R E G E N E R A T I V E C E S I U M - V A P O R - S U P P L Y S Y S T E M S F O R

T H E R M A L - E M I S S I O N N U C L E A R P O W E R P L A N T S

G. M. Gryaznov, N. I. Ezhov, E. E. Zhabotinskii, V. I. Serbin,

B. V. Slivkin, Yu. L. Trukhanov, and L. M. Sheftel' UDC 621.039.578:629.19

Regenerative supply systems with multiple use of cesium vapor are promising for long-lived thermal-emission nuclear

power plants (NPP) without a reserve.

A cesium-vapor-supply system mist maintain stably any specified pressure in the reactor within the working range during

the entire operating life of the NPP, and the cesium consumption must be as low as possible. For a scheme with one-way

diffusion of impurity vapors from the interelectrode gaps of the electric-generation channels into the cesium chamber of the

reactor, which combines either all of the electric-generation channels or a group of them, the average pressure of the gaseous

impurities in the interelectrode gap fig, assuming identical gas liberations in all channels, can be described by the expression

( Qg 4QgL d Td- Qg.r.. Tieg )

Pg=PCs "'Q'+ xd ZnPCsD T~t + 3~d"'~eAnPcsD r t ' (1) t

where Pcs is the vapor pressure in the cesium chamber; Q is the volumetric flow rate of vapor through the cesium chamber; Qg

is the total gas liberation in n electric-generation channels in a group that is serviced by the examined supply system; d e and A

are the diameter of the emitter unit and the size of the inlerelectrode gap; L and L d are the length of a duct inside a channel

and the length of the duct connecting the gap to the cesium chamber; D is the diffusion factor of the impurity gas in the cesium

vapor; and Tt, To, a n d Tieg are the average cesium temperatures in the throttle, the duct from the interelectrode gap to the

cesium chamber, and the gap (Fig. 1).

The first term in expression (1) describes the pressure in the cesium chamber; the second and third, the contributions of

the diffusion resistances of the exit duct and the interelectrode gap. An obvious condition for the advisability of increasing the

rate of vapor flow through the cesium chamber is that of reduction of the contribution of the first term to values that are

appreciably smaller than the total contribution of the second and third terms. Moreover, the contribution of the second factor

should be made the determining contribution. For this, cesium chambers through which vapors are pumped should be located as

close as possible to the interelectrode gap, and the cross-section of the exit ducts should not be smaller than that of the gap.

Calculations by formula (1) show that for L = 0.5-0.7 m, L o = 0.2-0.3 m, A = 4.10 -4 m, d e = (10-15)10 -3 m, d d > 5.10 -3 m,

Tieg = 1400-1600 K, T, = T d = 800-900 K, and a total of 60-100 generating channels for hydrogen and gases with a molecular

mass of 28, the maximum advisable cesium-vapor flow rate is 200-500 g/day. An increase in the flow rate above these values

weakly affects fig.

For a two-way diffusion scheme with identical conditions of impurity-gas output to cesium chambers, fig is determined by

the formula

( Og 2OgL d Ta 1 Q, gL Tieg ).

~g:PCs Q § r~d2nPcs D r t +2 ndeAnPcsD T E (2) d

Calculations by formula (2) with the indicated data show that in this case the required vapor flow rate rises to --1000

g/day. Gas liberation in the interelectrode gap decisively affects pg and for Q ~ ~ determines the minimum possible impurity-gas

pressure in the gap.

Scientific--Industrial Organization "Red Star." Translated from Atomnaya l~nergiya, Vol. 71, No. 6, pp. 573-575, Decem-

ber, 1991. Original article submitted November 19, 1990.

0038-531X/91/7106-1039512.50 �9 Plenum Publishing Corporation 1039

, -

N N+NI ) -~s 7--~ d, ~ ,, "-"~ 7

n f ~

6

Fig. 1. One-way diffusion scheme for electric-generation channels with three- (a) and five-layer collector packets

(b): 1) vapor-supply system; 2) throttle; 3) cesium chamber; 4, 5) electric-generation channels and their leads; 6)

interelectrode gap; 7) emitter unit; 8) electric-switching channels; 9) cermet seals for leads; 10, 11) cermet seals

and guard electrodes of electric-generation channels; - - ~ , ----,) cesium vapor and gaseous impurities.

6111!~iijll +iil ~ 5 z ~

"7

~ f

, x

+ 2 - I r

~t

7~ ii!i ti~++ :liiii'i i!!~!l L , + , , , + , , , i [ ~ +,

Fig. 2, Regenerative vapor-supply system: 1) container; 2)

control thermocouple; 3, 4, 5) evaporation, transport, and

condensation zones, respectively; 6) annular channel; 7, 9, 10)

trigger channels; 8) electric heater.

