ML20032B230
| ML20032B230 | |
| Person / Time | |
|---|---|
| Site: | Atlantic Nuclear Power Plant  |
| Issue date: | 10/28/1981 |
| From: | Haga P OFFSHORE POWER SYSTEMS (SUBS. OF WESTINGHOUSE ELECTRI |
| To: | |
| References | |
| NUDOCS 8111050321 | |
| Download: ML20032B230 (8) | |
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Uh?TED STATES OF_ AMERICA D00 ETED NUCLEAR REGULATORY COMISSION
-2 P4:i9 BEFORE THE ATOMIC SAFETY AND LICENSING BOARD
'0FFICE OF Sicpgij oc 00CKETIng g Sggyggj~
BRANCH In the Matter of
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0FFSHORE POWER SYSTEMS
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Dockt.t No. STN 50-437
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(Manufacturing License for Floating
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Nuclear Power Plants)
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AFFIDAVIT OF P. BLAIR HAGA REGARDING TURBINE-GENERATOR MATTERS
\\NI STATE OF FLORIDA
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~3 COUNTY OF DUVAL
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yil k/g I, P. BLAIR HAGA, being first duly sworn, do hereby depose and say:
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8111050321 811028 PDR ADOCK 05000437 0
Testimony on turbine generator matters was presented to the Board in e'
hearing sessions during the period between December 8,1976 and May 17, 1977/1. Since testimony was originally presented, additional technical infonnation, which relates to the question of turbine missile, has been developed as a result of the following events:
- 1) Cracks wem observed in low pressure discs in a number of operating nuclear turbines./2_
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- 2) Tests were conducted at the Electric Powt.r Research Institute (EPRI) and Westinghouse Electric Corporstion in which simulated discs at high speeds impacted with metal barriers. Data from these tests indicate that in some cases the energies with which missile fragments exit the terbine casing may be higher than previously estimated./5
- 3) A disc failure occurred in the low pressure unit of the Yankee-Rowe TurbineGenerator.O For the reasons presented below none of the relevant conclusions put forth in prior testimony are invalidated by these events.
OBSERVATION OF DISC CRACKING Subsequent to the conclusion of testimony on turbine-generator matters, cracks were discovered in the bore and keyways of a number of low pressure discs in operating turbines. The cracking phenomenon has been studied
/1 Tr. 4006 - 6001 and Tr. 6151-6172.
/2 This was reported to the Board in Board Notification BN-80-4 from Mr. S. A. Varga, January 25, 1980.
/3 This has been the subject of the following memoranda and notices to the Board:
S. M. Sohinki memorandum dated December 22, 1978; S. M.
Sohinki memorandum dated January 2,1979 and toard notification BN-80-4, Mr. S. A. Yarga, January 25, 1980.
/4 This ws reported to the Board in Board Notification BN-80-8 dated February 19, 1980 and in a subsequent memorandum date:d March 31, 1980, both from Mr. S. A. Varga.
extensively by Westinghcuse Electric Corporation, both to detennine the i
mechanisms responsible for crack initiation and to estimate the time required for a crack to grow to the critical size at which disc failure could occur.
Westinghouse has concladed th4t the disc cracking was induced by stress corrosion and is developing design modifications to provide greater margin.
These include:
o Affected discs have been redesigned to achieve lower bore stresses and utilize lower yield strength material.
o Designs which eliminate bore keyways are now being utilized.
o Methods to keep the disc / bore keyways dry are being explored, since no cracking has been found in discs operating in dry steam.
o Partial integral rotors where the first three discs are made a part of the shaft are being considered. Only the last few, less critical discs would have to be shrunk on in such a partial integral rotor.
At the present time there are no FNP turbines on order. Thus it is expected that significant design improvements will have been implemented by the time that the first turbine is manufactured.
In its study of turbine disc cracking in existing units, Westinghouse has also developed inservice inspection procedures and recommended interval s between inspection /5 The recomended inspection intervals are based on l
observed crack size and are intended to assure that cracks will not grow to I
the critical size before the next inservice inspection.
