Re: Silica Products - Path Forward RequiredFrom: William V. Slavin Sent: Monday, December 12, 2005 10:46 AM To: Geoffrey J. Gettelfinger; Jerry D. Levine Cc: Paul Goranson; Bradley E. Nelson; Wayne T. Reiersen; Erik D. Perry Subject: Re: Silica Products - Path Forward Required In the past we expressed some concerns over the use of these products, but not for the reasons you are mentioning here. The first major clarification I should make is that only the crystalline form of silica is considered a carcinogen (cancer causing material). This is the type found in concrete or portland cement. You can notice on the MSDS for Perlite, they list “Alpha Quartz” as an ingredient (Section II of the MSDS). This would be the carcinogenic form of silica (quartz is essentially crystallized silica) but they indicate a very low percentage (less than 0.05% by weight). Other forms of silica known as “amorphous” are not listed as carcinogens. This category includes products like diatomaceous earth and silica gel. This form is treated as a nuisance dust, a dust that will cause irritation to eyes, skin and respiratory tract on exposure, but will not likely have any serious lasting effects. As I recall, the main concerns we had about these products were that they cannot be exposed to the levels of heat we expect to get during bake out of the vessel. They could release toxic vapors and degrade when heated. So to answer your questions: 1.. How do we proactively assess how diligent we must be during NCSX construction and subsequent operate-modify-operate cycles to protect test cell accessors from the dust hazard? Answer: Whatever product we choose must be thoroughly reviewed by Industrial Hygiene, and all protective requirements for exposure to that material must be used when accessing. 2. Are shop vacuums acceptable or are HEPA units required? For most instances, a standard shop vac should be acceptable. This will depend on the particle size of the material being vacuumed. If the dust is extremely fine so that it will pass through a standard filter, then a HEPA filtered vacuum would be necessary. 3. What grade of dust masks will be required for our workers (fit checks, medical evals, etc.)? Unless airborne dust was being generated (by stirring, sweeping or blowing the particles), no respiratory protection would be required. For normal activities, such as sweeping, a standard disposable dust mask would be suggested, with only the quick information sheet for voluntary use of dust masks as training. If dust levels became more extreme, then a full respiratory protection program would be required with training, medicals and fit tests. I cannot foresee the need for this level of program. 4. **Are we allowed to accept MSDS’s as accurate?** I always review MSDS’s with a skeptical eye. One must accept the basic facts of an MSDS, such as the ingredient listing, as accurate since no other source of information exists. For the most part, the rest of the MSDS tends to be trustworthy, but we require a review by IH to ensure that the hazards and control measures listed are proper and correct for our application and use. I have never found a company to have any completely false information on an MSDS, but it is frequently incomplete or misleading. More often than not, an MSDS will actually be far more protective and restrictive than needed, requiring respiratory protection and excessive control measures, when none are needed in most applications. This is one of the reasons why I ask for usage information on the Chemical Review Sheet. I hope this answers all of your questions. If not, please let me know and I’ll work with you to resolve all of these issues. - Bill ============================================= William V. Slavin, MS, CIH Industrial Hygiene and Safety Princeton Plasma Physics Laboratory, MS 03 P.O. Box 451, Princeton, NJ 08543 (609) 243-2533, Fax: (609) 243-3375, e-mail: bslavin@pppl.gov ============================================= A day without Fusion is like a day without Sunshine. Visit the Princeton Plasma Physics Lab Home-Page at http://www.pppl.gov -------------------------------------------------------------------------------- From: "Geoffrey J. Gettelfinger" Date: Mon, 12 Dec 2005 10:21:11 -0500 To: "William V. Slavin" , "Jerry D. Levine" Cc: Paul Goranson , "Bradley E. Nelson" , "Wayne T. Reiersen" , "Erik D. Perry" Conversation: Silica Products - Path Forward Required Subject: Silica Products - Path Forward Required Bill/Jerry: I feel the NCSX Project and the PPPL/ORNL parent organizations need to come to a fully-considered position on the industrial hygiene aspects of the various thermal insulation materials that are being considered. A summary memo from the Project (including you fellows as Project stakeholders) should probably be generated so we can refer back to it as questions arise. Problem Statement: Loose gas-filled thermal insulation is required in the variable geometry "annulus" between the vacuum vessel and the modular coils. Separately, space constraints in the cryostat design may drive the Project in the direction of gas-filled insulation as well. Candidate insulations are silica aerogel and perlite. Using word association, one might relate the word "silica" with "silicosis" which could raise concern the minds of some. There is also a proposed use of silica aerogel in a blanket format which, while dusty, does not qualify as "loose" fill. Perlite is not without its own suggestive wording: It is primarily "fused sodium potassium aluminum silicate". A laymen's interpretation of the MSDS content for the above products quickly finds phrases like "nuisance dust hazard" and "non-carcinogenic". The layman assumes we can bathe in these products as long as we wear some ill-fitting discount store dust mask. The MSDS for silica-containing Portland cement, for comparison, uses phrases such as "carcinogenic". The Project will likely use many cubic feet of loose fill and *any* well-designed system will have some leaks because of the products' fine particle sizes. 1. How do we proactively assess how diligent we must be during NCSX construction and subsequent operate-modify-operate cycles to protect test cell accessors from the dust hazard? 2. Are shop vacuums acceptable or are HEPA units required? 3. What grade of dust masks will be required for our workers (fit checks, medical evals, etc.)? 4. **Are we allowed to accept MSDS’s as accurate?** I strongly suspect that I am over-agonizing on these themes but, at least until the Project signs off on a position, this remains an open item. Please advise, informally or by e-mail, on any path forward you feel is appropriate. Some links for those copied follow: MSDS for Portland cement: http://www.vincistone.com/library/msds_lehigh_masonry_cement.htm MSDS for loose perlite: http://www.schundler.com/msdsperl.htm MSDS for loose aerogel: http://www.aerogel.com/pdfs/msdsspaceloftar3100.pdf On the topic of silicosis: http://www.nlm.nih.gov/medlineplus/ency/article/000134.htm Thanks, Geoff