P. Mikoláš e-mail: [email protected] ŠKODA JS a.s. Orlík 266, 31606 Plzeň Czech Republic

17th Symposium of AER , Yalta

Information about WG A ... 1

17th Symposium of AERYalta, Ukraine, September 24-29, 2007

INFORMATION ABOUT AER WORKING GROUP A ON IMPROVEMENT, EXTENSION AND VALIDATION OF PARAMETRIZED FEW-FROUP LIBRARIES FOR

VVER-440 AND VVER-1000

P. Mikoláše-mail: [email protected]

ŠKODA JS a.s.Orlík 266, 31606 Plzeň

Czech Republic



ABSTRACT

• Joint AER WG A and WG B held their sixteenth meeting in Hrotovice (near NPP Dukovany), Czech Republic, during the period of 24-25 April 2007.

• The objectives of the meeting, content of presentations and future activities are shortly described in this paper.



INTRODUCTION

• Joint AER Working Group A on „improvement, extension and validation of parameterized few-group libraries for VVER-440 and VVER-1000“ and AER Working group B on „core design“ held their sixteenth Meeting in Hrotovice during the period of 24-25, April 2007.

• There were present altogether 14 participants from 8 member organizations (three states - List of participants is attached in the end of this paper) and read 10 presentations (List of presentations is also attached).

• Objectives of the meeting of WG A: Issues connected with spectral calculations and few-groups libraries preparation.



PRESENTATIONS

• Four papers were presented in the frame of WG A



GyGy. . Hegyi Hegyi presented paper entitled:presented paper entitled: ““Some new experience with ZR-6 measurements”Some new experience with ZR-6 measurements”

• In the beginning of his paper he described: NNURESIM (European Platform for NUclear REactor SIMulations)European Platform for NUclear REactor SIMulations) ,,• - Areas of interestreas of interest ( ( SP1 – Core physics SP1 – Core physics SP2 – SP2 –

ThermohydraulicsThermohydraulics SP3 – Multiphysics SP3 – Multiphysics SP4 – Sensitivity and SP4 – Sensitivity and Uncertainty AnalysisUncertainty Analysis SP5 – Integration), SP5 – Integration),

• - Participants in the SP1 task:Participants in the SP1 task: CEA, EDF, FZR, GRS, INRNE, JSI, Delft, KFKI, KTH, LUT, NRI, PSI + ASCOMP GMBH, UCL, Uni-KA, Upisa, UPM and VTT

• - Organization Structure of NURESIM SP1 Core PhysicsOrganization Structure of NURESIM SP1 Core Physics (Including List of programmes involved and short description of hort description of APOLLO2 code withAPOLLO2 code with main components)



Then he demonstrated:Then he demonstrated: Comparison of Zr-6 calculation with two codes APOLLO Comparison of Zr-6 calculation with two codes APOLLO and KARATEand KARATE

Cell/T [oC] keff calculated by APOLLO-

keff calculated by KARATE

12.7/3.6/0.0/20 0.999840500 1.0087 12.7/3.6/0.0/80 0.996407800 1.0040

12.7/3.6/0.0/130 0.995155200 1.0023 12.7/3.6/4.0/20 1.006214000 1.0037 12.7/3.6/4.0/80 1.001533100 1.0089

12.7/3.6/4.0/130 1.001824000 1.0131 12.7/3.6/5.8/ 20 1.003930000 1.0079 12.7/3.6/5.8/ 80 1.005295000 1.0094 12.7/3.6/5.8/130 1.002030400 1.0064 12.7/3.6/4.4/20 0.994803130 1.0037 11.0/3.6/0.0/20 0.986980910 0.9975 11.0/3.6/0.0/80 0.979347800 0.9897

11.0/3.6/0.0/130 0.977355800 0.9867 15.0/3.6/0.0/20 1.002438100 1.0087

12.7/4.4/0.64/20 1.001842000 1.0102 15.0/4.4/0.0/20 1.000538100 1.0033

11.0/3.6/0.96/20 0.992052100 1.0020 15.0/3.6/4.0/20 1.012356000 1.0137



• - Simulation of a ZR-6 critical assembly - Simulation of a ZR-6 critical assembly measurement measurement at room temperature was describedat room temperature was described

• - Structure of calculations (Reference deterministic,

Design and Monte-Carlo Reference) and Roadmap of Development, Validation and Qualification of Simulations Tools were presented



Boron Coefficient Boron Coefficient ρ/ρ/CCBBThe experimental technique used for the boron coefficient ρ/CB

was described.

