vver reactors

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1 VVER reactors: clean and reliable source of energy in the past and in the future V. Mokhov, N. Trunov International Conference on Opportunities and Challenges for Water Cooled Reactors in 21-st Century

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Page 1: VVER Reactors

1

VVER reactors:

clean and reliable source of energy in the past and in the future

V. Mokhov, N. Trunov

International Conference on Opportunities and Challenges for Water Cooled Reactors in 21-st Century

Page 2: VVER Reactors

2

“Reactors with water moderator combine high breeding factor with simple and compact design. In our opinion, they are promising reactors for a large-scale nuclear power engineering of the nearest future” *

* - quotation from the report of I.V.Kurchatov in Harwell, England, April,1956

Page 3: VVER Reactors

3

Contents

History, main features and peculiarities of VVER technologyOperation experience and the indicators achievedGoals of development and the challenges of todayDevelopment of VVER technologyAdvance designs of large powerAdvance designs of large powerInnovative designs of reactor plants

Page 4: VVER Reactors

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Main design features of VVER

Reactor core with hexahedral assemblies;Horizontal steam generators; Transportability of main equipment by railway;Arranging the spent fuel pool inside the containment;Absence of openings in the reactor bottom; Reactor vessel from forged shells without longitudinal welds;Fuel rod claddings of zirconium-niobium alloy;Reactor vessel of carbon alloy steel;SG tubes of stainless steel with relatively thick wall

Page 5: VVER Reactors

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Main safety features of VVER

Distinctive features of all VVER reactor plants are wide usage of RP inherent safety principle.Capability of VVER RP to limit the development of initiating events as well as of their consequences under accident conditions during a long period within the boundaries of design safety criteria, and is assured by the following structural and design features: –

increased coolant volume above the core; –

increased coolant volume in the primary circuit in respect to fuel mass and thermal power of the core;

increased capacity of the pressurizer; –

reliable natural circulation; –

considerable water inventory in horizontal steam generators on the secondary side.

Page 6: VVER Reactors

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VVER history

1955 – beginning of activities on VVER1964 – commissioning of the first VVER1971 – first standard VVER-4401980 - commissioning of the first VVER -1000

The oldest VVER at Unit 3 of Novovoronezh NPP has been operated since 1971 without replacement of SG, reactor top head and other main components (license till 2016)

Page 7: VVER Reactors

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VVER history

Totally there are 51 NPP Units with VVER in operation (about 20% of population of the pressurized light water reactors)To date accumulated operating life is more than 1290 reactor-years39 Units have been commissioned in the world since 1999 and 8 of them are Units with VVER reactors

Page 8: VVER Reactors

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Operating NPPs with VVER reactors and NPPs under construction

52 NPPs

under construction in the world, of which

14 Units with VVER reactors

Page 9: VVER Reactors

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Indicators achieved

Load factor time history

0

10

20

30

40

50

60

70

80

90

100

1970

1972

1974

1976

1978

1980

1982

1984

1986

1988

1990

1992

1994

1996

1998

2000

2002

2004

2006

2008

Years

Load

fact

or, %

PWR VVER VVER-Russia

Page 10: VVER Reactors

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Indicators achieved

Operating factor time history

30

40

50

60

70

80

90

100

1970

1972

1974

1976

1978

1980

1982

1984

1986

1988

1990

1992

1994

1996

1998

2000

2002

2004

2006

2008

Years

Ope

ratin

g fa

ctor

, %

PWRVVERVVER - Russia

Page 11: VVER Reactors

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Indicators achieved Malfunctions in NPP operation

0

1020

3040

5060

70

1999 2000 2001 2002 2003 2004 2005 2006 2007 2008

trips

important to safety

metal defects relealed

Years

Num

ber o

f mal

func

tions

Page 12: VVER Reactors

12

Trend of the reactor scrams in Russia and worldwide (according to WANO methodology)

0,55

0,250,27

0,49

0,11

0,44

0,270,34

0,480,41

0,50,42

0,56

0,65

0,72

0,60,72

0,490,550,51

0,57

0,66

0,87

0,730,75

1,111,07

0,95

0

0,2

0,4

0,6

0,8

1

1,2

1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008

Russia Worldwide

Scra

ms

per7

000

hrs.

