Fulfillment of User Requirement UR 1.6 independence of DiD ... 2... · RPS N/A JDH (ATWS) N/A Drop of the CPS absorbing rods into the core under gravitation GICS JDH (ATWS) N/A Drop

Denis Kolchinsky

Project Chief Engineer

Fulfillment of User

Requirement UR 1.6 –

independence of DiD levels

in AES-2006 design

19-22 November, 2013 INPRO Forum, IAEA, Vienna

State Atomic Energy Corporation ROSATOM

Branch of Joint Stock Company «East-European leading scientific research and design

institute for energy technology»

Saint-Petersburg R&D Institute “Atomenergoproject” (SPbAEP)


An assessment should be performed for an INS to

demonstrate that different levels of defense-in-depth are met

and are more independent from each other than for existing

systems.

User requirement UR1.6


Defense-in-depth is a main philosophy to ensure nuclear safety

for all nuclear power plants.

The independence of DiD levels is an essential strategy to

ensure the design safety concept success.

The fundamental states


Assessment of Defence in Depth for Nuclear Power Plants. Safety Reports Series No.46.

Guidance for the Application of an Assessment Methodology for Innovative Nuclear Energy Systems. INPRO Manual — Safety of Nuclear Reactors . Tecdoc 1575 Volume 8.

WENRA Report Safety of new NPP designs. Study by Reactor Harmonization Working Group RHWG, March 2013

References:


NPP safety is assured at the expense of sequential implementation of the

defense-in-depth concept based on using the system of physical barriers on the

way of spreading of ionizing radiation and radioactive substances into the

environment and the system of organizational and technical measures on

protection of the barriers and keeping their efficiency, as well as on protection of

personnel, population and the environment.

fuel matrix (pallets)

fuel rod cladding

reactor coolant system

boundary

primary containment

Physical barriers

Level 1. Prevention of abnormal operation

and failures.

Level 2. Control of abnormal operation and

detection of failures.

Level 3. Control of accidents within the

design basis

Level 4. Severe accident management.

Level 5. Emergency planning.

Organizational and technical measures

Defense-in-depth concept

The same for V-320

and AES-2006


Fundamental safety functions

Fundamental safety functions are aimed at fulfillment of the tasks

of physical barrier protection on the way of radioactive substances

propagation:

Reactivity monitoring and control;

Provision of reliable heat removal from the reactor core:

Keeping the coolant inventory with leaky primary

circuit;

Provision of primary circuit integrity (with leak-tight

primary circuit);

Provision of heat removal by the secondary circuit;

Localization and reliable retention of radioactive fission

products.


DBC and DEC definition


DEC

DBA

Level 3

3a

Control of accident

to limit radiological

releases and

prevent escalation

to core damage

conditions

Using engineering safety facilities and accident management

procedures:

- prevention of escalation of initiating events to DBA and of

DBA to BDBA by the use of reactor protection system, safety

systems and accident procedures;

- mitigation of consequences of accidents which failed to be

prevented, by localizing radioactive release;

- postulated single initiating events.

- prevention of core damage by additional safety features and

accident procedures in case of safety function failure at the

level 3a;

- postulated multiple failure events;

- considered CCF of I&C and CCF of mechanical equipment.

3b

In April 2013 there new report with defense in depth (DiD) requirements for

new reactors was issued by WENRA. In particular there has been stated that

the third DiD level shall be divided into two sub-levels:

New safety requirements and challenges


Guides and

Owner

Requirements

Design

Just

ific

atio

n

Assessment

Modification

Deterministic and Probabilistic Approaches

Generally independence justification analyze is performed using

deterministic approach (including hazards analysis) and than

technical solutions are verified by probabilistic method.


Deterministic Approach

Level 1

Level 2

Level 3a

Level 3b

Level 4

SSC-1

SSC-2

SSC-3

SSC-4

SSC-1

Set of SSC DiD level Each set of SSC includes:

-Mechanical SSC

-I&C

-Electrical sources

-etc

Saf

ety d

egra

dat

ion

In each defense-in-depth level the special set of SSC for implementation

of all necessary safety function is provided the design.


Safety Functions

Reactivity Control

Core Cooling

Primary Circuit Heat Removal

Prevention of Primary Circuit Damage

Prevention of Activity Release

Rea

ctor

con

trol

an

d

pro

tect

ion

syst

em

Low

an

d h

igh

pre

ssu

re i

nje

ctio

n t

o

the

pri

mary

cir

cuit

, P

ass

ive

inje

ctio

n f

rom

acc

um

ula

tors

, in

term

edia

te

cooli

ng c

ircu

it s

yst

em

Em

ergen

cy f

eed

wate

r

Ste

am

dis

cha

rge

to t

he

atm

osf

ere

Pre

ssu

rize

r sa

fety

valv

es

Pri

mary

cir

cuit

safe

ty v

alv

es o

f lo

w

pre

ssu

re

Cu

toff

valv

es s

yst

em,

Em

ergen

cy

spra

y s

yst

em,

Hyd

rogen

rec

om

bin

ers,

C

hem

ical

reag

ents

su

pp

ly

Reactor Coolant Inventory

• Secondary Heat Sink • Steam Generator Feed

Pressure Limitation in Reactor Coolant System

• Pressure Limitation in Containment • Cutoff the Containment • Heat Removal from the Containment