Results of comparisons:

Core Hcr

[cm]Bz

2 [m-2] Measured /CB [¢/g/l]

/CB [pcm*l/g]

calculated /CB

[pcm*l/g]

(C-E)/E[%]

161/161(1765)12.7/3.6/4.0

485.7 46.26 -256.5±7.2 -193.9 -222 14.4(7.4)

162/161(1765)12.7/3.6/1.1

329.2 25.75 -285.7±8.4 -219.9 -273 24.0(24.5)

163/161(1765)12.7/3.6/5.8

710.5 14.98 -248.2±5.6 -185.2 -204 10.3(13.6)



Conclusions:

• The measurements (old & new?) are important• The validation is as important as the

measurement itself• Further efforts are needed in these activities



Pavel Pavel Mikoláš Mikoláš presented paper entitledpresented paper entitled:: “Possibility of fuel cycles extension with up-rated power “Possibility of fuel cycles extension with up-rated power

at Dukovany NPP “at Dukovany NPP “

• Possibility of fuel cycles extension with up-rated power at Dukovany NPP was shown.

• Two ways were checked, the first is the enrichment increase in fuel of temporary FA and the other is FA design change.

• Some basic characteristics of cycles with these changed FAs were also presented.



1. Introduction

• Practically five years cycle has been achieved at NPP Dukovany in the last years.

• However, the efficiency of fuel cycle can be improved if six years cycles are applied.

• There are at least two ways how this goal could be achieved.

• The simplest way is to increase fuel enrichment.• The second possibility is to change fuel assembly

design.• In the paper presented, both possibilities were checked

individually.



2.Fuel assembly with higher enrichment • Enrichment of 4.95 w% of U235 in some of fuel pins in a fuel assembly is

supposed.• The other characteristics (it means excluding enrichment) are the same as for

fuel assembly of Gd-2 or Gd-2M for up-rated power.• It seems to be clear that this maximal enrichment can not be applied in all fuel

pins because in this case pin power non-uniformity would be very high (more than 1.15), which would be a problem from the point of view of pin power factor in the core.

• Therefore, enrichment is lower in some pins and one from possible solutions with only three different enrichments with pin power non/uniformity of 1.072 has been found.

• These fuel assemblies have been loaded into core in transient end equilibrium cycles of Dukovany NPP for up-rated power (cycles 27th to 34th of Unit III) and basic characteristics of these cycles are shown in Tables 1.

• It is seen that fuel cycles prolongation has been achieved, but this prolongation may not be sufficient for six-year cycle.



3. New fuel assembly design

• The other possibility how to extend the fuel cycle (and how potentially achieve six year cycle) is the application of fuel assembly with an improved design.

• The first one is higher mass content of uranium in a fuel assembly. This can be achieved by two ways:

• First, to remove central hole in fuel pellet and• Second, to enlarge fuel pellet diameter• In our checking, both conditions were applied together. Other

characteristics are the same as for FA for up-rated power (Gd-2M).

• The next possibility is to enlarge pin pitch. • It has been applied too.



3. New fuel assembly design (cont.)

• The “last” possibility is to “omit” FA shroud.

• This is practically not realistic, in any way; some other structural parts must be introduced in a FA; in our simplified model,

• Thickness of FA shroud was lowered in two steps, namely from 1.5 mm on 1.0 mm and then on 0.5 mm.

The basic characteristics of these cycles for up-rated power are shown in Table 5 showing that

possibilities of fuel assemblies with this improved design in enlargement of fuel cycles are very promising.



4. Discussion

• The values shown in Tables 1 and 5 cannot be supposed to be quite real because pin power non-uniformity is to high and different loadings must be found.

• Also, probably loading with lower number of fresh FA would be found instead of simple enlargement of the fuel cycle.

• Nevertheless, it seems to be clear that FA have still potential in the sense of fuel cycle economy.



5. Conclusions • Although only preliminary analyses described in the

paper have been performed,• it can be concluded that temporary design of VVER-

440 FA is not optimal (as it is well known) and it exists great potential how to increase FA reactivity, which is a necessary condition in achieving full six years loading strategy.

• (Potential in lowering core neutron leakage is practically exhausted as is also the possibility in reducing neutron absorption in construction parts of a FA.)



