Development of EOG for a RR

Hyeonil Kim

Safety Analysis

RR Core Design Division

2014. 11. 17

International Group on Research Reactor 2014 / IAEA Technical Meeting

San Carlos de Bariloche, Argentina, November 17-21, 2014

Contents

Regulatory Background of EOPs

Basic Concepts of EOPs

Red Line about Development of EOGs for a RR

EOG for a RR

Concluding Remarks

2

Regulatory Background of EOPs

Nuclear Power Plant

• NUREG-0578, 0660, 0737, 0899, 0800

− Guideline for the Preparation of EOPs

− Plant specific technical guidelines

− Safety analysis including Multiple failure

− Natural circulation included

3

Regulatory Background of EOPs

Nuclear Power Plant(Continued)

• INSAG Basic Safety Principles for NPP, 75-INSAG-3 Rev. 1, INSAG Series No. 12

− EOPs are established and documented and approved to provide a basis for suitable operator response to abnormal events.

− EOPs are an important component of the defense in depth concept for NPP operation.

• IAEA Safety Standards Series NS-R-2 Safety of NPPs: Operation

− OPs shall be developed which apply comprehensively for normal, abnormal and emergency conditions… The guidance provided in the procedures shall be clear, concise, and as far as possible verified and validated… Strict adherence to written operating procedures shall be an essential element of safety policy at the plant

− Either event based or symptom based procedures shall be developed for abnormal conditions and design basis accidents. Emergency operating procedures or guidance for managing severe accidents (beyond the design basis) shall be developed.

4

Regulatory Background of EOPs

Nuclear Power Plant (Continued)

• IAEA Safety Standards Series NS-G-2.2 OLC and OP for NPP

− Emergency operating procedures (EOPs) may be developed as event oriented or symptom oriented. For DBAs, both approaches can be used, although symptom oriented procedures are preferable for the reasons stated in para. 8.12. For beyond design basis accidents, owing to the wide variety of conditions that may exist, symptom based EOPs and accident management guidance are preferable.

− Event based EOPs specify operator actions on the basis of the determination of the event. For event based procedures, the decisions and measures to respond to accidents should be made on the basis of the state of the plant in relation to predefined events, which are considered in the design and safety analysis report. In using the event based approach, the operator must identify the specific DBA before the recovery and/or mitigatory operator actions have begun.

− Symptom based EOPs can resolve some of the limitations of the event based approach by formally defining and prioritizing the major critical safety functions. …

5

Regulatory Background of EOPs

Research Reactor

• IAEA Safety Standards Series NS-R-4 Safety of Research Reactor: Safety Requirements

− Para. 7.51: Operating procedures shall be developed for all safety related operations that may be conducted over the entire lifetime of the facility, including (a) ~ (o) .... (g: the reactor operator’s response to AOO, DBA, and, to the extent feasible, to BDBAs, h: emergencies)

− Para. 7.72: Emergency plans shall be prepared for a research reactor facility to cover all activities planned to be carried out in an emergency. Emergency procedures shall be prepared by the operating organization, in accordance with the requirements of the regulatory body, and in co-operation, where necessary, with the appropriate governmental and local authorities or other bodies, to ensure the effective co-ordination of all site services and of external aid in an emergency.

− Para. 7.74: The emergency plan shall be implemented by means of emergency procedures in the form of documents and instructions detailing the implementation actions and the arrangements required to mitigate the consequences of the emergency. The emergency plan and procedures shall be reviewed at specified periods and shall be amended as necessary to ensure that lessons learned are incorporated.

6

Regulatory Background of EOPs

Research Reactor (Continued)

• IAEA Safety Standards Series NS-G-4.4 Operational Limits and

Conditions and Operating Procedures for Research Reactor

− Para. 5.53: Emergency procedures should be prepared, and they should be a

component of the emergency plan. Their development should be based on the

evaluation and analysis of all aspects of possible emergencies. The procedures

should specify the methods and duties of intervention staff and the emergency

actions that are necessary to mitigate the possible consequences of the

emergency. They should refer to the emergency facilities and emergency

equipment.