of U

nit o

pera

tion

Years

Page 13: VVER Reactors

13

Collective radiation dose per personnel, VVER Units

0,76

0,570,57

0,6

0,79

0,90,9

0,8

0,70,8

1,1

0,9

1,3

1,4

0,91

1,48

0,6

1,2

1,49

0,59

0,56

0,6

0,7

0,8

0,7

0,9

0,90,9

1,11,2

1,3

0,5

0,6

0,7

0,8

0,9

1

1,1

1,2

1,3

1,4

1,5

1993

1994

1995

1996

1997

1998

1999

2000

2001

2002

2003

2004

2005

2006

2007

2008

RussiaWorldwide

Man

-Si

ever

tspe

r uni

t

Years

Page 14: VVER Reactors

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Goals of development

Challenges of today–

The goal is set to redouble the generation of electric energy at

nuclear power stations of Russia by 2030 having brought it to 25%-30% of total volume of generation. For this purpose 26 NPP Units are to be built. Solution of the problem on the basis of VVER technology.

Page 15: VVER Reactors

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Goals of development

Four Units of new advanced VVER-1200 design are under constructionCommissioning - 2012

Page 16: VVER Reactors

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Goals of development

Challenges of today–

Competitiveness of NPP with fossil-fired power plants:•

Reduction of capital costs and construction period.•

Increase in efficiency and load factor.•

Implementation of load-follow modes.–

Implementation of NPP of the following power range 1600…1200…1000…600…300

MW–

Effective use of VVER in the closed fuel cycle

Safety criteria:–

Meeting the safety requirements of Russian regulations, IAEA recommendations and EUR requirements;

Page 17: VVER Reactors

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Generations of nuclear power reactors

Page 18: VVER Reactors

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Goals of development

New designs of OKB “GIDROPRESS”

10

0-

30

04

00

-6

00

70

0 -

16

00

NP

P e

lect

ric

pow

er, M

W

Year of design development

1980 - 1990 - 1997 - 2006

VVER-1000

V-320

VVER-640

V-413, V-428

VVER-1500

V-392, V-412

V-392М

V-491

VVER-1200

AES-2006

V-466Б

AES-92

AES

-91В-466

AES

-91/99 “Belene”

NPP

Page 19: VVER Reactors

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Goals of development

New designs of OKB “GIDROPRESS”

10

0-

30

04

00

-6

00

70

0 -

16

00

NP

P e

lect

ric

pow

er, M

W

Year of design development

2006 - 2009 - 2015

V-392М

V-491

VVER-600

VVER-300

ВВЭР-1300

VVER-1200А

VVER-SCP

AES-2006

VVER-640

Page 20: VVER Reactors

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Comparison of VVER designsN

et e

ffic

ien

cy o

f U

nit

(%

)

32

34

36

38

40

42

VVER-1000 VVER-1500 AES-2006 VVER-600 VVER-300 VVER-SCP

Page 21: VVER Reactors

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Comparison of VVER designs

Service life (years)

20

30

40

50

60

70

V-392V-428

V-466B

VVER- 1500

AES- 2006

VVER- 600

VVER - 300

Tendencies in VVER

technology

NPP Main equipment Replaceable equipment

to 100 years

Page 22: VVER Reactors

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Conditions necessary for development

Obligatory requirements–

Optimal combination of evolutionary and innovative development–

Mature reference technology reduces risks and simplifies licensing–

Meeting the requirements of regulatory bodies and operators (EUR)–

Meeting the maneuverability requirements –

Possibilities for fuel cycle development including MOX and closing cycleCompetitiveness

Lowest unit capital investments–

Extension of design service life–

Increase in efficiency–

Increase in load factor–

Cut down of the construction time of the standard Unit–

Reducing operation expenses–

Reducing waste

Page 23: VVER Reactors

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AES-2006

Design of AES-2006 with VVER-1200

meets the mentioned trends to the highest extent

Power increased up to 1200 MWtDesign service life is extended to 60 years.Efficiency is increased to 36 %. Load factor is increased to 90 %.The requirements for Unit load-follow conditions are provided in the design

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AES-2006Design of AES-2006 with VVER-1200

meets the

mentioned trends to the highest extentEvolutionary development with application of reference technical solutions based on VVER-1000 and a wide use of up-to-date knowledge and advanced technologies. Current requirements of Regulatory documents and EUR requirements are met.Using of 121 CPS control rods in the reactor core presents wide possibilities for development of fuel cycles including those with MOX fuelDesign value of collective dose for operating personnel per one Unit throughout the whole service life at normal operation of all systems does not exceed 0,4 man·Sv/year.