Tables

Table 1 Cycles length with FAs with higher enrichment

Cycle\FA Base (QS3) QO3 (Gd-2+) QO3 (Gd-2M) QO5 (Gd-2+) 27 326 341 342 336 28 326 346 348 344 29 328 357 360 356 30 328 357 359 355 31 328 348 350 346 32 327 353 356 352 33 326 353 355 351 34 326 349 351 346



Table 5 Cycles length with different FAs types

Cycle\FA Base „G“ (QS3)

„Gbezd“ (QND)

„G124“ (QN4) „G12410“ (QN1)

„G12405“ (QN0)

27 326 329.91 329.91 331.16 341.46 28 326 333.82 333.82 336.36 345.50 29 328 339.81 339.81 343.68 351.70 30 328 343.74 343.74 348.96 355.77 31 328 347.68 347.68 354.29 359.85 32 327 346.62 346.62 353.21 358.75 33 326 345.56 345.56 352.13 357.65 34 326 345.56 345.56 352.13 357.65



V. V. KrýslKrýsl and J. and J. ŠůstekŠůstek presented paper entitled: presented paper entitled: „Influence of Hf plate on integral and differential „Influence of Hf plate on integral and differential

efficiency of CR”efficiency of CR”

• In their paper the efficiency of control rods (CRs) at the end of cycle (EOC) during the last few EDU NPP cycles has been investigated.

• When comparing behaviour of the last cycles of EDU NPP, different behaviour of the differential efficiency of CR was observed.



Two possible causes of this phenomenon were supposed:

• Lower burn-up of the lower part of the CRs, which are during the cycle out of the zone; consequently at the end of the cycle fuel with lower burn-up is inserted into the zone

• Using of the Hafnium (Hf) plates in the coupler of CRs • Material specification of FA was provided



Basic Calculations:

• Basic archives calculation was provided by MOBY-DICK programme following data of the EDU DATABASE, cycle 1-20, unit 3

• Cycles 17-21 with constant nominal power, with CR position 214 and 250 cm, for examination of influence of burn-up of the lower part of the regulatory CR

• Alternative calculation of the cycle 17 and 18 where CR with Hf plate (which were inserted into positions of non-regulatory CRs) with fictive CR without Hf plate were replaced, followed by the calculation of the cycle 19, in which these FA were in regulatory positions



Calculations of the CR Efficiency: • As a method of the determination of the efficiency of CRs

was used gradual insertion of CRs at the end of the cycle, with constant concentration of Xe and Sm. Integral reactivity is direct output of calculations, differential reactivity was calculated by differentiation of the integral reactivity. Scale of the differential reactivity was multiplied by 10, for better contrast. Also difference between integral reactivities (for height of CRs 214 and 250 cm) is shown. As we can see, this difference increases with number of cycle.



Examples of Results:

Fig. 3 Integral and differential efficiency of CRs, B3C19, EOC (SFR38ZRH, with Hf plate)

-2

-1,8

-1,6

-1,4

-1,2

-1

-0,8

-0,6

-0,4

-0,2

0

0 50 100 150 200 250

height [cm]

Ro

0

0,01

0,02

0,03

0,04

0,05

0,06

0,07

0,08

0,09

0,1

Ro_214

Ro_250

dRo250-214

der214

der250



Fig. 4 Integral and differential efficiency of CRs, B3C19, EOC (SUR38ZRH, without Hf plate)

-2

-1,8

-1,6

-1,4

-1,2

-1

-0,8

-0,6

-0,4

-0,2

0

0 50 100 150 200 250

height [cm]

Ro

0

0,01

0,02

0,03

0,04

0,05

0,06

0,07

0,08

0,09

0,1

Ro_214

Ro_250

dRo250-214

der214

der250



Conclusion:

• A Hafnium plate in coupler part of CA causes different differential efficiency of control rod.



Sándor Sándor Patai-Szabó Patai-Szabó presented paper entitled:presented paper entitled: “ “Impact of Gamma Smearing on Pin Power Distribution”Impact of Gamma Smearing on Pin Power Distribution”

Usual approach in codes: whole of the fission energy deposited in the fuel pin, where fission happened

Actually about 9-10 % of fission energy deposited in other parts of the assembly and in the moderator

Components of energy release due to fission, from ENDFB 6.8, without neutrinos were also shown.

Gamma energy is about 7 %Analysis of the spatial distribution is possible with HELIOS

code in coupled neutron-gamma transport calculationOutput parameter of HELIOS is kinetic energy of gammas

deposited by scattering and absorptionFuel assemblies with and without gadolinium were examined

in infinite lattice of assemblies



Gamma energy deposited in assembly and moderator:

clad shroud moderator fuel pin

% 10,6 3,4 5,9 80,2



80 % of gamma energy deposited in fuel pin, but in other pins than it was produced. The pin power distributions will be a bit different. Taking into account spatial gamma distribution is called ”gamma smearing”.

