Take 5 for Safety

1. Barriers for Access to Accelerator Enclosures Barriers for Rigging the Westinghouse Rotor and Stator Photo of the Week E. Lessard Collider-Accelerator Department 4-26-11 Take 5 for Safety

2. Barriers for Access to Accelerator Enclosures • The probability of two independent gate interlocks failing to remove beam and causing an accident as a result of an individual entering an interlocked gate is 0.00001 in a year (National Commission on Radiological Protection, NCRP 88 Appendix A, 1986); that is, once in 100,000 years • Each interlock was assumed to fail once every 100 years • For Administrative Controls failure, NCRP 88 assumed it to be 0.1 failures per year without explanation • C-AD adds a bolt-home interlock on C-AD gates to prevent forced access, which reduces the probability of an engineered control to once in 10 million years • Assuming 100 gates, the probability of failure at C-AD is once in 100,000 years similar to NCRP 88

3. Barriers for Access to Accelerator Enclosures – Admin Controls • Human performance shows the Administrative Controls fail at the rate 0.01 to 0.001 per use and not all failures cause an accident • Assuming all failures cause an accident and a failure rate of 0.01 per use, the probability of an accident due to two Administrative Control failures at C-AD is: •  Work Planning (0.01) • Training and Qualification of Workers (0.01) • That is (0.01)(0.01) = 0.0001 or once in 10,000 years • Assuming 10,000 entries per year into the accelerator enclosures at C-AD, that works out to 1 Administrative Control failure per year • Combining C-AD Administrative and Engineered Controls (100 doors and 10,000 entries per year) gives an estimated failure rate of once in 100,000 years verses the NCRP 88 value of once in 100,000 years for a one gate dual-interlocked accelerator and an assumed Admin Control failure rate of 0.1 per year • Estimates of probability are first order estimates

4. General View of Westinghouse Machine

5. Gantry Used for Lifting

6. First step of Rigging ProcessRemoval of Pedestal and Support Rotor

7. Breaking the Coupling, Hooking the Rotor, Hooking the Stator

8. Rotor and Stator Moved Together Away from Coupling

9. Rotor Supported Independently at CG

10. Rotor Moved Out To Access Stator

11. Stator Rewound in New Jersey Facility

12. Rewound Stator and Rotor Returning to Normal Position

13. Barriers for Rigging the Westinghouse Stator and Rotor • Four subcontractors were rigging the rotor and the stator • Barriers observed: • Work Planning (critical lift permit, PPE: hard hats, high-visibility vests, safety glasses, steel toed shoes, fall protection, gloves when pulling chains) • Experienced, trained and qualified subcontractors specializing in rigging this type of equipment • Lead person was present and controlling position of everyone including observers; hand signals between lead person and the three persons rigging the stator and rotor; each person was actively watching out for the others • Three administrative-control barriers; ~(0.01)3 • Crew performs similar task 100 times per year; one chance in 10,000 of failure

14. What barriers are here?