• Reactor Shutdown • Reactor Power limitation • Subcriticaly in Shutdown Condition

Em

ergen

cy b

oro

n i

nje

ctio

n

syst

em,

volu

me

an

d b

oro

n

con

trol

syst

em

Main

Poss

ibil

ity t

o u

se t

wo h

igh

p

ress

ure

in

ject

ion

pu

mp

s in

stea

d o

ne

low

pre

ssu

re p

um

p

Pass

ive

hea

t re

moval

syst

em v

ia

stea

mgen

erato

rs

Pass

ive

hea

t re

moval

syst

em f

rom

th

e co

nta

inm

ent

Div. Main Div.

Main Div. Main Div.

Main Div.

Safety Functions Diversity


Safety levels Level 1 Level 2 Level 3a Level 3b (DEC-A) Level 4 (DEC-B)

Level name Control under NO and Prevention of AOO Prevention of DBA

Control of DBA and

prevention BDBA BDBA management without core melting Severe Accidents

Technical Features Technical features of normal operation Technical features of normal operation Safety systems I&C Common Cause Failure Mechanical Features Common Cause Failure

Канал

электроснабжения

технологической

системы

5 / 6 1 / 2 / 3 / 4 Internal self-

protection

5 / 6 1 / 2 / 3 / 4 Passive principle

1 / 2 / 3 / 4 5 / 6 1 / 2 / 3 / 4 7 / 8 Passive principle 5 / 6 1 / 2 / 3 / 4 7 / 8 Passive principle 7 / 8 Passive principle

Reactivity control

Power limitation and/or

reactor shutdown

APC, GICS PP Feedback APC, PLC, PP,

SPP

PP Drop of the CPS

absorbing rods into

the core under

gravitation

RPS N/A JDH (ATWS) N/A Drop of the CPS

absorbing rods into

the core under

gravitation

GICS JDH (ATWS) N/A Drop of the CPS

absorbing rods into

the core under

gravitation

N/A Core melt is

subcritical

Control of self-

supporting fission

chain reaction

APC, GICS,

KBA

N/A N/A APC N/A ECCS HP,ECCS

LP, heat exchangers

of ECCS

N/A ECCS HP N/A JDH (ATWS)

Subcriticality assurance KBA, KBC

equipment

N/A N/A KBA, KBC

equipment

N/A N/A Elimination of boric

delution (cut-off

valves)

N/A Elimination of boric

delution (cut-off

valves)

N/A AT KBA and KBC

equipment

JDH (ATWS) N/A AT N/A Properties of the core

catcher sacrificial

material

Heat removal from

reactor core

Coolant reserve

maintenance at primary

circuit leakiness

KBA N/A Considerable

volume of the

coolant in PRZR

and PCP

KBA N/A N/A ECCS HP, AT,

ECCS LP

N/A ECCS HP N/A AT KBA JDH N/A AT N/A N/A

Pressure maintenance

in the primary circuit

TEH, controller

of the injection

into PRZR

N/A Design solutions

of PRZR

TEH, controller of

the injection into

PRZR, quick-acting

injection valves

N/A N/A PPOSV N/A N/A N/A PPOSV use of

spring

Controller of the

injection into

PRZR, quick-acting

injection valves

N/A N/A PPOSV use of

spring

N/A N/A

Provision of heat

removal by the primary

circuit systems

RCPS-SG-

Reactor

Under cooldown:

ECCS LP, heat

exchangers of

ECCS

N/A RCPS-SG-Reactor

(train 5/6) Under

cooldown:

ECCS LP, heat

exchangers of

ECCS (train

1/2/3/4)

Under cooldown:

ECCS LP, heat

exchangers of ECCS

Continuous inertial

rundown of RCPS

under the action of

special rotating

masses

ECCS LP, heat

exchangers of

ECCS

N/A N/A N/A Continuous inertial

rundown of RCPS

under the action of

special rotating

masses

N/A N/A N/A

(if required Feed

and bleed through

additional control

line of PPOSV)

Continuous inertial

rundown of RCPS

under the action of

special rotating

masses

SG PHRS, (

provision <1МПа)

Core catcher cooling

with water from

inspection shafts,

fuse valve

Pressure maintenance

in the secondary circuit

TG CV N/A Design solutions

of SG

BRU-K N/A N/A BRU-A, SG POSV N/A N/A N/A SG POSV (passive,

use of spring)

BRU-K N/A N/A SG POSV (passive,

use of spring)

N/A SG POSV (passive,

use of spring)

