ML19309C808
| ML19309C808 | |
| Person / Time | |
|---|---|
| Site: | Yankee Rowe |
| Issue date: | 03/07/1980 |
| From: | Eisenhut D Office of Nuclear Reactor Regulation |
| To: | Scott S NRC OFFICE OF ADMINISTRATION (ADM) |
| References | |
| NUDOCS 8004090288 | |
| Download: ML19309C808 (2) | |
Text
Y b ik
-.p * *ito,4, 6%
UNIT ED OTATES i i,..,qf[ h NUCLE AR REGULATORY COT.if.11SSION
} y c.., 4#,j WA S HINGTO fJ, D. C. 20555 se-tj
~
..o l.iG 7 G80
$(
D MEMORANDUM FOR:
Steve Scott, Acting Chief Distribution Services Branch, ADM F R0".:
Darrell G. Eisenhut, Acting Director Division of Operating Reactort
SUBJECT:
BOARD !;0TIFICATION, II;FOR"ATION A.
DISC CRACKING, WESTIriGHOUSE TUR3INES B.
YANKEE R0WE TURBINE FAILURE Please forward the enclosed material to Boards and parties to the procccdings of D0R assigned plants in hearing status.
dh/,
4.,f-M Darrell G. Eisenhut, Acting Director Division of Operating Reactors cc w/ encl:
H. Denton E. Case E. Christenbury S. Verga l!. Rcss V. NoCnan W. Hazelton L :lichols ge44000
s IjjF0EMATION TO ALL BOARDS OF OPERATING REACTORS Cracks have been observed in the key ways and bore sections of low pressure discs of turbines manufactured by Westinghouse in service at operating reactor facilities.
The cause of cracking is under investigation by Westinghouse and the staff.
It is apparent that the frequency of crack formation is greater than previously assumed.
Information has been obtained through inspection of turbine discs at several operating reactor units.
This information, obtained from ultrasonic examinations; turbino design and plant operational data; and tne cumulative hours of turbine operation, provide bases for calculations to determine the crack growth rate and the critical crack size that may result in disc failure at tie design overspeed of each turbine unit.
Overspeed may occur during an incident resulting in loss of generator load.
Control systems are used to prevent the turbine from exceeding design overspeed.
Westinghouse is inspecting turbines of operating reactor facilities using a priority method that is based primarily on the projected rate of crack growth.
The staff is continuously assessing the analyses and inspection plans and results provided by Westinghouse.
The staff is in the process of determining whether or not turbines supplied by other manufacturers in use at operating reactors have disc cracking problems.
The attached memorandum from W. S. liazelson to D. G. Eisenhut, dated February 21, 1930, discusses the failure of low pressure turbine discs at the Yankee Rowe facility.
Inspection of critical turbine discs at the facility had not been made because of lack of access for inspection due to design characteristics.
Also, available materials and turbine design data were inadequate for an evaluation of crack potential.
-(
5
gr tr.,
e
's U'llTE D S TATt S Ip f( l NUCLLMi HEGUL ATORY COMMISSION 2
lc e
v.v:e 'n on. o c. ma C
,j'.
s
.m IG.', !sgrj
- 4 ORTN00:' FOR:
D. G. Eisenht.t, Acting Director Division of Operating Reactors L
C. Shao, Acting Assistant Dir ector for Engineering prograr.s, DDR F Yi-W S. th:elton, Section A Leader, Engineering Branch Uin; ion ;f Oper. ti r,g i5 K ters ii _
V. S. Zonan, Chief. Engineering Branch Divisien ;f 0:.ereti:. Roactors S R JECT:
YA'E.EE RO';E TURBINE FAILURE ni Mut 9 30 c. on February 15,19EO, the Encineering Branch vias notified b,,
th. Y/ d ec Rev.e proj"ct
" pr, A. Burger, that he had just heard via t e l w.i n f rco %gian I that the Yankee Rwe turbir.e h!d es.perienced scre Li:'i e f c.ijor failure A call was put through to t'.r.
utio, the plant
- .a; crintonAnt, and the follouing preliminary infor: ition was obtained.
2 Engir..:ering Branch also contacted ISE Headquarters (J. Collins) and found that thcy had not yet hard of the incident.
DSS perscnnel s.ere also no-tified, and this preliminary information was aise given to them (M. Coyle).
- ne p unt had been shutdc.n since January 19, 1930, to impler:ent the Lessons L c.u ra: Cate:ory A itcis.
