Coordinator

CERN

55th INTC Meeting, 8-9 February 2017

https://indico.cern.ch/event/608383/contributions/2452589/attachments/1409013/2154387/INTC_8Feb2017.pdf

08/02/2017, 09:15

The neutron Time Of Flight Facility

Spallation

Target

EAR1

EAR2

20

m

D. Macina, 55th INTC Meeting, CERN, 8-9 Feb 2017 3

n_n_TTOOFF FluxFlux

Wk 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45

Mo 4 11 18 25 1 8 15 22 29 5 12 19 26 3 10

17 24 31 7

Tu

We

Th

Fr

Sa

Su

July Aug Sep

Imag

ing

0.2

x10

18 p

ot

237Np ;μGASͿ 2.0x1018 pot

Oct Nov

No full time beam due to

activities in the other area PS Technical Stop 36 hrs

μG

AS

FLU

X

0.5

x10

18 p

ot

Injector MD

Smal

l co

llim

ato

r

26Al 5.0x1018 pot

PP

AC

FLU

X

0.5

x10

18 p

ot

Measurements last part 2016

Wk 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45

Mo 4 11 18 25 1 8 15 22 29 5 12 19 26 3 10 17 24 31 7

Tu

We

Th

Fr

Sa

Su

July Aug Sep

TAC Com

1.0x1018 pot

233U TAC 4.3x1018 pot

Oct Nov

Recoil test 0.5x1018 pot

155,157Gd

2.4x10 pot 18

235 U 1.5x1018 pot

16O test 0.5x1018 pot

EAR

1


EAR

2

Detector SetUp

237Np (n,f) at EAR2 with μMGAS


Courtesy A. Stamatopoulos

237Np potential target of incineration in fast neutron reactors

Discrepancies of ~ 6% in the fission σ → • Measure 237Np (n,f) in EAR1 with PPAC • Measure 237Np (n,f) in EAR2 with μMGAS

235U & 238U to use for reference

One 237Np sample prepared at

IPN- Orsay from the same batch as

in the PPAC measurement, in order

to cross out discrepancies coming

from the sample

237Np (n,f) at EAR2 with μMGAS

237Np(n,f) resonances are already quite visible

(20% statistics and one 237Np sample)

α background from 237Np decay

Courtesy A. Stamatopoulos


DRAFT

Analysis on going

Е*Е* SSnn

JJKK

II

Spontaneous Spontaneous

fissionfission

Isomeric fissionIsomeric fission

SubSub--barrier fissionbarrier fission

Over barrier fissionOver barrier fission

= a / c= a / c 1,51,5 22 22..55

IIII

JJKK11

EEIIII EEAA EEBB

0 0 1 1 2 2 3 3 4 4 5 5 6 6 77

V(V())

nnoo

nnoo

gg

gg

nnthth

235235UU

236236UU

141141BaBa

9292KrKr

gg

I classI class

Compound

Nucleus state

II classII class

Compound

Nucleus state

II classII class

Vibrational

state

FullFull

DumpingDumping

Moderate Moderate

DumpingDumping

NoNo

DumpingDumping

ГГвв ГГIIII

ГГIIII

DDII

Intermediate

structure

Vibration

resonance

SSnn SSnn SSnn

DDIIII

ГГвв

Excitation energyExcitation energy , Е* = , Е* = SSnn + + EEnn

Fis

sion w

idth

Fis

sion w

idth

, Г, Г

ff

DDIIII

SSnn SSnn SSnn

DDII

J=KJ=K J=K+1J=K+1 J=K+2J=K+2

R o t a t i o n s t a t e s

ЕЕкккк ЕЕкк

кк -- энергия вибрационного состоянияэнергия вибрационного состояния ЕЕкккк

DD ЕЕкккк

A B C

Vibration

Resonance

Effects of fission barrier inEffects of fission barrier in GGf f

а

B B

I II I II I II I II I II I II

b c

Narrow stateNarrow state of IIof II classclass

with very weak couplingwith very weak coupling

Widened state of II class

with moderate coupling

Wide state of II class

with weak coupling

V, E

*V

, E

*

A A

A B B B

EEAA ~ E~ EBB EEA A < E< EBB EEAA > E> EBB

3 types of interaction between

the states of I и II type

Effects of fission barrier inEffects of fission barrier in ff

A B A B

b c Potential energy V

as function of

deformation

parameter

The course of

the fission cross

section in sub-

barrier fission

@ two cases:

