Working Group No. 5 came to the conclusion that its w o r k should be based on r e s e a r c h already done, p r o ceeding f r o m the principle of economy of r e s o u r c e s , t i m e , and e n e r g y of specialists who are engaged in fundamental r e s e a r c h in their own countries. The next meeting, which will be held in the Soviet Union in October, 1978, will discuss tentative variants of the review r e p o r t s f r o m all subgroups. By July 1, 1979, the Group will p r e s e n t its review paper to the TCC for consideration.

SOME

PROBLEMS E.

F.

OF

FAST-REACTOR

DESIGN

Arifmetchikov

An international s y m p o s i u m on the design, construction, and experience f r o m the o p e r a t i o n of liquidmetal fast r e a c t o r s was held in Bologna, Italy, in A p r i l , 1978, with some 500 r e p r e s e n t a t i v e s f r o m m o r e than 30 countries and international organizations attending. The great fund of experience recently accumulated in the USSR, the USA, F r a n c e , Great Britain, the F e d e r a l Republic of G e r m a n y , and Japan on the principal aspects of the design of fast r e a c t o r s makes it p o s sible to p r o c e e d with sufficient reliability with the construction of the f i r s t c o m m e r c i a l facilities. Efforts in this direction a r e fully justified since only fast r e a c t o r s can solve the p r o b l e m of the full use of uranium and p r o v i d e an e n e r g y s o u r c e that is guaranteed f o r c e n t u r i e s , Many countries are therefore taking a l o n g range i n t e r e s t in the development of fast r e a c t o r s and organization of an efficient fuel cycle for nuclear power generation. As a r e s u l t , p r o b l e m s pertaining to guarantees of the safety of the nuclear fuel cycle and the economic balance of the utilization of atomic power plants with r e a c t o r s of various types have a r i s e n and r e quire solution. The p r o c e s s of constructing c o m m e r c i a l fast r e a c t o r s can be a r b i t r a r i l y divided into three stages - e x p e r i m e n t a l , pilot-plant (demonstration), and c o m m e r c i a l - each of which is c h a r a c t e r i z e d by certain scientific and engineering p r o b l e m s . At p r e s e n t Great Britain, the USA, F r a n c e , and the USSR already have 10-15 y e a r s of experience in operating experimental fast r e a c t o r s with a t h e r m a l power of about 60 MW (Rhapsodie has a power of 40 MW) and in the F e d e r a l Republic of Germany and Japan s i m i l a r facilities are in the stage of being brought up to full power (Table 1). During this period experimental r e a c t o r s w e r e the principal instruments in p r o g r a m s of r e s e a r c h on the behavior of fuel and m a t e r i a l s under irradiation and played a significant role in safety investigations and in accumulating experience f r o m the operation of sodium technological equipment. The F F T F r e a c t o r under construction in the USA with a m a x i m u m design neutron flux of 7.1015 neutrons/cm 2 9 sec will provide unique capabilities for i r r a d i a t i n g m a t e r i a l s . The p r e s e n t period may be considered as the completion of the demonstration stage, which has been c h a r a c t e r i z e d by the construction and operation of pilot (demonstration) facilities with fast r e a c t o r s with an e l e c t r i c a l power of 250-350 MW, and as a transition to the construction of prototypes of c o m m e r c i a l f a c i l i ties with h i g h - p o w e r fast r e a c t o r s (Table 2). R e s u l t s Obtained in E x p e r i m e n t a l and Demonstration Stages. To begin with, the capabilities of the fast r e a c t o r as a b r e e d e r s y s t e m were confirmed. The t h e o r e t i c a l and experimental values of the breeding ratio - 1 for PhSnix are 0.13 + 0.04 and 0.16 9 0.05, respectively. It has been d e m o n s t r a t e d that the sodium-cooled f a s t r e a c t o r is capable of stable, reliable, and safe operation, p r i m a r i l y because of negative t e m p e r a t u r e p o w e r and void reactivity effects. The results also show that high burnup can be attained by using fuel e l e ments with mixed oxide fuel (Table 3). Results obtained in F r a n c e show that cladding of type-316 stainless steel does not allow the fuel burnup to be i n c r e a s e d above 66,000 MW- day/ton with a 6% m a x i m u m allowable change in its d i a m e t e r (Fig. 1). This c o r r e s p o n d s roughly to a fluence of 2 91023. n e u t r o n s / c m 2. The use of titanium-stabilized type-316 stainless steel is considered to be p r o m i s i n g (Fig. 2). T r a n s l a t e d f r o m Atomnaya t~nergiya, Vol. 45, No. 4, pp. 313-316, October, 1978.

