TÜRKİYE ATOM ENERJİSİ KURUMU
ÇEKMECE NÜKLEER ARAŞTIRMA VE EĞİTİM MERKEZİ
Ç<N*A>E>M> ” A>R " 245
CALIBRATION CALCULATIONS FOR THE TR-2 REACTOR
Mehmet Hulusi TURGUT, Gülsen ÜSTÜN
Nuclear Engineering Department
April 1988
TÜRKİYE ATOM ENERJÎSÎ KURUMU
ÇEKMECE NÜKLEER ARAŞTIRMA VE EĞİTİM MERKEZİÇ.N.A.E.M. - A.R - 245
CALIBRATION CALCULATIONS FOR THE TR-2 REACTOR
Mehmet Hulusi TURGUT, Gülsen ÜSTÜN
Nuclear Engineering Department
April 1988
Ö Z E T
T R - 2 R E A K T Ö R Ü Î Ç Î N H E S A P L A R I N K A L İ B R A S Y O N U
TR-2 reaktörünün ilk yükleme durumu ve o anda yapılan deneyler esas alınarak, iki boyutlu hesaplar eksenel yöndeki a k ıbüküm terimi değişti r i l m e k suretiyle kalibre edildi. Bu yeni a k ı b ü k ü m değeri k u l l a nılarak yapılan reaktivite hesapla- n n ı n den e y l e r l e çok iyi uyum içerisinde olduğu gözlendi.
A B S T R A C T
C A L I B R A T I O N C A L C U L A T I O N S FOR T H E T R - 2 R E A C T O R
The 2D X-Y calculations have been calibrated by a dj us t ments in the axial buckling term. The initial loading of the TR-2 reactor and the reactivity experiments done at that time are used as the bases of these calculations. The agreement between the experi m e n t a l results and the reactivity cal c u l a tions is very good, after this calibration procedure.
C O N T E N T S
P a B?_
I. I N T RODUCTION 1
II. C A L C U L A T I O N S 1
III. DIS C U S S I O N OF THE RESULTS 2
Ref e r e n c e s 3
T A B L E S
Table-1 : The initial U-235 contents of control and
standart fuel elements 4
Table-2 : Criticality experiment results 4
Table-3 : The calculational and experimental reactivity
values of the Be and A1 blocks 5
FIGURES
Figure-1 : The initial loading of the TR-2 reactor 5
Figure-2 : The variation of excess reactivity versus
axial buckling 6
Figure-3 : The calculated and experimental reactivity
values of the fuel elements 6
: The Xe+Sm anti-reactivity curves (50 hours
of reactor operation and 100 hours of shutdown) 7 Figure-4
I. I N T R O D U C T I O N
It is usually not possible to obtain exactly the
same the k - e f f ective value of the experiments with the cal c u lations. So generally, some modific a t i o n s in the group struc ture, in modelling of the reactor or adjustments in the
buckling terms are made in order to meet the same excess reactivity value.
In this study initial loading of the TR-2 reactor is taken as the basis of these calculations. It is known that the TR-2 reactor was slightly above critical with 7 fuel elements. This c o n fi g u r a t i o n is calculated in X-Y geometry for 5 groups and the axial buckling is adjusted according to the e x p e r i m e n t a l value. All successive loadings and the reactivity worths of each element are calculated with this adjusted buckling value and the results agreed very well with the e x p er i m e n t a l values.
II. C A L C U L A T I O N S
The 5 group cross-s e c t i o n s generated by EPRI-CELL^^^ / 2 /
at ANL are used in the calculations. GEREBUS code is
used for the 2D diffusion calculations. 48x50 meshes are used in X-Y geometry. Side plates are treated as seperate regions in the core modelling. The TR-2 initial core loading is shown in Figure-1. The U-235 content differs slightly
from one element to another. They are given for the 4 control and 10 fuel elements in Table-1.