En En

ff ff I class

resonances

II class

resonance

II class

resonance

I class

resonances

EEAA

EB

D < G >> G DI < G >> G D < G >> GDI < G >> G

EB

EEAA

VV VV

LynnLynn:: FissionFission resonanceresonance @@ 3939..9393eVeV isis 7171%% ofof classclass IIII..

WeigmanWeigman:: IfIf so,so, itsits radiativeradiative capturecapture gg--rayray mustmust differdiffer fromfrom classclass II

resonanceresonance spectraspectra,, whichwhich waswas notnot seenseen byby usus @@ GELINAGELINA.. ThereforeTherefore,,

underunder thethe clustercluster @@ 4040 eVeV therethere mustmust bebe aa widewide resonanceresonance ofof classclass IIII..

PayaPaya:: WeWe sawsaw itit @@ SaclaySaclay.. ItsIts parametersparameters areare:: EEoo== 4444..3535 eVeV;;

GGff == 1414 eVeV;; GGnn == 77..33xx101066 eVeV..

PlattardPlattard:: ButBut youryour ionizationionization chamberchamber waswas notnot optimizedoptimized againstagainst thethe

backgroundbackground fromfrom thethe multiplymultiply scatteredscattered neutronsneutrons.. Contrary,Contrary, inin ourour

measurements,measurements, thethe contributioncontribution ofof thisthis scatteringscattering @@ 4040 eVeV resonanceresonance

regionregion waswas lessless thanthan 33 mbmb.. WeWe obtainedobtained thethe followingfollowing valuesvalues forfor thisthis

resonanceresonance:: EEoo == 4040..5353 eVeV;; GGff <<214214 eVeV;; GGnn == 5656..33xx1010--66 eVeV.. But,But, itit isis notnot

clearclear whatwhat thisthis widewide resonanceresonance meansmeans.. WeWe assumeassume thatthat itit isis notnot thethe

resonanceresonance @@ 3939..9393 eVeV ofof classclass II,II, butbut thatthat @@ 3939..77 eVeV.. ForFor itit wewe

obtainedobtained GGff == 16871687 ueVueV..

Where is the II class resonanceWhere is the II class resonance

MooreMoore:: YouYou diddid notnot havehave sufficientsufficient resolutionresolution forfor aa reliablereliable

determinationdetermination ofof 3939..77 eVeV resonanceresonance parametersparameters.. HavingHaving betterbetter

resolutionresolution inin ourour experiment,experiment, wewe revealedrevealed itit inin thethe spectrumspectrum ofof thethe totaltotal

crosscross section,section, butbut itsits GGff == 22..55 ueVueV,, ratherrather thanthan 16871687 ueVueV.. AndAnd itit alsoalso hashas

aa spinspin 22,, notnot 33,, likelike allall thethe otherother resonancesresonances inin thethe clustercluster.. You,You, also,also, diddid

notnot havehave enoughenough statisticalstatistical accuracyaccuracy toto establishestablish thethe presencepresence oror absenceabsence

ofof aa widewide resonanceresonance ofof classclass IIII underunder thethe clustercluster @@ 4040 eVeV..

RR -- matrixmatrix formalism,formalism, whichwhich wewe usedused toto fitfit totaltotal crosscross sectionsection tt @@ OakOak

RidgeRidge andand fissionfission crosscross --sectionsection ff @@ LosLos Alamos,Alamos, givesgives equallyequally goodgood

resultsresults inin bothboth casescases.. True,True, thethe multiplemultiple nn--scatteringscattering effecteffect waswas aboutabout 33

timestimes higherhigher thanthan thatthat inin youryour experiment,experiment, butbut waswas takentaken intointo accountaccount byby

applyingapplying aa specialspecial procedureprocedure..

