Interpretation Response #10-0018 ([Symmetricon] [Ms. Susan Durr])
Below is the interpretation response detail and a list of regulations sections applicable to this response.
Interpretation Response Details
Response Publish Date:
Company Name: Symmetricon
Individual Name: Ms. Susan Durr
Location State: CA Country: US
View the Interpretation Document
Response text:
March 10, 2010
Ms. Susan Durr
Sr. Logistics Manager
Symmetricon
2300 Orchard Parkway
San Jose, CA 95131
Ref. No. 10-0018
Dear Ms. Durr:
This responds to your January 15, 2010 letter concerning the applicability of the Hazardous Materials Regulations (HMR; 49 CFR Parts 171-180) to a device containing non-radioactive cesium metal (Cs-133). Specifically, you ask whether a device containing ten micrograms (µg) or less of cesium, a Division 4.3 dangerous when wet material, is subject to the HMR.
According to information provided with your letter, the device is a chip scale atomic clock (CSAC) that contains = ten µgs of cesium metal enclosed in a hermetic cell filled with inert gas at < four psig (0.26 atm)). The cesium in the CSAC is contained within four layers of mechanical protection. A worst case scenario analysis of the temperature and pressure if the cesium is exposed to oxygen or water indicates about a 1°C temperature increase in the cell and about a six psig (0.40 atm) pressure rise. You also provide video evidence of destructive testing indicating no perceptible hazardous effects.
Based on your analysis and based on a prior interpretation provided to your company by PHMSA that less than one gram of rubidium (also a Division 4.3 dangerous when wet material) contained in an atomic clock does not pose a hazard during transportation, it is the opinion of this Office that a CSAC containing = ten µgs of non-radioactive cesium metal does not pose a hazard during transportation. Therefore, provided the material does not meet the definition of any other hazard class, the CSAC is not subject to the HMR.
I hope this information is helpful. If you have further questions, please contact this office.
Sincerely,
Charles E. Betts
Chief, Standards Development
Office of Hazardous Materials Standards
173.13, 171.1