7

Basic Concepts of EOPs

Reference: Basic Safety Principles for NPP 75-INSAG-3 Rev.1, INSAG-12 (1998)

8

Basic Concepts of EOPs

Reference: IAEA SRS NO. 48 Development and review of Plant Specific EOPs

9

Basic Concepts of EOPs

EOP terminology

• Scenario dependent/scenario independent approach

• Event based procedures: the 1st sets used at NPP before TMI

− A well defined set of anticipated events

− Operator recognizes which particular event is actually going on

− The event will evolve in a certain predetermined way

• Symptom-based procedures: events can evolve differently than predicted due to a combination of events and operator errors over time

− Not necessarily one from a limited predefined list

− The event evolves in a way that might be very different

− The tool for the operator to diagnose and recognize the possibly very complex event

10

Basic Concepts of EOPs

Human aspects of EOP development and implementation

• Format of EOPs

− Shown to affect the reliability of the control room team in upset situations -> writer’s guide

• Operator versus safety system logic

− Safety system logic is not optimized for lesser events -> override safety functions

• Level of computerization

− Full paper EOPs, no computerization: The easiest to develop and the least investment

− Stand-alone computerized EOPs/On-line computerized EOPs

• Role and attitudes of the control room staff

− Clearly defined roles and responsibilities

− Active involvement in the development of the procedures

11

Redline about Development of EOG for a RR

Principles about development of an EOG for a Research Reactor

a. Best available technical information for writing reactor-specific EOP

b. Reference system of EOP

c. Optimized to RRs based on practices in Power reactors

d. Symptom based

e. Consistent with the design bases and Defense-in-depth in RRs

f. Cope with all possible accident situations

Scope of the EOG: from reactor trip to safe shutdown

a. DBAs

b. Situations that cannot be clearly diagnosed

c. Multiple simultaneous failures

d. Continuous diagnosis

e. Shutdown accidents

12

EOG for a RR: Safety Functions

13

EOG for a RR: Structure of EOG

14

EOG for a RR: Structure of EOG(Continued)

15

EOG for a RR: Event-based Guidelines

Standard Post Trip Action (SPTA)

• Entry condition: reactor trip

• Exit condition: if all criteria met then reactor trip, otherwise go to Diagnostic Action

• Instructions and contingency actions

− Verify 5 safety functions against acceptance criteria

▫ Instruction: Power decreasing

▫ Contingency Action: RPS, APS manual trip switch on or de-energize power to CRDM electromagnets and SSDM solenoid valves

• Bases for each 5 safety functions

16

EOG for a RR: Event-based Guidelines(Cont’d)

17

EOG for a RR: Event-based Guidelines (Cont’d)

Diagnostic Actions

• Entry/Exit

• Diagnostic actions

• Safety Functions Status Check

• Supplementary information

• Bases

18

Diagnostic Action-Start

Reactivity ControlSatisfactory?

At least single Class 1E

125V DC bus powered?

Off-site power /PCS pumpssatisfactory?

Radiation controlSatisfactory?

Y

Y

Inventory ControlSatisfactory?

SRG

entr

y

N

Reactor Tripentry

LOCA

entr

y

N

Are All Safety Function acceptance criteria met?

Y

Y

Y

Y

N

LOO

P/LO

FCen

try

N

N

N

Perform DA's SFSC

EOG for a RR: Event-based Guidelines (Cont’d)

Reactor Trip (RT)

• Entry condition: all safety function acceptance criteria met

• Exit condition: not confirmed, any SFSC not met

• Instructions and contingency actions

− Verify 5 safety functions against acceptance criteria

• Safety Function Status Check

• Supplementary Information

• Placekeeper

• Bases

19

EOG for a RR: Symptom-based Guidelines

Procedure

• Entry/Exit

• Entry procedure

• Resource Assessment Trees

• Safety Functions Status Check

• Placekeeper

• Supplementary information

• 5 Safety Function control

• Long Term action

20

EOG for a RR: Symptom-based Guide... (Cont’d)

Resource Assessment Trees

21

Concluding remarks

EOP will be a increasingly important component of

defence in depth and is prepared as an essential element

of Emergency Plan

an EOP should be prepared to cover even BDBAs in

Symptom-based in a research reactor

A generic EOG focused on the critical safety functions

covering from reactor trip to safe shutdown is proposed,

possibly applicable to reactor-specific procedures

22

Gracias por suatencion!

Hyeonil Kim

KAERI