NUCLEAR POWER PLANTS

EXPERIMENTAL SUBSTANTIATION, TESTING, AND COMMISSIONINGOF A NOVEL SEPARATION SYSTEM FOR STEAM GENERATORSOF NUCLEAR POWER PLANTS WITH VVÉR-1000 REACTORS

B. I. Nigmatulin,1 A. G. Ageev,1 V. N. Blinkov,1 R. V. Vasil’eva,1 B. M. Korol’kov,1

Yu. G. Dragunov,1 N. B. Trunov,1 A. V. Nekrasov,1 and V. F. Ilyushin1

Translated from Élektricheskie Stantsii, No. 3, March 2003, pp. 16 – 22.

The separation system of a PGV-1000 steam generator is modernized on the basis of bench tests of modelPGV-1000 steam generators, full-scale tests of steam generators, and computational analysis of the results ofthese tests. The changes concern the configuration of the submerged plate and replacement of the louver sepa-rator by a receiver baffle. These measures increase the marginal evaporative capacity and the permissiblerange of variation of the water level, decrease the moisture content at the outlet from the steam generator, andimprove the conditions for control and repair of its internal surface.

Keywords: steam generator, steam moisture, louver separator, submerged perforated plate, vapor zone, masslevel, evaporative capacity.

At the present time, steam generators of nuclear powerplants (NPP) with VVÉR reactors are equipped with gravityseparation systems. The plants of the first generation(VVÉR-210, -365, -440) operated at a relatively low load onthe disengagement surface earlier tested in boiler engineer-ing. In later-generation NPP with a more powerful reactor,VVÉR-1000, this load was almost doubled for reasons in-cluding transportability. The problem was that the operatingpersonnel had no experience in running plants under such aload, and the load itself was assumed to be the maximumpossible one for gravity separation. A wide-scale study wasrequired for solving the problem, including a review of oper-ation of the acting equipment of NPP.

In contrast to steam generators (SG) of the precedinggeneration, generators of type PGV-1000 of the VVÉR-1000unit are additionally equipped with a submerged perforatedplate (SPP) for leveling the elevated load on the disengage-ment surface, which is a very important component of theseparation system.

ÉNITs VNIIAÉS has tested the operation of the separa-tion system of the PGV-1000 on a test bench with actual pa-rameters of the medium using a special installation for ã-

transmission. Since the tests were performed in the stage ofdesigning the PGV-1000, specialists studied different vari-ants of organization of the separation system with differentkinds of connection of the SPP to the circulation contour,varied its effective cross section, the length of the flange, andthe design height of the vapor zone, and studied the operationin the presence or absence of a louver separator.

1041570-145X�03�3702-0104$25.00 © 2003 Plenum Publishing Corporation

Power Technology and Engineering Vol. 37, No. 2, 2003

1 Elektrogorsk Research Center for Safety of Nuclear Power Plants of theAll-Russian Research Institute for Operation of Nuclear Power Plants(ÉNITs VNIIAÉS), Élektrogorsk, Russia; “Gidropress” Design Depart-ment, Podol’sk, Moscow region, Russia.

0.25 0.50 0.75

750

500

250

Hs, mm

W0��, m sec�

1

2

Fig. 1. Dependences of the height of the vapor zone correspondingto a moisture content of 0.2% on the superficial velocity of steam onthe disengagement surface at a pressure of 6.4 MPa: 1, horizontaldrum (shaped vapor zone); 2, vertical drum.

One of the most important results of the tests was the es-tablishment of the possibility of substantial forcing of theload on the disengagement surface in gravity separation (upto 0.7 m�sec, Fig. 1) with respect to the traditional values (upto 0.3 m�sec) due to the increase in the design height of thevapor zone. The conditions of steam separation in verticaland horizontal drums, which differ substantially due to thedifference in the configurations of the vapor zone, were dif-ferentiated for the first time. It was shown that, as applied tothe PGV-1000 steam generator, the load on the disengage-ment surface could be forced without the use of a louver sep-arator even with allowance for the residual nonuniformity atthe outlet from the SPP. These results were later confirmed intests of a full-scale model of the PGV-1000 on the test benchof the “Gidropress” Design Department.

