行政院原子能委員會核能研究所 stress test evaluations of taiwan's nuclear power...

行政院原子能委員會核能研究所行政院原子能委員會核能研究所

Stress Test Evaluationsof Taiwan's Nuclear Power Plants

Lih-Yih Liao

September 23, 2013


Outlines

2

General data of site/plant

AEC Actions Timelines

Taiwan Action Plan

Cliff edge results

Conclusions of the regulatory body

行政院原子能委員會核能研究所行政院原子能委員會核能研究所3

General data of site/plant

Site Unit Type Type of

Containment

Start of commercial operation

Current net capacity[Mwe]

Chinshan

1 BWR4 Mark I 12/1978 636

2 BWR4 Mark I 7/1979 636

Kuosheng

1 BWR6 Mark III 12/1981 1030

2 BWR6 Mark III 12/1983 998

Maanshan 1

PWR 3 Loop

CTMT 7/1984 960

2 PWR

3 Loop CTMT 5/1985 960

Lungmen 1 ABWR RCCV 1350

2 ABWR RCCV 1350


AECAEC

0909 1010 1111 1212 201220120101

02020808201120110707

Preliminary Safety Preliminary Safety Assessment ReportAssessment Report

First phase Safety First phase Safety Assessment ReportAssessment Report

(final)(final)

National ReportNational Report(Draft)(Draft)

Final Phase SafetyFinal Phase SafetyAssessment ReportAssessment Report

(draft)(draft)

First phase Safety First phase Safety Assessment ReportAssessment Report

(draft)(draft)

ENSREGStress testspecification

0303 0404

WENRA stress testspecification

1108 1st progress meeting

1207 2nd progress meeting

1229 3rd progress meeting

0119 4th progress meeting

0217 5th progress meeting

INER-Five review meeting with DNR

Two batches RAIs

LM stress testLM stress testUtility ReportUtility Report

Taipower

Final Phase SafetyFinal Phase SafetyAssessment ReportAssessment Report

(final)(final)

0505 0606 0707 0808 0909 1010 1111 1212 201320130101

National ReportNational Report(Final)(Final)

※※Special inspection reportSpecial inspection report

CS,KS, MS stress testCS,KS, MS stress testUtility reportUtility report※※Progress ReportProgress Report


EU Stress Test: Taiwan Action Plan

Checklist on the basis of “Compilation of Recommendations and suggestions – Peer review of stress tests performed on European nuclear power plants” to cover all the implementation status of Post-Fukushima improvements in Taiwan’s nuclear power plants

The checklist is compiled of the following items – E for ENSREG "Compilation of recommendations and

suggestions" – C for CNS Final Summary Report of 2nd Extraordinary

Meeting 2012 para. 21 “significant activities and action..."


EU Stress Test: Taiwan Action Plan ENSREG Main Areas of Improvement (European Level Recommendations)

Item Topic European Level

Recommendations Implementation Status Completion scheduled

Remarks E 2.1 gener

al European guidance on assessment of natural hazards and margins

Order XX-JLD-10101, 10102 (Issued on Nov. 5, 2012)

Hazard: June 30, 2014 Risk: June 30, 2016 LM: Before fuel loading

AEC Requirement (NTTF Tier 1, R2.1)

E 2.2 general

Periodic Safety Review CS: 2010, KS: June 2011, MS: Dec. 2011

CS, KS, MS: 3rd run completed

AEC Regulation

E 2.3 general

Containment integrity Order XX-JLD-10114 (Issued on Nov. 5, 2012)

CS: 1EOC28, 2EOC27 KS: 1EOC25, 2EOC24 MS: 1EOC23, 2EOC23 LM: Dec. 2015 (Unit 1)

AEC Requirement (NTTF Tier 1, R5.1, Tier 3, R5.2)

E 2.4 general

Prevention of accidents resulting from natural hazards and limiting their consequences See also CNS 21.2

Order XX-JLD-10113 (Issued on Nov. 5, 2012)

CS: April 2016 KS: Aug. 2016 MS: April 2016 LM: Before fuel loading

AEC Requirement (NTTF Tier 1 R4.2)


EU Stress Test: Taiwan Action Plan ENSREG and CNS Considerations (Items to be considered)

Item Topic Topic 1 - Natural Hazards Implementation Status Completion scheduled Remarks

E 3.1.1 1 Hazard Frequency

See also CNS 21.1

Order CS-JLD-101101

(Issued on Nov. 5, 2012)

CS: Dec. 2016 AEC Requirements:

0.4g minimum peak

ground acceleration

for earthquakes and

return frequency of

10-4/year

Order XX-JLD-10101,

10102

(Issued by Nov. 5, 2012)

Refer to Item 2.1

C 21.1 1 Hazards posed by external events Refer to Item 3.1.1 Refer to Item 3.1.1 Refer to Item 3.1.1

E 3.1.2 1 Secondary Effects of Earthquakes CSA-08-01 is incorporated

Into the Order

XX-JLD-10105

(Issued by Nov. 5, 2012)

Note: CSA, Comprehensive

Safety Assessment

CS, KS, MS: Completed in

March 2013

LM: Before fuel loading

AEC Requirement

(SRP, Safety

Re-assessment

Programs,

approved on April

19, 2011)

(NTTF Tier 1, R2.3)

E 3.1.3 1 Protected Volume Approach Order XX-JLD-10104

(Issued on Nov. 5, 2012)

CS, KS, MS, LM: Dec.

2016

AEC Requirement

Order XX-JLD-10118

(Issued on Nov. 5, 2012 )

CS: April 2014

KS, MS: Dec. 2014

LM: Dec. 2015


EU Stress Test: Taiwan Action Plan ENSREG and CNS Considerations (Items to be considered)

Item Topic Topic 1 - Natural Hazards Implementation Status Completion scheduled Remarks

E 3.1.4 1 Early Warning Notifications Automatic Seismic Trip

System

CS, KS, MS, LM:

Completed

AEC Requirement

Seismic/Tsunami

Warning

Central Weather Bureau

E 3.1.5 1 Seismic Monitoring Unit 1 of each NPP

CS, KS, MS, LM:

Completed

AEC Requirement

Unit 2 of each NPP CS, KS, MS: 2016

LM: Completed

E 3.1.6 1 Qualified Walkdowns Order XX-JLD-10105

(Issued on Nov. 5, 2012 )

CS, KS, MS: Completed

in March 2013


AEC Requirement

(NTTF Tier 1,

R2.3)

E 3.1.7 1 Flooding Margin Assessments CSA-08-06 Under review AEC Requirement

(SRP approved on

April 19, 2011) XX-JLD-10102 Refer to Item 2.1

XX-JLD-10104, and

XX-JLD-10118, etc.

Refer to Item 3.1.3

EU Stress test

specifications

CS, KS, MS, LM:

Completed


EU Stress Test: Taiwan Action PlanE 3.1.8 1 External Hazard Margins XX-JLD-10101, and

XX-JLD-10102

Refer to Item 2.1 AEC Requirement

(NTTF Tier 1,

R2.1) EU Stress test

specifications

CS, KS, MS, LM:

Completed

Item Topic Topic 2 - Loss of Safety Systems Implementation Status Completion scheduled Remarks

C 21.2 Enhance safety systems to

withstand an unexpected natural

event.

Refer to Items 2.4, 3.2.1,

3.2.2

Refer to Items 2.4, 3.2.1,

3.2.2

Refer to Items 2.4,

3.2.1, 3.2.2

E 3.2.1 2 Alternate Cooling and Heat Sink

See also CNS 21.2

XX-JLD-10111 CS: 2EOC26, 1EOC27

KS: TBD

MS: TBD

LM: TBD

AEC Requirement

(ENSREG)

E 3.2.2 2 AC Power Supplies

See also CNS 21.2

XX-JLD-10106 Follow the USNRC

rulemaking

AEC Requirement

(NTTF Tier 1

R4.2) XX-JLD-10107 End of 2013

XX-JLD-10109 Proposal submitted at

end of 2013

XX-JLD-10120 CS: Dec. 2015

KS: Feb. 2016

MS: Feb. 2014

LM: TBD




E 3.2.3 2 DC Power Supplies Movable equipment CS, KS, MS, LM:

Completed

AEC Requirement

XX-JLD-10108 CS: Completed

KS: 1/2EOC23

MS: 1/2EOC23

LM: TBD

E 3.2.4 2 Operational and Preparatory

Actions

Supply of consumables CS, KS, MS, LM:

Completed

AEC Requirement

(SRP approved on

April 19, 2011) Exercise and drills Annual

E 3.2.5 2 Instrumentation and Monitoring XX-JLD-10106 Refer to Item 3.2.2 AEC Requirement

(NTTF Tier 1

R4.1)

(NTTF Tier 1

R7.1)