OurOur datadata differsdiffers fromfrom yoursyours ~~22..9191 times,times, andand inin thethe regionregion ofof thethe

resonanceresonance clustercluster @@ 4040 eVeV agreeagree withwith thethe datadata ofof JacolettiJacoletti andand BrownBrown

@@ PhysicsPhysics 88 withwith anan accuracyaccuracy ofof ~~ 1010%%..

Where is the II class resonanceWhere is the II class resonance

237237237Np fission barrier parametersNp fission barrier parametersNp fission barrier parameters

References

EII

[MeV]

EA

[MeV]

EB

[MeV]

ħA

[MeV]

ħB

[MeV] Ti

f Tig

Paya ’72 1.851.85 6.086.08 5.355.35 0.500.50

0.550.55 0.460.46 2 s2 s 0.4 y

Plattard et al. ’76 1.881.88 6.086.08 5.425.42 0.510.51

0.650.65 0.440.44 50 s50 s 4300 s

Weigman-Theobald ’72 2.22.2 6.336.33 5.745.74 0.720.72 0.400.40 52 s52 s 2.3 s

Wagemans ’98 5.95.9 6.06.0

S. Plattard:

The only way to have additional information about

the 238Np fission barrier is to look for the decay of

the state of class II, either via fission or through the

g-radiation of the 238Np isomer (of the form)

M. S. Moore:

Аn experiment capable to separate the g-quanta of

II-class state decay from the fission g-quanta

can solve this dilemma.

What to doWhat to doWhat to do ???

Dubna pulsed reactors IBR-30

(resonance neutrons): 1990-1999

Pulsed reactor IBR-30:

1. Study of the yields i.e. multiplicities of fission gamma-rays and

their variation in 233U, 235U, 237Np and 239Pu fission resonances.

2. Study of the sub-barrier fission of 237Np; measurements of σf, σ0Γf

and Γf values.

3. Search for the (n,γf)-reaction, evaluation of the Γγf value.

Jülich, Fed. Rep. of Germany, 13–17 May 1991

RResonance neutron induced fission esonance neutron induced fission

of of 237237NpNp

( n( n , , g g f )f ) –– реакция реакция ??

Physics of Particles and Nuclei· March 1990

MotivationMotivationMotivation MotivationMotivationMotivation

TheThe existenceexistence ofof veryvery weakweak resonancesresonances inin thethe

subthresholdsubthreshold fissionfission ofof 237237NpNp byby resonanceresonance neutronsneutrons

withwith valuesvalues ofof GGff ~~1010--66 eVeV and,and, consequently,consequently, thethe

relativelyrelatively longlong lifetimeslifetimes ofof thesethese excitedexcited statesstates ofof thethe 232388NpNp compoundcompound nucleusnucleus tt ~~ 1010--99 s,s, suggestssuggests thatthat thethe

probabilityprobability ofof emissionemission ofof thethe prepre--fissionfission gg--quantumquantum

mightmight bebe greatergreater thanthan thethe probabilityprobability ofof thisthis reactionreaction

toto occuroccur inin thethe fissionfission resonancesresonances ofof 235235UU ии 239239PuPu

[BDG[BDG9595 +]+]..

TheThe existenceexistence ofof veryvery weakweak resonancesresonances inin thethe

subthresholdsubthreshold fissionfission ofof 237237NpNp byby resonanceresonance neutronsneutrons

withwith valuesvalues ofof GGff ~~1010--66 eVeV and,and, consequently,consequently, thethe

relativelyrelatively longlong lifetimeslifetimes ofof thesethese excitedexcited statesstates ofof thethe 232388NpNp compoundcompound nucleusnucleus tt ~~ 1010--99 s,s, suggestssuggests thatthat thethe

probabilityprobability ofof emissionemission ofof thethe prepre--fissionfission gg--quantumquantum

mightmight bebe greatergreater thanthan thethe probabilityprobability ofof thisthis reactionreaction

toto occuroccur inin thethe fissionfission resonancesresonances ofof 235235UU ии 239239PuPu

[BDG[BDG9595 +]+]..

