Mitsubishi Silicon America - South Campus - Executive Summary

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Mitsubishi Silicon America (MSA) is a division of the Mitsubishi Corporation and is a full service supplier of electronic grade polished and epitaxial silicon wafers to the semiconductor industry.  MSA has two facilities in Salem: the North Campus and the South Campus.  The MSA - South Campus has two processes within the campus boundary which use a chemical subject to the RMP regulation: anhydrous hydrogen chloride (HCl) for the epi process (CVD reactor etching) and anhydrous ammonia (NH3) for wet cleaning of wafers.  The HCl system is owned by MSA, however it is operated and maintained by BOC Edwards employees permanently onsite.  The NH3 storage and delivery system is owned, operated, and maintained by Air Liquide.  MSA received permission from the EPA to complete the RMP submittal for all covered process systems onsite. 
 
Pursuant to the Accidental Release Risk Management Planning regulations (40 CFR 68) and the Process Safety Management (PSM) standard, MSA has developed a comprehens 
ive PSM written program to protect workers and the surrounding community from exposure to the hazardous chemicals onsite.  The facility personnel completed a series of process hazards analyses for each covered chemical process using the Hazards and Operability (HAZOP) methodology.  The PHAs were completed using technical and operations staff from the MSA facility (including contract employees from Air Liquide and BOC Edwards responsible for the design, operation, and maintenance of the systems) as well as experienced facilitators from an outside engineering firm. 
 
MSA's implementation of PSM includes employee education in the hazards of the covered chemicals and measures that can be used to reduce employee and community exposure to accidental releases of these chemicals. The PSM plans include preventive maintenance programs (mechanical integrity) for the HCl and NH3 systems as well as programs for both pre-startup safety reviews and management of changes (MOC) to these systems. The pro 
gram also includes specific requirements for safe work practices (such as safe approaches to welding and similar hot work) and safety requirements for contractors who may be hired to work on the systems. MSA also periodically audits Air Liquide's and BOC Edwards' systems to ensure they meet their requirements with respect to Process Safety Management. 
 
Lastly, the PSM written program incorporates the MSA - South Campus' emergency response plan and places special emphasis on handling accidental releases of hazardous chemicals and coordination of emergency response with local fire departments and other emergency response organizations. 
 
As part of the RMP requirements, MSA undertook a review of the potential offsite consequences of the accidental releases of the largest vessels in each of the HCl and NH3 processes at the South Campus.  Although such a release is highly unlikely, the regulation requires this review.  The following is a description of the results: 
 
Toxic Materials - Ammoni 
a and Hydrogen Chloride Processes 
MSA stores two regulated toxic chemicals onsite - anhydrous hydrogen chloride in tube trailers and anhydrous ammonia in a pressure vessel. An analysis of the worst-case scenario was completed for both chemicals, both of which assumed the release of the entire contents of the largest vessel in ten minutes. The worst case scenario for HCl was assumed to be the release of the entire contents of one of the tubes on the tube trailer, and resulted in a potential exposure area reaching offsite receptors.  The worst case for NH3 assumed the release of the entire contents of the storage vessel (taking into consideration the 85% level control on the tank) and resulted in a greater radius of affect than that for the HCl system.  As only the worst case with the largest potential impact is reported, the ammonia release results are included in the submission document.  
 
In determining the alternate case scenario for HCl, MSA analyzed incidents occurring at other sem 
iconductor facilities and the results of the internal process hazards analysis (PHA).  MSA chose a conservative alternate release scenario for the HCl system which assumes a shear of the HCl delivery line from the tube trailer manifold resulting in a release with the potential to affect offsite receptors including residences and businesses.  A more likely scenario for the HCl system would be a release through a relief valve; this was not chosen as it would not be likely to reach an offsite receptor as the relief valves are routed directly to a scrubber system onsite.  The alternate scenario chosen for the NH3 system assumes a leak through a hole in the storage vessel.  Such a release would have the potential to affect local businesses and residences are located in close proximity to the facility. 
 
MSA is committed to minimizing accidental releases of hazardous chemicals from the processes at its facility.  Facility management is involved in the design, operation, and maintenance of the 
toxic chemical systems onsite, both those owned by MSA as well as those owned by contractor chemical suppliers.  Facility personnel at all levels have been involved in the development of the PSM and RMP programs.  MSA management has committed to working with local agencies and the community to educate the public regarding the hazards of ammonia and to ensure a safe workplace and surrounding community.  Requests for information should be addressed to MSA's Public Relations Manager, Ms. Janet Clark.
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