ID 1108 Laser-Safety Program at the National Ignition Facility (NIF)

K. Barat1, F. Rainer2

1 Lawrence Livermore National Laboratory, NIF Directorate, Livermore, California, USA

E-mail Barat1@llnl.gov2 Consultant, Livermore, California, USA

E-mail rainer3@comcast.net

Abstract. When completed, the National Ignition Facility (NIF) at the Lawrence Livermore National Laboratory (LLNL) will be the largest laser in the world. NIF is designed to be a 192-beam, 1.8-MJ laser for creating plasma conditions of extreme temperatures and pressures in the laboratory. Experiments with NIF will access high-energy-density and fusion regimes with direct applications to stockpile stewardship, energy research, basic science, and astrophysics. The facility is the size of a sports stadium, and the laser system, produces 1000 times the electric-power-generating capacity of the United States. In addition to the NIF facility itself, approximately 70 laser laboratories at LLNL make up the NIF Directorate. This poster explains what NIF is and some of the laser-safety problems and solutions utilized by the NIF Directorate Laser Safety Office to provide laser safety in a research setting. 1. Description of NIF The National Ignition Facility (NIF) at Lawrence Livermore National Laboratory is a stadium-sized facility containing a 192-beam, 1.8-Megajoule, 500-Terawatt, ultraviolet laser system together with a 10-meter diameter target chamber with room for 100 experimental diagnostics. NIF is the world's largest and most energetic laser experimental system, providing a scientific center to study inertial confinement fusion and matter at extreme energy densities and pressures. NIF's energetic laser beams will compress fusion targets to conditions required for thermonuclear burn, liberating more energy than required to initiate the fusion reactions. Other NIF experiments will study physical processes at temperatures approaching 10e8 K and 10e11 bar, conditions that exist naturally only in the interior of stars and planets. NIF has completed the first phases of its laser commissioning program. The first four beams of NIF have generated 106 kilojoules in 23-ns pulses of infrared light and over 16 kJ in 3.5 ns pulses at the third harmonic (351 nm). NIF's target experimental systems are being commissioned and experiments have begun. 2. Laser Safety Challenges In addition to the NIF project a large number of laser-research laboratories support the NIF project. Both areas fall under the jurisdiction of the NIF Directorate Laser Safety Office. The research setting presents the greatest challenge to the Laser Safety Officer (LSO). This is because the personnel using lasers are deliberately manipulating optics and beam paths, placing individuals into potentially hazardous situations. Some of the challenges needed to be addressed by the Laser Safety Office at NIF are: multiple laser set ups linked together, use of vertical laser tables, fiber optic propagation, use of extremely high-power laser beams, varied work force (users, technicians, construction staff), required active beam manipulations, wavelength variation, long and expanding beam paths, adaptive optics, and the providing of laser safety in a timely manner to meet project milestone goals. 3. Description of Laser Safety Program