It was noted in
!0 prior testimony by both the Applicant and the Staff - that the FNP turbines i
/5 The Staff Safety Evaluation Report, " Criteria for Low Pressure Nuclear Turbine Disc Inspection" was transmitted to Westinghouse Steam Turbine Division by Mr. S. A. Yarga's letter dated August 26, 1981.
/6 See for example t:.a Staff's written direct testimony, pp. 32, 33 ar.d Tr.
5534-5538.
will receive inservice inspection at approximately ten year intervals. This interval will be adjusted if necessary based initially on analyses of each FNP turbine using as-built data and subsequently on the results of each inservice inspection.
EPRI MISSILE PENETRATION TESTS Additional test data on interaction between simulated turbine missiles and steel barriers have become available since May 1977.
Tests performed at Sandia under EPRI sponsorship and additional tests performed by Westing-house suggest the need to recalculate tissile energy absorption by steel barriers such as the turbine casing. Westinghouse is in the process of
. ecalculating the residual energy of disc fragments which penetrate the turbine casing.
These calculations are being performed on each turbine utilizing as-buiit data.
Results to date for machines similar to the FNP turbine show increased energy for some disc fragments. As part of its investigation into disc cracking, Westinghouse has estimated the probability of individual disc rupture at design conditions based on various inspection intervals for both existing and modified designs. Results of the calculations on existing Building Block 281 turbines indicate that the turbine failure probability assumed by Offshore Power Systems will remain appropriate for disc no. 2 at speeds up to design overspeed considering appropriate inspection intervals. It is expected that tt. ' probability will M further reduced by design improvements. These calculations also indicate that failure prob-ability of discs nos. 3, 4 and 5 will be substantially reduced. Failure of disc no. I at speeds up to design overspeed does not result in a missile.
Reanalysis of the FNP turbine is planned during the final design process.
It is the judgment of Offshore Power Systems that when both the updated missile exit energy data and the disc rupture probability data are con-sidered, the probability of damaging a vital target will be no greater thar.
that stated in testimony presently befort the Board for the design over-speed case. -
None of the recently developed infomation affects the probabili2y of occurcence of destructive overspeed.
Thus, there is no impact on the previous conclusion of Offshore Power Systems that the probability of damage to a vital target from a destructive overspeed missile is less than 10-7 per year, because the probability of failure of the overspeed protec-tion system is calculated to be on the order of 1 x 10-7 per demand. The
$ s based on a higher estimated Staff's analysis of destructive overspeed i
probability of occurrence of destructive overspeed and therefore includes consideration of the probability of striking a vital target, given a missile. The Staff analysis considers three targets.
In two cases (con-tainment and main steam piping) the staff's calculation of strike prob-ability depends only upon FNP geometry, i.e., it is assumed that a missile with the correct trajectory has adequate energy to reach the target.
In the third case (spent fuel pool) the calculated strike probability depends upon missile energy in addition to geometric factors. However, the energy dependence is such that increased missile exit energy will not result in increased strike probability.
As a result of the foregoing, it is concluded that recent observations of disc cracking, missile penetration tests and revised Westinghouse exit energy cMculations will not adversely affect the conclusions put forth in prior testimony respecting the probability of unacceptable damage from a turbine missile.
YANKEE-ROWE DISC FAILURE l
On February 14, 1980, two discs in the low pressure unit of the Yankee-Rowe turbine generator failed with the turbine running at nomal operating speed. The materials of the Yankee-Rowe turbine are similar to the Ship-7 pingport turbine, whose failum was addressed in prior testimony. Neither the Shippingport failure nor the Yankee-Rowe failure re 11ted in missile fomation. Both machines failed from stress corrosion cracking af ter many
\\7_ Calculations previously entered into evidence by both the Applicant and the Staff are based on an assumed alue of P (the probability of turbine missile generation) of 1 x 10 g/ year from the Bush Report.
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\\8, Staff's written direct testimony, pp. 2-11.
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years of service, and in neither case did the failed turbine receive periodic ultrasonic disc inservice inspection.
The fail ure at Yankee-Rowe does not alter the conclusion in testimony presently before the Board that the FNP turbine is net expected to experi-ence Shippingport-type failures.
