ML20029D411
| ML20029D411 | |
| Person / Time | |
|---|---|
| Site: | Pilgrim |
| Issue date: | 03/01/1994 |
| From: | Studds G HOUSE OF REP. |
| To: | Rathbun D NRC OFFICE OF CONGRESSIONAL AFFAIRS (OCA) |
| Shared Package | |
| ML20029C549 | List: |
| References | |
| NUDOCS 9405050328 | |
| Download: ML20029D411 (4) | |
Text
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.GERRY E. STUDDS.
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Co-mE ON EN,a-AND COMMERCE ptvuoVTH S"lll";"',':,;" ";'"
Riottgr of Representatibts
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SUSCOMMifTit ON TRANSPORT ATs04 h
9 AND HAJA#Dous MAT &PtALs Hvament. MA 02601 March 1, 1994 Dennis Rathbun Director, Office of Congressional Affairs' Nuclear Regulatory Commission Washington DC 20555 I am contacting you on behalf of my constituent, Ms. Mary Ott.
Please see enclosed correspondence.
I would appreciate your attention to Ms.
Ott's
- concerns, specifically the discrepancies between the attached memo and your response to my earlier inquiry on this matter.
Please respond to me at: 1212 Hancock St, Quincy, MA 02169, Attm Mary Lou Butler.
S i.nce J y, N
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Ge E
St dds Enclosure
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-i 9405050328 940418 PDR ADOCK 05000293 PDR p
,1 THIS STATIONERY PRINTED ON PAPER MADE OF RECYCLED FIBERS k
Citizens Urging Responsible Energy J
c February 17, 1994 The Honorable Gerry E. Studds United States House of Representatives Washington, DC 20515-2110
Dear Congressman Studds:
In his February 1, 1994 letter to you on behalf of the Union of Concerned Scientists (UCS), nuclear safety expert Robert Pollard cites compelling new evidence that raises questions about the justification for continued operation of the Pilgrim Nuclear Power Station (PIIGRIM) in Plymouth.
UCS cautions that a turbine failure at PIIGRIM is not merely an economic concern for the Boston Edison Company, as the Nuclear Regulatory Commission (NRC) suggests, but "could result in a serious nuclear accident with significant radiological consequences for the public."
These are sobering considerations for your constituents in Massachusetts and all New England as well.
We are writing to support UCS's request for additional analysis of the risks posed by PIIGRIM's cracked turbine, to provide information refuting claims by Boston Edison, and to request an investigation to determine whether the NRC attempted to deceive you about the risks posed by continued operation of the PIIGRIM plant.
and The Christmas day turbine fa:,1ure at the Fermi 2 nuclear plant,ilures recently issued fGC Informat: on Notice 64-01, " Turbine Blade Fa Caused by Torsional Excitation (i.e., vibration) From Electrical System Disturbance," offer insights into UCS's concerns with the potential dangers of PIIGRIM's cracked main turbine.
Boston Edison dismisses the lessons to be learned from the turbine failure at the Fermi plant by stating that the Femi turbine'was made by -
a different manufacturer than the PIIGRIM turbine. However, UCS cited the Fermi turbine failure as evidence that a failure of an_y,
~
turbine can cause large vibrations.
In the case of PI1 GRIM, the vibrations could increase the force on the existing cracks, but the NRC analysis of PIIGRIM did not consider this.
Similarly, UCS cited NRC Information Notice 94-01,which describes how routine electrical disturbances can cause turbine vibrations that:would significantly increase the force on the cracks in PIIGRIM's turbine.
(617) 934-0498' Duxbury, Massachusetts 02331 Post office _ Box 2621
Boston Edison has denied that PI1 GRIM is subject to the electrical However, our research of NRC disturbances the NRC varned against. By 1987, the NRC had documented reports contradicts Edison's claim.
In the 20 events which caused loss of 345kV offsite power at PIIERIM.
Eeh"7 M6 kSe specih[$aESfc[Ech b"hieECNNe N pNo 2 as having the potential to perturb the existing cracks.
We Finally, Congressman Studds, somothing else is seriously wrong here.
17, 1993 NRC internal memo, "PIIGRIM UNIT have obtained a copy of a JuneASSESSMENT OF IDW PRESSURE TURBINE ANAL Director, Walter Butler by Engineering Chief, Jack Strosnider, which 1:
was the basis for Chaiman Selin's August 4,1993 response to you and A comparison of the internal memo and.
