ML19011A448

Workshop 3 System Modeling 2019-01-17

ML19011A448
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Issue date:	01/16/2019
From:	Office of Nuclear Regulatory Research
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Nathan Siu 415-0744
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Text

Plant Systems Modeling Workshop 3 1

Learning Objectives

• Introductory knowledge of typical NPP systems, structures, and components (SSCs) modeled in PRAs

• Practice with thought process, elements, and mechanics of NPP PRA Important:

a) The workshop problems can be performed as group exercises.

b) The purpose is to exercise the modeling thought process, not to get the right answer.

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Fenwick 1 NPP - Background In an effort to expand its footprint in a global marketplace, the Grand Duchy of Fenwick has decided to build a distillery to mass produce a brandy based on their famous Pinot Grand Fenwick wine. akaKaro Engineering, a boutique firm known in some circles for its excellence in technical editing but not yet well-practiced in nuclear power plant design, has proposed that the Duchy use a small boiling water reactor to provide process heat to the distillery, as well as electric power for domestic use and export.

The proposed plant would be located at the foot of Mount Fenwick and overlooking the scenic Fenwick River, the Duchys lone river. (This location would provide a unique and attractive location for aprés skiing events.)

Substantial capital cost reductions would be achieved through: a) the elimination of multiple components found in most nuclear power plant designs and b) the use of identical components (e.g., for valves and electrical breakers) whenever possible.

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Fenwick 1 NPP - Other Notable Features Other notable features of the proposed, conceptual design are as follows.

• Use of the Fenwick River to provide the normal and emergency ultimate heat sinks

• Direct use of reactor steam to provide process heat to the distillery

• A novel, submerged condenser for normal heat rejection

• A backup, water-cooled emergency diesel generator to provide onsite power should offsite power be lost

• A backup, dual-drive safety injection pump to provide cooling water. The pump would normally be electric-motor driven, but a steam-driven turbine could be connected to the pump should all power be lost.

• A direct vent to the atmosphere for reactor steam used to drive the backup safety injection system turbine

• A containment building to contain radioactive releases, should a severe accident occur

• Major components in the Nuclear Steam Supply System (NSSS) and electrical distribution system (with key loads) are shown on the following pages. The mechanical components are designated by system (e.g., SI for safety injection and type (e.g., P for pump). The electrical components are designated by electrical bus (e.g., A for the 6.9 kV emergency power bus) and type (e.g., X for transformer).

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Fenwick 1 Location and Plan 5

Fenwick 1 - NSSS and Safety System (Schematic)

Designator Description Pre-hyphen FW Feedwater NS NSSS SI Safety Injection SW Service Water Post-hyphen C Condenser F Filter P Pump R Reactor V Valve T Turbine Other NSSS Nuclear Steam Supply

©akaKaro Engineering, 2018 6

Designator Description Fenwick 1 - Electrical Distribution Pre-hyphen A 6900 VAC non-vital bus A B 4160 VAC non-vital bus B C 250 VDC non-vital bus C FW Feedwater NI 125 VDC non-vital I&C bus NV Notes: NS NSSS

1) Small box indicates SI Safety Injection a breaker SW Service Water VI 125 VDC vital I&C bus VI

2) Large box indicates X 6900 VAC vital bus X a load Y 4160 VAC vital bus Y Z 250 VDC vital bus Z Post-hyphen B Battery C Condenser F Filter G Emergency Diesel Generator M MGS P Pump R Reactor S Switchgear/M-CC/Distribution Panel V Valve T Turbine X Transformer Other Bat. Battery M-CC Motor Control Center MCR Main Control Room MGS Motor Generator Set NSSS Nuclear Steam Supply System VAC Volts (Alternating Current)

VDC Volts (Direct Current)

©akaKaro Engineering, 2018 7

Exercises*

1. Initiating Event Identification

a. Identify some potentially important initiating events for the plant. For each event, describe: (i) why you think it is an initiating event, and (ii) why you think its potentially important.

b. Identify some potentially important external hazards for the plant. For each hazard, describe why you think its potentially important.

2. Event Tree Development Select an initiating event and develop an event tree for plant response following that initiating event.

3. Fault Tree Development

a. Develop a fault tree for the SI system. Identify the minimal cut sets.

b. If time permits, (i) develop fault trees for all of the top events in your event tree and (ii) identify some minimal cut sets for core damage.

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