ÚJV Řež, a. s.

Energoprojekt Praha division

Design implementation of Stress-test measures on Czech and Slovak NPPs

11/2013

After Fukushima activities – CZ and SK NPPs

This presentation focuses design activities on

CZ NPPs (Temelin12, Dukovany1234)

SK NPP MO 34 (still under construction)

The result of stress test analyses (~National reports) quite well defined needed actions and improvement of safety functions.

Technical solution of safety measures was defined very generally (no feasifibility studies performed), accenting these main aspects:

High withstand level against more severe extreme external events (combinations)

All Units on site can be affected

Reactor and SFP can be affected simultaneously

Various modes of the Unit considered (power operation, refueling,….)

Added safety measures should be diverse/independent on existing systems

Mobile equipment strongly preferred

Big press on short deadlines (conceptual design, detailed design, commissioning)

2

3

Example of original technical ideas

TB30

2x500m3

TX

3x500m3

GA201,500m3

TX10,20,30

PG2 PG3 PG4

TQ22

TQ30

TM

TG11,12,13

M 140kW

alternativně

III.kat.NZN

M

III.kat.NZN

880kW

I.kat.ZN

CV02

(CW02)

CV03

(CW03)

TQ14(24),

TL, UV

40kW

nová zařízení/potrubní trasy – technologie

flexibilní propoje

nová zařízení elektro

Diverse Makeup System

(Reactor / SFP / Sump)

Diverse EFW System

140kW

SBO DG

4

Before Fukushima status of NPPs

(example of MO34)

External AAC (Grid) not

available for several days

– SEISMICITY,…

Interconnections 6kV

cannot be used because

ALL UNITS

are affected by the

EVENT

Functionality for SA with

just SINGLE common DG is

under question (for min.

3days, after seismicity ???)

The SBO „After Fukushima“

is not solved !!

5

Design considerations

Design environment

CZ legislation does not cover DEC (SBO, SA) ( ̶ )

CZ NPPs are in operation ( ̶ )

SK legislation includes requirements on DEC (SBO, SA) (+)

SK NPP MO34 is under construction – Basic desig level still opened (+)

Diversity and independence of new safety measures

New equipment is only partly diverse. No time for technical development of new robust principles.

Independence / separation resolved quite well (because it is standard design principle in NPPs)

6

Design considerations

Targeting of safety measures

It is difficult to forecast the type of disaster in Central Europe. New safety measures

are therefore focused on improvement of essential safety principles of NPPs

More robust Defence in Depth (in all DID levels, main accent to level DID 4 – IAEA system)

Additional safety functions for DEC

DID

sublevel

Purpose Description Note CZ SK (MO34)

4.1 A SA

prevention

SBO single unit, other unit in

DBC, external AAC

Designed before

Fukushima

4.1 B SBO single unit, other unit in

DBC, internal AAC

4.1 C SBO ALL units, internal AAC,

with UHS

New after Fukushima

4.1 D SBO ALL units, internal AAC,

without UHS

4.2 A SA

mitigation

SA single unit,

other unit in DBC

Designed before

Fukushima

4.2 B SA single unit,

other unit in SBO

New after Fukushima

4.2 C SA ALL units,

after SBO development

7

Mobile or stable equipment?

Feature (vlastnost) Mobile Stable

Protection against event

-On site (close)

-On site (distant)

By transport

Bunker

Bunker

By distance

Bunker

Bunker

Transport Expected problems (mainly with

heavy, powerfull equipment)

N/A – stable equipment

Connection (připojení) Where? How? Who?

(difficult in real disaster situation)

Permanently

connected, prepared

Start of function

(Náběh funkce)

After connection, with large

time delay

Fast (minutes),

automatic

Voltage and Power

(Napětí a výkon)

LV (400V) close to consumers

Low power - (sensitive on

behavior of consumers and failures

in distribution)

MV (6kV) – protection by

distance possible

High power – non

sensitive, tolerates

mistakes, transients

Compatibility with EEPS

Kompatibilita s SZN

Incompatible (selectivity

corrupted)

Compatible (selectivity

is kept)

Testing – for functionality in

real disaster situation

Testovatelnost – pro

funkčnost v reálné situaci

Test of transport, connection …

impossible (simulation will be

demanding for operation staff –

military skill needed)

Regular periodical

tests possible (similar

as for design EEPS)

8

Design considerations

Location of stable equipment

SZN 1

SZN 2

SZN 3

Blok č. 2

R

Strojovna

Výměn. stanice

2GX

2GW

2GV

1GX

1GW

7GK

7GJ

1GV

BJ CJ

BK CK

DGS

SZN 4, 5

Strojovna

Výměn. stanice Rozv.

normál. napá-jení

Blok č. 1

BJ CJ

BK CK

Rozv. normál. napá-jení

DGS DGS

NPP Temelin: Layout scheme of EEPS and AAC grid

R R

9

Design considerations

Location of stable equipment

AAC DG 1 AAC DG 2

SZN 1

SZN 2

SZN 3

Blok č. 2

R

Strojovna

Výměn. stanice

2GX

2GW

2GV

1GX

1GW

7GK

7GJ

1GV

BJ CJ

BK CK

DGS

SZN 4, 5

R

Strojovna

Výměn. stanice Rozv.

normál. napá-jení

Blok č. 1

BJ CJ

BK CK

Rozv. normál. napá-jení

DGS DGS

NPP Temelin: Layout scheme of EEPS and AAC grid

10

Design considerations

Common features of stress tests safety measures-1

NPPs will have following significantly improved safety features after

design and implementation of stress test measures:

Increased robustness of DID (further independent sublevels in relation to

every detected “cliff edge” effects).

Wider scope of NPP accident operating modes and accident scenarios

addressed. DEC considered even at all Units on site.

Previous safety measures and procedures sufficient for coping with less

difficult events are usually preserved

New safety measures must not decrease performance of design basis

safety functions

11

Design considerations

Common features of stress tests safety measures-2

Minimization of the need of human intervention during the first phases of accident

scenarios declared in some cases is not realistic. Particularly due to effort for more

economical design significant scope of direct human actions is needed.

Higher preference is given to “passive” or manually operated systems (i.e. storages

of coolant, longer battery autonomy time, battery supplied or manual actuations,

etc.)

Emphasis was given to keep the plant in “safe” conditions within 72 hours from the

accident onset, also with the support of in-site contributions. Later is assumed

effective external help and repair of some portion of DBC systems.

The combination of mobile and stable means is used. Hardened stable means are

more essential, mobile more backup. Use depends on the event and scenario of

solution. Flexibility is accented.

Design solution enables fulfillment of safety functions even upon failures of

equipment. The principle of functional groups (FSK) is used. Preventive measures

(coping with SBO) have higher ability to cope with failures. For SA mitigation

measures is this ability at least partial.

12

Mochovce 3,4 – „stress test measures“

SAXSNAXS

DGDGDG

EE

PS

1

EE

PS

2

EE

PS

3DG DG DG

EE

PS

1

EE

PS

2

EE

PS

3DG

Common DG

SBO sectionK L M KLM

G

H

DG

mDG mDG

X XX X X

Supply selected LV part

DG

X

3BMH55

M

ESW

G

H

X X

M ESW

Supply selected LV part

EMO12

EMO12affected by SBOX

XX XX

Contacts

Addressa: Vyskočilova 3/741, 140 21 Praha 4

Jan Anděl

Tel.: +420 241 006 910

E-mail: jan.andel@ujv.cz

Web: www.ujv.cz

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