ARTICLES FROM HUNGARY
THE
NUCLEAR
INSTITUTE D.
REACTOR
OF
THE
POLYTECHNIC
IN BUDAPEST UDC 621.039.55
Csom
The u s e of nuclear and isotope techniques in v a r i o u s a r e a s of utilization of atomic energy calls f o r a steadily i n c r e a s i n g n u m b e r of s p e c i a l i s t s with adequate t h e o r e t i c a l and p r a c t i c a l backgrounds. Higher e d u c a tional institutions a r e shouldering this w o r k of training c a d r e s and a r e providing students with adequate fundamental knowledge to lay f i r m groundwork for t h e i r work a f t e r completing t h e i r c o u r s e s . R e s e a r c h r e a c t o r s s e r v e t h e s e needs to a p a r t i a l extent, p a r t i c u l a r l y r e a c t o r s designed specifically f o r t r a i n i n g p u r poses. The expanded u s e of nuclear techniques and the c o m m i s s i o n i n g of H u n g a r y ' s n u c l e a r - r e a c t o r power station, scheduled to go on line in the Seventies, will call for an ample supply of s p e c i a l i s t s in this field. Training of p e r s o n n e l h a s to be intensified, p a r t i c u l a r l y at the Polytechnic Institute and at the University of Budapest. In p r e v i o u s y e a r s , attention has been c e n t e r e d on t h e o r e t i c a l p r o b l e m s in p r e f e r e n c e to p r a c t i c a l p r o b l e m s . The u n i v e r s i t y r e a c t o r at Budapest is intended to eliminate this rift between the needs of p r a c t i c e and the p r e s e n c e of s p e c i a l i s t s . The r e a c t o r will be used in the training of students in t h r e e d e p a r t m e n t s of the Polytechnic Institute (mechanics, c h e m i s t r y , and e l e c t r i c a l engineering) and of the University, as well as to conduct v a r i o u s lines of r e s e a r c h engaging the efforts of i n s t r u c t o r s , r e s e a r c h w o r k e r s , and students at both g r a d u a t e and u n d e r g r a d u a t e levels. T h e p r i m a r y training t a s k s a r e a s follows: 1) to m e e t the needs of higher educational institutions in organizing the t r a i n i n g of students for p r a c t i c a l n u c l e a r engineering work; 2) training of p e r s o n n e l who lack any p r a c t i c e or have v e r y little e x p e r i e n c e in this specific a r e a (the points s t r e s s e d in the design of the r e a c t o r w e r e reliability and e a s e of operation). The r e a c t o r is being built on the grounds of the Polytechnic Institute, in the vicinity of o t h e r educational f a c i l i t i e s and l a b o r a t o r i e s . Construction is scheduled for completion in J u n e - J u l y , 1970. Description
of the
Reactor
The g o a l s and p r o b l e m s alluded to n e c e s s i t a t e d some c o m p r o m i s e solutions in the design and building of the r e a c t o r . A r e a c t o r using w a t e r m o d e r a t o r and enriched u r a n i u m fuel e l e m e n t s h a s a negative t e m p e r a t u r e c o e f ficient of r e a c t i v i t y o v e r the r a n g e of operating t e m p e r a t u r e s , so that r e a c t o r safety is enhanced. The fuel e l e m e n t s u s e d a r e a Soviet type (]~K-10) m e e t i n g safety r e q u i r e m e n t s of a higher o r d e r , and can be used even at power l e v e l s 100 t i m e s higher, while their reliability has b e e n s u c c e s s f u l l y p r o v e n in the o p e r ational s e r v i c e of fuel e l e m e n t s of that type for the past two decades. Below we cite the b a s i c r e a c t o r c h a r a c t e r i s t i c s : Type of fuel e l e m e n t . . . . . . . . . . . . . . . Fuel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Moderator ........................ Coolant . . . . . . . . . . . . . . . . . . . . . . . . . . . Reflector .........................
I~K-10 (in fuel a s s e m b l i e s ) U r a n i u m enriched to 10% H20
H20 Graphite + H20
Polytechnic Institute, Budapest, Hungarian P e o p l e ' s Republic. T r a n s l a t e d f r o m A t o m n a y a Energiya, Vol. 28, No. 4, pp. 342-344, April, 1970. 9 Consultants Bureau, a division of Plenum Publishing Corporation, 227 West 17th Street, New York, N. Y. 10011. All rights reserved. This article cannot be reproduced for any purpose whatsoever without permission of the publisher. A copy of this article is available from the publisher for $15.00.
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Maximum e x c e s s r e a c t i v i t y , % . . . Peak power, kW . . . . . . . . . . . . . . . . Neutron flux in c o r e (at 10 kW power level), n e u t r o n s / c m 2.sec: t h e r m a l (peak) . . . . . . . . . . . . . . . t h e r m a l (average) . . . . . . . . . . . . fast (peak) . . . . . . . . . . . . . . . . . . . Biological shielding: top . . . . . . . . . . . . . . . . . . . . . . . . . . side . . . . . . . . . . . . . . . . . . . . . . . . .