0038-531X/78/4504-1021507.50 9 1979 Plenum Publishing Corporation

1021

TABLE

i.

Principal Experimental Fast Reactors Powerp

FacilRy

Country

Start -up MW thermal)

State

60

t959

Shut down in 1977 upon completion of research program

60

1969

in operation

FFTF

] 62,5 [ 400

1963 i979

In operation 9b'~oof construction completed

France

Rapsodie

40

1967

in operation

FederalRcpublic of Germany

KNK II

58

1977

in stage of being brought up to full power.in operation as thermal reactor in 1973-1974

Japan

/OYO

i00

i977

In stage of beIng brought up to 50 M W

Italy

PEG

120

St .BritaIn

DFR

3SSR

BOR-6 0

U.S.A.

T A B L E 2.

EBR-II

Under eomtmetion

D e m o n s t r a t i o n F a c i l i t i e s with F a s t R e a c t o r s

Country

Power, MW

Facility

Arrival Start-up at full

Gt. Britain

PFR

State

)ower

(clec .) 250

t974

i977

In operation

BN-350

t50"

t973

BN-600

600

Operating at 60~ nominal power since March, 1976 Under construction

Operated at full (allowed) power in 1970-1972 Shut down in 1972. Construction halted,

I

USSR

U.S.A.

EFFBR CBBRP

60 350

t963

France

Ph6nix

250

1973

SNR-300

327

Early 1980"S

300

1985

Federal Republic of Germany Japan

I MONIU

t974

In stage of being brought up to power after repairs to heat exchangers Under construction since 1973

I

Constmction to begin in 1979

*Plus 5000 tons/h distilledwater.

W o r k done in the USA h a s m a d e it p o s s i b l e to r e l i a b l y a s c e r t a i n that a b u r n u p i n e x c e s s of 80,000 MW. d a y / t o n c a n be a t t a i n e d i n m i x e d oxide f u e l . I n the DFR the oxide fuel e l e m e n t s r e a c h e d the d e s i g n b u r n u p of 10~o h e a v y a t o m s u n d e r n o m i n a l o p e r a t i n g c o n d i t i o n s w i t h o u t a n y d a m a g e . T h e f l u e n c e in this c a s e w a s 1.5" 1023 n e u t r o n s / c m 2. E x p e r i e n c e h a s a l s o b e e n g a i n e d f r o m the o p e r a t i o n of fuel e l e m e n t s a t a h e a t r e l e a s e of up to 79 kW/m. It w a s found t h a t fuel e l e m e n t s i n one a s s e m b l y s u f f e r e d m a s s i v e d a m a g e ( v e r t i c a l c r a c k s i n t h e i r cladding) a t h e a t r e l e a s e s of 60-63 k W / m . S u b s e q u e n t i r r a d i a t i o n of the d e f e c t i v e f u e l e l e m e n t s for 300 days l e d to s e c o n d a r y c r a c k i n g and a n i n c r e a s e in the c l a d d i n g d i a m e t e r but t h e r e w a s m i n i m a l e s c a p e of fuel and no "flow clogging" w a s o b s e r v e d . It w a s c o n c l u d e d t h a t b u r s t f u e l e l e m e n t s c a n r e m a i n i n the r e a c t o r for 5 0 - 1 0 0 d a y s w i t h o u t a n y p a r t i c u l a r r i s k . T h i s c o n c l u s i o n c a n n o t , h o w e v e r , be c o n s i d e r e d to be f i n a l as f a r as c o m m e r c i a l r e a c t o r s a r e c o n c e r n e d .

1022

TABLE 3. R e s u l t s of I r r a d i a t i o n of Fuel E l e ments with Oxide Fuel No.offuel zl~menu irradiated

Facility

Rapsadie

20 000

Linearheat release, kW/m

MaximumImrnup fraction i5,45% heavy atoms

11 000, 50 00O MW- day/ of which65~ t o n (U, Pu)O2 95O 60 000 MW. day/ton 21,5% heavy " i 20O atoms