The use of ã-transmission made it possible to develop amodified method for designing the SPP for gravity separa-tion systems [1]. This method allowed for the way of connec-tion of the SPP to the circulation contour, the length of theflange, and the removal of moisture through the perforationof the SPP with steam. The method was used for designingthe SPP for the PGV-440 of the Kola NPP (Fig. 2). The testsof the PGV-440 with the SPP were aimed at showing that theSPP efficiently operating in boiler drums 1400 – 1600 mm indiameter were also suitable for NPP steam generators with adiameter twice as great. The method was also used to designthe SPP for the PGV-1000 steam generator.

The conventional PGV-1000 steam generator of theVVÉR-1000 unit had been equipped with a separation sys-tem with an SPP having a 730-mm-long flange, which par-tially enclosed the heat-exchange bundle, and a louver sepa-rator traditional for SG of the preceding generations. How-

ever, due to the enhanced load on the disengagement surface,the vertical size of the separator was considerably increasedand amounted to about 500 mm. The design height of the va-por zone from the SPP to the lower edge of the louver wasthen equal to 750 mm. Full-scale tests of the PGV-1000 inthe head unit of the VVÉR-1000 showed excess emission ofthe water-steam mixture into the vapor zone from the clear-ance between the body of the SG and the flange of the plateon the side of the “hot” collector. For this reason, the mois-ture at an output of 80 – 85% exceeded the standardizedvalue [2]. Since the louver separator did not provide steamdrying, the extreme rows of the louvers on the side of the“hot” collector were covered by a deflector in order to realizethe rated output of the unit (Fig. 3). This decision was in facta temporary one, because it removed the consequences of theextra emission rather than its causes and in addition causedthe appearance of a deflected transverse steam flow in thevapor zone of the generator, which worsened the efficiencyof the separation.

The tests of the SG of the head unit also showed that themarginal evaporating capacity of the SG does not exceed8 – 10%, which approximately corresponds to the differencein the thermal hydraulics of the circulation loops. Therefore,some of the SG operated at the limit of the capacity of theseparation system even at the rated power. In addition, thepermissible range of variation of the level above the SPP,which directly influences the safety of the turbounit, wasvery narrow, and the operation of the SG had to be controlledby an indirect parameter, i.e., the level in the clearance be-tween the flange of the SPP and the SG body in its end. Theposition of this level did not exceed the SPP mark, whichlimited the water reserve in the SG.

A Novel Separation System for Steam Generators of NPP with VVÉR-1000 Reactors 105

2820

40

2856

3210

540

120

20

80

40

40 40

23

1

2

3

4

Fig. 2. Configuration of submerged perforated plate in the PGV-440 steam generator of the Kola NPP: 1, louver separator; 2, submerged perfo-rated plate; 3, hydraulic lock; 4, heat-exchange bundle.

Some of the users attributed the extra emission of the wa-ter-steam mixture into the vapor zone to the too small watersection of the SPP. However, when the water section was in-creased from 3.7 to 8, 12, and 20%, the emission did notchange, and the withdrawal of the SPP did not make it possi-ble to realize the rated capacity of the unit. Other specialistspresumed that the emission was connected with inappropri-ate arrangement of the water section relative to the pipe bun-dle, in particular, with the absence of a hydraulic lock. Thisallowed the steam, which was squeezed by the outlet flow ofthe heating agent and generated by the part of the bundle notcovered by the flange, to get freely into the mentioned clear-ance and cause the emission. The best way to prevent theemission at the existing configuration of the SPP consists ofclosing the clearance between the body of the SG and theflange of the SPP on the side of the “hot” collector by addi-tional perforated plates and simultaneous opening of thescuttles in the flange in order to provide free flow of thesteam. In this case, water is discharged from the SPP onlyover its end faces and on the side of the “cold” collector,which in fact corresponds to the actual flow pattern. It iseven expedient not to use flanges in this part of the SG,which will increase the water section of the discharge chan-nel and improve the hydrodynamics of the water zone.

The configuration of the SPP was changed in the de-scribed way in steam generator No. 4 (SG-4) of the Balakov-skaya nuclear power plant (BaAÉS). In order to check the ef-ficiency of the suggested design solutions, SG-4 wasequipped with a system of experimental control that includedhydrostatic vapor content meters and turbine flow meters fordetermining the speeds and directions of the flows.

