Barriers for Access to Accelerator EnclosuresBarriers for Rigging the Westinghouse Rotor and Stator

Photo of the Week

E. LessardCollider-Accelerator Department

4-26-11

Take 5 for SafetyTake 5 for Safety

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

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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

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General View of Westinghouse Machine

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Gantry Used for Lifting

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First step of Rigging ProcessRemoval of Pedestal and Support Rotor

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Breaking the Coupling, Hooking the Rotor, Hooking the Stator

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Rotor and Stator Moved Together Away from Coupling

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Rotor Supported Independently at CG

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Rotor Moved Out To Access Stator

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Stator Rewound in New Jersey Facility

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Rewound Stator and Rotor Returning to Normal Position

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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

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What barriers are here?

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