Ph~nix DFR

42,5--37,6 (at end of run) 43--45 45

15

4 10

3

~2 5

I

g5 I

9

I

Bumup fraction,%heavy atoms Fig. I

0

i

40

60

80

loo

120

I

1~0

160

Deformation. displacemems/atom Fig. 2

Fig. 1. Maximum relative change in d i a m e t e r of cladding of fuel elements of Ph~nix r e a c t o r . Fig. 2. Deformation of: 1) type-316 stainless steel and 2) t i t a n ium-stabilized type-316 stainless steel. Sodium technological equipment and s y s t e m s have been d e m o n s t r a t e d to function satisfactorily. Howe v e r , there have been c a s e s of heat-exchange equipment breaking down: four leaks in the heat exchangers of Ph~nix in 1976-1977 as the r e s u l t of c r a c k s f o r m i n g and 12 small leaks in the steam g e n e r a t o r s of the PFR in October, 1974. The leaks were due to s t r e s s c o r r o s i o n . It was decided that 9%-chromium steel developed by industry for the AGR would be used in the e v a p o r a t o r s and s t e a m g e n e r a t o r s of the CDFR. Elimination of such failures provided much experience in r e p a i r operations. Distinctive F e a t u r e s and P r o b l e m s of T r a n s i t i o n to Construction of Atomic Power Plants with H i g h - P o w e r F a s t R e a c t o r s . All countries a r e considering d e m o n s t r a t i o n r e a c t o r s , which either a l r e a d y exist or are on t h e drawing b o a r d s , as the basis for the construction of c o m m e r c i a l installations with a rating of 1000-18000 MW (electrical). M o r e o v e r , the f i r s t c o m m e r c i a l r e a c t o r s in G r e a t Britain, F r a n c e , the F e d e r a l Republic of G e r m a n y , and Japan will be built with minimal changes in design as c o m p a r e d to the corresponding demonstration facilities (Table 4). These changes are d e t e r m i n e d p r i m a r i l y by scaling-up f a c t o r s , experience f r o m the o p e r ation of d e m o n s t r a t i o n facilities, and economic considerations. The atomic plant at C r e y s - M a l v i l l e m a r k s the beginning of a large p r o g r a m for the construction of c o m m e r c i a l r e a c t o r s in F r a n c e , envisaging the construction of two power plants two to three y e a r s after Superph~nix, with two m o r e plants with a power like that of Superph~nix or g r e a t e r to follow two or three y e a r s afte]c that. The Japanese p r o g r a m is roughly the same in s t r u c t u r e , with a period of 6-7 y e a r s for the construction

1023

T A B L E 4. F i r s t C o m m e r c i a l F a s t - R e s o n a t o r Facilities Country

Gt.Br~ain USSR

Facility

POWel, (elee.)

'

Planned start-up

CDFR

t320

Constructionto begin in 1982

BN'I60O

f600

Constructionto begin when trial operation of BN-600is completed

i~ance

(elee.)

t200 i300

t983

Construction to begin afte~ 1

year's onexation

Japan

~Demo,

bf Sl~-~00 1000--1500 1992

TABLE 5. N u m b e r of Units of Equipment in R e a c t o r s Equipment

Fuel assembly Loop of primaW circuit ~vaporator ~up~.theater turbine

PFR

CDFR

78 3 3 3 t

342 8 16 i6 2

of MONJU and Demo facilities. Such an organization of the p r o g r a m should help create a powerful base and should considerably i m p r o v e the e c o n o m i c s of the e a r l y c o m m e r c i a l fast r e a c t o r s . It is believed that by the end of the century f a s t - r e a c t o r power plants will constitute a considerable f r a c tion of the nuclear power industry of the world, i.e., the principal c o m m e r c i a l benefits f r o m their operation are expected to come in the next century. Designs f o r c o m m e r c i a l facilities a r e being worked out with both loop and integrated layout of the p r i m a r y circuit. It s e e m s that in the d e m o n s t r a t i o n stage the disadvantages and advantages of these conceptions compensate each other and, t h e r e f o r e , the v a r i o u s conntries a r e continuing to develop their own national conceptions. In some countries the designs f o r h i g h - p o w e r r e a c t o r s a r e based on the use of a large n u m b e r of c o m p o nents and not l a r g e - s i z e d components; this is true above all in r e f e r e n c e to the fuel a s s e m b l i e s and steam g e n e r a t o r s (Tables 5 and 6). A l m o s t all designs for the e a r l y c o m m e r c i a l fast r e a c t o r s provide for reduced t e m p e r a t u r e conditions in the r e a c t o r core so as to improve t h e reliability of the facility. All the countries have settled on mixed oxide fuel. In view of the growing role of the fuel r e c h a r g i n g operation on high-power r e a c t o r s , there are plans for improving the relevant s y s t e m s . Countries opting for the closed fuel cycle plan the construction of plants for fuel p r e p a r a t i o n and r e p r o c e s s i n g . In p a r t i c u l a r , F r a n c e p r o p o s e s to build a fuel p r e p a r a t i o n plant with a capacity of 100 tons/yr and the F e d e r a l Republic of Germany plans to build a fuel r e p r o c e s s i n g plant with a capacity of 1500 t o n s / y r . It is important for many countries to obtain licences for the construction of f a s t - r e a c t o r power plants. And the development of technically sound safety r e q u i r e m e n t s is r e g a r d e d as being a t o p - p r i o r i t y task. R e s e a r c h , design, a n d experimental w o r k is being continued on the basis of conceptions and c h a r a c t e r i s t i c s of atomic power plants with h i g h - p o w e r fast r e a c t o r s . In the domain of physics this involves p r i m a r i l y the study of the possibilities of extending the operating period and i n c r e a s i n g the breeding ratio. Much attention is being paid to the study of heterogeneous r e a c t o r c o r e s containing b r e e d e r m a t e r i a l W o r k is continuing on the r e finement of nuclear data, the i m p r o v e m e n t of computational methods, the construction of complex (including multidimensional) computational codes, as well as integrated experiments on critical a s s e m b l i e s . 1024