XX-JLD-10109 Refer to Item 3.2.2

XX-JLD-10115 CS: Dec. 2014

KS: 1/2 EOC24

MS: 1/2 April, Dec. 2015


E 3.2.6 2 Shutdown Improvements National Report

Section 5.3, Item 2

TBD AEC Evaluation

(Stress Test)


EU Stress Test: Taiwan Action Plan Item Topic Topic 2 - Loss of Safety Systems Implementation Status Completion scheduled Remarks

E 3.2.7 2 Reactor Coolant Pump Seals Temperature-resistant

seals

Completed in 1990s AEC Requirement

MS-JLD-101301 MS: TBD

E 3.2.8 2 Ventilation XX-JLD-10109 Refer to Item 3.2.2 AEC Requirement

E 3.2.9 2 Main and Emergency Control

Rooms

XX-JLD-1013003:

Seismic isolation TSC

CS: Reinforce TSC to

Seismic category I

KS, MS, LM: 2015-2016

AEC Requirement

Emergency MCR Not under consideration All NPPs have

Remote Shutdown

Panel

E 3.2.10 2 Spent Fuel Pool

See also CNS 21.3

XX-JLD-10112 CS, KS, MS: Completed


AEC Requirement

(NTTF Tier 1

R7.1) XX-JLD-10115 Refer to Item 3.2.5

C 21.3 2 Ensure cooling of spent fuel

pools

Refer to Item 3.2.10 Refer to Item 3.2.10 Refer to Item

3.2.10

E 3.2.11 2 Separation and Independence XX-JLD-10111 Refer to Item 3.2.1 AEC Requirement

E 3.2.12 2 Flow Path and Access

Availability

XX-JLD-10108 Refer to Item 3.2.3 AEC Requirement




E 3.2.13 2 Mobile Devices Mobil pumps, power

supplies, air compressors,

quick connectors, etc.

CS, KS, MS, LM:

Completed

AEC Requirement

(SRP approved on

April 19, 2011)

(NTTF Tier 1

R4.2)



XX-JLD-10113 Refer to Item 2.4

E 3.2.14 2 Bunkered/Hardened Systems XX-JLD-10110: EDG/GT

building

CS: Dec. 2013 KS: Oct. 2013 MS: Feb. 2015 LM: Construct a seismic isolation G/T building, before the operating licensee

AEC Requirement

XX-JLD-10119: Fire

brigade building

CS: Evaluation completed by Dec. 2013 KS: Evaluation completed by Oct. 2013 MS: Evaluation completed by 1/2 EOC21 LM: Evaluation completed by Sep. 2013




E 3.2.15 2 Multiple Accidents XX-JLD-10113 Refer to Item 2.4 AEC Requirement

(SRP approved on

April 19, 2011)

(NTTF Tier 1

R9.3)

XX-JLD-1013002 CS: Aug. of 2013,

additional item TBD

KS: end of 2013

MS: Sep. 2013

LM: end of 2013

XX-JLD-1013004 CS, KS, MS: Under

regulatory review

process

LM: TBD

E 3.2.16 2 Equipment Inspection and

Training Programs

XX-JLD-10113 Refer to Item 2.4 AEC Requirement

E 3.2.17 2 Further Studies to Address

Uncertainties

XX-JLD-10109 Refer to Item 3.2.2 AEC Evaluation




Item Topic Topic 3 - Severe Accident

Management

Implementation Status Completion scheduled Remarks

E 3.3.1 3 WENRA Reference Levels URGs To improve

Continuously

AEC Requirement

(SRP approved on

April 19, 2011)

(NTTF Tier 1

R5.1)


XX-JLD-10122 MS: Dec. 2016

E 3.3.2 3 SAM Hardware Provisions URGs Refer to Item 3.3.1 AEC Requirement

(NTTF Tier 1

R4.2, R8) XX-JLD-10113 Refer to Item 2.4

XX-JLD-10116 Follow the USNRC

rulemaking

E 3.3.3 3 Review of SAM Provisions

Following Severe External

Events

URGs Refer to Item 3.3.2 AEC Requirement

(NTTF Tier 1

R4.2, R8) XX-JLD-10113

XX-JLD-10116

E 3.3.4 3 Enhancement of Severe Accident

Management Guidelines

(SAMG)

See also CNS 21.4

URGs Refer to Item 3.3.2 AEC Requirement

(NTTF Tier 1

R4.2, R8) XX-JLD-10113

XX-JLD-10116

C 21.4 3 Evaluation of the guidance to

manage emergency situations

Refer to Items 3.3.4, 3.3.5 Refer to Items 3.3.4, 3.3.5 Refer to Items

3.3.4, 3.3.5




Management


E 3.3.5 3 SAMG Validation

See also CNS 21.4


(NTTF Tier 1 R8)