R e s e a r c h equipment: h o r i z o n t a l i r r a d i a t i o n channels . i r r a d i a t i o n tunnel . . . . . . . . . . . . . V e r t i c a l channels: for i r r a d i a t i o n . . . . . . . . . . . . . . . with p n e u m a t i c equipment . . . . . .
0.5 to 0.6 i0
1.6. i011 i0 il 7.10 il to 8.10 It H20 (5 m e t e r s thick) 110 cm of heavy c o n c r e t e (density 3.2 g / c m 3) and 90 cm o r d i n a r y c o n c r e t e 5 1 14 Two inside r e f l e c t o r , with t h e r m a l flux 1.4.10 ll n e u t r o n s / c m 2 . s e c at 10kW o u t put; 1 i n s i d e c o r e with f a s t flux 5.10 l l n e u t r o n s / c m 2 . sec at 10 kW output
W a t e r s u b j e c t e d to f o r c e d c i r c u l a t i o n is e m p l o y e d as both m o d e r a t o r and coolant in the r e a c t o r , but n a t u r a l c i r c u l a t i o n alone is adequate at a c e r t a i n power l e v e l . A g r a p h i t e r e f l e c t o r c o n s i s t i n g of a s s e m b l i e s of the s a m e d i m e n s i o n s as the i n - c o r e fuel a s s e m b l i e s is p l a c e d around the c o r e . This d e s i g n allows options for a l t e r i n g and modifying the shape of the c o r e with e a s e . By r e m o v i n g five g r a p h i t e a s s e m b l i e s , a h i g h e r intensity of t h e r m a l flux can be achieved in the s a m e w a t e r - f i l l e d s p a c e . The c r i t i c a l m a s s is 22 to 23 fuel a s s e m b l i e s (depending on the e x p e r i m e n t ) . The peak e x c e s s r e a c t i v i t y value alluded to above e l i m i n a t e s p r o m p t r e a c t o r c r i t i c a l i t y . W a t e r acting as a s e c o n d a r y r e f l e c t o r is allowed b e t w e e n the g r a p h i t e r e f l e c t o r and the r e a c t o r tank. The r e a c t o r m e a s u r e m e n t s which will be p e r f o r m e d c a l l f o r neutron fluxes of d i f f e r e n t i n t e n s i t y l e v e l s . In s o m e e x p e r i m e n t s a t h e r m a l flux of 109 n e u t r o n s / c m 2 . s e c will be r e q u i r e d , c o r r e s p o n d i n g to a r e a c t o r power output of the o r d e r of s e v e r a l w a t t s . I n o t h e r r e s e a r c h e f f o r t s , as f o r e x a m p l e in isotope production, r a d i a t i o n - c h e m i c a l i n v e s t i g a t i o n s , e t c . , a t h e r m a l flux of 10 ll n e u t r o n s / c m 2 . s e c will be r e q u i r e d , c o r r e sponding to a power output of 10 kW. The p e a k r e a c t o r output level was set at 10 kW in line with t h e s e c o n s i d e r a t i o n s . R e a c t o r d e s i n g i n c o r p o r a t i o n g m o r e s t r i n g e n t safety r e q u i r e m e n t s will make it p o s s i b l e to r a i s e the output of subsequent m o d i f i c a t i o n s of this r e a c t o r to a l e v e l of 100 kW. A study of such m o d i f i c a t i o n s has a l r e a d y been c a r r i e d out, but a d e f i n i t i v e d e c i s i o n on the choic~ of power level f o r subsequent r e a c t o r m o d i f i c a t i o n s will be m a d e o n ly a f t e r the r e a c t o r has been built and some o p e r a t i n g e x p e r i e n c e has been a c q u i r e d . The c o r r e c t n e s s of choosing the r e a c t o r p o w e r output in the 1 to 100 kW r a n g e has been c o n f i r m e d by d a t a on the p e r f o r m a n c e of r e a c t o r s in s o m e c a p i t a l i s t c o u n t r i e s (41gc of the u n i v e r s i t y r e a c t o r s o p e r a t e within this power range). R e a c t o r s p r o d u c i n g l e s s power m u s t be used in n a r r o w e r a p p l i c a t i o n s , while r e a c t o r s d e s i g n e d f o r s t i l l h i g h e r power l e v e l s a r e m o s t l y intended f o r r e s e a r c h a p p l i c a t i o n s . The top b i o l o g i c a l s h i e l d i n g is a l a y e r of w a t e r five m e t e r s thick. T h i s d e c i s i o n f a c i l i t a t e s m a n i p u l a tion o p e r a t i o n s and v i s u a l m o n i t o r i n g , the l a t t e r being p a r t i c u l a r l y i m p o r t a n t in view of the t r a i n i n g p u r p o s es u n d e r l y i n g the r e a c t o r design.~ A c r o s s s e c t i o n through the r e a c t o r is shown in F i g s l 1 and 2. The hot c h a m b e r situated next to the r e a c t o r is a l s o shown.
