VENUS-1# 装置脉冲源实验分析

NEAL-Nuclear Energy & Application Lab, University of South China

第一届新型反应堆安全及发展研讨会，中国兰州， 2013.10.10 ～ 12

VENUS-1# 装置脉冲源实验分析谢金森（ [email protected]）

南华大学

第一届新型反应堆安全及发展研讨会

CONTENTS

Background and Purpose Core Composition & PNS Experiment of VENUS-

1# Preliminary Results from PNS Experiment Simulation of PNS Experiment on Certain

Condition Comparison of Simulated and Experimental

Results Summary & Future Suggestions

第一届新型反应堆安全及发展研讨会BACKGROUND AND

PURPOSEBackground

R&D on Accelerator Driven System for MA and LLFP Transmutation

Supported by two “973” Projects The World-first Fast-Thermal Coupled ADS core- VENUS-1# has

been built in 2005; Abundant research works on Sub-critical neutronics have been

carried out on VENUS-1#.

Supported by Chinese Academy of Science 5MWt~10MWt Pb-Bi cooled ADS core will be built (First-step,

Critically Operation; Second-step, Accelerator coupling with sub-critical core );

Although massive meaningful results has been obtained, some issues on Sub-criticality measuring still exist.


PURPOSEBackground

To support the development of sub-criticality measuring technique, Pulsed Neutron Source experiments on VENUS-1# has been performed

2005, VENUS-1# was coupled with CPNG (CIAE Pulsed Neutron Generator), five different Sub-critical levels;

2007, the first PNS experiment analysis work was published (Thesis of Shanghai Jiaotong Univ.) ;

2011, PNS experiment simulation work was performed, three different Sub-critical levels, D-T, 252Cf, Am-Be neutron sources(Thesis of CIAE).

All the above works indicate: Prompt neutron attenuation constants depend on detectors’ locations & driven source energy.


Fuel pins of Thermal

blanket

Prompt neutron attenuation constants

Detector_6th Detector_10th Detector_R Detector_S

2046 1627.6±22.4 (1)

795.33 (2)1705.0±25.0

763.762495.4±67.8

709.701350.4±36.4

--2022 1716.2±26.4

840.021702.0±14.4

832.112426.2±23.4

758.171576.4±17.9

--1998 1771.8±41.4

960.641888.0±48.0

985.873056.6±83.2

879.901671.2±62.0

--1962 1823.6±14.4

967.851922.4±16.4

985.873868.8±32.2

921.401646.6±17.5

--1926 1928.8±14.4

1119.501946.4±11.9

1076.404311.4±18.2

1076.401662.4±33.6

--(1) Experimental results of CIAE;(2) MC simulation results of SJTU.

BACKGROUND AND PURPOSE


PURPOSE

Purpose

Confirm the results from former researches;

Feasibility study of PNS method on Fast-thermal coupled core;

Investigate the potentially special phenomenon of Fast-thermal coupled core under pulsed neutron condition.

第一届新型反应堆安全及发展研讨会CORE COMPOSITION & PNS EXPERIMENT OF VENUS-1#

Core Composition Main parameters of VENUS-1#

External source region: coupled with accelerator, neutron tube, or isotopic neutron source;

Fast spectrum blanket: natural uranium pins + aluminum block, 10 layers;

Thermal spectrum blanket : 3wt% uranium pins+ CH2 block, 15 layers maximum;

Reflector: CH2 block, 200mm thick;

Shield: CH2+B, 200mm thick;

第一届新型反应堆安全及发展研讨会CORE COMPOSITION & PNS EXPERIMENT OF VENUS-1#

CPNG neutron generator(CIAE Pulse Neutron Generator )

Main parameters of CPNG

Type: Cockcroft-Walton

High voltage: 200~600kV

Pulse beam frequency: 50~200Hz

Pulse width:1~5us


Experimental conditions & instrument system

Detectors

Sub-criticalities: adjusted by thermal fuel pin loading; 1926, 1962, 1998, 2022, 2046;

Detectors: 3 3He tubes (6th, 10th layer of fast blanket & reflector); 1 BF3 tubes (Shield)

Electronic system: 60 multi-channels; 50us/channel;

Data collection: 3 groups data; 105 pulses; statistical errors for first several channels < 1%;