Page 25: VVER Reactors

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AES –2006 as an example of VVER advantages

Inherent safety properties: –

usage of additional water inventory in hydroaccumulators

of the second stage core cooling system (for NV NPP-2 as compared to VVER-1000 and to PWR).

actuation of control rods under scram due to gravity forces;–

properties of self-limitation of the core power due to negative reactivity coefficients by fuel and coolant temperature and by power;

usage of passive elements, isolation, limiting and discharge devices;

usage of inertia coastdown

of special flywheel masses of RCP set to provide the required drop of flow rate through the core under loss of power.

Page 26: VVER Reactors

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Fuel cycles

To date the 12-month fuel cycle is accepted as the base cycle with annual loading of 43 FAs (4-year fuel cycle) that makes possible to assure the following:

meeting the requirements for length of fuel cycle considering the mass of FAs

loaded;–

limitation of power non-uniformity.In implementation of 18-month fuel cycle:

number of FAs

makeup in equilibrium cycle –

78 pcs.;–

fuel mass in one FA–

530 kg

(первый

этап

модернизации);–

average enrichment of makeup fuel -

4,85 % in

235U;–

operation length

-

521 EFPD

(load factor

~ 0,95);–

maximum burnup

fraction of FAs

(without engineering safety factor) -

64MW*day/kgU;

average burnup

fraction of FAs

unloaded –

46,7 MW*day/kgU.In principle, implementation of 24-month fuel cycle. With this, usage of long-term fuel cycles makes increase in NPP load factor and decrease in efficiency of fuel utilization.

Page 27: VVER Reactors

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Conditions AES-2006 EURPrimary control

Change in Unit power not more than ±5 % Nnom ±5 % Nnom

Rate of power change 1 % Nnom/s Not regulatedNumber of cycles 7·106 Not regulated

Secondary controlChange in Unit power not more than ± 10 % Nnom not more than ± 10 % Nnom

Rate of power change not more than 5 % Nnom/min not more than 5 % Nnom/min

Number of cycles 5·106 Not regulatedPower change of the Unit according to the schedule

Power change of the Unit 50-100-50 % Nnom 20-100-20 % Nnom

Rate of power change not more than 5 % Nnom/min not more than 3 % Nnom/min

Number of cycles 15000 (5 times a week) 2 time/day, 5 times/week 200 times/year

ManeuverabilityOne of the main requirements for current design of RP and NPP is the requirement for possible operation of the Unit in the conditions with changing the load. The list and characteristics of these conditions are prepared taking into account the lists of Russian utility and EUR requirements. Comparison of characteristics of main conditions with changing of load is presented in the Table.

Page 28: VVER Reactors

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Prospective RP designs of large power. Alternative design VVER-1200A (V-501)

Design aim is to minimize cost of construction, manufacturing, mounting and maintenance due to 2-loop arrangement and enlargement of main equipmentDesign concept:–

Cutting down the scopes and periods of construction and mounting work, reducing amount of equipment, delivery of maximum-finished equipment to mounting site;

Increase in unit power of SG and RCP set; –

Increase in the secondary parameters to improve the Unit efficiency.

Keeping the principal VVER solutions, except for SG transportability by railway;

Page 29: VVER Reactors

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Prospective RP designs of large power. Alternative design VVER-1200A (V-501)

Plan view at the elevation of steam generators

Steam generator:–

diameter

5,2 m–

length

20 m–

mass

790 t

Page 30: VVER Reactors

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Prospective RP designs of large power. Alternative design VVER-1200A (V-501)

Vertical section of reactor building

RCP

Pressurizer

Steam generator

HA-2

Reactor

Page 31: VVER Reactors

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Prospective RP designs of large power. Alternative design VVER-1200A (V-501)

Current approaches to optimization of safety systems are realized:

Scheme solutions exclude failures dependent of initiating event:

Simultaneous failures of channels of passive and active systems,

Simultaneous failures of active SS within one channel (HP ECCS and LP ECCS).

The requirement of SS diversity, independency, and redundancy is met;

Redundancy of two-channel system of emergency power supply, during maintenance of station diesel-

generator.