The data on the true-volume vapor contents and circula-tion speeds obtained for typical parts of the water zone ofSG-4 and the influence of the capacity and the water level onthese characteristics agree with the data obtained earlier forthe conventional SG of the head unit of the VVÉR-1000. Anadditional positive effect consisted of a decrease in the vaporcontent in the clearance between the flange of the SPP andthe heat-exchange bundle in the region of the “hot” collectorfrom 0.8 to 0.53, which improved the circulation conditionsin this zone of the SG.

Figure 4 presents the dependences of the moisture con-tent on the position of the mass level in the SG in three char-acteristic parts of the vapor zone of the SG-4 at the BaAÉSand, for comparison, in the same parts of a conventionalSG-3 of unit No. 5 of the Novovoronezhskaya nuclear powerplant (NVAÉS). The mass level in the steam generators wasmeasured in the gap between the SPP flange and the SG bodyon its end face on the side of the “cold” collector. The lowermark of the level meter was 320 mm below the horizontalplate of the SPP, which was treated as the zero level.

It can be seen from the dependences of Fig. 4 that themoisture content is high in the conventional SG under the de-flector, on the lower edge of the louver, and at the mark of180 mm below the louver, whish is explainable by the emis-sion of water-steam mixture into the vapor zone. In the SG-4with a modernized SPP the moisture content in the men-tioned zones is substantially lower, which indicates that theemission of the water-steam mixture was eliminated. It is im-portant in principle that the moisture at the lower edge of the

106 B. I. Nigmatulin et al.

1

2

3

4

5

6

7

8

9

Fig. 3. Steam generator with a conventional separation system withan SPP and a louver separator: 1, steam extraction pipes; 2, body; 3,louver separator; 4, deflector; 5, submerged perforated plate; 6, SPPflanges; 7, packets of heat-exchange bundle; 8, “hot” collector; 9,“cold” collector.

60.00

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10.00

6.004.00

2.00

1.00

0.60

0.40

0.20

0.10

0.060.04

–300 –200 –100 0 100 Hl, mm

ù, %

3 3

2

2

11

Fig. 4. Dependences of the moisture content in the vapor zone ofsteam generator No. 4 of BaAÉS (solid line) and steam generatorNo. 3 of the fifth (1000-MW) unit of NVAÉS (dashed line) on thereading of the level meter: 1, 2, 3, moisture content at the lower edgeof the louver, under the deflecting plate, and in the vapor zone at the180-m mark below the louver, respectively.

louver fell below the rated values in a specific range of varia-tion of the water level, which means that it is not necessary toinstall a louver separator. The decrease in the moisture levelat the lower edge of the louver also explains the lower mois-ture content in the steam duct at the outlet from the SG-4 ascompared to conventional steam generators (curve 5 inFig. 5).

The elimination of the emission of steam into the vaporzone made it possible to advance the separation system of thePGV-1000 further and, in particular, to replace the louverseparator by a ceiling receiver baffle.

The design with the SPP was theoretically and experi-mentally developed at the Polzunov Central Boiler and Tur-bine Institute by K. A. Blinov and G. N. Kruzhilin in 1938 asapplied to marine steam boilers and at first did not contain alouver separator. Steam removal was performed with thehelp of an extraction pipe mounted along the drum and de-signed for uniform extraction of steam over the drum’slength. Later, the SPP design was widely used by theORGRÉS Company and in stationary drum boilers; a ceilingreceiver baffle was mounted for uniform extraction of steamalong the drum. ORGRÉS made an attempt to install an addi-tional louver separator in the drum, but it was not successful.

Model studies and the experience of operation of steamgenerating equipment of nuclear power plants have con-firmed that in the case of the use of gravity separation incombination with a SPP, a louver separator becomes unnec-essary and can even give a negative result under specificconditions. It is known that separator drums of nuclear powerplants with RBMK reactors work without a louver separator,and their separation system is organized with the help of anSPP and a receiver baffle. In the operational range of varia-tion of the level above the SPP, separator drums producesteam with 0.01 – 0.03% moisture.

The possible negative result due to the use of a louverseparator is connected with the fact that its installation de-creases the height of the vapor zone, lowers the level ofsteam extraction, and thus increases the initial moisture con-tent of the steam. For this reason the effects of the installa-tion of a louver separator should be analyzed for each spe-cific case with allowance for the final moisture content, themarginal evaporative capacity, and the permissible range ofvariation of the level. As applied to the PGV-1000 steamgenerator, the replacement of a louver separator by a ceilingreceiver baffle and the corresponding increase in the designheight of the vapor zone from 750 to 1200 mm cause a de-crease in the moisture content of the steam and an increase inthe marginal evaporative capacity and widen the permissiblerange of variation of the level relative to the conventionalvariant of the separation system.

