ML20137M921

Requests Permission to Publish Encl Figure from Proceedings of Sixth Intl Symposium on Environ Degradation of Matls in Np Sys,Water Reactors,930901-05

ML20137M921
Person / Time
Issue date:	04/01/1997
From:	Chaffee A NRC (Affiliation Not Assigned)
To:	Makowski R PENNSYLVANIA, COMMONWEALTH OF
References
NUDOCS 9704080200
Download: ML20137M921 (3)

Text

.

April 1, 1997 Robert A. Makowski

' Director of Publishing The Minerals, Metals & Materials Society 420 Cominonwealth Drive Warrendale, Pennsylvania 15086

SUBJECT:

REQUEST FOR PERMISSION TO PUBLISH FIGURE COPYRIGHTED BY TMS We. request permission to publish a figure (enclosed) from Proceedings of the Sixth International Symposium on Environmental Degradation of Materials in Nuclear Power Systems -- Water Reactors, August 1-5, 1993, San Diego, California, p. 846.

A modified version of the figure will appear in a U.S. Nuclear Regulatory Commission (NRC) generic communication titled "NRC Generic Letter 97-01, Degradation of Control Rod Drive Mechanism and Other Vessel Closure Head Penetrations," to be issued in early April 1997.

Your prompt faxed response is appreciated. My fax number is (301) 415-1032.

If you have any questions, please call me at (301) 415-1168. Thank you.

Sincerely, Original signed by Alfred E. Chaffee, Chief Events Assessment and Generic Communications Branch Division of Reactor Program Management Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission

Enclosure:

As stated DISTRIBUTIOE:

Centra 1> File:

CECarpenter (l

PECB R/F AEchaffee

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I PUBLIC JWShapaker V D hN Y C*'CcV G

r DOCUMENT NAME: MAK0WSKI. FAX recoive copy of thi. doet,n.nt, indic.t. in the box c= copy W/o attachment / enclosure E= Copy with attachment / enclosure N = No copy 0FFICE C:PECB:DRPM s

NAME AECHAFFEE DATE' 04/01/97 0FFICIAL RECORD COPY 9704000200 970401 DR

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. April 1, 1997 Robert A.'Makowski

Director of Publishing The Minerals, Metals & Materials Society r

420 Comonwealth Drive Warrendale, 'e :nnsylvania 15086

SUBJECT:

REQUEST FOR PERMISSION TO PUBLISH FIGURE COPYRIGHTED BY TMS i

We request permission to publish a figure (enclosed) from Proceedings of the Sixth International Symposium on Environmental Degradation of Materials in Nuclear Power Systems -- Water Reactors, August 1-5, 1993, San Diego, California, p. 846.

A modified version of the figure will appear in a U.S. Nuclear Regulatory Comission (NRC) generic comunication titled "NRC Generic Letter 97-01, Degradation of Control Rod Drive Mechanism and Other Vessel Closure Head Penetrations," to be issued in early April 1997.

Your prompt faxed response is appreciated. My fax number is (301) 415-1032.

If you have any questions, please call me at (301) 415-1168.

Thank you.

Sincerely, Original signed by Alfred E. Chaffee, Chief Events Assessment and Generic Communications Branch Division of Reactor Program Management Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Comission

Enclosure:

As stated DISTRIBUTION:

Central File CECarpenter PECB R/F AEChaffee PUBLIC JWShapaker DOCUMENT NAME: MAK0WSKI. FAX fo recilve a copy of this doctanent, indicate in the box C= Copy w/o attachment / enclosure E= Copy with attachment / enclosure N = No copy 0FFICE C:PECB:DRPM NAME AECHAFFEE DATE 04/01/97 0FFICIAL RECORD COPY

P O. &5'}'&

f1@ 31 '97 02:50Pt1 Lf11TCO Af EP essidar W

Mer W W Cans cf W

- CPY senes 6 of tne 6 inspected unes (40 000 to

% am msactey and W 6 m @g 2) j 84.000 hours0 days <br />0 hours <br />0 weeks <br />0 months <br /> on line) exhibit cracked perwirations an1 out of 459 penetrations examined. 20 are affected.