CORE COMPOSITION & PNS EXPERIMENT OF VENUS-1#

第一届新型反应堆安全及发展研讨会PRELIMINARY RESULTS FROM PNS EXPERIMENT

0 10 20 30 40 50 60

-0.010.000.010.020.030.040.050.060.070.080.090.100.110.120.130.140.150.160.170.18

6th 10th R S

Nor

mar

ized

Neu

tron

Cou

nt R

ate

Channel Number

Thermal blanket with 1926 fuel pins

0 10 20 30 40 50 60

-0.010.000.010.020.030.040.050.060.070.080.090.100.110.120.130.140.150.160.17

6th 10th R S

Nor

mar

ized

Neu

tron

Cou

nt R

ate

Channel Number


0 10 20 30 40 50 60

0.00

0.02

0.04

0.06

0.08

0.10

0.12

6th 10th R S

Nor

mar

ized

Neu

tron

Cou

nt R

ate

Channel Number


0 10 20 30 40 50 60

0.0000.0050.0100.0150.0200.0250.0300.0350.0400.0450.0500.0550.0600.0650.0700.0750.0800.085

6th 10th R S

Nor

mar

ized

Neu

tron

Cou

nt R

ate

Channel Number


0 10 20 30 40 50 60

0.00

0.02

0.04

0.06

0.08

0.10

0.12

6th 10th R S

Nor

mar

ized

Neu

tron

Cou

nt R

ate

Chanel Number


Fuel pins of

Thermal blanket

Prompt neutron attenuation constants

6th 10th R S

2046 1627.6±22.4 1705.0±25.0 2495.4±67.8 1350.4±36.4

2022 1716.2±26.4 1702.0±14.4 2426.2±23.4 1576.4±17.9

1998 1771.8±41.4 1888.0±48.0 3056.6±83.2 1671.2±62.0

1962 1823.6±14.4 1922.4±16.4 3868.8±32.2 1646.6±17.5

1926 1928.8±14.4 1946.4±11.9 4311.4±18.2 1662.4±33.6

第一届新型反应堆安全及发展研讨会PRELIMINARY RESULTS FROM PNS EXPERIMENT

Discussion on the experimental results

Prompt neutron attenuation constants show strong spatial dependence;

The attenuation constants obtained by detectors show large discrepancies;

The experimental results conflict with theory of experimental reactor physics (lumped parameter Point Reactor Dynamics) ;

Which attenuation constant should be used as a sub-critical indicator, or how to make spatial corrections.

第一届新型反应堆安全及发展研讨会SIMULATION OF PNS EXPERIMENT ON CERTAIN CONDITIONTheoretical considerations

Harmonics neutron flux seriously affects detector responses in deep sub-critical condition (both static & transient ) ;

For Fast-thermal coupled system, typical prompt neutron life time is 10-5 second, width of multi-channel should be correspond to the condition for better inferring of harmonics (can be easily realized in simulation);

To obtain the prompt neutron attenuation constants (fundamental mode), harmonics should be filtered.


( , ) ( ) ( )r t r T t

In transient conditions, neutron flux can be expressed as:

Consider Alpha Eigen-value problem, neutron density in PNS:

1

00 )()()()()(),(i

tii

tt ierrAerrAerStrN

Contribution of external source

Contribution of fundamental Alpha mode

Contributions of the ith harmonic Alpha modes

terS )(terrA )()( 00

tii

ierrA )()(


Relationship of each attenuation constant:

When harmonics and source contribution disappeared:

i21

constrrArrA

trNtrN

tt

)()()()(

),(),(

2020

1010

2

1

0

第一届新型反应堆安全及发展研讨会SIMULATION OF PNS EXPERIMENT ON CERTAIN CONDITIONMethodology of simulation Simulation conditions:

MCNP4CTM selected as PNS simulation code;

2046 thermal fuel pins loading for comparison with experiment;

Multi-channel width set as 5us for better inferring harmonics effect, totally 600 channels (0~3000us, the same as experiment);

Data processing technique:

Detector response of R selected as benchmark;

Relative responses to R used for fundamental attenuation time region search;


