ML18025A619
| ML18025A619 | |
| Person / Time | |
|---|---|
| Site: | Susquehanna  |
| Issue date: | 01/19/1978 |
| From: | Curtis N Pennsylvania Power & Light Co |
| To: | Parr O Office of Nuclear Reactor Regulation |
| References | |
| Download: ML18025A619 (7) | |
Text
REGULATORY INFORMATION DISTRIBUTION SYSTEM
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DISTRIBUTION FOR INCOMING MATERIAL 50-387 REC:
PARR O
D NRC ORG:
CURTIS N
W PA PWR S: LIGHT DOCDATE: 01/19/78 DATE RCVD: Oi/31/78 DOCTYPE'ETTER NOTARIZED:
YES COPIES RECEIVED
SUBJECT:
LTR 1
ENCL 0 INFO COI4CERNING THE CURING PERIOD AND PROTECTION FROM FREEZING OF CONCRETE DURING COLD WEATHER CURING.
PLANT htAl"IE: SUSQUEHANNA Ul'lIT 1
SUSQUEHANNA UNIT 2 REVIEWER INITIAL:
XBT DISTRIBUTER INITIAL:
DISTRIBUTIOi4 GF THIS MATERIAL IS AS FOLLOWS PSAR/F AR At'IDTS AI4D REl ATED CORESPGNDENCE (DISTRIBUTION CODE B001)
FOR ACTION:
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TWO NORTH NINTH STREET, ALLENTOWN
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January 19, 1978 Director of Nuclear Reactor Regulation Docket Nos. 50-387 50-388 Attention:
~ Olan D. Parr, Chief Light Water Reactors Branch No. 3 U.S. Repulatory Commission Washington, D.C.
20555
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fO SUSQUEHANNA STEAM ELECTRIC STATION COLD WEATHER CONCRETE REQUIREMENTS ER 100450 FILES 840-2 & 150-1 PLA-210 We have received your letter of December 29, 1977, and note that your staff agrees with our proposal to provide a minimum period of 3 days for protection of concrete from freezing.
However, there has obviously been a misunderstanding by your staff of the state-ments in our letters regarding cold weather curing of concrete.
We assure you that we did not have "... the misconception that freezing protection and curing of concrete are one and the same..."
This is a misleading conclusion apparently drawn from the combined statement of PROPOSAL in our letter of March 30, 1977, our letter number PLA-168, which is worded "Proposal to reduce the minimum required period of curing and protective measures for concrete
- members, 2s feet or less in the least dimension, during cold weather, from seven days to three days and the requirements of Table 1.4.2 of ACI 306."
We particularly must take exception to the accompanying staff statement which reads "Because of this misconception, the stipulations in various ACI specifica-tions have been erroneously interpreted as indicated in the following comments...".
Freeze protection and cold weather curing during the first few days must occur within the same environmental space and must occur simultaneously.
ensure that the water in freshly placed concrete does not crystallize due to freezing prior to the time when the concrete has attained a strength level of 500 psi.
ACI 306-66 recognizes this, as we previously stated in our letter of June 14, 1977.
Curing of concrete is defined as the protection of new concrete from drying out so that adequate hydration may be achieved.
The rate of hydration which takes place in new concrete generally determines the rate at which the concrete will gain strength, all other mix design features Hydration is primarily influen'ced by the cement content, heat, and
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Page 2
water content in the freshly mixed concrete.
We reiterate the statements of ACI 306-66, Chapter 9, COLD WEATHER CURING REQUIREMENTS AND METHODS:
1)
Paragraph 9.1:
"It is essential that new concrete in all weather be protected from drying out so that adequate hydration may be ach1eved.
This requirement normally means that positive measures must be taken to prevent excessive evaporation of moisture from concrete.
During the winter however when the air temperature is below 50 F 10 C), atmospheric conditions in most parts of the country are such that undesirable dry will not occur.
Furthermore, new concrete is vulnerable to freezing in a saturated condition.