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i F i g . 1. H o r i z o n t a l c r o s s s e c t i o n t h r o u g h r e a c t o r . Experimental
Capabilities
T h e r e a c t o r f e a t u r e s f i v e h o r i z o n t a l e x p e r i m e n t a l c h a n n e l s (of w h i c h f o u r w e r e i n t h e r a d i a l d i r e c t i o n , one t a n g e n t i a l ) . T h e s e w i l l b e u s e d m o s t l y f o r r e s e a r c h in n e u t r o n p h y s i c s and n u c l e a r p h y s i c s , and a l s o f o r training purposes. T h e " t u n n e l " d e s i g n e d f o r i r r a d i a t i o n p r o j e c t s u s i n g n e u t r o n s of d i f f e r e n t e n e r g i e s can a l s o b e u s e d a s a t h e r m a l c o l u m n , w h i c h w i l l r e q u i r e only v e r y s l i g h t m o d i f i c a t i o n s . A l a y e r of w a t e r 7 c m t h i c k ( s e e F i g s . i and 2) w i l l i n t e r v e n e b e t w e e n t h e end of the tunnel a n d t h e r e a c t o r tank, in o r d e r to a v e r t any i n f l u e n c e by the v a r i o u s d e v i c e s u s e d in t h e t u n n e l on t h e c o r e .
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Fig. 2. Vertical c r o s s section through r e a c t o r . There will also be a few vertical channels for irradiation in the interior of the graphite m o d e r a t o r (in isotope production and other irradiation applications). The two v e r t i c a l channels connect to the tunnel, and the two channels containing water communicate via a pneumatic rabbit shuttle channel. The irradiation channel with the pneumatic shuttle feature has its counterpart within the c o r e itseif. According to p r e l i m i n a r y z e r o - p o w e r m e a s u r e m e n t s , the expected thermal flux level in the water present in the experimental channels is 1.4.1011 n e u t r o n s / c m 2 . s e c , while the fast flux is 5.1011 n e u t r o n s / c m 2 . s e c at 10 kW power. The pneumatic shuttle channel r e f e r r e d to connects the r e a c t o r to radioehemical l a b o r a tories, as required mainly in activation analysis work. The pneumatic shuttle channel also p a s s e s between several radiochemical l a b o r a t o r i e s . Hot c h a m b e r s will be built alongside the r e a c t o r . The manipulator s y s t e m is designed with spherical (ball and socket) joints. A conventional tube for conveying radioactive isotopes will be installed between the c o r e and the hot c h a m b e r s . The hot c h a m b e r s are intendedfor various operations a n d m e a s u r e m e n t s . Itwill be possible to extract isotopes f r o m the hot c h a m b e r s by m e a n s of c o n t a i n e r s or by utilizing a secondary pneumatic shuttle channel. L a b o r a t o r i e s for neutron beam investigations are available within the r e a c t o r building. Each such lab o r a t o r y has been provided with a connecting cable linking it to one of the horizontal experimental channels and to the data m e a s u r i n g c e n t e r s . There will also be communciations cables between the m e a s u r i n g center and the radiochemical l a b o r a t o r i e s . Utilization
of the
Reactor
Possibilities open for utilization of the r e a c t o r in training activities include the following: 1) conducting r e s e a r c h within the f r a m e w o r k of existing training c o u r s e s , with the participation of a large number of students;
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2) introducing special c o u r s e s for r e l a t i v e l y s m a l l groups of students (8 to 10 people); 3) aiding students in individual work p r o j e c t s throughthe organization of scientific t e a m s , and so on. The following special training c o u r s e s a r e scheduled: r e a c t o r physics, r e a c t o r technology, n u c l e a r e l e c t r o n i c s , isotope engineering, r a d i a t i o n shielding, and d o s i m e t r y . Each c o u r s e will involve 8 to 12 r e a c tor experiments. A tentative agenda f o r the r e a c t o r physics c o u r s e includes, for example, the following topics: 1) t e m p e r a t u r e distribution of neutrons, diffusion length, t h e r m a l neutron s p e c t r u m , d e l a y e d - n e u t r o n fraction, neutron c r o s s sections, diffusion p a r a m e t e r s of the m o d e r a t o r , neutron diffraction; 2) t h e r m a l flux and f a s t flux, utilization f a c t o r of t h e r m a l neutrons, r e s o n a n c e c a p t u r e e s c a p e p r o bability, neutron lifetime, safety f a c t o r fi, a - m e a s u r e m e n t s b y the Rossi method, v a p o r coefficient. Some p r e l i m i n a r y p r o g r a m s have also been developed for other special c o u r s e s . In addition to the c o u r s e s already r e f e r r e d to, special c o u r s e s will be organized for g r a d u a t e students. R e s e a r c h p r o g r a m s a r e also envisaged (in the field of activation analysis, r e a c t o r physics, shielding, d o s i m e t r y , etc). It is c r u c i a l that the work to be done by the r e a c t o r p e r s o n n e l be closely coordinated with the investigations of the students. An i m p o r t a n t added advantage should be noted: the u n i v e r s i t y r e a c t o r will set up conditions for joint work of students in different d e p a r t m e n t s , and will provide a solid groundwork for the f u r t h e r p r a c t i c a l work of those students.
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