ML19257C437
| ML19257C437 | |
| Person / Time | |
|---|---|
| Issue date: | 01/09/1980 |
| From: | Ross J Office of Nuclear Reactor Regulation |
| To: | Schwencer A Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8001290125 | |
| Download: ML19257C437 (5) | |
Text
.
~ [p a'49[0, NUCLEAR REGULATORY COMMISSION UNITED STATES y $ # (-
h WASHINGTON. D. C. 20555
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,o HEMORANDUM FOR:
A. Schwencer, Chief Oserating Reactors Branch #1 Division of Operating Reactors William J. Ross, Project Manager FROM:
Operating Reactors Branch #1 Division of Operating Reactors
SUMMARY
0F MEETING WITH WESTINGHOUSE RELATED TO CRA SU3 JECT:
TURSINE ROTORS representatives of Westinghouse presented new information On December 17, 1979 1500/1800 RPM turbines to the staff on indication of cracking in Westinghouse A list of and to representativ2s of several licensees who use these turbines.
attendees is attached.
The Westinghouse presentation was similar to one given to electric utility executives on October 30, 1979 and consisted of a reevaluation of the probability for turbine missiles being formed through cracking of the turbine discs and bores.
New information that was provided relative to disc keyway cracking indicates that such cracks are formed through stress corrosion mechanisms and cot '.d lead to disc Additional studies are in progress to bursts if allowed to grow to criticality.
(a) study the mechanism of crack initiation and propagatice both in disc ker,tays and in the disc bore, (b) reanalyze the probability of missiles after an inservice disc inspection program is factored into the analysis and (c) further study the energyThes of missiles formed from turbine disc failure.
in 1980.
Westinghouse anticipates that its probability of a turbine m to calculation of the annual rupture probability and the future use of inservice disc inspection wherin flaws can be detected and removed before becoming critical.
On the other hand, recent tests that were performed to acquire information on turbine missiles indicate that the energy of the missiles and their capability to Missile reports are escape from the turbine shell were previously underestimated.
now being reevaluated for operating nuclear power plants to update information on The first energies, velocities and degree of containment within the turbine shell.
of these reports will be available in January,1980.
Since the initial observation of cracks in the disc keyway, Westinghouse has been training teams to inspect the turbines of all units, both nuclear and fossil-fueled, To date,19 rotors have been inspected and 10 have been observed Cracks that are suspect.
Of the 183 discs inspected 14 have been cracked.
to have cracked discs.
up to 0.4-inch in depth have been observed in discs with as litt to have bore cracks of up to 1.2-inches depth and 2.5-inches service.
cracks.
Analytical examinations reveal the, presence. of in the lip of the spacer groove.
1832.322 0GC 800 129 C.
h yJ JML chloride and hydroxide in the keyway cracks, but the initiation of stress corrosion has not been correlated quantitatively with se:ondary water The cracks in the discs bores do not appear to be caused by stress chemistry.
Westinghouse has developed ultrasonic techni:;ues that do not corros ion.
require removal of the discs, however an inspection requires s 14 weeks for one end or s 19 weeks for both ends when performed at the Westinghouse facility at Charlotte, North Carolina. It is hoped that inspections can be performed in the field in 1980.
A series of programs are also underway to redesign turbine discs and to provideThe results additional margin of protection in hostile environments. Westinghous j
and will be provided to users for reassessing other factors in the probability is the probability cf a turbine missile, P2 where P equation:
P = P xP xP is the probabiliky bf a missile striking a vital target, P, is the probabilityis the pro 5 3 4 of a missile penetrating a vital target, and P4 unacceptable damage.
1500/'300 RPM with low pressure, All nuclear power plants that have a Westinghouse snrunk-on disc construction ' plants now operating or under construction) have l
d been placed in one of two categories on the basis of pe ceivec priority deve op inservice time; environment of rotor; critical crack size; Westinghouse urges that tre 19 plants in the from four f actors:
highest (AA) priority be made available by completion of their Spring 1930 and material yield strength.
The other plants should be inspected as their inservice periods approach 5 yea or in the event of evidence of significant corrosion.
At the conclusion of the Westinghnuse presentation the staff requested that th following actions be taken by Westinghouse:
the information presented in tnis meeting should By December 20, 1979, be updated, and the staff provided with a status report of the 1.
ins:ection program that includes a complete list of nuclear pcwer s'iants already inspected and information related to rotors where cracks have been observed.