TABLE 6. S c a l e - u p for Some P a r a m e t e r s in T r a n s i t i o n f r o m PFR to GDFR Parameter Electrical power Diam.eter of primary-circuit tank Lengt~ ot luel assembly Power of fuel assembly Capacity of primary-circuit pump Power: intermediate heat exchangers evaporator supertaeater

Factor X5,3 Xt,9 • Xi,l X2.5 X4,0 Xi,3 Xi,0

In the r e a l m of fuel and m a t e r i a l s r e s e a r c h is being done (especially in F r a n c e ) on effects which limit the life of fuel e l e m e n t s , p a r t i c u l a r l y the c h e m i c a l i n t e r a c t i o n between the fuel and the cladding, on the possibility o f depositing p r o t e c t i v e coatings on the inner s u r f a c e of the cladding and introducing stabilizing additives to the fuel, on the p r o p e r t i e s of t i t a n i u m - s t a b i l i z e d type-316 steel, and on carbide fuel. In the r e a l m of s a f e t y , the m o s t i m p o r t a n t thing is to build up a fund of e x p e r i e n c e f r o m the operation of existing f a c i l i t i e s , to i m p r o v e s y s t e m s for m o n i t o r i n g t h e i r s a f e o p e r a t i o n , and to obtain p r o o f that even " a l m o s t i m p o s s i b l e " hypothetical accidents will not have g r a v e consequences for the population and the e n v i r o n ment. In the l a s t c a s e , it is not a m a t t e r of c a r r y i n g out e x p e r i m e n t s "in the large" but e l a b o r a t i n g applicable computing p r o g r a m s and v e r i f y i n g them. Intornational cooperation is an i m p o r t a n t component of the development of f a s t - r e a c t o r p r o g r a m s , e s p e cially in E u r o p e a n countries. In 1972, three European industrial f i r m s (the W e s t G e r m a n RWE, the Belgian EN, and the Danish SEP) f o r m e d a s u b s i d i a r y company, SBK, for contracting and operating the SNR-300 in Kalkar. Under a 1973 a g r e e m e n t SBK e n t e r e d into a b r o a d e r E u r o p e a n c o n s o r t i u m with the F r e n c h national utility company EDF and the Italian E N E L , f o r m i n g two c o m p a n i e s , NERSA (EDF 51%, ENEL 33%, SBK 16%) and ESK (SBK 51%, ENEL 33%, EDF 16%), for contracting and o p e r a t i n g Superph~nix in F r a n c e and SNR-2 in the G e r m a n F e d e r a l Republic, r e s p e c t i v e l y . The c o n s o r t i u m INB was s e t up in 1972 by INTERATOM, N e r a t o o m , and Belgonucl~aire f o r the c o n s t r u c t i o n of SNR-300. Under the t e r m s of i m p o r t a n t a g r e e m e n t s concluded by the G o r m a n F e d e r a l Republic and F r a n c e , e x p e r i e n c e which the G e r m a n F e d e r a l Republic and its p a r t n e r s , on the one hand, and F r a n c e , on the o t h e r , a c q u i r e in the r e a l m of f a s t r e a c t o r s will be concentrated in the c o m p a n y SERENA. The c o m p a n i e s INB and NOVATOlVIE (France) will build f a s t - r e a c t o r p o w e r plants u n d e r l i c e n c e s f r o m SERENA. Since 1974 t h e r e h a s b e e n c l o s e - k n i t cooperation between F r a n c e and