The contents of this Affidavit were developed under my guidance, super-vision and direction and are true and correct to the best of n1y knowledge, information and belief.
,m P.BlairHaga,grector Power Systems Wechnology Sworn to and subscribed before.ne this d day of October 1981.
-sf-uh ce pye Smith v tary Public, State of Florida at Large My Comission Expires:
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DOCKETED USNRC UNITED STATES OF AMERIC A NUCLEAR REGULATORY COMMISSION 51 M -2 P4 :19 BEFORE THE ATOMIC SAFETY AND LICENSING BOASQ ggg l)CCKETING & SERVICL BRAdCH In the Mattir of OFFSHORE POWER SYSTEMS Docket No. STN 50-437 (Manufacturing License for Floating Nuclear Power Plants)
CERTIFICATE OF SERVICE I hereby certify that copies of the " Affidavit 4
of P. Blair Haga Regarding Turbine-Generator Matters" were served upon the persons listed on Attachment 1 to this Cer-tificate of Service by deposit in the United States mail, postage prepaid, this 28th day of October, 1981.
V hn R Kenrick Co for Offshore Power Systems
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ATTACHMENT 1 t
OPS SERVICE LIST b
Sholdon J. Wolfe, Esq., Chairman Barton Z. Cowan, Esq.
JAtomic Safety and Licensing Board John R.
Kenrick, Esq.
U.S. Nuclear Regulatory Commission Eckert, Seamans, Cherin & Mellott Waehington, D.C.
20555 42nd Floor, 600 Grant Street Pittsburgh, Pennsylvania 15219 Dr. Dnvid R. Schink, Member Atomic Safety and Licensi'ng Board Thomas M. Daugherty, Esq.
y Offshore Power Systems j
Dspartment of Oceanography Texao A & M University 8000 Arlington Expressway
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P. O. Box 8000 College Station, Texas 77840 Jacksonville, Florida 32211 Mr. Glenn O.
Bright, Member Atomic Safety and Licensing Board Carl Valore, Jr., Esq.
U.S. Nuclear Regulatory Commission Valore, McAllister, DeBrier, Aron &
Washing +.on, D.C.
20555 Westmoreland P.
O. Box 175 Dr. David L.
Hetrick, Alternate Member Northfield, New Jersey 08225 Atomic Safety and Licensing Board Professor of Nuclear Engineering Richard M.
Hluchan, Esq.
State of New Jersey The University of Arizona Tucson, Arizona 85721 Department of Law & Public Safety 36 West State Street Alan S.
Rosenthal, Esq., Chairman Trenton, New Jersey 08625 Atomic Safety and Licensing Appeal S. Jaccb Scherr, Esq.
Board Panel U.3. Nuclear Regulatory Commission Natural Resources Defense Council Washington, D.C.
20555 1725 I Street, N.W.,
Suite 600 W&,.ington, D.C.
20006 Alternate Chairman Atomic Safety and Licensing Appeal Keith A.
Onsdorff, Esq.
Assistant Deputy Public Advocate Board Panel U.S. Nuclear Regulatory Commission State of New Jersey i Washington, D.C.
20555 P.O. Box 141 Trenton, New Je_ sey 08601 Chief Hearing Counsel Office of the Executive Legal Director Mr. George B. Ward l
ti.S. Nuclear Regulatory Commission Nuclear Power Plant Committee l Washington, D.C.
20555 City Hall Brigantine, New Jersey 08203 Docketing and Seroice Section Dr. Willard W. Rosenbt.g Office Lf the Secretary Atlantic County Citizens Council on U.S. Nuclear Regulatory Commission Environment Wcshington, D.C.
20555 8 North Rumson A"enue Margate, New Jersey 08402 Stephen M.
Schinki, Esq.
Of fice of the Executive Legal Direrror Mr. John H. Williamson U.S. Nuclear Regulatory Commission Atlantic County Citizens Council on Washington, D.C.
20535 Environment 211 Forest Drive Director Division of Nuclear Peactor Regulation Linwood, New Jersey 08221 U.S. Nuclear Regulatory Commission Washington, D.C.
20555
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