First, the criti c a l i t y experiment is simulated. The TR-2 reactor was slightly above critical with 4 Be blocks on one side, 2 A1 blocks on the other 2 corners, 4 control elements inserted to core positions 34, 43, 55, 63 and 7 fuel e l e m e n t s inserted to core positions 33, 35, 44, 45, 53, 54, 64. The excess reactivity is measured to be 695
pern. The axial buckling term is adjusted until the calculated excess rea c t i v i t y matches to this value. The variation of excess r e a c t i v i t y versus the axial buckling is given in Figure-2. This adjusted axial buckling is used in all d i f fu sion c a lculations.
2
Approach to criticality experiment is simulated by the X-Y calculations. The results of calculations and the experiments are given in Table-2. As can be seen the m a x i mum difference is less then 3%.
The effect of Be reflectors on the excess reactivity is investigated. Be blocks are replaced by water and the experimental reactivity worths are compared with the results of calculations on Table-3. The worths of A1 blocks are
also calculated, but there is no experimental value at that time for comparison. One experiment has been made in the
r d
3— cycle, that means after some depletion of the fuels,
and the reactivity value of the 2 A 1 blocks is found to
be around 90 pern. The maximum error in the reactivity values of Be blocks is 6.8% and the average error is less then
3%.
The reactivity worth of each fuel element is c a l c u la ted. The results are given in Figure-3. The average error between the experiments and the calculations is found to be less then 2%, and the maximum error is 4.13%.
The a nti-reactivity effects of Xe+Sm during 50 hours of operation of the reactor at 3 and 5 MV/s power levels, and afterwards 100 hours of shutdown are given in F ig ur e- 4 . The equilibrium Xe+Sm values are 2888 pem and 3297 pem, the peak values after shutdown are 4358 pem and 6397 pem for 3 and 5 MW power levels respectively, which are very close to the results of previous calculations (2872, 3270,
/ 3 / 4278 and 6412 pem, in the same order)
III. D I S C U S S I O N OF THE R E S U L T S
The agreement between the experimental values and the calculational results after the calibration is very good. The average error is about 2% and the maximum error is about 7%. The maximum error (6.8%) occurs for Be block at position 32, but in reality it is not very serious, since the difference in reactivity is 50 pem v/hich is quite small (less then 1% of the total excess reactivity).
3
E r r o r s in e x p e r i m e n t s may come from the u n c e r t a i n i t i e s in c a l i b r a t i o n c u rves of the 4 co n t r o l rods, and some small c o n t r i b u t i o n of f i s si o n p r o d u c t a c c u m u l a t i o n on the a n t i r e ac ti v i t y during o p e r a t io n of the reactor. The e rr o r s in the c a l c u l a t i o n s may come from the m o de l li ng and the group structure. Also, all the c o n t r ol rods assumed to be out for all c a l c u l a t i o n s w h i c h does not r e f l e ct the reality. The p a r t i a l or total i n s er ti o n of one or two cont r o l rods effect the flux d i s t r i b u t i o n and so the r ea ct i v i t y worths. But, s i n c e we are a l w ay s loking for the r e a ct i vi ty d i f f e rences the real error b e c om es quite small.
The c a l i b r a t i o n c a l c u l a t i o n s will co n t i n u e for the c o nt r o l rods. Aft e r the d e v e l o p m e n t of a simple mod e l l i n g , it will be p o s s i b le to s i m ul at e the c on tr ol rod i ns e r t i o n s for the T R - 2 reactor. The fuel s hu ff l i n g after each loading and the c o r r e s p o n d i n g fuel d e p l e t i o n during each cycle can be c a l c u l a t e d more p r e c i s el y by using this new m odelling.
