ML19317E946
| ML19317E946 | |
| Person / Time | |
|---|---|
| Site: | Oconee  |
| Issue date: | 03/16/1971 |
| From: | US ATOMIC ENERGY COMMISSION (AEC) |
| To: | |
| Shared Package | |
| ML19317E945 | List: |
| References | |
| NUDOCS 8001070740 | |
| Download: ML19317E946 (3) | |
Text
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_U, DUXE PO'.1ER COMP ANYi-OCOMEE NUCLEAR STAT!0N DOCXET i.D.
5S-25s TECHMICAL S?ECIFICATIOWs - Es. Sis FOR 6?ERATING LIMITS t
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The proposed operating limitations for the initial tuo years of plant operati'on are based primarily on: (a) f recent findings on thicknc,ss effect on the fracture toughness of heavy sectio ferritic steels, and (b) on.the available fracture tcughn5ss data obtained from tests on the actual material of the reactor vessel.
Current ASME Section III Code rules permit that a vessel be pressurized only above a temperature equal to the sum of the Nil buctility Transition (NDT) temperature and 60* F.
The EDT temperature, according to paragraph N-331 of the Code, can be obtained by either the drop-weight test (DWT) or the Charpy V-notch (Cv) impact However, recent fracture toughness test data test.
indicate that the current ASME Code rules are not always sufficiently conservative, and may not guarantee adequate fracture toughness of ferritic materials.
While the Charpy V-notch tests continue to be useful in measuring the upper shelf fracture energy valu'e, the Cv specimens, generally, do not predict correctly the NDT temperature.
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The la t'ter,.therefore, must be obtained from other tests, such as the DWT test.
Quite of ten, also, considerable difficulty'e'xists in defining from the Cy test curves the
-transition temperature region.in which fracture toughness of ferritic-m[?terials increases rapidly with temperature.
In' addition, Ithis transition temperature regien shifts to e
j higher temperatures when the thickness of the specimen 1
i tested is increased (size effect).
The proposed heatup and cooldown limitations are based on the available fracture toughness test data for the reactor vessel material, and several assumptions.
These assumptions relate _primarily to the interpretation of the
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available Charpy V-notch test data, and are necessary
_because DWT test results, weld metal prop'rties, or, the e
Cv upper shelf fracture energy levels, were not required
,r by the ASME Code rules.
Specifically, the maximum initial 1
NDT temperature for the materials of the reactor vessel l
(including welds) was-assumed 'to be 50 F.
To assure adequate i
f fracture toughness _ level at the11nitial lowest pressurization L
temperature * (LPT), a ' temperature margin of 80* was added-t
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. pressurization temperc:ure of a. component is the lowest temperature at unich the pressure within the componen:
exceeds 25 percent of the system normsi c?arating pressura, or at; which the rate of temperature change in -the componsn mater.ial ~excecos 50*F/hr. under normai oparation, systam hydrostatic tests, or transient conditions.
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.. -to the assumed NDT temperature of unirradiated material, plus a size effect of 80*F, obtained from the formula:
I size effect = 27'F/ t - 1/ 2,
.;here t is the maximum section thickness in inches.
The LPT for the unirradiated vessel was thus es.imated t
to be 210* F.
Using the estimated shif t in the transition j
' temperature, due to neutron irra'diation, of 6o F, the LPT of 275*F has been'specified for the first two years of plant operation.
These operating limitations will
. require rev'lew, and.probably ravision, when the data are i-made availatle from the material surveillance program test resultNh.following the first capsula withdrawal.
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