From practical point of view - to refine the nuclear data, such

as g and f The reaction (n, gf) leads to a change in Gg , g , Gf

и f , which influence is significant (~ 10-15% for 239Pu at En =

1 keV) by t and = g /f , especially at low excitation energy

region of the compound nucleus.

From scientific point of view, the (n, gf) reaction provides a lot of

important information about the process of nuclear fission, i.e.

about:

Height and structure of fission barriers;

The structure of transition states to fission and the degree of

their damping;

The strength of the coupling between the collective mode of

motion with internal excitations of the compound nucleus in

the process of fission;

The influence of the quantum characteristics of the excited

states of a compound nucleus on the properties of the fission

fragments;

The scheme of g-transitions between highly excited states of the

fissioning nucleus and, in particular, about the fission

resonances;

The strength of the connection between states with different

deformations (classes I and II) of the compound nucleus.

MotivationMotivationMotivation MotivationMotivationMotivation

Commonly Commonly Commonly

accepted accepted accepted

mechanism ofmechanism ofmechanism of

( n( n( n , , , g g g f )f )f ) –––

reactionreactionreaction Prompt

fission Е*,Е*,

Nucleus’ deformation,

( |J-1|,…,J+1 )

(|J-1|,…,J+1)

(I + 1/2)

(I 1/2)

(J+1)

J = (I 1/2 )

(J+1)

A+1A+1

JJ

AA

II

11n n (En , l = 0, s = 1/2) Compound

Nucleus

and

Liquid

Drop

Models

ЕЕ

11 M1M1

Nucleus deformation,

ЕЕ22**

ЕЕ11**

ЕЕ33**

Radiation CaptureRadiation Capture

PromptPrompt FissionFission

Form isomer

< < GGggff I I >> ~ 2x10~ 2x1044 ueVueV

[[VtjurinVtjurin & Popov’& Popov’7777]]

(n ,(n , gg f )f ) and feeding the isomeric stateand feeding the isomeric state

In sub-barrier fission, the radiative decay of a class II state can compete

with the fission process. The de-excitation of the CN by emission of a

cascade of g-quanta between low-lying class II states can lead to the

formation of a metastable form-isomer.

Decay of the isomeric stateDecay of the isomeric stateDecay of the isomeric state

It is possible after a significant timeIt is possible after a significant time--delay trough the external barrier delay trough the external barrier

(fission isomer) or trough the inner barrier in the I valley, where via the (fission isomer) or trough the inner barrier in the I valley, where via the

class I states the irradiation of class I states the irradiation of gg--rays continues till the ground state is rays continues till the ground state is

reached or till a state from which the spontaneous fission is possible.reached or till a state from which the spontaneous fission is possible.

DelayedDelayed DecayDecay

g ЗР

Nucleus Deformation, Nucleus Deformation,

IsomericIsomeric

FissionFission

g g SF

SSpontaneouspontaneous FFissionission

g g IFIF

g (n,gf)-reaction

< < GGggff I I >> ~ 2x10~ 2x1044 ueVueV

[[VtjurinVtjurin & Popov’& Popov’7777]]

Method for studying Method for studying Method for studying Method for studying

Method of measurement the Method of measurement the fluctuation of fission fluctuation of fission gg--rays yieldsrays yields

Method of measurement the Method of measurement the fluctuation of fission fluctuation of fission gg--rays yieldsrays yields

Fluctuation of g-ray and fission neutron yield

(multiplicity) from resonance-to-resonance

Neutron Time-of-flight spectrometry. Registering

the gamma-ray and neutron yields in coincidence

with fission fragment one

(n ,(n , gg f )f )--processprocess (n ,(n , gg f )f )--processprocess

Study of Fission g-ray Yields from

Low-energy Resonances of 237Np

A study of fission g-ray yields from 237Np low-energy

resonances has been performed at the Dubna IBR-30

pulsed reactor.