Provision of heat

removal by the

secondary circuit

systems

TG, BRU-K,-

SN,-D SEFP,

EFP, CP, RP

N/A Considerable

volume of SG

boiler water

BRU-K,-SN,-D

SEFP, EFP, CP, RP

N/A N/A EEFP, BRU-A N/A N/A SG PHRS, makeup

pump of PHRS and

fuel pool

SG POSV (passive,

use of spring)

BRU-K,-SN,-D

SEFP, EFP, CP,

RP, Technical

Condencer

N/A SG PHRS, makeup

pump of PHRS and

fuel pool

SG POSV (passive,

use of spring)

SG PHRS N/A

Limitation of fission

products release

Limitation of pressure

inside the containment

NO ventilation N/A Design solutions,

safety margins

NO ventilation N/A N/A JMN (spray system) N/A N/A Makeup pump of

PHRS and fuel pool

Containment vessel

PHRS, passive

autocatalytic

hydrogen

recombiner

N/A N/A Makeup pump of

PHRS and fuel

pool

Containment vessel

PHRS, passive

autocatalytic

hydrogen

recombiner

Make up pump of

PHRS and fuel pool

Containment vessel

PHRS, passive

autocatalytic

hydrogen recombiner

Localization inside the

containment

NO ventilation N/A Design solutions,

safety margins

NO ventilation N/A N/A Localization of SV

JMN (spray system-

chemicals supply

into SV)

N/A N/A N/A Containment N/A N/A N/A Containment N/A Containment, core

catcher

Localization in the

annular space

HVAC

(Ventilation in

the annular

space) (NO)

N/A Design solutions,

safety margins

HVAC (Ventilation

in the annular

space) (NO)

N/A N/A KLC (Ventilation in

the annular space)

KLG (isolation of

ventilation in the

annular space from

ventilation systems)

N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A

Localization in SG N/A N/A Design solutions,

safety margins

N/A N/A N/A MSIV, localizing

valves of SG

blowdown, valves

of feedwater,

emergency

feedwater, isolation

gate valve upstream

BRU-A) JDH on

injection in PRZR -

during primary-to-

secondary leakage.

N/A MSIV, localizing

valves of SG

blowdown, valves

of feedwater,

emergency

feedwater, isolation

gate valve upstream

BRU-A) JDH on

injection in PRZR -

during primary-to-

secondary leakage.

N/A N/A N/A Motor-operated gate

valve in steam line

N/A N/A N/A N/A

Localization in

auxiliary systems

N/A N/A Design solutions,

safety margins

N/A N/A N/A Localizing valves

on auxiliary systems

N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A

Supporting systems

I&C system NO I&C NO I&C N/A NO I&C NO I&C N/A ESFAS N/A Hard Wired Deversity I&C N/A NO I&C ESFAS I&C for BDBA N/A I&C for BDBA N/A

Power supply NO power supply NO power supply N/A NO power supply,

RGM, ASB, unit

SB

Emergency DG N/A Emergency DG,

emergency SB

N/A Emergency DG,

emergency SB

SB for BDBA,

movable DG

N/A Unit SB emergency SB SB for BDBA,

movable DG

N/A SB for BDBA,

movable DG

N/A

HWAC HWAC for NO HWAC for NO N/A HWAC for NO HWAC for NO N/A Ventilation in

Safety building

N/A Ventilation in

Safety building

N/A N/A HWAC for NO N/A HWAC for BDBA N/A N/A N/A

Cooling water PGB KAA, PEB N/A PGB KAA, PEB N/A KAA, PEB N/A KAA, PEB N/A N/A PGB N/A N/A N/A N/A N/A

Safety class of

technical features

(according Russian

standards)

2

3

4

Conservative and

passive means

Analyzing Approach


Probabilistic Assessment

IAEA requirement:

CDF=10-5 1/r*y

LRF=10-7 1/r*y

AES-2006 result:

CDF=5,9 10-7 1/r*y

LRF=3,7 10-9 1/r*y


Denotation Postulated Initiating Event Loss of a safety system

ATWS Anticipated Transient Fast shutdown

Station blackout Loss of off-site power Emergency power supply

Total failure of all computer I&C systems

Loss of normal operation I&C ESFAS

Total loss of feed water Loss of main feed water Emergency feed water supply

CCF at LOCA Small LOCA High pressure emergency injection system.

“Heavy” commercial aircraft crush

Extremely external impact Dismantling of safety building and loss of all safety systems in it

Some examples of common cause failure events postulated

in the design are presented in the following table.


Conclusions

Assessment in accordance with INPRO methodology

hadn’t been implemented for AES-2006 design, but

All necessary information for the assessment is

contained in the design documentation

Analyzes implemented by other method had improved

that Criterion 1.6.1 is met

THANK YOU FOR THE ATTENTION !


Documents

Fulfillment of User Requirement UR 1.6 independence of DiD ... 2... · RPS N/A JDH (ATWS) N/A Drop of the CPS absorbing rods into the core under gravitation GICS JDH (ATWS) N/A Drop