R e f e r e n c e s
/!/
B. A. Z olotar, et. a l ., " EP R I - C E L L Code D e s c r i p t i o n ” , A d v a nced R e c y c l e M e t h o d o l o g y P r o g r a m S y s t e m D oc um en t a t i o n , Part II, C h a p t e r 5, E le ct r i c Power R es ea rc h I ns ti t u t e (Sept. 1977)
/2/ M. C on s o l e , A. Danery, and E. Salina, "EREBUS : A Multi-
G r ou p D i f f u s i o n - D e p l e t i o n P ro gr am in Two Dime n s i o n s " , F N - E -8 8 (FIAT-1967)
/3/ M. H. Turgut, " N e ut r o n ic s C a l c u l a t i o n s of the TR-2 R e a c tor P r e s e nt Core", T e c h n i c a l Report No.: 30 (Sept. 1986)
4
Table-1 : The initial U-235 contents of control and standart
fuel elements Core position Element Type U-235 content [gr]
33 Standart fuel element 281.23
53 t? Î! tt 281.73 44 t t I» TT 281.97 54 tt ÎÎ TT 280.80 64 TT tt TT 281.83 35 tt tt TT 280.13 45 Tt Tt TT 280.74 65 »7 TT Tt 280.47 46 Tt ft TT 281.56 56 ?r Tt TT 281.33 43 Control tt TT 207.77 63 tt ft TT 208.21 34 TT TT 77 208.38 55 TT tt TT 207.68 T a b l e - 2 : C r i ti c a l i t y experiment results Core position U-235 content [gr] Total U-235 content [gr] Calculated k-eff Calculated excess reactivity [pern] Measured excess reactivity [pem] Difference % Initial loading 1676.54 0.8556444 - -33 281.23 1957.77 0.9054114 — _ 64 281.83 2239.60 0.9462967 - - -45 280.74 2520.34 0.9813906 - - -35 280.13 2800.47 1.0070080 696 695 0.14 65 2 8 0 . 4 7 3080.94 1.0290724 2825 2749 2.76 56 281.33 3362.27 1.0510585 4858 4971 2.27 46 281.56 3643.83 1.0722899 6742 6652 1 .35
5
Table-3 : The calculational and experimental reactivity values of the
Be and A1 blocks Element Core positions Calculated k-ef f Calculated reactivity worth [pcmj Experimental reactivity worth [pcm] Difference % Be 32 1.0644746 685 735 6.8 Be 42 1.0583603 1228 1228
0.0
Be 32+42 1.0519350 1805 1848 2.33 Be 32+42+62 1.0449724 2438 2424 -0.58 Be 32+42+52+62 1.0361876 3250 3191 -2.43 A1 36 1.0714130 77 - -A1 66 1.0713829 79 - -A1 36+66 1.0705128 155 - -32* 42 52 62 Be Be Be Be 33 43 SRI 53 63 SR2 ixx CE FE CE 34 CR1 44 54 64 CE FE FE 2 35 45 55 CR2 65 4 3 CE 5 36 46 56 66 A1 7 6 A1 CE : Control element FE : Fuel element Be : Be block A1 : A1 blockSRI : Safety rod No.l
SR2 : Safety rod No.2
CR1 : Control rod No.1
CR2 : Control rod No.2
x) Core position xx) Loading step No.
1 S t 4 -1— step 0nd 2— step rd step , th . 4— step -th step r t h step -.th . 7— step
Reactor not critical Reactor not critical Reactor not critical Reactor critical; SRI, Reactor critical; SRI, Reactor critical; SRI, Reactor critical; SRI,
SR2, CR1 out, CR2 at position 683
SR2, CR1 out, CR2 at position 441
SR2, CR1 out, CR2 at position 271
SR2 out, CR1 at position 780, CR2 in
6
B U C K L I N G
Figure-2 : The variation of excess reactivity versus axial buckling
Be Be Be Be 2590* 3939 4- SRI 4031 SR2 2542 CR1 4732 4688 2891 4781 4674 2833 2462 3383 CR2 2302 2522 3294 2397 1899 2136 A1 1884 2085 A1 Be Be Be Be 48** 1.85* SRI -92 -2.34 SR2 CR1 -49 -1.04 14 0.30 58 2.01 -60 -2.44 89 2.63 CR2 -95 -4.13 A1 15 0.79 51 2.39 A1
x) Experimental reactivity worth [pcm] +) Calculational reactivity worth [pcm]
xx) Difference (Experimental-Calculational) [pcm] x) Difference in percent (Difference/ExperimentalxlOO)
Figure-3 : The calculated and experimental reactivity values of the fuel
7 F igu re-4 : The Xe +Sm an ti -r eactivity curve s ( 5 0 h o u r s o f re ac tor operat io n a n d 1 0 0 ho urs o f s h ut do w n)
