ML20148J665

Discusses Reassessment of Fracture Toughness & Potential for Lamellar Tearing of Steam Generator & Reactor Coolant Pump Support Matls Re Licensing Action for North Anna 1 & 2. Requests Addl Info

ML20148J665
Person / Time
Site:	North Anna, Yankee Rowe
Issue date:	10/04/1977
From:	Schwencer A Office of Nuclear Reactor Regulation
To:	Groce R YANKEE ATOMIC ELECTRIC CO.
References
NUDOCS 8011250198
Download: ML20148J665 (4)

Text

. _ . _ . _

% 'b f v; ...f::u{,:.

5::

h.

- f.

Docket No. 50-29 OCT 4 1977 r(?

j .[

c- -

I.

VE Yankee Atocic Electric Company h ATTN: Hr. Robert H. Groce t Licensing Engineer. .

20 Turnpike Road E Westboro, Massachusetts 01581 Gentl emen:

RE: FRACTURE TOUGHf!ESS AND POTENTIAL FOR LAMELLAR TEARlhG OF STEAM GENERATOR Al;D REACTOR C00 lid!T PUHP SUPPORT HATERI A.'.S During the course of the licensing action for Horth Anna Power Station Unit Hos.1 and 2, a number of questions were raised as *,o the potential , . . . ,

for lamellar tearingl/ and low fracture toughness of the steam generator P" and reactor coolant pump support materials for that plant. Two different lN steel specifications ( ASTil A35-70a and ASill A572-70a) covered most of the

[.? .

material used for these supports. Toughness tests, not originally spect- G ....

fied and not in the relevant ASTM specifications, were nade on those ~ 3 heats for which excess caterial was availaole. The toughness of the A36 steel was found to be adequate, 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 temperature of the ASTN A572 beens in the steam generator supports to a minimum tenperature of 225 F prior to reactor coolant systen pressurizatior, to levels above 1000 psig. Auxil- -

iary electrical heat will be ecployeo to supplenent the heat derived fron the reacter coolant loop as necessary to obtain the required operating tennerature of the structures.

THIS DOCUMENT CONTAINS

, POOR QUAL.lTY PAGES 1/ Lauellar tearing is a cracking phenor.cenon which occurs b wath welds and is principally found in rolle:J steel plate fabrications. The tearing always lies within the parent plate, often outside the transforned (visible) heat-af fected zon (HAZ) and is generally parallel to the weld fusion boundary. Lamellar tearing occurs at certain critical joints usually within larga weldeo structures +

involving a hich degree of stiff ness anc restraint. Restraint uay be defined as a restriction of the novenent of the various joint components that would norcally occur as a result of expansion and -

contraction of welc netal and adjacent regions during welding.

("Lacellar Tearing in Welded Steel Fabrication", The Welding y ,

]

4 4 > L 6 Lu W J .

or ric E *

.u . m * ...

oavs * . . . . . .

NRC FORM 318 (9 76) NRCM 0240 W u. s. oovanmuswr paiwrino orricus vers - ens.e 4

' ^

go 112 5 on[ }

. i

I <

....:.. , (.l Yankee Atomic Electric Company OCT 4 1977 A

Since similar materials and designs have been used on other nuclear plants, the concerns raised on the supports for the North Anna plant may

'be applicable for other operating PWP, plants. It is therefore necessary  ;;

to reassess the' fracture toughness and potential for lamellar tearing of r

.the steam generator and reactor coolant pump support materials for all operating PWP, plants. ~

t We will require certain information to make the necessary reassessment of [?;

the steam generator and reactor coolant pump support materials for your '

plant; therefore, please provide the following infomation within sixty ik (60) days after receipt of this letter: b

1. Provide ngineering drawings of the steam generator and reactor coolant pump supports sufficient to show the geometry of all principal el ements. Provide a listing of materials of construction.

2. Specify the detailed design loads used in the analysis and design of W".

^

the supports. . For each loading condition (normal, upset, energency and faulted), provide the calculatea maximum stress in each principal ele--

pent of the support system and the corres'ponding allowable stresses.

3. Describe how all heavy section intersecting nember weldaents were ,

designed to minimize restraint and lanellar tearing. Specify the actual section thicknesses in the structure and provide details of typical joint designs. State the naximua design stress used for the p" through-thickness direction of plates and elements of rolled shapes.

4. Specify the ninimum operating tenperature for the supports and describe the extent to which material temperatures have been measured at various points on the supports during the operation of the plant.

5. Specify all the materials used in th2 supports and the extent to which nill certificate data are available. Describe any supplemental ,

[

requirements such as melting practice, toughness tests and through- ,_ ,

thickness tests specified. Provide the results of all tests that may V better define the properties of the naterials used.

6. Describe the welding procedures and any special welding process requirements that were specified to ninimize residual stress, veld and heat affected zone cracking and lamellar tearing of the base '

netal .

6 e  ;

.1 099EC L % .

q oan + .-..

NRC FORM 318 (9 76) NRCM 0240 W u. s. oovraw w awr eniNTING CPFIC ri t,78 - 426-42J .

l

\ .,,,

) , ,

7 Yankee Atomic Electric Company OCT 4 1977

7. Describe all inspections and non-destructive tests that were perfonned on the supports during their fabricatien and installation, as ucll as  :

any additional inspections that were perfonaed during the life of the  ;.

facil i ty. c p

In addition to the infomation requested above, please provide your own l' evaluation of the fracture toughness of the stea:n generator and reactor coolant pump support materials for your plant. Please infom us within thirty (30) days af ter receipt of this letter of your schedule for pro-viding us with your evaluation. This generic request was approved by GAO, B-180225 (R0072), clearance expires July 31, 1980. Approval was  !

given under a blanket clearance specifically for identified generic "

problems.

Sincerely, '

l l

A. Schwencer, Chief Operating Reactors Dranch v1 Division of O')erating Itcactors  :-

cc: See next page DISTRIBUTION ,

Docket '

NRC PDR Local POR ORB #1 Reading

'I ASchwencer SMSheppard ABurger -

RSnaider  ;

OELD Ol&E(3) l DEisenhut '

TBAbernathy , ,

JRBuchanan ACRS(16)

$$ bl/  ;

. . . , . _ ORB;ti 1

Rfi#2 ORB #1 x27433,tsViABfid,g[ RSnaider A,Schwer er. .._. _

....J naat 10d.277 .10t. L77 _ i, ,

NI,C IOHAf $18 (9 76) NRCM 0240 N us e. ouve nuuawi raiNtiae orricke tere eas esJ i L

'" 9 '

{ ,,,

. Yankee Atomic Elect 71c Company OCT 4 1977 I:b cc: .Mr. Donald G. Allen, President .

Yankee Atomic Electric Company 20 Turnpike Road

~

Westboro, Massachusetts 01581 Greenfield Public' Library ...

402 Main Street g

Greenfield, Massachusetts 01581 !i.

[8..

De

+

e e

m

f. ;

r h

l<'.

. p J.

.