Manufactunna 1300MW senes 5 of the 10 insoected units (30.000 The penetration is shnnk fitted with liquid nitrogen into the to 50 000 hours0 days <br />0 hours <br />0 weeks <br />0 months <br /> on line) exh: bit cracked penetrat'ons and.

vessel head dome so as to obtain an interference fit wrth a out of 469 penetrabons examined,10 are at octed.

d;ameter between 0 08 and 0 09 mm. This shrink. fit provides high accuracy for mour ting the penetration on the vessel j

Note that only seven penetrations exhibited cracks wrth a head while limiting the dimensional irnpact of the welding depth exceeding mid-thickness operation.

1 This large amount of non-cestructive examinations reflects The penetration is joined to the vessel head on the inner en unprecedented e' fort made t>y EDF to essess with side of the come by a non stress-reheved, partial penetration optimum precision the condition of its PWR capacity with the g

gg cim of imsementing the maintenance pohey best surted to g

p g

g

~

the situation depcsited with the same filler metal in the groove machined into the ferntic steel of the vessel head, it unoergoes the Prmnts*m final stress-relieving heat treatment of the vessel head before the penetrations are welded in place Due to the Equ'oment desgreppgr) vesset head bhape, the weld seam which is symmetrical for The function of the penetrations is to provide a channel the penetration located at the center of the corne, becomes through the vessel closure head. for the control too cluster increasing!y asymmetncal the further away the penetration is located from the center; thus, the angle between tne (RCCA) drive shafts and the thermocouple columns (fig 1) penetration axis and the inner surface of the vessel head The 900MW reacters are equipped with 65 penetrations, tne

' set uo angle) may reach resoectrvely 42' and 47* for the

• 00MW reactors with R in both cases 4 are used for penpheral penetrations en the.J0MW and 1300MW reactors the mocouples. The RCCA penetrations each compose a r

thermal sleeve whose morn functions are protection of the (fig 2) penetration against cold water downflows caused by raising When the first vessel heads were manufactured it was the dove shaft, and for enve shaft guidance when the vessel noticed, particulady for the highly asymmetrical assemblies, head is put in place (f gure 2) that welding caused cstortion of the lower part of the s-

,N,,

penetration. Th's distorbon could in some cases, prove

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y-l g incompatible witn passage of the internal geometry gege it 3

ZgNhk corresponds to an ovahzation of the penetration at the f

p lowest part of the weld and to lateral deflection of the part i

,i 1 y protruding under the head towards the outside of the dome (fig 3) The manufacturer therefore decideo to machine, D

A.

f ! [:

before mounting on the vessel head, a counterbore at the h,'>

h not exist in the first three PWR units (CPO teries). in these base of the penpheral penet'ations This counterbore does

~ " * ' *

• d*y[j cases. Onnding in the inside of the penetrations may have a,W f

been pertermed after welding when the gage passage problems arose The counterbore is cylindncal for the next g

a :

q=;

four unrts (CPO senes and i unit of the CPY senes, fig 4) and becomes tape'ed for the rest of the PWR plants it is

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noteworthy that the internal continuous section of the c

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penetration is honed after (nachining. wh.ch is not the case f[

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l for the counterbored gones i

g bw,

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The penetrations are machined from alloy 600 bars s

u.,,u produced by press or hammer forging These bars are heat-treated between 710 and B60*C over 1-4 hours when tne s

,y:

lj\\

post-forging rnechanical properties are high (yield strength

• 343 MPa). in order to soften the material This process leods q g to a wide scatter of mechanical propemes (yield strengths y

d, betusn 260 and 500 MPa for a specified minirnom value of i

g

/T' 241 MPa) and of rnicrostructures (partial or full f

~/l recrystalhzation. grain size, intra and/or intergranutar carbide precipitation) The chemical cha:acteristics too are scattered but rema:n witnin the required spec:fications (ASTM)

Figure 2 Vessel head penetration. Outhne However, each set of mechanicai prope ties is only known for one end of one bar from one lot, so knowtedge of ine The penetration body is made of a:loy 600 (AFNOR properties for each peneirabon is necessanly only partial.

NC15Fe) and its top pa t is austentt:c stain ess steet (AFNOR 2.2CN1810). these two components are pned by a 846