ML20237L199
| ML20237L199 | |
| Person / Time | |
|---|---|
| Issue date: | 08/29/1985 |
| From: | Higginbotham L NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS) |
| To: | Lempges T NIAGARA MOHAWK POWER CORP. |
| Shared Package | |
| ML20237L079 | List: |
| References | |
| REF-WM-91 NUDOCS 8709080277 | |
| Download: ML20237L199 (2) | |
Text
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WM FILE 202.2 WMEG NMSS i
AUG 2 9 E5 REBrowning 202.2/TLJ/8/8/85 MJBell j JTGreeves TCJohnson TLJungling --_-
i Materials Section Mr. Thomas E. Lempges HJMiller 4
I Niagara Mohawk Power Corporation J0 Bunting 300 Erie Boulevard West LBHigginbotham Syracuse, NY 13202
Dear Mr. Lempges:
This letter is in response to your correspondence dated June 17, 1985, which presented your views concerning stability requirements for non-brittle waste forms or, more specifically, for asphalt.
We are currently considering means of addressing the behavior of bitumen under the compressive loads of burial which maintain the intent of the stability requirements of 10 CFR Part 61.
We appreciate your input towards the resolution of this matter.
In your letter, you have raised two objections to the possibility of requiring administrative controls for the backfilling of asphalt waste foms.
Restating your objections, they were; first, that voids created by the viscoelastic creep of the waste form will contribute nothing to trench subsidence and secondly, since 10 CFR Part 61 already requires backfilling of the void spaces it is unnecessary to impose additional requirements on asphalt waste foms.
In response to the first objection, we submit that while the creep of an asphalt waste form into adjacent void spaces, does not increase the total void volume within a trench, it may allow the redistribution of the voids so as to permit wastes at higher elevations to move downward.
It is this scenario which may lead to eventual trench subsidence.
This concern will intensify as more asphalt systems come on-line and the volume of asphalt waste forms become a significant percentage of the trench volume.
Regarding your second objection. please consider the stability requirements of Section 61.56(b) which state that " stability is intended to ensure that the waste does not structurally degrade and affect overall stability of the site through slumping, collapse, or other failure of the disposal unit.. "
It further states that a " structurally stable waste form will generally maintain its physical dimensions and its form, under the expected disposal conditions..."
The waste forms which are currently being buried at the disposal sites (brittle waste forms) meet these requirements and in so doing they meet the intent of the Performance Objectives of Part 61, particularly those concerning the release of radioactivity, 961.41 and the stability of the disposal site, {61.44 Since these waste forms meet the intent of the Performance Objectives it is unnecessary to insist that stringent backfilling procedures be exercised to completely eliminate the void spaces.
However, since asphalt waste forms 8709000277 870010 PDR WASTE WM-91 PDR
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AUG 2 91985 may not maintain their physical dimensions they raise doubt and uncertainties as to whether they can meet the intent of the Performance Objectives with the current backfilling practices (as mentioned in the preceding paragraph).
In order to address the uncertainties regarding asphalt's viability,a we are:
proposing the following options-for those waste. forms which defonn in a non-brittle manner.
q 1.
A creep test similar to ASTM D-621 in which the. constant test load simulates the burial load.
Failure may be defined, for example, as greater than 10 percent deformation extrapolated to 300 years.
2.
Alternatively, the vendor could show;that a plan for' administrative controls on backfilling has been established with~ the site operator before their waste forms are emplaced at the disposal site.
The j
controls will insure that the voids between the waste forms are i
eliminated, thereby providing the ' structural stability required by i
10 CFR Part 61, assuming that the waste form is not subject to degradation by other burial-site mechanisms..
3.
Any other approach which demonstrates consistency with the Performance Objectives will be considered.
We hope these conenents help to clarify our position on this issue.
Should you i
have any further questions or suggestions, please contact Mr. Timothy C. Johnson (301) 427-4088 or Mr. Thomas Jungling (301) 427-4540.
Sincerely, Original egncu by Im B. W Leo B. Higginbotham, Chief Low-Level Waste and Uranium Recovery Projects Branch Division of Waste Management
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