Page 32: VVER Reactors

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Prospective RP designs of large power. Alternative design VVER-1200A (V-501)

VVER-1200 VVER-1200AReactor 940 t 940 tMCP 252 t 145 tSteam generators 4 x450

= 1800

t 2 x790

= 1580 tPressurizer 215 t 215 тRCP set 4 x139

= 556 t 2 x200

= 400

tTotal weight of the primary equipment 3763 t 3280 t

Relative weight of the primary equipment, t/MW(th)

1,18 1,03

Comparison of weights of the primary equipment

Page 33: VVER Reactors

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VVER-1200

EPR

EDF-1300

AP-1000

VVER-1200A

Page 34: VVER Reactors

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Design of horizontal SG for VVER

Does not contradict the idea of reducing the basement area. Allows for compact arrangement of the equipment, easy maintenance and simplifies withstanding of seismic loads;Keeps advantages in the part concerning: –

Reliability (absence of vibrations, damages from foreign objects, no accumulation of sludge at the tube sheet).

Safety (reliable natural circulation, effective gas removal, water inventory, “thick”

tube).–

Convenience of maintenance and repair (easy access on the primary and secondary sides, low irradiation).

Page 35: VVER Reactors

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RP designs of medium power

RP designs of medium power include RP designs for NPP of power range of 300-700 MW el. to meet the regional demands and export to developing countries.Designing of RP of medium power is proposed on the basis of main equipment of RP of large power. This leads to:–

extension of the main equipment service life; –

increase in heat engineering margins of the core cooling; –

less stringent requirements for characteristics of safety systems;

more flexible fuel cycle.

Page 36: VVER Reactors

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RP designs of medium power

RP designs of medium power :–

VVER-640 (V-407)–

VVER-600 (V-498)The designs differ in ratio of application of passive and active safety systems and the systems for BDBA management and methods of their technical feasibility. In both designs the proven technologies, units and systems are used in general, based on experience in operation of the preceding generation of NPPswith VVER.

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RP designs of medium power

Main conceptions of RP with VVER-600:–

usage of the available equipment of designs V-392M and V-491;

2-loop arrangement of RP;–

reactor with 2 inlet and 2 outlet nozzles; –

implementation of optimal application of redundancy, independence and diversity principles for structuring the safety systems with the optimal composition and effectiveness;

implementation of the concept of the core melt confinement under severe accidents inside the reactor vessel owing to inside and outside cooling.

Page 38: VVER Reactors

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RP designs of medium power. RP design VVER-600 (V-498)

Ø 36 m.

Pressurizer

HA-1

RCP

Spent fuel pool

Steam generator

Reactor

Page 39: VVER Reactors

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RP designs of medium power. RP design VVER-600 (V-498)

VVER-1200 VVER-600

Reactor, t 940 700MCP, t 252 115Steam generators, t 4 3450 = 1800 2 3450 = 900Pressurizer, t 215 215RCP set, t 4 3139 = 556 2 3139 = 278Total weight of the primary equipment, t 3763 2208

Relative weight of the primary equipment, t/MW(th) 1,18 1,38

Comparison of weights of the primary equipment:

Page 40: VVER Reactors

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RP designs of small power

RP designs of small power include RP designs for NPP with electric power of 300 MW for the regions with small grids.In OKB “GIDROPRESS” the design of 2-loop reactor plant VVER-300 is on the stage of feasibility study.The design is based on technical solutions on the equipment of the preceding designs of RP V-407.

Page 41: VVER Reactors

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RP innovative designs. One-circuit RP VVER-SCP with supercritical coolant pressure

VVER-SCP meets the target indicators of IV-generation VVER to the highest extent.Advantages of the proposed design: –

High efficiency

(42 -

45%);–

High breeding factor (>0,8);–

Low capital costs (reducing of: metal consumption; nomenclature and number of equipment and systems; containment sizes);

Application of the proven VVER technology and SCP boiler-turbine units.

Reactor VVER-SCP with the core of single pass of coolant

Page 42: VVER Reactors

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Conclusion

VVER reactor plants are based on technical solutions that proved their reliability and effectiveness in the course of morethan 40-year operation experience.The developed designs implement the evolutionary concept of VVER reactor plants oriented not only towards safety assurance of Units, but also towards increasing their economic efficiency.The main ways in improving the economic efficiency of reactor plants are demonstrated. The considered trends in development are indicative of high potential of VVER technology development for solving the problems of power engineering in the long-term outlook.