• Fuel assemblies investigated:

Profiled 3,82 % assembly with 1,23 cm pin pitch

Gd-2 fuel, 4.25 % enrichment, 6 pins with Gd2O3

Modified Gd assembly, containing 3 pins with Gd2O3



Example of results: Comparison of energy release

(without and with “gamma smearing”)





In realistic situations the gamma transport between different assemblies can be more significant

The determinant parameter is the (whole) power of neighbouring assembly

Using a simple assumption the gamma power from neighbouring assembly was added to the investigated assembly, influence on neighbouring assembly can bee checked



Conclusions:

The usual approach is conservative in assemblies without gadolinium, the difference is negligible

The increase in pins containing gadolinium is significant, but the pin power is very low in these pins – they are negligible

During burn-up the pin power in these pins increases, but as the gadolinium burns out, the difference between usual approach and gamma smearing becomes negligible

Effect of neighbourhood is significant, refinement of investigation is necessary

Results should be checked by other codes (e.g. MCNP) Considering the fuel pins containing gadolinium: Should the

thermo-hydraulics analyses take into account the higher pin power or not?



CONCLUSION

• Four papers were presented on WG A devoted tasks, which are important.

• More effort should be concentrated on special effects, like historical dependences of cross sections or / and boundary conditions.



APPENDIX

List of presentationsWG A

• A-1: György Hegyi (MTA KFKI AEKI ):• Some new experience with ZR6 measurements • A-2: Pavel Mikoláš (ŠKODA JS a.s.):• Possibility of fuel cycles extensions with up-rated power on NPP Dukovany • A-3: Václav Krýsl (ŠKODA JS a.s.), Josef Šůstek (ŠKODA JS a.s.):• Influence of a hafnium plate on integral and differential efficiency of control

rod • A-4: Sándor Patai-Szabó (TS Enercon Ltd.):• Impact of Gamma Smearing on Pin Power Distribution



WG B

• B-1: István Pós (Paks NPP):

• Study of the application of Finite Element method for 2-and 3-dimensional diffusion calculations

• B-2: György Hegyi (MTA KFKI AEKI):

• New challenges in core calculations

• B-3: Petr Dařílek (VÚJE, a.s.):

• Informal information about high power at VVER-440

• B-4: Radim Vočka (ÚJV Řež, a.s.)

• Macrocode ANDREA: state of development for VVER-1000 reactors

• B-5: Juraj Breza (VÚJE, a.s), Ctibor Strmenský (VÚJE a.s.):

• Gd benchmark calculations in VUJE

• B-6: Josef Bajgl (Dukovany NPP), Miroslav Lehmann (ÚJV Řež, a.s.):

• Optimisation of VVER-440 core loadings - Common and Special Tasks



List of participants

István Pós

Company NPP Paks Telephone 3 675 508 130 Facsimile

Email [email protected]

Tamás Parkó

Company NPP Paks Te lephone 3 675 508 130 Facs imile 3 675 505 074 Email [email protected]



Zsolt Szécsényi

Company NPP Paks Telephone 3 675 505 073 Facsimile 3 675 505 074 Email [email protected]

György Hegyi Company MTA KFKI AEKI Reactor Analysis Department Telephone +36 1 392 2222/ext.: 1499 Facsimile +36 1 395 9293 Email [email protected]

Sándor Patai-Szabó

Company TS Enercon Ltd. Telephone 36309372628 Facsimile

Email pa ta is zabosandor@t-online .hu

Petr Daøílek

Company VUJE, a .s . Te lephone +421 33 5991312 Facs imile +421 33 5991191 Email darilek@vuje .sk



Juraj Breza Company VUJE, a.s. Telephone +421 33 5991317 Facsimile +421 33 5991191 Email [email protected]

Miroslav Lehmann

Company SÚJB ÈR Telephone 420 221 624 722 Facsimile

Email Miros [email protected]

Radim Vo èka

Company ÚJV Øe?, a .s . Te lephone 420 266 172 478 Facs imile


Pavel Mikolás

Company SKODA JS a .s . Te lephone 420 378 042 828 Facs imile 420 378 042 407 Email pave l.mikolas@skoda-js .cz



Josef Sùstek Company SKODA JS a.s. Telephone 420 378 042 828 Facsimile 420 378 042 407 Email [email protected]

Josef Bajgl

Company ÈEZ a.s. EDU Telephone 420 561 104 652 Facsimile

Email josef.ba [email protected]

Danes Burket Company ÈEZ a .s . EDU Telephone 420 561 104 665 Facs imile

Email danes .burke [email protected]

Viktor Kocek

Company ÈEZ a .s . EDU Telephone 420 561 103 428 Facs imile


Documents

P. Mikoláš e-mail: [email protected] ŠKODA JS a.s. Orlík 266, 31606 Plzeň Czech Republic