Formulas (1) and (2) pertain to the case in which the gas from the fuel-core cavities of the emitter units goes directly

into the interelectrode gap. For electric-generation channels with separate ducts for the core cavities and the interelectrode gap,

the quantity aQg is introduced into the second and third terms of formulas (1) and (2), where a is the percentage of the total

gas liberation directly into the gap, which is a function of the tightness of the sealing devices between the ducts. If a << 1, the

first term in formulas (1) and (2) will be determining up to a high cesium flow rate. If the gas-discharge duct does not go to the

cesium chamber but, for example, to the zone after the throttle 2 (see Fig. la), the first term can be reduced sharply. The suit-

1040

ability of one or another version is ultimately determined by the gas liberation into the interelectrode gap and the permissible

impurity-gas pressure in the gap for long-term stability of the output electrical parameters of the generation channels.

The main part of the supply system is the cesium-vapor regenerator. One of the possible designs, which is shown in Fig.

2, is implemented as a hermetically sealed annular container, which is filled by a fiber capillary structure and up to 1.5 kg of

liquid cesium; a channel is formed in it for the passage of uncondensed gas impurities, which connects the gas-discharge duct to

outer space. The structure has evaporation, transport, and condensation zones, and the porosity of the latter is greater than the

porosities of the evaporation and transport zones, which ensures a directional capillary head. The specified temperature in the

evaporation zone, which ensures the required cesium vapor pressure in the interelectrode gap, is maintained by an electric

heater, whose power is controlled by the automatic-control system of the NPP. It is advisable that the range of evaporation-zone

temperatures be 290-340~ that the number of temperature settings in that range be five to seven, and that the temperature in

the condensation zone be 150-200~ to minimize cesium leakage from the supply system and prevent blocking of the capillary

structure by solid compounds of cesium with the gaseous impurities. Under such conditions, cesium leakage can be limited to

values that ensure a vapor-generator life of up to 5 yr or more for a liquid-phase supply of 1.5 kg. The radial dimensions of the

regenerator and the heights and pore sizes in the evaporation and condensation zones are selected to hold the cesium at the

maximum possible orbital g-loads. The internal cavity of the regenerator is sealed by one-time membrane valves.

To check the operation of the described cesium-vapor regenerator design, several specimens were tested independently

in the range of evaporation-zone temperatures of 300-350~ at vapor flow rates through cesium-chamber simulators of up to

300-500 g/day. The tests confirmed the stability of maintenance of a specified cesium vapor pressure. The maximum duration of

one of the tests was more than 10,000 h. The vapor regenerator retained its operating capacity with any amount of liquid cesium

in the capillary structure. The latter factor, considering the small cesium leakage from the condensation zone, indicates that the

described design can operate for several years, provided that solid residues are not formed in the condensation zone.

M A I N P R I N C I P L E S O F C O N T R O L O F " T O P A Z " T H E R M A L - E M I S S I O N

N U C L E A R P O W E R P L A N T I N V A R I O U S M O D E S

M. S. V o l ' b e r g , G. M. G r y a z n o v , E. E. Zhabotinskii,

A. N. Makarov, and V. I. Serbin UDC 621.039.577

In the creation of the "Topaz" nuclear power plant (NPP), one of the most-complicated problems was that of selection

and adjustment of the control algorithms in all operating modes to maximize NPP performance and provide the required

accuracy in maintaining the output electrical parameters. Below we shall examine the main requirements on the "Topaz" NPP in

various operating modes, methods for their satisfaction, and control algorithms whose validity is confirmed by ground and flight

tests of the NPP.

The operation of the "Topaz" NPP includes prestart-up preparation and entry into orbit, a start-up mode, in which the

reactor output is brought up to an electrical power of about 6 kW, a nominal mode for several thousand hours, and shutdown of

the NPP. The start-up mode consists of prestart-up preparation and entry of the space vehicle into working orbit, start-up of the

NPP, raising the thermal heating power, heating of the ducts for cesium-vapor supply to a level that allows the cesium-vapor

generator to be actuated and vapor to be delivered to the electric-generation channels (EGC), and setting of the NPP to a

specified electrical power.

Scientific--lndustrial Organization "Red Star." Translated from Atomnaya t~nergiya, Voi. 71, No. 6, pp. 575-578, Decem-

ber, 1991. Original article submitted November 11, 1990.

0038-531X/91/7106-1041512.50 �9 Plenum Publishing Corporation 1041