ML19309A940
| ML19309A940 | |
| Person / Time | |
|---|---|
| Site: | Rancho Seco, North Anna |
| Issue date: | 09/14/1977 |
| From: | Reid R Office of Nuclear Reactor Regulation |
| To: | Mattimoe J SACRAMENTO MUNICIPAL UTILITY DISTRICT |
| References | |
| NUDOCS 8004010696 | |
| Download: ML19309A940 (4) | |
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r WJu aJJ1N"o September 14, 1977 R
Docket No.:
50-312 ORBf4 Rdg
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, ]!E L01shan TT Sacramento flunicipal Utility District RSnaider
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ATTH: Hr. J. J. Mattisaore TCarter 5.
Assistant General fianager Attorney, OELD E ~~
and Chief Engineer 0I&E (3) 1.:
6201 S Street DEisenhut il; P. O. Box 15830 TBAbernathy 7
Sacranento, California 95613 JRBuchanan
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ACRS (16)
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Gentlemen:
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RE: FRACTURE TOUGHNESS AHD POTENTIAL FOR LAHELLAR TEARING OF STEA*1 i
S=E GCliERATOR AND REACTOR C00LMT PUMP SUPPORT ISATERIALS y =::
During the course of the licensing action for North Anna Power Station in Unit !!os.1 and 2, a 7ber of questions were raised as to the potential
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for lamellar tearing-and low fracture toughness of the steam generator
(.3 and reactor coolant pump support naterials for that plant. Two cifferent g
steel specifications (ASTM A36-70a and ASTH A572-70a) covered most of the F
naterial used for these supports. Toughness tests, not originally spect-
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fied and not in the relevant ASTM specifications, were made on those heats for which excess naterial was available. The toughness of the A36 steel was founa to be adecuate, but the toughness of the A572 steel was relatively poor at an operating tenperature of 80 F.
In this case, the applicant has agreed to raise the tenperature of the AST!! A572 beams in the stean generator supports to a ninintra temperature of 225 F prior to r:eactor coolant systen pressurization to levels above 1000 psig. Auxil-
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f ary electrical heat will be employed to supplenent the heat derived fron
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the reactor coolant loop as necessary to obtain the required operating tenperature of the structures.
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Lamellar tearing is a cracking phencaenon which occurs beneatn welds and is principally found in rolled steel clate fanrications. The r
tearirig always lies within the parent plate, often outside the transforecd (visible) beat-affectec zone (HAZ) and u generally parallel to the wld fusion' boundary. Lacellar tearing occurs at certain critical joints usually within large velded structures 10g h
involving a high degree of stiffness and restraint. Restraint reay M
bo defined as o restricticn of the r.!ovenent of the various joint components t%t would pornally occur as a result of expansion and
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contraction of veld Petel and acjacent regions during miding.
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M li h;Wif Since sf ailar caterials and designs have been used on other nuclear plants, the concerns raised on the supports for the florth Anna plant may
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be applicable for other operating Pi!R plants.
It is therefore necessary to reassess the fracture toughness and potential for lamellar tearing of b
the steam generator and reactor coolant pump support materials for all p
operating PWR plants.
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We will require certain information to nake the necessary reassessment of the stean generator and reactor coolant puup support materials for your
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plant; therefore, please provide the following infomatibn within sixty L.
(60) days after receipt of this letter:
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1.
Provide engineering drawings of the steau generator and reactor r
coolant pu.'p supports sufficient to show the geometry of all principal Fw elenents.
Provide a listing of materials of construction.
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2.
Specify the detailed design 1 cads used in the analysis and design of g
the supports. For each loading condition (nomal, upset, emergency and faulted), provide the calculated caximum stress in each principal ele-(
nent of the support system and the corresponding allowable stresses.
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Describe how all heavy section intersectinc acaber welduents were designed to nininize restraint and lanellar tearing. Specify the E
actual section thicknesses in the structure and orovide details of typical joint cesigns. State the naxinua design stress used for the i+
through-thickness airection of plates and elenents of rolled snapes.
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4.
Specify tie raininto operating tenperature for the supports and describe tne extent to Lt.ich natorial temperatures have been neasured at various points on the supports during the cperation of the plant.
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Specify all the natorials used in the supports and the extent to I:
which mill certificate data are available. Descrice any suppleeental h
requirenents such as celting practice, toughness tests and through-thickness tests specificc. Provide tne results of all tests that may k
better define the properties of the aaterials used.
6.
Describe the welding procedures and any special welding process recuireuents that were specified to minimize residual stress, wold and heat affected zone cracking and lamellar tearing of the base tetal.
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7.
Describe all inspections and non-destructive tests that were perfomed H2 on the supports during their. fabrication and installation, as well as
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any additional inspecticas that \\ vere perfomed during the life of tne E
facil ity.
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In addition to the infomation requested above, please provide your own
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evaluation of the fracture toughness of the steam generator and reactor
.f.g.3 coolant pump support natorials for your plant. Picase infom us within thirty (30) days after receipt of this letter of your schedule for pro-L viding us with your evaluation. This generic request was approved by E
GAO, B-180225 (R0072), clearance expires July 31, 1960. Approval was b
given under a blanket cicarance specifically for identified generic P...
prob 1cras.
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F Sincerely, 7g.;
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i Robert W. Reid, Chief p
Operating Reactors Branch #4 i
Division of Operating Reactors tc: See next page
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==... 1 David S. Kaplan, Secretary and
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General Counsel MEj 6201 S Street jE=(
Post Office Box.15830
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Business and Municipal Department
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Sacramento City-County Library 2
828 I Street Ee Sacramento, California 95814
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