Assessment of stress state of Kalinin Kalinin Unit 2 Unit 2 - - PowerPoint PPT Presentation

Assessment of stress state of Assessment of stress state of Kalinin Kalinin Unit 2 Unit 2 Containment Containment

V. V.Medvedev Medvedev, F. , F.Ulyanov Ulyanov, , A. A.Kiselev Kiselev, A. , A.Kiselev Kiselev, V. , V.Strizhov Strizhov

Sixth International Information Exchange Meeting Sixth International Information Exchange Meeting 8 8-

• 12 April 2002, Kiev

12 April 2002, Kiev

Russian Academy of Sciences Nuclear Safety Institute (IBRAE)

Computer Code CONT

I I Designed for numeric simulation of concrete

Designed for numeric simulation of concrete containment behavior under quasi containment behavior under quasi-

• static operational

static operational and accident loads and accident loads

I I Program capabilities:

Program capabilities:

N N Non

Non-

• linear elastic and plastic problems

linear elastic and plastic problems

N N Reinforcement and

Reinforcement and prestressing prestressing

N N Cracking of concrete

Cracking of concrete

N N Temperature distribution

Temperature distribution

I I Realization

Realization: :

N N 2D Axial symmetry model

2D Axial symmetry model

N N 3D model with the use of

3D model with the use of superelements superelements

I I Certified in the

Certified in the Gosatomnadzor Gosatomnadzor of RF

• f RF

CONT Code Verification

I Verification against analytical problems I Validation against experimental data:

N Small scale model experiments conducted in

Russia

N 1:6 Sandia reinforced containment test N 1:4 Sandia prestressed containment tests (in

progress)

I I Comparison to NPP data (

Comparison to NPP data (Kalinin Kalinin VVER VVER-

• 1000)

1000)

Kalinin-2 NPP Containment Main Geometrical parameters

I I

Main design peculiarities of Main design peculiarities of the containment the containment

N N

Geometry of the containment Geometry of the containment

N N

Reinforcement Reinforcement

N N

Presstressing Presstressing system system

I I

Methodology of analysis for Methodology of analysis for prestressed prestressed concrete concrete containment containment

I I

Nodalization Nodalization scheme of the scheme of the containment containment

I I

Results of the analysis under Results of the analysis under normal operation and normal operation and accident conditions accident conditions

Computational model of the Kalinin Unit-2 Containment The computational The computational model includes model includes 67946 finite elements 67946 finite elements and 76014 nodes and 76014 nodes

Computational model of the concrete wall

I I

1 1 – – metallic liner metallic liner

I I

2, 4, 6, 7, 9, 11 2, 4, 6, 7, 9, 11 – – concrete concrete layers layers

I I

3, 10 3, 10 – – meridian meridian reinforcement reinforcement

I I

5, 8 5, 8 – – hoop reinforcement hoop reinforcement

.

Scheme of the reinforcement in the middle of cylindrical part of containment

Location of tendons in the cylindrical part of Kalinin-2 containment

Methodology of analysis

Factors considered:

I Concrete cracking in

case of reaching ultimate stretching strengths

I Presence of internal

metallic liner

I Concrete reinforcement

including its strengthening in the areas of stress concentration Loads considered:

I Tendons prestressing I Inherent weight of

containment

I Thermostresses due to

non-steady state temperature gradients under operational and accident conditions

I Variation of internal

pressure in course of accident

Peculiarities of simulation prstressing of tendons

I Real tendons trajectories I Strength reduction along tendons due to friction I Strength reduction from the jack to anchor I Real strength of tendons according to plant data

Stresses in liner (internal surface) and concrete (outer surface) due to inherent weight (MPa) Meridian stresses (SM) Meridian stresses (SM) Hoop stresses (ST) Hoop stresses (ST)

Defornmation of containment due to prestressing of tendons

I Real strengths in

tendons were applied

I Scale factor for

deformations 500

Meridian stresses in the concrete due to prestressing of tendons

Hoop stresses in the concrete due to prestressing of tendons

Stresses in liner (internal surface) and concrete (outer surface) due to internal pressure 1 MPa Meridian stresses (SM) Meridian stresses (SM) Hoop stresses (ST) Hoop stresses (ST)

Temperature distribution in the concrete in normal

• peration conditions

Inside temperature +40 °С Outside temperature –20 °С

Stresses in liner (internal surface) and concrete (outer surface) due to operational temperature Meridian stresses (SM) Meridian stresses (SM) Hoop stresses (ST) Hoop stresses (ST)

Calculated temperature variation at different location in the time interval between 13.09.99 through 29.12.99 at different depths

• 30
• 20
• 10

10 20 30 40 50 200 400 600 800 1000 1200 1400 1600 1800 2000 2200 2400 2600 2800 3000 Time , hr Temperature, C

Облицовка (внутре нняя пове рхность) Внутре нняя арма тура Сре динный слой Наружна я а рма тура Наружна я пове рхность 1507 1508 1509 2501 2502 2503 3505 3506 3507 T-сре ды внутри T-спе ды сна ружи

Air temperature inside Air tempera ture outside Liner Internal reinforcement Middle reiforcement Outer reinforcement Outer surface

Temperature distribution through containment wall on 29.12.1999 with the account of inside and outside temperature variations

Hoop stresses in the concrete due to temperature gradients

Variation of temperature and pressure in the containment for design accident t - time (hr) from accident

Stresses in liner (internal surface) and concrete (outer surface) due to operational temperature Meridian strength (SM) Meridian strength (SM) Hoop strength (ST) Hoop strength (ST)

Meridian and hoop strength [MN] in the horizontal sections, Z=25 m (a) и Z=60.5 m (b) at the initial time instant a) a) b)

Conclusions

I The state of the Kalinin Unit 2 containment is at the

reasonable level under actual strength (800 tones) both for operational and accident conditions

I The CONT code allows to account for a number of

factors influencing stress-strain state of the containment under operational and accident loads

I Assessments performed with the CONT code allows

to develop methodology of operational safety control accounting for actual state of prestressing tendons which require strengthening to recover necessary prestressing level