The chief role of the NIF Laser Safety Office is to develop control measures that strike a balance between providing safety and not unreasonably constricting work activities. With the buy-in by laser users this yields the highest level of compliance. The overall guidance for laser safety comes from the American National Standard Institute, Z136.1, and “Safe Use of Lasers”. 3.1 Integrated Safety Management (ISM) ISM is the management system for doing work safely and has been adopted throughout LLNL and the NIF Directorate. It has five functions: define the scope of work; analyze the hazards; develop controls; perform the work; provide feedback and improvement. ISM has seven guiding principles: line management is responsible for safety; roles and responsibilities are clear; competence must be commensurate with responsibility; priorities need to be balanced; safety standards and requirements are identified; hazard controls are tailored to the work; and operations are authorized. 3.2 Operational Safety Procedure Documentation The hazard management philosophy of ISM has been embraced by the Department of Energy (DOE), LLNL and the NIF Directorate. Part of that is identifying hazards and setting appropriate controls. A safety-review document, called an Operational Safety Procedure (OSP), is required for laser laboratories using Class-3b or Class-4 lasers. It identifies the reasons for the requirements, responsibilities, work activity descriptions, hazards and controls, training, maintenance, emergency response, references, and review and management approval chain. In addition the OSP contains a Laser Table which itemizes each laser with its output specifications, Maximum Permissible Exposure (MPE), Optical Density (OD) required for direct and diffuse exposure protection, Nominal Hazard Zone (NHZ) if applicable, and skin exposure MPE. The NIF LSO assembles a binder for this OSP documentation. 3.3 OSP Binder The binder contains a copy of the OSP, relevant Environmental, Safety and Health (ES&H) Chapters for user guidance, laser-based lessons learned, a log for interlock checks, contact information, laser alignment guidelines, emergency instructions, answers to frequency asked laser-related questions, and a matrix which shows training requirements and compliance for each user. In addition, every six months, each user is required to sign a form indicating he or she has read the OSP and understands its requirements. 3.4 Audits At a minimum an annual audit is conducted in each laser laboratory for all possible hazards (laser, electrical, mechanical, chemical, etc.) as part of the annual renewal process for each OSP. For new projects a management pre-start walk through is also required. The LSO, in addition to this annual review, performs an informal walk through of laboratories and follows up to see that interlock access checks are performed and documented. The LSO also advises laser users on control options for new projects, and off-normal conditions such as service or initial start up. 3.5 Postings It is the responsibility of the NIF LSO to generate all laser-related laser warning signs and labels used within the NIF Directorate, i.e. for doors, protective housings, and beam tubes. This allows customization of signs and greater transmittal of information regarding the true nature of hazards and controls. 3.6 Training

At LLNL, basic and refresher laser-safety training is web based. In addition the NIF LSO gives supplemental laser-safety training when requested for special audiences needing laser-awareness training or for laser-related hazards, such as laser robotic activities. The NIF LSO attends varies research group meetings where focused training and lessons-learned sessions are given. 3.7 Laser Updates The NIF Laser Safety Office routinely distributes updates on laser-safety issues to laser users. This may cover new laser-safety tools (such as hands-free viewers or eyewear), upcoming conferences, accident news, or science-based humor. These updates serve both an informational and safety-booster function. 3.8 Laser Table The Laser Table, noted above, is used to characterize all laser sources used within a facility. It gives the user a means to quickly see what OD would be required for laser protective eyewear. It allows the LSO to approve the use of alignment eyewear and aid the user in determining the correct OD for such eyewear. Indirectly it can help reinforce the rationale for other control measures. 4.0 The NIF Project Site The NIF Project presents further unique challenges to the implementation of laser safety because of its large size and the great number of individuals working there. 4.1 Safe Plan of Action (SPA) Prior to beginning any work activity at NIF, each work group is required to conduct a SPA. Its goal is to ensure all workers understand what activities they are expected to complete that day, what hazards they might encounter, and what the appropriate controls are. As part of the SPA process, each worker signs a SPA form each day acknowledging his or her understanding of the work activity. 4.2 Work Permit The work permit is part of the NIF work-authorization process. The permit is generated, reviewed, approved and issued prior to the commencing of a well-defined work activity to assure that it is done safely in conjunction with other potentially competing activities. 4.3 Laser Safety Gram (LSG) Unique laser-hazard evaluations are documented with an LSG, which provides a detailed laser-hazard analysis for particularly complex NIF-specific laser activities. These LSG’s are used to determine the level of hazard and what controls need to be described in the OSP. 5.0 Conclusion The Laser Safety Office at the NIF Directorate provides guidance for administrative and engineering controls for laser-safety issues. It encourages the development of a user culture receptive to a strong safety message both by laser workers and management. Such activities support the Directorate’s goal of zero accidents. The control measures used by the NIF Directorate are intended to be flexible and adaptable for laser use at all NIF Project and ancillary NIF laboratory facilities.