The mentioned inefficiency of the use of a louver separa-tor in systems with preliminary gravity separation above thebubbling layer has a physical explanation. Probing of the va-por zone has shown that the majority of the drops jumpingover the disengagement surface rise to a height of at most150 – 200 mm at a pressure of 3 – 7 MPa and then fall back.

Within this height the moisture content varies from the maxi-mum value of 50 – 70% directly above the disengagementsurface to less than 0.1%. This means that at a physical level150 – 200 mm below the louver separator the moisture con-tent in front of it is at most 0.1%. However, it is sufficient toraise the mass level by 70 – 100 mm for the louver separatorto be flooded by a double-phase layer, because in the consid-ered case the increase in the physical level is almost twice asrapid as that in the mass level due to swelling. Therefore, itcannot be guaranteed that the initial moisture at the inlet tothe louver will remain within the design 5 – 10%, becausethe fluctuations of the level may cause flooding of the louver.For this reason, the actual level in steam generators of NPPwith a VVÉR reactor of the first generation is kept so as toguarantee dry steam at the inlet to the louver (ùin < 0.1– 0.2%). This creates what seems to be efficient operation ofthe louver, while in fact the conditions of steam separationmay be improved after the louver is removed.

The local speed of steam over the height of the vaporzone in the cylindrical body of the PGV-1000 steam genera-tor is elevated, which should be allowed for when designingthe steam-separation system. On the lower edge of the louverthe speed increases by a factor of 1.2 relative to that on the dis-engagement surface and by a factor of 1.73 at the level of thereceiver baffle. In the latter case, the permissible steam load

A Novel Separation System for Steam Generators of NPP with VVÉR-1000 Reactors 107

1.00

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ghtf

ract

ion

ofm

oist

ure

inS

Gst

eam

,%

–100 0 100 200 H, m

1

4 2

5 6 83

7

Fig. 5. Comparison of separation characteristics of SG with con-ventional and modernized separation systems: 1, SG-3, fifth unit ofNVAÉS, conventional separation devices; 2, SG-1, first unit ofZaporozh’skaya NPP, conventional separation devices; 3, SG-3, firstunit of BaAÉS, conventional separation devices; 4, SG-3, first unitof Zaporozh’skaya NPP, conventional separation devices; 5, SG-4,first unit of BaAÉS, closed extraction channel between the SPP andthe body on the hot side; 6, SG-4, fourth unit of BaAÉS, closed ex-traction channel between the SPP and the body on the hot side, thelouver is replaced by receiver baffle, metal fasteners of the louverare preserved; 7, SG-4, second unit of BaAÉS, flat receiver baffle,metal fasteners are removed; 8, SG-4, first unit of Volgograd nuclearpower plant, flat receiver baffle, metal fasteners are removed.

should be evaluated with the use of data obtained for drumseparators of RBMK reactors that are characterized by an ap-proximately equal degree of shaping of the vapor zone [3].

The submerged perforated plate does not provide fullleveling of the load on the disengagement surface and leavesa residual nonuniformity that leads to local growth inthe steam speed in the region of maximum heat emission atthe “hot” collector. Steam separation should be designedfor this very speed, because in fact it determines the removalof moisture to the steam conduit. According to the dataobtained for Balakovskaya NPP, this speed amounts to0.41 m�sec. Other studies have given comparable values ofmaximum local speed.

Computation of the moisture content by different meth-ods (VEI and VTI [4, 5]) shows that the final moisture in thesteam is substantially lower than the rated value at a steamspeed of 0.41 m�sec and a design height of the vapor zone of1200 mm. At the same time, these methods are based on ex-perimental data obtained for cylindrical columns, i.e., theydo not allow for the effect of the shape of the vapor zone overthe height on the moisture content.

The experimental material on steam separation availabletoday for steam generators and drum separators of nuclearpower plants with RBMK reactors and obtained for a pres-sure of 6.3 – 6.8 MPa allows us to analyze the conditions ofsteam separation in the PGV-1000 for different variants oforganization of the separation system. Figure 6 presents the

generalizing dependences of the necessary height of the va-por zone on the speed of steam on the disengagement surfaceat a constant steam speed over the height (unshaped vaporzone, dependences 2 and 3), and at a steam speed increasedby a factor of 2.1 at the level of the receiver baffle (shapedvapor zone, curve 1). Dependences 1 – 3 have been obtainedunder the conditions of uniform load on the disengagementsurface; dependences 1 and 2 correspond to a final moisturecontent of 0.2%; dependence 3 corresponds to a final mois-ture content of 10 – 15%, which is considered to be the limit-ing one for efficient operation of the louver.

