ML19262C517
| ML19262C517 | |
| Person / Time | |
|---|---|
| Site: | North Anna  |
| Issue date: | 01/09/1980 |
| From: | Ross W Office of Nuclear Reactor Regulation |
| To: | Schwencer A Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML19262C516 | List: |
| References | |
| NUDOCS 8002140207 | |
| Download: ML19262C517 (5) | |
Text
.
p =
- t e g'o UNITED ST ATES
/
, [ \\* ^.,. ~ g NUCLEAR REGULATORY COMMISSION W ASHINGT ON, D. C. 20555
.p D p#
JAMIMT 09 580 HEMORANDUM FOR:
A. Schwencer, Chief Operating Reactors Branch #1 Division of Operating Reactors FROM:
William J. Ross, Project Manager Operating Reactors Branch #1 Division of Operating Reactors SU3 JECT:
SUMMARY
OF MEETING WITH WESTINGHOUSE RELATED TO CRACKING IN TURBINE ROTORS
~ On December 17, 1979 representatives of Westinghouse presented new information on indication of cracking in Westinghouse 1500/1800 RPM turbines to the staff and to representatives of several licensees who use these turbines.
A list of 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 bursts if allowed to grow to criticality.
Additional studies are in progress to (a) study the mechanism of crack initiation and propagation both'in disc keysays 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 energy of missiles formed from turbine disc failure.
These tests will be completed early in 1980.
Westinghouse anticipates that its probability of a turbine missile (8.2x10-9) will not be invalidated by the new analysis because of major conservative features related to calculation of the. annual rupture probability and the future use of inservice disc inspection wherin tiaws 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 escape from the turbine shell were previously underestimated.
Missile reports are 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 that are suspect.
to have cracked discs.
Of the 183 discs inspected 14 have been cracked.
Cracks up to 0.4-inch in depth have been observed in discs with as little as 40 months In addition, two discs in a turbine with 78 months service were observed service.
to have bore cracks of up to 1.2-inches depth and 2.5-inches length but no keyway Other cracks hava been observed in the face of discs behind a spacer and cracks.
in the lip of the spacer groove. Analytical examinations reveal the presence of 800214020 7
. I chloride and hydroxide in the keyway cracks, but the initiation of stress corrosion has not been correlated c.uantitatively with se:ondary water chemistry.
The cracks in the disci bores do not appear to be caused by stress corrosion.
Westinghouse has develo;.od ultrasonic techniques that do not require removal of the discs, however an inspection requires s 14 weeks for one end or s 19 weeks for both ends w an performed at the Westinghouse facility at Charlotte, North Carolina. It is hotad that inspections can be performed in the field in 1980.
A series of programs are also underway to redesign turbine discs and to provide The results of all of additional margin of protection in hostile environments.
3)
Westinghouse's studies will be used to modify the probability of missiles (n and will be provided to users for reassessing other factors in the probability where P is the probability of a turbine missile, P2 P = P xP,xP xP4 j
equation:
is the probability 5f a missile striking a vital target, P is the probability j
3 3
is the prooability for incurring of a missile penetrating a vital target, and P4 unacceptable damage.
All nuclear power plants that have a Westinghouse 1500/i800 RPM with low pressure, shrunk-on disc construction (plan'ts now operating or under construction) have been placed in one of two categories on the basis of perceived priority developed inservice time; environment of rotor; critical crack size; from four factors :
Westinghouse urges that tne 19 Diants in the and material yield strength.
highest ( AA) priority be made available by completion of their Spring 1980 outage.
The other plants should be inspected as their inservice periods approach 5 years or in the event of evidence of significant corrosion.
At the conclusion of the Westinghouse. presentation the staff requested that the following actions be taken by Westinghouse:
the information presented in this meeting should By December 20, 1979, 1.
be updated, and the staff provided with a status report of the inspection program that includes a complete list of nuclear power plants already inspected and information related to rotors where cracks have been observed.
If agreeable to Westinghouse and utilities, Westinghouse will take 2.
tne lead in forming an owners group to address turbine disc cracks.
Tne status of this group stould be reported to William J. Ross (301) 492-7173 or A. Schwencer (301) 492-7810 by December 20, 1979.
Information requested from each utility on De: ember 14,1979 (summary of actions taken in response to Westinghouse cresentation of October 30, 1979) may be funneled through this group for :ransmittal to the staff by December 27, 1979.
Respond to staff requests for additional information.
30, 1979.
3.
Tnese requests will be available for transmittal on December Reevaluate inspection schedule for "AA" and "A" categories by December 20, 1979 and provide NRC with a plant by plant rationale 4.
of the absence of a safety problem associated with disc cracks by December 27, 1979.
The staff concluded that these actions were adequate as an interim measure because Westinghouse's presentation did not identify a significant change in
3-our safety analysis, although the new information does erode our degree of conservatism.
It is the staff's position that cracking of turbine discs 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.
O feb v1 William J. Ross, Project Manager Operating Reactors Branch #1 Division of Operating Reactors
Attachment:
List of Attendees I
e
- f;s T..
DECEMBER 17, 1979 TCRBINE DICS MEETING O
NAME AFFILIATION John F. Burdoin flRC/ DOR J. C. Mullane, Jr.
Westinghouse Pierre Oubre SMVP C. W. Krause W
in Electric D. Swanson
'RC J. J. Sheppard Carolina Power and Light Company Edwin G. Hollowell Carolina Power and Light Company Kim Kay Yankee Atomic Electric Company Louis J. Briskman Westinghouse Barton Z. Cowan Eckert, Seamans, Cherin H 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 P'ower and Light Lee Mayor Northern States Power V. P. Buscemi Gibbs and Hill R. A. Wiesemann Westinghouse J. A. Schmieder PASNY R. A. Hermann NRC/ DOR W. S. Hazelton NRC/ DOR William J. Collins NRC/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 end 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 Public Service Electric and Gas John L. Legier 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/ DOR /0RB#1 Richard Licciardo NRC/NRR/ DOR /0RB#1 Albert Schwacer NRC/NRR/ DOR /0RB#1 V. 5. Anderso.'
Westinghouse W. J. Ross NRC/NRR/ DOR / ORB #1
2-
.O;i 5, c....,
.s 2 %,. ',;...
t, -.. < 3. :
,b f.' ' '
gobert Gaul Westinghouse fde,i-Charles R. Luoma Wisconsin Public Service
- 9. '
Loyle M. Hunnecutt NRC/ Region IV Mark A. Smith Ark. Power and Light G
m 9
9