ee Table E-1 inAppendix E for uranium values evaluated for specific release years). For example, thepreviously evaluated 1956 annual releases included 1.6 Ci/yr for U234, 0.08 Ci/yr forU235, and 3.5 Ci/yr for U238.
As the much higher 1956 releases did not result in off-site exposures of public healthconcern, the measured 1985 emissions from uranium metal production in C-340 are belowlevels of public health concern. We will make appropriate revisions in the Public HealthAssessment document to ensure that potential releases from C-340 uranium operations areexplicitly referenced even though such emissions do not constitute a significant source.
ATSDR Response: The Commentor is correct in indicating that the entire smelting processincluded several operations in addition to the smelting furnace. Scrap nickel was subjected tophysical grinding in order to produce a small, uniform feed material. According to airpermit documents and personal communications  this process occurred in enclosedcontainers and emissions were subject to filtration before release to the atmosphere. Aftergrinding, the nickel chips were processed through the calciner to remove hydrogen fluoride(HF). This process was designed to remove gaseous HF and did not release particulatematerials. Although both of these processes may contribute to contamination of the on-siteprocessing facilities, only the smelting furnace emissions served as a significant source ofnickel particulates for off-site dispersion.
ATSDR Response: We will review the document to ensure that all conclusion statementsexplicitly indicate that the results are referenced as modeled (or estimated) airconcentrations. In the absence of directly measured air concentrations, modeled datarepresent the best available information. It is also important to point out that thisconsultation does use measured stack concentrations as the basis for determining the sourceor emission concentrations which is the source term for the dispersion modeling. We haveevaluated extensive amounts of air monitoring data. However, the available data do notinclude ambient nickel analyses. Even if such data did exist, it is very unlikely that themonitor locations would have been appropriately located so as to assess the spatiallyrestricted areas affected by emissions from the nickel smelter. As our modeled ambient airconcentrations are based on measured stack concentrations and are consistent with measuredsoil concentrations, we are confident that the results of the evaluation are protective of publichealth.
ATSDR Response: According to the information available , stack concentrations weremeasured for three separate trial runs of the batch smelter using an average of 96% of themaximum charging capacity. The average annual smelter output was ~72% of the annualmaximum charging capacity. Therefore, the trial runs were conducted using conservativeestimates of operating capacity. ATSDR used an estimated instantaneous nickel emissionvalue that was 13% greater than the measured average trial run value. Overall, theseemission and production values indicate that ATSDR employed health protective estimatesof annual production and instantaneous emission rates in estimating airborne nickelconcentrations to off-site areas.
The odd thing about some of the slag was it's tendency to roll onto the surface of themelt in the form of golf ball sized spheres which were sometimes kept as souvenirs onworker's desk. A more accurate estimation of releases could be made by having thesespheres tested (they are still around, no pun intended) or better still performing amass balance (drums of flakes were weighed and sampled before and ingots weretested after they were cast so total material lost could be estimated). [redacted name]in the C-710 building closely studied distribution of materials within the meltingprocess and his documents detail his findings (a search of the database using his nameas the author should kick out some good information, e.g. K/TL 338-339-443 andK/PS230). If nothing is easily available I could provide some of the analytical result