All. ort was coapleted and on February 14, 1980,
,ti:'n to return th: uni t to p 2r,are underway.
All turbine testing was cc:mic ted shnaing all canditions to be nornal.
The reacter was at 2-31
, suer to provide su f ficient s tean for turbine startup.
The turbine was rolled, Fr w ht up to 1E00 rpm full spced and put on governor control.
At 11:35 am ca.di ticr.s w-re achieved to synchronize the genera tor and load the turbine.
[t fere syrdenniting, a thu y was heard from an apparent severe jarring of the turbine.
The turbine coasted dov,n for about E5 ninutes compared to the normal coas tdonn tirae of 45-00 r.inutes.
It is belicved that the turbine tripped dutomatically on thrust bearing Goat.
But the r anual trip t;as also in adiately activated, so it is not ir.oun which action actually caused the trip.
There are no vibriticn t r.? devices on this unit.
There was severe turbine vibration.
Th; vibration *:ters on Na, 3 and !;o. 4 L' earing read off s
i scale (10 nils upper scale limit).
The other bearings read between 6 and 7 3
ilt.
V nal vibratien ;} eil ar lcts.
AttWts to ;iut the turbine on v
1 t.. d. e CE 2rcati:
at the
a,M tion ports N
t u i r. i r.j
- c ir f
- t ilc d to ;a i ' 11 c a tC n; app :rcnt :'
to th..
li; t r tJ'c
-li tn the Cm,er r 90Ved at 4
the 3rd pain t i.< trac t ion li:,
sc a de', is v.as An, aM a se: tion of disc c j\\ >
\\
abeat I ft. long war rc "d,
toct3 in.; cr b'?Je vcared at i.ts dovetail, h
nather blade tteisted.
d
)${
c o m nt u rm c, tm teru ~ failure 1h< mr do et e mm.mm m
m m 1 m#,
i
I L
L Fu
'a3 D. Eisenhut L. Snac shutdown and no condition to cause a reactor trip.
The reactor was left critical f or about 1/2.to I hour then was shutdown normally and was placed in a cold shutdcun condition.
There was no loss of condenser vacuum.
Conditions in the reactor cooling system and the secondary system appeared nonra l.
Yankee Atomic Electric Company (the licensee) contracted Westinghouse to perform an investigation of the turoine failure and to do the repairs.
The licensee anticipated a prolonged shutdown of the facility.
Since February 15, members of the Engineering Branch (DOR) (Sellers, floonan) have visited the site, and Consultants to the Engineering Branch from Lawrence Livermore Labnratory and Brookhaven National Laboratory were also sent to the site to help evaluate the primary cause of the failure. Addi-
- ional information available to us as of 10:00 am February 21, is as follnws.
The turbine outer and inner casings have been removed and an initial visual inspection was performed.
It was found that both first stage discs in the low pressure rotor are completely failed.
They are broken in several major pieces and many smaller fmgments.
itajor damage was also observed at several adjacent rows c. ulades and stators.
preliminary information indicates extensive cracking in the bore of the first stage disc at the generator end.
The mechanism of cracking is not known at this time, but is censidered most likely to be primarily stress corrosion.
It appears that one large piece of a first stage disc got wedged against the shaf t during turbine'coastdown ar.d r.ay have Caused signifiCant damage to the shaf t.
The inner housing as severely cracked and distorted, and cracks were found in the outer hous-ing.at the centering pin area.
Warren S. Hazelton, Section A Leader-Engineering Branch Division of Operating Reactors cc:
H. R. Denton K. M. Kampe E. G. Case W. J. Collins V. Stello S. A. Treby r-D. F. Ross D. T. Swanson D. B. Vassallo E. S. Christenbury L. R. flichols J. F. Stolz 1
R. C. DeYoung R. L. Baer H. D. Thornburg
- 0. D. Parr T. F. Engelhardt L. S. Rubenstein
';. C. Moseley A. Schwencer n
P B. K. Grimes W. J. Rcss 9 (iW D
l0 b
J. P. Knight C. L. Ziemann g
LJ Mh b
i W. E. Kreger T. A. Ippolito
- 5. S. Pawlicki R. W. Reid I
R. M. G rble' S. Varaa Boy 5e H. F. Conrad.
R. A. Hermann R. W r.leckcr C. D. Sellers
% it. Enichten
,