Therefore, all concrete should be allowed to undergo some drying before being exposed to f'reezing teraperatures."
2)
Paragraph 9.2:
"Although concrete exposed to cold weather is not likely to dry out at an undesirable rate, particular attention should be given to concrete that is undergoing the protection required by Table 1.4.2.
As long as forms remain in place, surfaces adjacent to the forms are adequately cured in cold weather...".
We have restated these fundamentals because we wish to make it perfectly clear that we hav'e no misconception about the similarities or differences in the requirements for protection from freezing an%r the requirements for cold weather curing; We have been placing high quality concrete - generally much higher than required by existing codes and regulatory requirements - since the beginning of our construction project in 1973.
We have no desire to reduce this high quality standard - either now or in the future.
- However, when we have sufficient evidence that supports an improvement in field procedures and the implementation of this improvement will meet regulatory requirements as well as reduce project costs, without sacrificing the high quality of our
- concrete, we are obligated in the interest of maintaining our costs as low as possible, to implement these improvements.
We strongly believe that a minimum cold weather curing time of three d
is within the scope of ACI 306-66.
We refer to Chapter 9, and in par c
to Paragraph 9.3, "Following the removal of the temperature protection, no positive measures to prevent excessive evaporation are required as long as the air temperature remains below 50 F (10 C).
An exception is coBcrete placed in extremely arid regions where the relat)ve hum)dity at 50 F (10 C) may be expected to be below 40 percent and at 40 F (4.5 C) below 60 percent...".
Weather records from the AVOCA, Pennsylvania Airport weather station conf1rm that the average winter humidity for the region near our project job site is above these minimums and. meets the requirements of this specificat1on.
We have submitted extensive test data to verify that our own project concrete mixes will comply with the curing requirements of ACI 306-66, Chapter 9 when
I y1
cc-Messrs:
R. W. McNamara H. L. Harris J. R. Schmiedel M. R. Muir R. J. Shovlin W. E. Barberich E. M. Mead A. M. Male A. R. Sabol J.
W. Geiling G. E. Shamis Letter File N-5 Susq.
SES Bechtel Bechtel N-4 N-4 N-5 N-5 N-4 N-5 N-2 N-3 NWC/RR4/gaf
Page 3
cured for the minimum 3-day period..
Although ACI 301-72, Chapter 12, refers to a minimum concrete curing period of 7 days, it also refers to ACI 306 for detailed recommendations concerning cold weather concrete curing procedures.
We have prev1ously submitted justification to you for the use of flyash in our concrete and the establishment of a 'minimum curing period of 7<<days for massive structural concrete, as well as other specific design requirements supplemental to the ACI 301-72, ACI 306-66, and ACI 318-71 specifications.
These modifications have been approved by your staff, PSAR changes have been submitted, and the field construction work is being performed accordingly, as verified by your conrpliance inspectors.
Please refer to our letter (PLA-70) to NRC dated July 1, 1975.
Amendment $17 to our PSAR, dated March, 1975, Paragraph 5.2.5.1 d states "Admixtures shall conform to ASTM C-618 for pozzolans...".
Almost all of our concrete, since the beginning of our pro-ject concrete work in 1974, has contained pozzolan (flyash) and has a design strength specified. to be attained at 90 days.
PSAR Amendment No. 16 dated November ll, 1974, contained this specification, but it was inadvertently omitted from subsequent PSAR Amendments.
It has been incorporated 1nto the PSAR Amendment No. 20 which was submitted. recently.
We request that you review the above mentioned considerati.ons, including the intent of ACI 306-66, and concur with our proposed minimum cold weather curing period of 3-days for the Susquehanna Steam Electric Station Project concrete.
This procedure is also subject to the conditions of Paragraphs 9.3 and 9.4 of ACI 306-66.
If you would like further clarification or justificat1on for our statements on cold. weather curing of concrete, we would be happy to d1scuss these with you, either by telephone or in a meeting at your convenience.
Very truly yours, Vice President - Engineering and Construction Sw rn to and subscr bed before me this
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