Figure 6 also presents dependences of the availableheight of the vapor zone in the PGV-1000 in the presence ofa louver, in the case of its replacement by a receiver baffle,and in the variant without an SPP but in the presence of alouver.

The height of the vapor zone in these dependences wascalculated by the formula

Hs = Hd – Hm�(1 – ö), (1)

where Hd is the design height of the vapor zone equal to 750,1200, and 1010 mm respectively; Hm is the mass level as-sumed to be equal to 150 mm; ö is the steam content on thestabilized region of the double-phase layer [6].

The intersection of the dependences of the available andnecessary heights of the vapor zone characterizes the speedof the steam on the disengagement surface, which can be re-alized for each considered case.

For a conventional separation system with Hd = 750 mmthe effect of the shape of the vapor zone can be neglected,and we may use curves 2 and 3. Specifically, curve 3 is thelimiting speed of the steam at 15% moisture content at the in-let to the louver, which is equal to 0.46 m�sec. With allow-ance for the maximum local speed of the steam Wmax = 0.41m�sec, the marginal evaporative capacity of the conventionalseparation system is 0.46�0.41 = 1.1, which has been con-firmed experimentally. Curve 3 and Eq. (1) can be used fordetermining the limiting mass level above the SPP in thezone of maximum steam loads at the “hot” collector. At Wmax

= 0.41 m�sec, Hs = 350 mm, and ö = 0.515. Then we findfrom the equation that the height of the mass level Hm = 195mm for Hd = 750 mm. It is known from practice that whenthe level at a conventional SG is positioned 200 mm higherthan the SPP, the final moisture amounts to 0.1 – 0.2%. Ifthis level is exceeded, the moisture content in the steam con-duit rapidly rises.

In the louver-free separation system with receiver baffle(curve 1 in Fig. 6) the maximum steam speed at a moisturecontent of 0.2% amounts to 0.58 m�sec, and the marginalevaporating capacity is 0.58�0.41 = 1.41, i.e., is substantiallyhigher than in the conventional system. At Wmax = 0.41 m�secand Hs = 600 mm (curve 1), ö = 0.515 whence, by Eq. (1),the limiting position of the level above the SPP at a moisturecontent of 0.1% is equal to 290 mm. Thus, the removal of thelouver makes it possible to increase the maximum levelabove the SPP by about 100 mm.

108 B. I. Nigmatulin et al.

1000

750

500

2500.25 0.50 0.75

Hs, mm

W0 , m/sec��

Hd = 1200 mm

Hd = 750 mm

1010

5

6

1

2

3

4

Fig. 6. Dependences of the necessary (1 – 3) and available (4 – 6)heights of the vapor zone on the speed of steam on the disengage-ment surface: 1, shaped vapor zone, 2.1 ratio of the speed on thesteam level to the speed on the disengagement surface, 0.2% mois-ture; 2, unshaped vapor zone, 0.2% moisture; 3, the same, 10 – 15%moisture; 4, available height of the vapor volume in the variant with-out a louver with a receiver baffle and an SPP at a mass level abovethe SPP equal to 150 mm and design distance Hd from the SPP to theextraction level of 1200 mm; 5, available height with a louver with-out an SPP at a mass level of 150 mm and Hd = 1010 mm; availableheight with a louver and an SPP at a mass level of 150 mm andHd = 750 mm.

Analyzing the plots in Fig. 6, we may also conclude thatwithout the SPP but in the presence of a louver the ratedpower of the PGV-1000 is not realizable despite the increasein the structural height of the vapor zone to 1010 mm. In thiscase, according to curve 3, the maximum attainable steamspeed at 15% moisture content at the inlet to the louver is0.7 m�sec. At the same time, the local speed of steam abovethe heat-exchange bundle near the “hot” collector is 0.94 m�secat the rated load. Therefore, the expected capacity of thesteam generator, for which the separation will be worseneddue to flooding of the louver by the double-phase layer, willbe 0.7�0.94 = 0.75 of the rated capacity. This has been con-firmed by tests of a steam generator without an SPP at theSouth-Ukraine nuclear power plant.