CURE, " Enclosure 2" (appended).the NRC response to you shows that the "inside", and another on the "outside", about the danger of PIIGRIM's cracked turbines.
The NRC's response to you is essentially a verbatim repetition of the internal memo, but there are glaring changes and omissions which,'at best, could be viewed as an attempt by the NRC to downplay the safety At vorst, they could represent a hazards of PIIGRIM's cracked turbine.
deliberate attempt to withhold vital safety information to deceive our Congressional leaders about potentini dangers of PI1 GRIM's continued operation.
The critical importance of turbine deck orientation is outlined in NRC REGUIATORY GUIDE 1 115, Protection Against low-Trajectory Turbine It warns,
"..it is necessary to Missiles, provided to you by the UCS.
It show that the risk fran turbine missiles is acceptably small."
recites five principal means of safeguarding against such missiles and concludes, "...The first of these, turbine orientation and_ placement, provides a high dogree of confidence that low-trajectory missiles resulting from turbine failures will not damage essentihl systems."
(e.g., spent fuel storage pool, or impairment of vital' control room functions) emphasis added.
Yet in response to you, the NRC removed key language from the assessm bly which reveals that PIIGRIM's "... turbine dock is orientated unfavoraAlso, in with respect to the reactor building."the NRC says, "...(it) desir ility k
be 1E-5 each year or lower for an unfavorably orientated tu (emphasis added) that the turbine missile failure probability be 1E-5 per year or lower for an unfavorably orientated turbine." (emphasis added) i
./
i On behalf of the 1,600 members of CURE, we ask you to lend the full
- support of your office to:
- ceek an immediate cornitment from the NRC to provide all information and analyses requested by UCS
- request the Government Accounting Office, the NRC Inspector General or other appropriate agency conduct an investication to determine the reasons why the NRC's 6/17793 internal memo differs from the NRC's 8/4/93 response to you In recent weeks, the media has extensively exposed the past abuses of the atomic era.
There is little comfort in this progress, when contemporary abuses are flagrant. We believe that the NRC has abdicated its role as a regulator, abused its authority and violated our trust.
{IIERIM'.s continued gargng an unacceptable rggoing " cost versus safety r tion has become an o ttle," and we are sk These are strong sentiments from a conservative safe energy group. But cngrs!$nafh6daEhNrYan s"eis$nNakfSes$Ne i
uni 1E atomic abuses of today be revisited 50 years from now, and it will be too late.. Help us be a voice for change.
We greatly appreciate your involvement in our behalf on PILGRIM safety issues and look forward to hearing from you at your earliest convenience.
Sincerely yours,
/ d4A& h
-.s.
Dr. Donald M. Muirhead Jr.
Mary C. Ott Co-Chairmen 4
m
/
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UNino sTAMS
't4 e k NUCLEAR REGULATORY COMMi$8 ION'
+
S w aneu m ore n, o s. se a w o m
/
JUN 17'1993 k[,,/
Walter R. autler, Project Director l
NEhCSANDUM FORT Ject Directorate I-3 Pro:
Divanion of Reacter Projmote I/II Jeok R. Stroenider, chief Meterials and Chemical Engineering Branch FROMt Division 4f Engineerinq u
PILGRIN UNIT la Assammeumy op Low
SUBJECT:
PRESSURE TURNINE ANAL 1f8IS General $1ectrio - (GB)
/
During the refuellag outage in April 1942,
(
at Pilgria inspected the rotor in the low pressure turbine 5, and 7 Unit 1 and found flaw indications in disk numbere 4 stage disk beform or w rrm the LPA Stor subsequently, the licenses retained W1 Integrityt (7GA) on the generator side startup.
Associates, Inc.
(sIA) 1993, the licensee provided to the NRC M oct ma disk.
on May 12, wteether he, perform a the SIA analysis (aeference 1).
(ENCW1 the Materials and chemical Engineering sceneh re is. any 1
review of the SIA analysis to determine 1)the potentiali impact to grose error in the SIA entlysis and 2) l i d LPR, with f
plant safety.