A multiplate fission chamber with 1.5 g of high-purity

237Np for detection of fission events.

A large 210 liters 6-section liquid scintillation detector, for

detection of 3 or more g-quanta in coincidence with

fission fragments, were used for fission g-ray yield

measurements.

A 1/Gf - dependence was found for the g-ray yields in 237Np

fission resonances.

This experimental result may be interpreted as an indication

of a possible pre-fission g-ray emission, which might arise

from the existence of (n, gf) – process.

Comparison of the averaged resonance

neutron fission cross sections of 237Np

10001000

100100

1010

11

00..11

< f > , mb

Еn , eV

10 100 100010 100 1000 2 3 4 5 6 72 3 4 5 6 7

(2)

(1)

(3)

10001000

100100

1010

11

00..11

< f > ,

mb

Еn , eV

10 100 100010 100 1000 3 4 5 6 7 3 4 5 6 7 2 3 4 5 6 72 3 4 5 6 7 2 3 4 5 6 72 3 4 5 6 7 2 3 4 5 6 72 3 4 5 6 7

(2)

(1)

(3)

(1) Jacoletti et al. [JBO72]

(2) Plattard et al. [PBP76]

(3) Kimura et al. [KYK92+]

(4) Dermendjiev et al. [GDR93+]

(( n,n, gg ff )) -- reactionreaction

<g > = <go> + D<g> = <go> + (Ggf / Gf) < gf >

f

f

E

E

ifff

f

fii badEEE

RR

RR

f

fG

><G

G

1)()(

11

2

193,3993,39

ggggg

gg

g

[RTS73+,[RTS73+, Tro79,Tro79, Щер90Щер90,, Rya97]Rya97]

Fluctuation of the Fluctuation of the 237237Np resonance Np resonance neutron induced fission neutron induced fission gammagamma--ray yield ray yield

0,000 0,005 0,010 0,015

0,95

1,00

1,05

1,10

1,15

0,00 0,05 0,10 0,15 0,20

1,0

1,5

2,0

2,5

GGff11, мкэВ 1 GGff

11, мкэВ 1

RR

39,9

3 э

В39,9

3 э

В

41,3

5 э

В

41,3

5 э

В ;

; 4

6,0

4 э

В46,0

4 э

В

37,1

5 э

В37,1

5 э

В

30,4

1 э

В30,4

1 э

В

26,5

6 э

В26,5

6 э

В

50,3

4 э

В50,3

4 э

В

88..9

7 э

В97 э

В

5,7

9 э

В5,7

9 э

В

7,4

2 э

В7,4

2 э

В

3,8

7 э

В3,8

7 э

В

10,6

7 э

В10,6

7 э

В

(a)

(b)

(c)

(a)

(b)

(c)

a = 1,006 0,035 (a)

b = 2,81 0,56

2 = 0,04

r = 0,65 0,40; 0,81

a = 1,001 0,004 (b)

b = 1,02 0,26

2 = 1,55

r = 0,55 0,26; ,75

a = 1,005 0,004 (c)

b = 0; 2 = 2,17

r = 0 -0,33; 0,33

a = 0,999 0,007 (a)

b = 2,38 0,76

2 = 0,0005

r = 0,58 0,19; 0,81

a = 0,999 0,003 (b)

b = 1,75 0,76

2 = 1,04

r = 0,47 0,04; 0,75

a = 1,003 0,003 (c) b = 0; 2 = 1,26

r = 0 -0,44; 0,44

RR = = aa + + b.b.GGff11

RR

The presence of a

statistically significant

correlation between (R,

Gf1) shows that in these

cases the effect of the

probable (n,gf) reaction

on the observed

fluctuations in g-ray

yields can not be

completely ruled out.

At least r2-part of this

variation can be because

of such a process.

Elimination of possible methodological errors during our experiment can be

excluded by conducting more accurate experiments with simultaneous registration

of the energy spectrum and multiplicity of the fission g-quanta.