E 3.3.6 3 SAM Exercises Exercise and drills Annual AEC Requirement

(NTTF Tier 1 R8) XX-JLD-10116 Refer to Item 3.3.2

E 3.3.7 3 SAM Training Exercise Regularly AEC Requirement

Full Scope Simulator Regularly

E 3.3.8 3 Extension of SAMGs to All Plant

States

Section 6.6 of National

Report, item 3 of

paragraph

Improvements and

integration of EOPs,

SAMGs and EDMGs

TBD (it might be

incorporated with the

requirement of

XX-JLD-10116)

AEC Requirement


E 3.3.9 3 Improved Communications

See also CNS 21.7


(NTTF Tier 1

R9.3)




Management


C 21.7 3 Improving radiation monitoring

and communications capabilities

CSA-10-06 Completed AEC Requirement

(SRP approved on

April 19, 2011)

(NTTF Tier 1

R9.3)

RL-JLD-1012042

CS, KS, MS, LM: end of

2013

XX-JLD-1013002

Refer to Item 3.2.15

E 3.3.10 3 Presence of Hydrogen in

Unexpected Places


(NTTF Tier 1

R5.1)

E 3.3.11 3 Large Volumes of Contaminated

Water

Potential storage space

CS, KS, MS, LM:

Completed

AEC Requirement

(SRP approved on

April 19, 2011) Conceptual preparation TBD

E 3.3.12 3 Radiation Protection

See also CNS 21.7

CSA-05-06~08, 10

Completed AEC Requirement

(SRP approved on

April 19, 2011)




Management


E 3.3.13 3 On Site Emergency Center

See also CNS 21.8


(SRP approved on

April 19, 2011)

C 21.8 3 Regional, off-site and on-site

emergency response centres

Refer to Item 3.3.13 Refer to Item 3.3.13 AEC Requirement

No regional center

E 3.3.14 3 Support to Local Operators

See also CNS 21.8

CS, KS, LM could

provide support to others

within hours; MS has to

wait 24 hours

Completed AEC Requirement

(SRP approved on

April 19, 2011)




Management


E 3.3.15 3 Level 2 Probabilistic Safety

Assessments (PSAs)

All operating NPPs have

completed the level 2 PRA models since 1990s

LMNPP in 2007.

The last paragraph in Section 1.5 of National

Report mentioned that “Furthermore, TPC

should finish the integrated PRA

analytical model based on ASME PRA

standards”

Risk-informed

applications adopt the measures of CDF and

LERF from PRA models.

TPC will submit the results of data updated

every three-year TPC will follow the PRA

standards to build up, update and maintain the

PRA models.

AEC Evaluation

E 3.3.16 3 Severe Accident Studies See also CNS 21.5

All NPPs have MAAP model to simulate severe

accident phenomena

Continuous efforts to improve the SAMG

AEC Evaluation

C 21.5 3 Probabilistic safety assessments

to support severe accident

management

TPC has the same

practices in PSA

Improve the PSA models

continuously

AEC Requirement

(SRP approved on

April 19, 2011)


Plant Design Basis Cliff-edge as original design

CS 0.3g1.05g(core support structure)

KS 0.4g0.77g(RCIC DC Switchgear)

MS 0.4g1.48g(DC Bus Switchgear)

LM 0.4g2.0g(RBSW injection pump)

Initiation Event: : Earthquake

Cliff edge results

*All values are peak ground acceleration values


PlantDesign Basis

Cliff-edge as original design

Cliff-edge with countermeasure

CS10.7run

up(m)

11.2 m(RCIC)

16.7 m(TPC is now planning to build tsunami wall with height of 10.7+ 6 m)

KS10.3run

up(m)

12.3 m(RCIC)

16.3 m(TPC is now planning to build tsunami wall with height of 10.3+6 m)

MS12.0run

up(m)

15 m(DC Bus)

18.0 m(TPC is now planning to build tsunami wall with height of 12+6 m)

LM8.0run

up(m)

12m(RCIC..etc)

14.0m(TPC is now planning to build tsunami wall with height of 8+6 m)

Initiation Event: : Tsunami

Cliff edge results (cont.)


