ML20237L102
| ML20237L102 | |
| Person / Time | |
|---|---|
| Issue date: | 03/13/1985 |
| From: | Johnson T NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS) |
| To: | Day J ASSOCIATED TECHNOLOGIES, INC. |
| Shared Package | |
| ML20237L079 | List: |
| References | |
| REF-WM-91 NUDOCS 8709080216 | |
| Download: ML20237L102 (2) | |
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NUCLE AR REGUL ATORY COMMISSION WASHINGTON. D C. 20555 l
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J. E. Day Senior Vice President Associated Technologies Incorporated Suite 300 212 Snuth Tryon Street Charlotte, NC 28281
Dear Ar. Day:
1 This letter is in response to your correspondence dated February 7,1985, discussine the waste fonn stability of products solidified in bitumen. We are currently preparing a Draf t Regulatory Guide on Waste Form Stability and desire to address behavior of bitumen under mechanical loads.
It is our objective to present ccepressive strength recommendations consistent with the 30 CFR Part 61 stability requirements. We appreciate your input into the resolutier. of this matter.
Your letter cites many of the attributes which make bitumen an econorical, leach-resister.t disposal form for low-level radioactive waste.
Recognizing that bitumen lacks the characteristic of physical strength. ATI states that it believes that waste form strength need not correlate with radionuclides releases. While this may be true in some instances, the dimensional stability (i.e., the viscosity) of the waste form may effect radionuclides releases from the disposal unit.
The performance objective for site stability, !61.44, states that "the discesel f acility must be sited, designed, used, operated and closed to achieve lofig-term stability of the site and to eliminate to the extent practicable the neec for ongoing active maintenance of the disposal site following closure so that only surveillance, monitoring, or minor custodial care are required."
Therefore, a disposal system should minimize the need for custodial care and the repair of trench subsidence effects. Considering evidence that bitumen waste forms may flow under their own weight (i.e., they may be dimensionally unstable under burial conditions), it is likely that once the container has corroded the waste form will tenc to flow into adjacent void 50 aces. This r.ay pennit settling of material from above, and the eventual need for remedial care.
In addition to the perfonnance objectives which require the minitrization of active maintenance, there are also other concerns. As recognized in the letter, trench subsidence provides a means for water to collect and enter the trench. And even though bitumer weste forms exhibit very good RECEIVED 8709080216 070818 N4k I $ Q,
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i leach-resistance, adjacent waste forms of a different tyoe may be less leach l
resistant, thereby creating a pathway for radionuclides releases. There are i
options which could reduce the likelihood of trench subsidence or its impact on j
other waste forms, such as, greater administrative procedures on backfilling or segregation of bitumen waste forms into an engineered structure which would provide stability. However, any such ootion would add additional cost to the disoosal of a bitumen waste form. This cost penalty may decrease the competitiveness of bitumen as a waste form.
Increased cost wnul d also be reflected in the remedial care necessary to repair trench subsidence, which l
frorr cast experience is neither simple nor inexpensive.
Although leach resistance is an important product quality a degree of product stability must be present to achieve the long-tem goal of site stability. The.
issue then becomes, what is necessary to produce the assurance-that bitumen waste foms will contribute to the goal of trench stability and minimal custodial care.
The NC.C believes this is an important issue which needs a resciution. We appreciate your current response and believe further discussion would be advantageous in reaching a solution.
1 If you have any questions, ple::se call me at (301) 427 4088.
i Sincerely,
/
mothy
. Je nso, Section Leader T
Materials Engineering Section Engineering Branch Division of Waste Management
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