If agreeable to Westinghouse and utilities, Westinghouse will take tne lead in forming an owners group to address turbine disc cracks.
2.
The status of this group should be reported to William J. Ross or A. Schwencer (301) 492-7810 by December 20, 1979.
14,197 9 (summary (301) 492-7173 Information requested from each utility on De: ember cf actions taken in response to Westinghouse :resentation of 0:tocer 30, i.79) may be funneled through this group for :ransmittal to the staff 0
of Decemoer 27, 1979.
- escond to sta ff requests for additional inic-mation.
31 on December 30, 1979.
3.
7nese requests will be available for transmit:
- eevaluate inspection schedule for "AA" and "A" catecories byby plant rationale 4.
De:emoer 20, 1979 and provide NRC witn a plar.:
of tne absence of a safety problem associatec with disc cracks by De: ember 27, 1979.
The staff concluded that these actions were adequate a 323 i
4 our safety analysis, although the new information does erode our degree of It is the staff's position that cracking of turbine discs conservatism.
impacts not only the probability for missile generation (P ) but also 3
the probability of a missile striking,a vital target (P ) and the probability of a missile penetrating a vital target (P3*
The staff's position will be re-evaluated upon review of responses by Westinghouse and licensees to additional staff requests and upon plant specific justification of continued operation after receipt of information related to potential rotor disc cracks,
$1$
b '.41n1 William J. Ross, Project Manager Operating Reactors Branch #1 Division of Operating Reactors
Attachment:
List of Attendees
'1832 324-
DECEMBER 17, 1979 TURBINE DICS '4EETING AFFILIATI0ft NAME John F. Burdoin flRC/ DOR J. C. Mullane, Jr.
Westinghouse Pierre Oubre SMVP C. W. Krause Wisconsin Electric D. Swanson NRC/ ELD J. J. Sheppard Carolina Power and Light Company tdwin G. Hollowell Carolina Power and Light Company Yankee Atomic Electric Company Kim Kay Louis J. Briskman Westinghouse Barton Z. Cowan Eckert, Sear.ns, Cherin and Mellott Mae Haley Westinghouse J. D. Dickinson Westinghouse R. E. Warner Westinghouse B. Seth Westinghouse D. H. Shuffer Westinghouse P. K. Colvert Commonwealth Edison Company R. J. Tamminga Commonwealth Edison Company Frank Almeter NRC/ DOR -_ Engineering Brar.ch Jerry N. Burford Florida Power and Light Lee Mayor Northern States Power V. P. Buscemi Gibbs and Hill R. A. Wiesemann Westinghouse J. A. Schmieder PASNY R. A. Hermann fiRC/ DOR W. S. Hazelton NRC/ DOR William J. Collins fiRC/IE C. D. Sellers NRC/ DOR H. S. Smith So. Cal. Edison D. O. Hunter Westinghouse R. N. M. Hunt Baltimore Gas and Electric George Wrobel Rochester Gas and Electric A. Toboada NRC/ DOR F. Rooney NRC/ DOR Daniel J. Garner NRC/ DOR E. S. Grecheck Virginia Electric Power Company James N. Christman Hunton and Williams (VEPCO)
Virginia Electric Power Company Curtis E. Necessary M. L. Wohl NRC/NRR/ DOR /EEB K. M. Campe NRC/NRR/DSE/AAB Stefan Pawlicki NRC/ DSS /MTEB Helmut Baroneb Public Service Electric and Gas John L. Legier Public Service Electric and Gas R. W. Klecker NRC/ DOR /EB Paul M. Pivawer Consolidated Edition of New York Edward A. Reeves NRC/NRR/ DOR /0RB#1 Don Neighbors NRC/NRR/COR/0R8#1 Richard Licciardo NRC/NRR/ DOR /0RB#1 Albert Schwencer NRC/NRR/ DOR /0RB#1 V. S. Anderson Westinghouse W. J. Ross NRC/NRR/ DOR /0RB#1 U32525
2-Robert Gaul Westinghouse Wisconsin Public Service Charles R. Luoma NRC/ Region IV Loyle M. Hunnecutt Ark. Power and Light Mark A. Smith 1832 626