Plant

Design Basis

Cliff-edge as original design

Countermeasure forCliff-edge

CSKSMSLM

8 hours

DC power: 24 hours(isolate non-vital DC load)

• upgrade the capacity of DC power to 24 hour

‒ without load shedding for the first 8 hour

• Evaluation: extending coping time to 24 hours

• Autonomy of 72 hours with portable D/G

Coping time: 8 hours

Initiation Event: : Station black out



PlantCliff-edge as original

designCountermeasure for

Cliff-edge

CS40 hours (CST storage capacity)

With fresh water from reservoir(There is no limitation for water supplying from creek or sea )

KS24 hours (CST storage capacity)


MS

40 hours (CST storage capacity)


LM21 hours (CST storage capacity)


Initiation Event: : Loss of ultimate heat sink



scope and content The regulatory body identified some areas to improve the scope

and content of the assessments:1. The analysis postulates that only one unit is affected. The consequences of

both units in one site being affected shall be addressed.2. The accident scenario, the availability of the mitigation systems and the cliff

edge effects of the unit during shutdown conditions may be quite different from those of normal operation. However, the accident scenarios during shutdown conditions are not addressed in TPC stress test report. The missing assessment is considered necessary for a complete assessment.

3. Extreme external hazards (including earthquake, flooding, Tsunami, etc.) may result in SBO and complete loss of heat sink, the consequential impact to spent fuel pool (including the integrity of pool structure) should be evaluated.

4. TPC should finish the integrated PRA analytical model based on ASME PRA standard.



Earthquake General Comments:Based on the review of TPC’s reports and the supporting documents, the

subsequent technical meetings, the AEC considers that the resulting action plan of this seismic reassessment is adequate.

The AEC identified additional recommendations for TPC to further improve the seismic robustness of the plant facilities:

1. Although the preliminary results showed the DBEs of the three plants remain some margin, the maximum potential earthquake caused by the Shanchiao fault and Henchun fault are still to be evaluated, as they are so close to the Chinshan/Kuosheng and Maanshan NPPs respectively.

2. Spent fuel pools are almost filled up with spent fuels in Chinshan and Kousheng plants. The TPC should take steps to speed up the process of moving these spent fuels to ISFSI(Independent Spent Fuel Storage Installation).



Earthquake (cont.)

3. AEC requested TPC to submit the seismic action items based on the requirements set forth in section 2.1 and 2.3 of USNRC NTTF report tier 1 recommendation.

4. Referring to the international nuclear safety actions in response of the Fukushima Daiichi nuclear accident, AEC requested TPC to accomplish the following items

(1)Seismic/Tsunami hazard and event scenario simulation

(2)Seismic enhancement for the non-seismic TSC structures

(3)SSCs enhancement evaluation followed by the SSE upgrade from 0.3g to 0.4g for CSNPP

(4)Functionaility upgrade for emergency response facilities including adopting seismic base isolation or damping devices.

(5)Seismic upgrade of plant fire brigade building structures.

(6)Upgrade the raw water reservoir capacity as well as its reliability.

(7)Enhance the power durability of seismic monitoring sensors.



Flooding

General Comments:AEC basically confirms the information and assessments provided by the

licensee, especially the information regarding the licensing basis. In general, the assessments of safety margins are acceptable and the resulting action plan for improvements is adequate.

The regulatory body identified additional requests and recommendations to further improve the robustness of the units and the sites:

1. Referring to the tsunami analysis result by National Science Council and the guidelines or assessment results for tsunami evaluation from major nuclear industrial countries (such as NUREG/CR-6966), the licensee should further review the appropriateness of the design basis tsunamis and take the associated improvements to its nuclear power stations.


Flooding (cont.)

2. The licensee should review the appropriateness of the DBF in FSAR considering the rapid climate changes in the recent years. Associated improvements should be taken to increase the robustness of the plants against flooding. These should be reviewed and approved by the regulatory body through the process of periodic safety review every ten years.

3. Regarding the ground level of the buildings of Chinshan Power Station, the re-measured elevation (11m)is already 1m lower than the original design value (12m), which might not have enough margin even though it is still larger than the design basis tsunami run-up height (10.7m). Licensee’s action plan of improvements concerning this issue should be envisaged as soon as possible.


Flooding (cont.)

4.TPC should follow the first stage recommendations of USNRC NTTF report, especially the Recommendations 2.1 and 2.3 concerning the flooding and/or tsunami.