The efficiency of the measures taken to replace the lou-ver by a ceiling baffle was tested for a modernized steamgenerator SG-4 of the fourth unit of the Balakovskaya NPP.The modernization of the separation system included closureof the clearance between the SPP and the body of the steamgenerator on the side of the “hot” collector by additional per-forated plates for eliminating excess emission of the wa-ter-steam mixture and removal of the blinds from the over-flow windows in the top part of the flange on the same side.Out of fear of negative consequences and in order to preservethe possibility of back installation of the louver packets, thebearing structures in the vapor zone of the steam generatorwere not withdrawn. For this reason, the receiver baffle had aC-shape in order to make it mountable into the SG. Tests ofthe SG-4 at 90 and 100% capacity of the unit showed that theseparation characteristics of this steam generator were sub-stantially improved with respect to a standard steam genera-tor. At the rated level on the end face of the SG at H = 0 (thelevel of the submerged plate) the moisture content of thesteam was substantially diminished and the permissible posi-tion of the level increased (curve 6 in Fig. 5).

At the same time, the presence of the bearing metalstructures of the louver separator in the tests of SG-4 of thefourth unit, which closed almost half of the cross section ofthe vapor zone, and the C-shape of the receiver baffle insteadof the flat variant finally chosen for the louver-free separa-tion system prevented the experimenters from seeing all theadvantages of the novel design.

The efficiency of the separation system with the louverreplaced by a flat receiver baffle (Fig. 7) has been proved byseparation tests of steam generators of the second unit of theBalakovskaya NPP and of the first unit of the VolgodonskayaNPP. The tests showed that in contrast to standard steam gen-erators the water level in the newly designed ones could beraised by 200 mm and the moisture content did not exceed0.05% (curves 7 and 8 in Fig. 5).

Analyzing experimental data, we established that the re-placement of the louver separator by a ceiling perforated baf-fle, which increased the height of the vapor zone from 750 to1200 mm, improved the separation characteristics by providing

— higher marginal evaporating capacity;— wider permissible range of variation of the water

level;

— lower moisture content at the outlet from the steamgenerator.

By removing louver separators from steam generators ofNPP with VVÉR reactors the consumption of expensivestainless steel will be decreased by 8 tons per PGV-1000steam generator, and the labor effort for the production of thenew design will be reduced by 2500 standard hours, whichamounts to about 4% of the total working hours for the pro-duction of a steam generator. It is also important that the con-ditions of control and repair of the internal surface of thesteam generator will improve too.

Thus, the use of a louver separator in the design of steamgenerating equipment with a gravity separation systemshould be preliminarily substantiated, because in some casesit may be ineffective and even harmful.

REFERENCES

1. I. S. Dubrovskii and A. G. Ageev, “Hydrodynamics of submergedperforated plates,” Teploénergetika, No. 8 (1974).

2. A. G. Ageev, R. V. Vasil’eva, A. I. Dmitriev et al., “A study of thehydrodynamics of the PGV-1000 steam generator,” Élektr.Stantsii, 6 (1987).

3. A. G. Ageev and V. D. Bainyakshin, V. I. Belov, et al., “A study ofthe efficiency of gravity separation for separator drums of NPPwith an RBMK-1500,” Élektr. Stantsii, No. 7 (1987).

4. L. S. Sterman, “On the theory of steam separation,” Zh. Tekh.Fiz., XXVIII(7) (1958).

5. Yu. V. Kozlov and G. A. Ryabov, “A study of steam separation asapplied to separator drums of NPP,” Teploénergetika, No. 4(1987).

6. D. A. Labuntsov, I. L. Kornyukhin, and E. A. Zakharova, “Vaporcontent of double-phase adiabatic flow in vertical channels,”Teploénergetika, No. 4 (1968).

A Novel Separation System for Steam Generators of NPP with VVÉR-1000 Reactors 109

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Fig. 7. Steam generator with modernized separation system with anSPP and a receiver baffle: 1, steam-extraction pipes; 2, receiver baf-fle; 3, body; 4, submerged perforated plate; 5, closed gate on the“hot” side; 6, overflow windows; 7, flanges of the SPP; 8, packets ofheat-exchange bundle; 9, “hot” collector; 10, “cold” collector.