Simulation results

SIMULATION OF PNS EXPERIMENT ON CERTAIN CONDITION

0 100 200 300 400 500 60010-4

10-3

10-2

10-1

100

101

102

6th

R10th

6th 10th R S

Rel

ativ

e N

eutro

n C

ount

(s-1)

Time(5s)

S

0 50000 100000 150000 200000 250000 3000000.01

0.1

1

10

100

1000 6th/R 10th/R S/R

Rel

ativ

ed N

eutro

n C

ount

rate

Time(10-8s)

Fundamental decay mode

Simulated detector responses Simulated relative detector responses


Simulation results

Detector responses in time interval 500~3000us selected as fundamental attenuation constant fitting

SIMULATION OF PNS EXPERIMENT ON CERTAIN CONDITION

Detectors 6th 10th R SAlpha values 1430.30±8.7

11436.76±3.9

91436.60±3.4

91417.35±1.1

2Correlationcoefficients 0.99087 0.99809 0.99853 0.99984

第一届新型反应堆安全及发展研讨会COMPARISON OF SIMULATED AND EXPERIMENTAL RESULTS

Comparison of detector responses The simulated data use the same channel width of experiment; Quite different attenuation trends observed.

0 10 20 30 40 50 60

1E-3

0.01

0.1

6th 10th R S

Nor

mar

ized

Neu

tron

Cou

nt R

ate

Channel Number0 10 20 30 40 50 601E-3

0.01

0.1

1

10

100

6th 10th R S

Neu

tron

coun

t rat

e

Channel number

Simulated data Experimental data


Comparison of Alpha constants Original experiment data; harmonics filtered simulated data; harmonics filtered experimental data.

0 10 20 30 40 50 60

1E-3

0.01

0.1

6th 10th R S

Nor

mar

ized

Neu

tron

Cou

nt R

ate

Channel Number

10 20 30 40 50 60

1E-3

0.01

0.1

B C D E

Neu

tron

Cou

nt ra

tes

Channels(50s/channel)

Original Exp. data

Harmonics filtered Exp. Data(500~3000us)

Alpha values 6th 10th R S

Original Experimenta

l data1627.6±22.4 1705.0±25.0 2495.4±67.8 1350.4±36.4

Harmonics filtered

Experimental data

1664.2±55.8 1521.0±30. 2 2902.0±78. 7 1385.6±59.0

Harmonics filtered

simulated data

1430.30±8.71 1436.76±3.99 1436.60±3.49 1417.35±1.1

2


Comparison of Alpha constants original experimental data; harmonics filtered simulated data; harmonics filtered experimental data.

6th 10th R S1200

1400

1600

1800

2000

2200

2400

2600

2800

3000

Original experiment Alpha Simulated Alpha with harmonics filtering Original exp. data with harmonics filtering

Alp

ha v

alue

s

Detector label

The Alpha indicated by detector 10th has been improved;

The Alpha value obtained by detector S is closest to simulated one;

The Alpha value of detector R still show big discrepancy.


Verification of the simulated Alpha In one neutron generation time, the prompt neutron

population:pkTlT )0()(

For sub-critical system:

( ) (0) lT l T e

Relationship between kp and Alpha:l

p ek

kp 6th 10th R SFrom α 0.92492 0.92460 0.92461 0.92558MCNP 0.94117±0.00266△kp* -1.727% 1.761% 1.760% 1.656%


SUMMARY & FUTURE SUGGESTIONS

Using relative neutron count rates as an indicator, time region for fundamental Alpha mode decay can be easily obtained (a harmonics filtering technique);

The simulated data with harmonics filtering technique give a spatially independent prompt neutron attenuation constants;

Some Alpha values from experiment is improved by harmonics filtering, however some other values are worsen.

Summary


SUMMARY & FUTURE SUGGESTIONSSuggestions

Since the big discrepancy between experiment and simulation, as well as the short neutron life time and harmonics influence in the Fast-thermal couple ADS core, more rapid electronics data collection system should be used in future PNS experiment;

Although the harmonics filtering technique show the capability for Alpha measuring, the accuracy of calculated prompt neutron generation time plays a key role in verification work (consider the coupling between external neutron source region, fast blanket, thermal blanket and reflector, the effective generation time should be introduced, as well as its calculation theory)


Thanks for your attention!

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VENUS-1# 装置脉冲源实验分析