5.Referring to the experiences of other nuclear countries, it is recommended that TPC should conduct the following improvements to its nuclear power plant:

(1)a detailed scenario simulation of seismic and tsunami hazard;

(2)building sea walls or reinforced concrete flood barrier walls or watertight facilities to provide better protections against tsunami;

(3)upgrading the watertight capability of doors of buildings containing important equipments, fire-fighting doors as well as pipeline penetrations seals.


General Comments:AEC basically confirms the information and assessments provided by the

licensee, especially the information regarding the licensing basis. Generally speaking, the potential consequences of extreme weather conditions (typhoon, storm, heavy rain, etc.) are covered by the major event – flooding. Most of the considered hazards were taken into account in the design basis of the facilities, and are hence not likely to affect the safety functions of the units.

The regulatory body identified additional requests and recommendations in order to further improve the robustness of the facilities when faced with extreme weather conditions:

1. Given the fact that typhoons of high intensities were observed in the past years in Taiwan, the protection of the buildings containing safety related equipment against projectile should be confirmed in case of a beyond design typhoon with wind speed exceeding 70.2 m/s (Beaufort Force 17).

Extreme natural events


2. Climate changes have caused severe rainfall via the form of typhoons and/or tropical storms in recent years. The licensee should review the appropriateness of the design basis PMP (probable maximum precipitation). Associated improvements of the drainage systems should be envisaged to increase the robustness of the plants against heavy rain. These should be reviewed and approved by the regulatory body through the process of periodic safety review every ten years.

3. The watertight capability of fire-fighting doors and pipeline penetrations seals should be further investigated and clarified.

4. A systematic evaluation of combinations of extreme nature events should be performed.

Extreme natural events (cont.)


Extreme natural events (cont.)

5. TPC should follow the tier 1 recommendations of USNRC NTTF report, especially Section 2.3 concerning the external natural disasters.

6. Referring to the experiences of other nuclear countries, it is recommended that TPC should conduct the following evaluations or improvements to its nuclear power stations:1) a quantitative risk assessment concerning the menace of volcanic

hazard;

2) installation of the second ultimate heat sink.


Loss of electrical power and loss of ultimate heat sink

The original design of plant power supply system and the enhanced measures to increase robustness after Fukushima accident

General comments on utility reports regarding to Loss of electrical power and loss of ultimate heat sink

Additional areas being identified to further improve the robustness of all the units


power sources

Site

Back-up

power

sources

Swing

DG

Air cooled G/T

Enhanced measures to increase robustness of emergency 4.16kV/480V

AC power

Chinshan 2EDGs/unit 1 2 1. Swing EDG

provides emergency power to both units

2. provide power to safety-related essential buses from two black-start DGs of gas turbines

mobile diesel generators added

12 sets 480V 500kW 1 set 4.16kV 1500kW

Kuosheng

2EDGs/unit

1EDG/unit

for HPCS

1 2 4 sets 480V 200kW

1 set 4.16kV 1500kW

Maanshan 2EDGs/unit 1 2 10 sets 480V 370kW

2 sets 4.16kV 1500kW

Lungmen 3EDGs/unit 1 2 5 sets 480V 100kW

2 sets 4.16kv 1500KW


Good practice

Seismic Category I

POST-FUKUSHIMA

Portable Equipment

34

Enhance mitigation resources – Electric power source

LOOP due to earthquake

AC power supply DC power supply

Emergency D/G

5th (7Th) D/G

Air-cooled G/T

G/T black-start D/G

4.16kV power vehicle

480V portable D/G

Portable generato

r

Spare battery

SS

S S

S

S

S S

F F

FF

F

Response to Fukushima Accident


General comments:The reports of the licensees essentially conform to the ENSREG requirements. The approach adopted by the licensee to re-assess the management of the loss of electrical power and loss of ultimate heat sink complies with the regulations of the ROCAEC that is based on the regulations of the country of the reactor vendor.

The regulatory body identified additional areas to further improve the robustness of all the units:1.In response to the Fukushima accident, the AEC requires the TPC to accomplish the following regulatory requirements:

(1)After the SBO event of Higashidori NPS on April 7, 2011, NISA issued a Direction to require at least 2 emergency DGs to be in an operable state all the time even when the reactor is shut down. The same position was adopted by the ROCAEC.

• If one unit is shut down with one EDG under inspection and the swing EDG is assigned to it according to the new requirement, the capability of the swing EDG to back up the other unit is restricted. Envisaged measures to resolve this issue are required.



