1. Graphical Expert System for Analyzing Nuclear Facility Vulnerability David Sulfredge Oak Ridge National Laboratory December 3, 2002 O AK R IDGE N ATIONAL L ABORATORY U.S. D EPARTMENT OF E NERGY

2. 2 Facility Vulnerability Analysis  Objectives  Develop models to predict facility response to military or terrorist weapons  Determine critical locations for enhanced protective measures  Predict collateral effects

3. 3 Nuclear Facilities are Vital Assets  Must safeguard U.S. plants  About 20% of U.S. generating capacity  Considerable public concern  Need targeting tool for some facilities  Defeat energy infrastructure  Defeat WMD production  Potential for serious radiological consequences  ORNL developing Visual Interactive Site Analysis Code (VISAC) to meet these needs

4. 4 Facility Kill Probability Facility Collateral Effects Estimates Facility Downtime Estimates Facility Model Editor Event/Fault Tree Editor VISAC Integrates the Following Functions in one Code Provides VERY FAST “what if” Analysis for Various Accident/Incident Scenarios

5. VISAC 5 Core damage probabilityFacility kill probability

6. 6 VISAC Weapon Selection Equipment sabotage option Blast location – Chosen from model editor – Chosen from viewer Type of blast calculation – Uniform ray trace mode – Direct ray trace mode – Air region mode

7. 7 VISAC Blast Propagation  Uniform ray tracing  Directed ray tracing  Air region method

8. 8 VISAC Downtime Calculation  DT based on fault tree for facility kill  Single component failure  Multiple component failure  VISAC uses a weighted DT sum DT net = (1/ P kill )  P i * DT i  Compute both serial and parallel repair times to bound answer

9. 9 VISAC Geometric Model Viewers Image from 2-D Viewer, showing a triple orthographic projection of a turbine building Image from 3-D Viewer, showing an image of the entire plant

10. 10 Viewing Components by Floor Level First Floor Second Floor Third Floor

11. 11 Building Critical Component List by Floor Title and highlighted critical component point to each other

12. VISAC BRL-CAD Model Editor Model editor – Create new models – Customize existing models – Move, delete objects Creates a BRL-CAD output file Creates Customized Models in BRL-CAD in Minutes Instead of Days 12

13. 13 Construct Facility from VISAC Library Buildings Buildings chosen from libraries Building positions and orientations can be varied Screen grid available to aid building placement Ground level and building “sinkages” can be edited

14. Event/Fault Tree Editor Tree editor – Create new tree – Customize existing trees – Delete trees – Add/Edit consequences – Change failure probability Creates Customized Event/Fault Trees for use with Customized Geometric Models VISAC 14

15. 15 VISAC Event Tree Editor Edit targets on canvas – Green arrow ( Add or delete column) – Green fork (Split the branch) – Red X (Collapse the branch) Consequences assigned by the user

16. 16 VISAC Fault Tree Editor Fault trees can be modified – New gates added – New subtrees can be added – Options to copy and paste Add new basic events

17. 17 Example VISAC Calculation (1)  Sabotage Option  Switchyard (S) 50%  Steam Generator (SG1A) 50%  Overall Kill Probability 75%  Downtime  Serial repair 7.33 months  Parallel repair 6.67 months

18. 18 Example VISAC Calculation (2)  Most likely sequence leading to core damage highlighted in red

19. 19 Simple vs. Detailed Model VISAC Damage Maps for a Generic Two- Loop PWR Building-level geometry Detailed plant geometry

20. 20 Conclusions  VISAC successfully integrates geometric modeling, damage assessment, and event/fault tree consequence analysis  VISAC’s graphical editing routines can customize library models as needed  VISAC can analyze a wide variety of nuclear facility vulnerability scenarios  Code development work is continuing