Lessons Learned Events at SLAC · 2012-09-14 · Lessons Learned Events: Summary Comments ....

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Lessons Learned Events at SLAC Mike Woods, SLAC National Accelerator Laboratory

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  • Lessons Learned Events at SLAC

    Mike Woods, SLAC National Accelerator Laboratory

  • SLAC Lessons Learned Compilation

    Definition of a Lessons Learned Event event or observation that identifies a best practice, improvement opportunity or the lack of a required safety barrier. This can be related to any of the following

    • safety configuration • engineering controls • administrative procedures • laser eyewear requirement • posted signs and labels • how training is done

    Lessons learned are routinely compiled from SLAC’s laser operations and communicated to SLAC laser personnel. Each event report includes fields for event description, cause, corrective actions and lessons learned.

  • SLAC Lessons Learned Compilation

  • The compilation has 28 events in last 4 years of laser operation, including: • 3 ORPS-reportable incidents:

    - eye exposure injury (2009, reported on at LSOW-2010) - “Class 1” laser not enclosed (2011) - laser operator enters NHZ without protective eyewear (2012)

    • required laser safety barrier compromised (13 events) • safety configuration control issues (3 events) • engineering configuration design issues (7 events) • malfunctions in the engineered laser safety system (9 events)

    - safety shutter (2) - unlocked door (2) - electronic warning sign (2) - safety cabling (2) - programming error (1)

    • administrative procedure mis-steps (9 events) • electrical safety issues (3 events) • laser eyewear issues (4 events) • best practices identified (5 events)

    SLAC Lessons Learned Compilation

  • 5

    LL Example: Shutter Failure

  • 6

    LL Example: Stray Beam Not Blocked

  • 7

    LL Example: Safety System Programming Error

  • 8

    LL Example: Exposed Electrical Hazards in some flashlamp-pumped lasers

    → some commercial lasers have exposed HV hazards when covers are removed for service/maintenance (ex. cavity optics tuning or aligning injection seeder) + need to address CoHE and evaluate need for LOTO when changing flashlamps

    SLAC has add to add protective barriers on some flashlamp-pumped lasers (shown in photo with associated warning labels)

  • 9

    LL Example: Entry Door Closer needed for Hutches that are often “uncontrolled” areas

  • Laser source inside enclosure

    Laser beam path (shown in red) if temporary beam block removed

    Shutter enclosure with safety shutter removed and 2 covers removed

    Incident Description: • Laser operator noticed red laser beam on shirt sleeve while locating a new laser optic in “stretcher” enclosure downbeam of the shutter enclosure, during “Class 1” operation mode when laser beams are required to be fully enclosed • No PPE laser eyewear was being worn, since not required for Class 1

    2011 “Class 1 Enclosure” Incident

  • 2011 “Class 1 Enclosure” Incident

    Root Causes – Lessons Learned: 1. Inadequate Work Planning and Control to assess potential hazards associated with moving

    a safety shutter and to determine if supervisor approval was needed. 2. Inadequate configuration control for laser safety devices. 3. Priority given to laser optics work rather than to restoring functionality of a laser safety device. 4. Failure to verify laser safety enclosures to ensure that a zero energy condition exists to

    allow Class 1 operation mode with no laser eyewear required.

    Incident Details • Day prior to incident, safety shutter removed to accommodate a new optic being installed (Faraday isolator to prevent back reflections into oscillator). • Laser system then operated in Class 4 maintenance mode

    (PPE required) but safety shutter functionality not restored. • At end of day, laser system is put to Class 1 mode, but without the required safety shutter and 2 covers • Following morning, laser operator enters to work in Class 1 (PPE not required) when event occurs.

  • 2011 “Class 1 Enclosure” Incident: Corrective Actions

    For Laser Lab • OJT and SOP updates to address configuration control and verification procedures when setting Laser Off and Class 1 modes • Relocated safety shutter and implemented smaller enclosure for safety shutter • Laser safety device label over securing bolts for safety shutter • Posted procedure for setting Class 1 mode at point-of-use at control panel

    For Laser Safety Program/Other laser labs

    • Safety configuration control requirements: - OJT syllabus and SOP must include these (ex. moving a safety shutter)

    • Class 1 Operation: - Unattended Class 1 should not be permitted if removable enclosures are not

    interlocked or secured with administrative locks - In uncontrolled areas, removable Class 1 enclosures must have non-defeatable

    interlocks (exception may sometimes be approved for administrative control lock) - Class 1 conditions must be verified when setting Class 1 mode and when

    entering or exiting the lab in this mode • Lessons Learned document on this incident distributed to SLAC personnel and DOE laser safety group

  • 2012 Incident – Laser Operator forgets to put on Eyewear PPE when entering NHZ









    Nominal Hazard Zone

    Key Controlled


    Outer Entry Door

    PPE Storage

    (Eyewear) Laser Entry


    Inner Entry Door

    Laser Curtain

    Work Area 0utside NHZ

    (No PPE Required)

    Computer Station

    Location Worker realizes not wearing protective

    Laser Eyewear

    NHZ (PPE Required)

    Key Controlled


    Shared Optics System

    Computer Station


    les L




    Operator realizes mistake after ~5 minutes, when notices light at an uncovered enclosure when returning to a computer work station outside the NHZ

  • 2012 Incident – Exposure to Diffuse Scattered Laser Light

    Beam paths at unenclosed UV tripler Color-coded beam paths added to photo. Camera has much better sensitivity to 760nm than eye. Laser worker would likely have perceived a low level of diffuse scattered 380nm radiation rather than 760nm radiation.

    → determined that no credible exposure risk to primary or stray beam, and that exposure to diffuse radiation was below MPE

  • 2012 incident: Causes, Corrective Actions, Lessons Learned

    Contributing Causes • Human error forgetting to put on eyewear • Lab configuration: lack of robust warning barrier indicating eyewear required at curtain entry to NHZ • Laser operator worked in this lab infrequently

    Added sign-barrier above that you bump into as entering NHZ through laser curtain maze

    Corrective Actions • Sign-barrier added at NHZ entry • Root cause analysis investigation (just completed) • Incident communicated to all SLAC laser personnel

    Lessons Learned • Mistakes occur. Need fault-tolerant systems so single mistake won’t lead to an exposure • Laser personnel need awareness of diffuse exposure hazards and importance of eyewear protection for this • Best Practice: lab has very good barriers, enclosures – so no credible exposure risk to primary/stray beam • Extent of Condition: this is only SLAC lab with a work area inside an LCA that is outside the NHZ, but expect similar configurations in future → NHZ entryway requirements for these

  • Lessons Learned Events: Summary Comments

    Important to identify and communicate lessons learned!

    Lessons learned and near misses are precursors to injury accidents • understanding these and implementing corrective actions can help prevent an injury

    Identify best practices as well as needed corrective actions Encourage reporting

    • regular communication of lessons learned can foster this

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