ML20012E319
| ML20012E319 | |
| Person / Time | |
|---|---|
| Issue date: | 03/07/1990 |
| From: | Kane J NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS) |
| To: | Surmeier J NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS) |
| Shared Package | |
| ML20012E320 | List: |
| References | |
| REF-WM-3 NUDOCS 9004030221 | |
| Download: ML20012E319 (3) | |
Text
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At \\JK-SURME.NTE f
j MAR 61 190 MEMORANDUM FOR:
John J. Surmeier, Chief o
I Technical Branch Division of Low-Level Waste Managemer.t and Decommissioning, NMSS l
THRUt Michael Tokar, Section Leader l
Technical Branch Division of Low-Level Waste Management and Decommissioning, NMSS FROM Joseph D. Kane Technical Branch Division of Low-Level Waste Management l
and Decommissioning, NMSS
'L
SUBJECT:
TELECON RECORD OF DISCUSSIONS ON TECHNICAL DIFFERENCES REIATIVE TO USE OF CONCRETE IN STRUCTURES BUILT AT LLW DISPOSAL FACILITIES t
In ef forts to coordinate the BGV PIASAR review, J. Kane became
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aware of differences in technical opinions between the U.S. Army Corps of Engineers (COE) and the National Institute of Standards and Technology (NIST) relative to the use of concrete in structures proposed to be bililt at LLW Disposal Facilities.
Enclosures 1 and 2 to this telecon record summarizo the technical opinions on this subject from both the NIST and the COE, I
respectively.
i To address the differences in technical opinions, J. Kane arranged a telecon on February 15, 1990 between NIST (Dr. James Clifton) and the COE (Dr. Robert Denson).
To keep the l
discussions focussed on the major differences, it was agreed at i
the start of the telecon to address the three main issues which included (1) what unconfined compressive strength, f' (4,000 psi j
versus 12,000 psi) should NRC recommend for portland,ement i
c concrete to be used in stntctures at LLW disposal facilities, (2) i should NRC continue to recommend the use of Type V portland l
cement, and (3) the appropriateness of using accelerated tests for evaluating the long-term performance of sealants and moisture i
barrier coatings.
i Item No. 1 - 4.000 r,gLyersus 12.000 osi Concrete Strenath.
NIST stated the opinion that requiring a 4000 psi unconfined
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compressive strength was too low and would permit concretos to be
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provided that were not dense, nor of low-pertneability or good durability and quality characteristics as needed for the 300 to i
500-year period of performance.
The COE indicated a high level of workmanship, that was directed at obtaining a dense, minimum Mgd
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strength 4000 psi concrete that would include mixtures to reduce l
the water-cement ratio (w/c), would result in a low-permeability NIST fcit the higher strength criteria waspM /[
i and durable concrete.
9004030221 900307 3
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reasonnble and obtainable by current concrete companies and the higher strength concrete was not that more expensive.
The COE cautioned that adoption of a higher strength concrete could possibly result in attempts by designers to reduce the size and thicknesses of concrete elements.
After considerable discussion, an agreement was reached that was acceptable to all participants in the telecon.
The agreement reached suggested that NRC continue to recommend a minimum unconfined compressive strength of 4000 psi at 28 days age with words to be added to state "as necessary to meet imposed loading conditions."
In addition, to better ensure the attainment of a dense, durable, low-permeability concrete, NRC should consider establishing limits on the w/c ratio.
It was suggested that w/c ration ranging from 0.4 to 0.5 be considered for concrete mixes without water-reducing admixtures (WRA) and W/c ratios ranging between 0.2 to 0.3 for mixes using WRA.
Item No. 2 - Recommendina Tvoe V Portland Cement.
NIST questioned the COE about its experience with problems associated with the use of Type V portland cement that included a slower gain in compressive strength than normal, and micro-cracking of the concrete.
The COE acknowledged that the gain in compressive strength for Type V cement was slower, but not unusually slow to where it presented problems.
Also, the extent of micro-cracking needs to be controlled in concrete structuren, but the use of Type V cement was not considered to be a problem in causing unusual micro-cracking.
It was indicated that micro-cracking may be caused for a variety of differen0 reasons (e.g.,
improper curing).
In the discussions on this item it was recognized that the COE#s recommendation to use Type V cement also permitted alternatives to be selected, such as the use of Type II cement with partial replacement of the cement with a pozzolan or silica fume.
Based on the telecon discussions, NIST indicated that it no longer had concerns related to the COE's recommendation to use Type V cement.
In the course of the discussions on this item, the COE had indicated that superplasticizers would always be needed when silica fume was to be added as an admixture.
NRC requested the COE to reexamine their recommendations, in NUREG/CR-5041 to verify that this is clearly stated in the COE's recommendations to the NRC.
Item No. 3 - ADDropriattness of Usina Accelerated Tects.
NIST questioned the COE's statement in Encl. 2 related to favoring long-term tests over acce'ierated testing with regard to the performance of moisture barrier coatings and sealants.
HIST noted the scarcity of information and history that is avai)able to support conclusions on the long-term performance of barrier i
coatings and sealants.
The COE clarified its statement in to indicate that it did not have problems with requiring accelerated tests, but that there is a need to avoid l
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3 prejudicing the re Cit 3 Cf cccelcr;ted tC t because Cf L.'
preconceived cssumptions.
The COE C; knowledged thtt it doe 3 j
conduct accelerated tests in its work at WES and that accelerated i
i tests, if properly conducted, would be useful in addressing the i
scarcity of data and information on the long-term performance of
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p barrier coatings and sealants.
p At the conclusion of the discussions, J. Kane noted that the telecon had permitted a consensus opinion to be reached on the three major differences.
Mr. Kane expressed gratitude for the professionalism and frankness of the consultants in addressing these apparent differences which began with their willingness to openly express, and communicate their technical opinions in 6
Enclosures 1 and 2.
t Both the NIST and the COE noted that their experiences would I
i indicate that problems often develop when moving from design and l
specification requirements to actual field construction.
Both consultants strongly recormended that NRC attempt to eliminate f
these problems by requiring regulatory quality assurance audits i
of the hardened in-place concrete at LLW disposal facilities to
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demonstrate that dense and durable concrete was actually provided.
The contents of this Telecon Record have been reviewed and concurred on by J. Clifton and R.
Denson.
Joseph D. Kane 0%ul:4nd by Technical Branch Division of Low-Level Waste Management and Decommissioning, NMSS -
f Dec. 4, 1989 Ltr. w/ encl. from NIST Jan. 19, 1990 Ltr. v/ encl. from COE cc:
J. Kane J.
Philip, RES J. Clifton, NIST l
R.
Denson, COE Distribution:
R.
Bangart NOTE:
Correct and proper spacings J. Greeves appear on the original J. Surmeier document.
Room had to be M. Tokar compromised for the B. Jagannath concurrence chain on NRC's j
K. McDaniel internal copy.
R. Shewmaker E. Wick D. Widmayer Distribution:
,contralSFilos t?
LLTB r/f NMSS r/f JSurmeier PDR Yest/ 5( /
PDR No:/
Reason:
Proprietary /
/ or CF Only /
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ACNW Yes:/
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Nos/
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OFC :LLTB LL B
- LLTB
- LLWM JKane/ljh MToka M
DATE: 3/6/90 pr /00
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