Italy, this being e s p e c i a l l y t r u e in r e s p e c t to work on the c o n s t r u c t i o n of Superph~nix and the construction of an e s t a b l i s h m e n t of a r e s e a r c h c e n t e r at B r a s i m o n e (Italy) with PEC. The U.S. F a s t - R e a c t o r P r o g r a m . At the p r e s e n t t i m e , in r e l a t i o n to the development of n u c l e a r e n e r g y the United States has decided it is n e c e s s a r y to use a t o m i c p o w e r plants with l i g h t - w a t e r r e a c t o r s to satisfy the e l e c t r i c i t y demand, postponing f o r an indefinite period the r e a l i z a t i o n of national p r o g r a m s for the c o n struction of c o m m e r c i a l f a s t r e a c t o r s and n u c l e a r - f u e l r e p r o c e s s i n g plants. In view of the new a p p r o a c h by the g o v e r n m e n t , funds for the p r o j e c t for the CRBRR phased facility have been cut off. Industrial f i r m s will, h o w e v e r , c o m p l e t e the designs for the s y s t e m s of this r e a c t o r , and p r o t o types of the m a i n c i r c u l a t i n g p u m p s , and the s t e a m g e n e r a t o r s will be built and tested. The e l e c t r i c a l e n g i n e e r i n g institute EPRI r e q u e s t e d that the d e s i g n e r s of the PLBR (prototype c o m m e r c i a l f a s t r e a c t o r with a power of 1000 MW (electrical)) complete the design and c o n s i d e r , for c o m p a r i s o n , the possibility of a tank layout f o r the p r i m a r y circuit. Models of 70-MW heat e x c h a n g e r s for the PLBR a r e being designed in two v e r s i o n s (single-walled and double-walled) and will be tested on the SCTI stand in the Liquid-Metal Design Center. The D e p a r t m e n t of E n e r g y has r e q u e s t e d C o n g r e s s i o n a l approval for consideration of a p r o j e c t for a f a s t - r e a c t o r p o w e r plant with a power of 650 MW (electrical). The 1978 a p p r o p r i a t i o n s f o r the f a s t - r e a c t o r p r o g r a m c a m e to 483 million d o l l a r s , which is h i g h e r than the annual a p p r o p r i a t i o n s f o r 1975 and 1976. This can m e a n only that even g r e a t e r r e s o u r c e s will be applied to the i m p l e m e n t a t i o n of the fundamental r e s e a r c h p r o g r a m s on f a s t r e a c t o r s , including the development of facilities b e s t p r o t e c t e d against the p r o l i f e r a t i o n of the nuclear weapon. A t the p r e s e n t time the m a i n effect of the U.S.A. in the r e a l m of f a s t r e a c t o r s is linked with the c o m p l e tion of the construction of the F F T F , 95% of which had been finished at the end of 1977. According to the plans,

1025

the filling of the s y s t e m with sodium should be completed in August, 1978. August, 1979, and full power is to be r e a c h e d in F e b r u a r y , 1980.

INTERNATIONAL SAFETY FOR

SYSTEMS

NUCLEAR I.

SYMPOSIUM

S.

AND

POWER

Krasheninnikov

ON C O N T R O L

C r i t i c a l i t y is to be r e a c h e d in

AND

MONITORING-MEASURING STATIONS and V.