(2) With respect to the SBO, the TPC is required to establish the equipment, procedures, and training necessary to implement an “extended loss of all AC” time of 72 hours

‒ for core and spent fuel pool cooling ‒ for reactor coolant system and primary containment integrity

‒The design of the systems supporting the 72-hour extended coping time should cover the same scope of functions as the 8-hour minimum coping time‒It can be based on realistic analysis with reasonable operator action using portable or permanently installed equipment governed by established procedures and training.

‒The evaluation should include the technical items of NUMARC 87-00 with all operating states (full power operation, low power operation and shutdown) considered.



(3)In a case of an event caused by an external hazard, all the units on a site may be affected. Sufficient supplies of emergency AC power for coping with such events is essential for enhancing robustness because resources need to be shared. Therefore TPC is required to perform an evaluation regarding to the installation of an additional air-cooled DG or equivalent measures at the NPS.

(4)TPC is required to perform an evaluation regarding to the establishment of an additional alternate heat sink such as the water fed by groundwater wells.

(5)Envisaged measures are required to increase robustness of the plant in dealing with the primary coolant pump seal LOCA issue during SBO (for Maanshan NPP only).

(6) Referring to the emergency management and requirements in Japan, the TPC is required to enhance the off-site power system and increase its reliability.



Ultimate heat sink

Site Ultimate heat

sink

SBO water

makeup

Enhanced measures to increase robustness of UHS

Chinshan

Circulating Water system (CW)

emergency Service water system

(ESW)

HPCI and RCIC 1. Seismic enhancement

for raw water supply 2. move fire raw water

pipe from underground to above ground

3. enhance the containment venting capability

4. Measures taken to prevent flooding

5. add fire engines 6. add engine driven

water pumps

Plant specific

– Spare ESW pump motors

– SFPACS

Kuosheng

Circulating Water system (CW) emergency

circulating water system (ECW)

RCIC Spare ECW pump motors

Maanshan Nuclear Service Cooling Water

(NSCW) system

turbine driven AFP

diesel driven AFP

diesel engine fire pump

Spare NSCW pump motors

Lungmen TBSW, RBSW, and

CCW system

RCIC and RHR ACIWA

MODE

Spare RBSW pump motor


POST-FUKUSHIMA

Seismic Category I

Portable Supply(additional fire truck/pump)

39

Enhance mitigation resources – Diversify water resources

LUHS due to tsunami

AC power supply DC power supply

Design make-up system

RCIC/HPCIManual OP

RAW water make up

Creek/Well/Lake

Sea Water/Dam

Onsite Tank/Condenser

S S

SS

F F

F

F

Alternateheat sink

Reactor safety cooling

S

S

S S

S

Response to Fukushima Accident-- BWR


Injecting Water into Steam Generator

42

diesel driven auxiliary feedwater pump

diesel engine fire pump

Fire engines


RCS Water Makeup by Hydro Test Pump (RCP Seal Injection Path)


Loss of electrical power and loss of ultimate heat sink(cont.)

2. With respect to the SBO, the AEC requires the TPC to strengthen SBO mitigation capability at all operating and new reactors for design-basis and beyond-design-basis external events as it is recommended in item 4 of USNRC NTTF report.

3. Regarding to the nonconventional means, the AEC requires:

(1) The operability of the nonconventional means should be justified on the basis of technical data (design, operation, alignment and connections, periodic testing, preventive maintenance, etc.).

(2) A systematic review of the nonconventional provisions should be performed, focusing on the availability and appropriate operation of plant equipment in the relevant circumstances, taking account of accident initiating events, the extreme external hazards and the potential harsh working environment they may be subject to during the whole period of operation.

(3) Nonconventional means including mobile equipment, fire trucks, etc. should be stored in locations that are safe and secure even in the event of general devastation caused by events (significantly) beyond the design basis. The facilities where the mobile equipment is stored should be evaluated and reinforced if necessary.


4.The operability of the URG is required to be justified on the basis of rigorous systematic review and thorough accident analysis. The importance of the justification of the URG is illustrated by the following example:

In BWR, the licensee has applied for measures aimed at using a fire water pump to sustain low-pressure feed to the reactor. These measures require depressurization of the reactor beforehand.

In URG, a two step depressurization strategy has been adopted for prolonged SBO. – In the early stage of SBO, a slow and controlled depressurization of the reactor

is performed while the RCIC is still available. – In the second stage, a fast and emergency depressurization of the reactor is

performed while the RCIC is no longer available. In this example, the controlled depressurization should not be confused with the

emergency depressurization. However, the two terminologies are not well distinguished in the utility’s stress test report.