Fluctuation of fission Fluctuation of fission gg--rays rays from resonancefrom resonance--toto--resonanceresonance Fluctuation of fission Fluctuation of fission gg--rays rays

from resonancefrom resonance--toto--resonanceresonance 25 year ago

Fluctuation of fission Fluctuation of fission gg--rays rays from resonancefrom resonance--toto--resonanceresonance Fluctuation of fission Fluctuation of fission gg--rays rays

from resonancefrom resonance--toto--resonanceresonance

237Np / 235U

now

RomashkaRomashka and TANGRAand TANGRA RomashkaRomashka and TANGRAand TANGRA

24 hexagonal 78x90x200mm 24 hexagonal 78x90x200mm NaINaI(Tl) scintillation gamma(Tl) scintillation gamma--spectrometers: spectrometers: DDE~7E~7--8%, 8%, DDt~3nst~3ns

16/32/4816/32/48--channel channel digitizers, in digitizers, in the form of one or several the form of one or several PCIPCI--E cards. Sampling E cards. Sampling frequency 100 MHz The frequency 100 MHz The digitized signals are digitized signals are transmitted via the PCItransmitted via the PCI--E bus E bus in the computer's memory, in the computer's memory, where all the data processing where all the data processing and storage takes place. and storage takes place. Maximum load of the system Maximum load of the system is ~ 10is ~ 1055 events per secondevents per second

INGING--2727

Electron gunElectron gun

Accelerator section Accelerator section

in in the solenoidthe solenoid

Klystron 2Klystron 2

Magnetic speMagnetic spe

ctrometerctrometer

ModulatorsModulators

Neutron Neutron

Producing Producing

targettarget

http://flnp.jinr.ru/244/

http://flnp.jinr.ru/244/

http://f

lnph.ji

nr.r

u/e

n/f

aci

litie

s/iren/p

ara

mete

rs

IREN IREN

ParametersParameters

Neutron source (Laboratory) <In>,

1015 n/s

Δt,

ns

Q,

1030 n/s³

ORELA (ORNL, USA) 0.13 30 0.14

GELINA ( IRMM, Belgium) 0.05 1

50

LANSCE (LANL, USA) 10 125 0.64

CERN PS n_TOF (CERN, Switzerland) 0.4 10 4

LUE-40+IBR-30 (JINR, shutdown) 0.5 1600 0.0002

IREN (JINR, project) 1.0 400 0.0062

GNEIS (PNPI, Gatchina) neutron beam N5 0.3 10 3

http://isinn.jinr.ru/past-isinns/isinn-23/progr-2805_2015/Shcherbakov.pdf_ http://flnph.jinr.ru/en/facilities/iren/parameters

2.6x106y

1972-1973

2.90

2.88

2.86

2.84

2.82

2.80

2.78

2.76

2.74

2.72

2.70

2.68

2.90

2.88

2.86

2.84

2.82

2.80

2.78

2.76

2.74

2.72

2.70

2.68

20 30 40 50 60 70 80 90 100

20 30 40 50 60 70 80 90 100

ENDF/B-VII.0

JEFF-3.1.1

Yu.V. Ryabov, Investigations of (n,gf)-reaction for U-235 and Pu-239

resonances and structure of fission barriers (1972?), ISINN-5, (1997) 422.

The average fission g-rays multiplicity as a function

of the neutron multiplicity (r = 0.77)

ААmplitudemplitude,, keVkeV

Co

un

tsC

ou

nts

,

, a

rbit

rary

un

its

arb

itra

ry u

nit

s

Щербаков О.А., Щербаков О.А., Экспериментальные исследования (n,Экспериментальные исследования (n,ggf)f)--реакции, реакции,

ФЭЧАЯФЭЧАЯ, Т. 21, Вып. 2, 1990., Т. 21, Вып. 2, 1990.

ScherbakovScherbakov, O.A., O.A. Experimental investigation on the Experimental investigation on the (n,(n,ggf)f)--reactionreaction, ,

PEPANPEPAN 2121//2, 1990.2, 1990.

Trochon et al. [1978]

Scherbakov et al. [1988]

np neutron induced fission - Объединенный...

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