S. F i l o n o v

More than 300 s p e c i a l i s t s f r o m 35 countries and a l s o the r e p r e s e n t a t i v e s of 5 international o r g a n i z a tions p a r t i c i p a t e d in the Symposium held at Cannes, F r a n c e , and organized by the IAEA in cooperation with the F r e n c h A t o m i c E n e r g y C o m m i s s i o n . A t the p l e n a r y s e s s i o n the i n c r e a s i n g role of n u c l e a r p o w e r generation in the w o r l d balance of generated e l e c t r i c p o w e r was e m p h a s i z e d and it was noted that its s u c c e s s f u l d e v e l o p m e n t was due to the f u r t h e r i m p r o v e m e n t of m o n i t o r i n g and control s y s t e m s of nuclear p o w e r stations. At p r e s e n t the a v e r a g e o p e r a t i n g efficiency of nuclear p o w e r stations amounts to 60-65%: the utilization of the 35-40% r e s e r v e will depend on i n c r e a s i n g the r e l i a b i l i t y of the equipment and e n s u r i n g the o p e r a t i n g control of nuclear power stations in v a r i a b l e load conditions. The p a r t i c i p a n t s in the s y m p o s i u m w e r e concerned about the n e c e s s i t y for developing international equipm e n t s t a n d a r d s , e n s u r i n g safety m o n i t o r i n g of n u c l e a r power s t a t i o n s , and the d e v e l o p m e n t of equipment for m o n i t o r i n g the e n v i r o n m e n t . During the five w o r k i n g days of the S y m p o s i u m 68 r e p o r t s w e r e h e a r d and d i s c u s s e d : these w e r e d i s tributed o v e r 7 sections: e x p e r i e n c e in the installation, s t a r t u p and o p e r a t i o n of control and safety s y s t e m s and equipments of nuclear power stations (16 r e p o r t s ) ; o b s e r v a t i o n s y s t e m s f o r r e a c t o r units (11); power d i s tribution in the r e a c t o r c o r e , and control (4); safety s y s t e m s and e m e r g e n c y signalling (8); new designs of m o n i t o r i n g and control s y s t e m s (7); m o n i t o r i n g i n s t r u m e n t s (19), and r e l i a b i l i t y (3). An a n a l y s i s of the r e p o r t s allowed the p r i n c i p a l future trends to be decided, along which r e s e a r c h will be conducted, and new developments for the p u r p o s e of achieving a higher o p e r a t i n g efficiency of n u c l e a r power s t a t i o n s , e s t i m a t i o n of m o n i t o r i n g and control, and a significant i n c r e a s e of equipment reliability. G r e a t attention was paid to the w i d e s p r e a d use of c o m p u t e r s y s t e m s for the p u r p o s e of effecting flexible control of nuclear power stations in v a r i a b l e load operating conditions, f o r reducing the effect of o p e r a t o r s on the operation of nuclear power stations and f o r the elimination of negative a f t e r a f f e c t s caused by faulty o p e r a tion. B a s e d on the a n a l y s i s of the o p e r a t i n g r e s u l t s of 39 r e a c t o r s , o p e r a t i n g f o r a t o t a l of m o r e than 200 r e a c t o r - y e a r s , the f i r m of Westinghouse a r r i v e d at the conclusion that e v e r y o p e r a t o r in 1 y e a r m a k e s an a v e r a g e of 1.32 e r r e r s , w i t h t h e l o s s of 27.26 h in each case. The loss amounts to about 350,000 d o l l a r s p e r y e a r . The f i r m had succeeded in cutting.considerably the n u m b e r of faulty o p e r a t i o n s , by the introduction with displays on cathode r a y tubes. The use of m i c r o p r o c e s s o r s in the c r i t i c a l p a r t s of the c o m p u t e r s y s t e m s i n c r e a s e s significantly the o p e r a t i n g r e l i a b i l i t y and, as supposed, will even p e r m i t t h e i r use in safety s y s t e m s . 9 An i m p o r t a n t f a c t o r f o r the d e v e l o p m e n t of automated c o m p u t e r i z e d s y s t e m s is the development of models of the p r o c e s s e s and a l g o r i t h m s for handling the information. The complexity of the models can be judged by the d e s c r i p t i o n of the t r a i n i n g equipment for the AGR r e a c t o r . The b e h a v i o r of the r e a c t o r is considered on the b a s i s of 50 differential f i r s t - o r d e r equations and 130 a l g e b r a i c equations. C o m p u t e r techniques a r e being used p a r t i c u l a r l y s u c c e s s f u l l y in s y s t e m s for m o n i t o r i n g the p o w e r potential distribution. When p r o c e s s i n g the data on the power potential distribution, s e v e r a l a p p r o a c h e s will be used. The J a p a n e s e s p e c i a l i s t s consider the distribution f i r s t of all as two-dimensional (with r e s p e c t to radius) with the subsequent introduction of e r r o r s in height. By using the data f r o m 32 f o u r - s e c t i o n neutron T r a n s l a t e d f r o m Atomnaya E n e r g i y a , Vol. 45, No. 4, pp. 317-318, October, 1978.

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0038-531X/78/4504-1026 $07.50 9 1979 Plenum Publishing C o r p o r a t i o n