Comparisons of Water Injection Systems

46

SYSTEMQuantity and

Capacity/eachDesign flow/each

Pressure

RangePower

HPCI 1×100﹪ 4,250gpm@1120psi1120~150psi

DC

SRV 10×25﹪(Including ADS×5) 800,000 lb/hr1110~50psi

DC

CS 2×100﹪ 3,720gpm@113psid265~0psi

EDG A/B

LPCI 4×33.3﹪ 6,560gpm@20psid217~0psi

EDG A/B

CS ECCS design:

CS Alternative water injection:

Chin Shan Station Fire EnginesName Quantity Capacity

(Liter)DischargePressure

Remark

Fire FoamVehicle

1 3,000 0 ～ 20 kg⁄cm2 Discharge flow rate :3000 liters/min (792 gpm) ＠ 8.78 kg⁄cm2

Reservoir Vehicle 1 10,000 0 ～ 20 kg⁄cm2 Discharge flow rate :3000 liters/min (792 gpm) ＠ 10.97 kg⁄cm2


With the slow and controlled depressurization process, the reactor can be brought

to and maintained at a relatively safe state (namely, a high/normal water level and low pressure state) while at the same time, the RCIC trip set point will not be reached.

Under this safe state, the impact of the emergency depressurization of the reactor following the failure of RCIC will be minimized and the reactor water inventory can be supplemented by various low pressure injection methods.


Without the slow and controlled depressurization process the reactor is at

relatively danger state (namely, a high pressure state), fast depressurization of the reactor will lead to a core uncover even the water level is high before depressurization.


5. The hydrogen and containment pressure control strategies in the URG shall take into account various accident scenarios.

6. The TPC is required to study the feasibility of adding the mobile heat exchanger to remove the heat from the containment and/or the reactor.



Procedures, training and exercises1. AEC required TPC to combine the additional equipment and operations into

the procedures or guideline;2. AEC required TPC to re-evaluate the feasibility of EOPs and SAMGs with

the involvement of new procedures/guidelines;3. AEC required TPC to ensure that the SAMGs are appropriate for multi-unit

events and to promote them from guidelines to procedures if required;4. AEC requests TPC to strength SBO mitigation at operating reactors for

design basis and beyond design basis external events;5. AEC requests TPC to improve the emergency preparedness staffing and

communications per NRC NTTF report.

Severe accident management


The establishment of URGs TPC needs to identify the URG and its implementation timing, the subsequent

measures and monitoring strategy after implementing URG, including the monitor of radioactive releases, backup ability of present systems and equipment, etc.

Multi-event accidentsAEC required TPC to estimate the duration of independent response capability

for various severe accidents, beyond design accidents, and multi-event accidents. The materials and equipment in contracting the off-site supports should also be identified.

Severe accident management (cont.)


The improvement of main control room in case of an accident beyond design basis

AEC required TPC to:1. ensure the capability of DC power for instrumentation and control systems of MCR,

TSC, backup TSC, etc. in case of monitoring unit conditions during SBO accidents. The duties, associations, and implementations of these staffs should also be identified;

2. improve the seismic level of MCR, TSC, backup TSC, and their inside-equipment; 3. assess the adequacy of MCR human arrangement in case of multi-unit events.

Design and reliability of containment hardened vent with filters (only for Chinshan NPP)

Per the recommendation item 5.1 in USNRC NTTF report, AEC recommended TPC to add a robust and reliable containment system in Chinshan NPP (Mark-I), in which the hardened vent and filters are involved, for long-term operations in case of extended SBO accidents. The drywell or wetwell hardened vent system shouldn’t be shared with the other units. The hardened vent system will be able to operate either with electrical power or manual operation.



Improvements and integration of EOPs, SAMGs and EDMGs1. Per the recommendation item 8 in USNRC NTTF report, AEC recommended TPC to:

1) integrate EOPs, SAMGs, and EDMGs;2) identify the commands and control strategies of implementations.

2. The current severe accident management guidelines are designed for full power condition, which cannot cover the conditions of low power and shutdown. Each nuclear power plant should prepare the response action before revision of current SAMG.

3. Provide appropriate training and qualification to the decision-maker. 4. AEC also required TPC to involve the URG into the integration of EOPs, SAMGs, and

EDMGs if URG is available.

Spent fuel poolAEC requests TPC to enhance the spent fuel pool instrumentation per NRC NTTF report.



Thank YouThank YouFor Your AttentionFor Your Attention

行政院原子能委員會核能研究所 stress test evaluations of taiwan's nuclear power...

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