Pilgrim Unit i has two low pressure turbines, LPA an
-with The_ turbine dock js_o_rientated
"*P '- ? '"bo 7GA
?
t 2me s N oations)of t shrunk-on disks. respect to the reactor W id and web.
Aithenegh thfl4th and stb 4 h t in tlpe 74& disk, disk are located in teeth the stage disks have more and-larger flaws than t d on l
operating conditions, disk failure.
consequences of the ffects bf fracture 4
SIA performed parametrio studies to determ na efresturd toughnese toeperature (FART),
e intensity transitionming, orsak growth rate end both the SS appearenos variability, ENCS staff compared key parameters used l Parameters
- y. m and SIA analyses to our estimates (see Atte-esment 1)
The analysis I
models.
the used in the 65 analysis were extracted 1senavailable_ at _ tjhe because GE's analysis wags I
f m eesoment.
I t
l John Tsaa, on/ENCS,
Contact:
so4-2702 Q(p 0hb
.....,...u......j
Jane I'l - /\\/RQ, G\\CR1Q !
~
2 ed one indication of 0.14 i For the 7aA disk, os r the web which as could natl nch in theaccurately k hub and an indication mise.
For that indication, GE assumed a'orack size based on flaw indications from other poser plants' ins (of 0.25 inch pection data and labornt6ry ' data.
The staff hell
-that--tha._jaitial orpok size of 0.25 inch is conservative staff could p'ot quapti 1W the uncertainty associated with the sise at th.is time.
/p 7-( < *> '
4R used a fracture mechanios model of an edge orack in an infinite plate having eenstant loading.
ea's model is ::z w4ive because it la more compliant than the actual geometry which is a radial-crack emanating from the keyway.
Moreover,inits sonatant loading does not consider the radial decrease hoop 6 tress with increasing distance tros the here.-
sIA'a modai la b hele in an infinite plate with attenuated leading along the ersch, The staff
,j assuesd a model of a thick wall cylinder with attanud$ed loading.
L)M 4E used 0.08 inch par year for the orsak growth rate W iah was the s' median valge-taken from a statistioni study of the average erask F
growth ratpd vs.p1 operating temperature from turbino laspection data of noth _wa and PWR <plants.
SIA used 0.0144, OJ2 and 0.08 s
inch par year in its atu E as.
The staff calculated a 4ra,ak 4
rate of 0.02 inch per year from previous inspection daj,a of t5 LFA 7
7hr' rotor.
The staff believes that the actual diiaok granth rate may p/g, lie between 0.02 and 0.06 inch per year.
Wowever, secording to og's data, the uppos' hound growth rate (2 standard b'intions, at an operating temperature of 172*F oculd be as high as n,os inch per year.
The critical strees intensity (Em) is an indicator 'of fracture toughness of the diak material.
The lower the 5, used in the irecture mechanics analysis the more conservative the %nwhichwas 1ts will i
be.
GE's analysis used a lower bound value of 105 kalt taken from the graph 'of aritioni stress intensity; vs.
amosas temperature (Test Temperature - FATT).
The staff judgas that the value of los kaiVin is senservative.
1 GM and gIA salculated a critical crack size (depth) of 0.34 inch and 0.54 inch, respectively.
SIA conservatively assusied that the crank length is the length of the keyway here.
SIA isdioated that if the orsak aspect ratio is known, the eritical erset I sine may ha i
inrger than 0.54 inch.
Based en SIA's nalculation, khe critical l
craon size for the think wall sylinder model is about,0.48 inen.
Based on the aheve paramaters, the staff estimated 4 factor er safety on flaw sian ranging from 1.21 to 3.s based pa the' ratio
=
between the craak length at and of the
- (-t
==? -P i
- --il 1pstto that of the aritica1Meise of the cylindent model.
The Mr of safety en streme intaneity (Es) ranges fresW 1.1 to 1.89 which was estimated by taking square root of the safety femtor on flaw size.
r 3
i The Wac requirse that the turbine missile fmilure probability be 1E-5 per ymer or' lower for an unfavorably orientated Nrbine.
GB's analysis is based on a turbine missile generation probability of it-6 failure per year.
814 l die m*
r--
- a=
a nrah-hill'stio fruture mechanics analysis.
Scaed os engineering judgement, the Etwrr 1Welsated that una miselle failure probability for the LFA turi, tem 2.s betws4A 18-S and 15-4 per year.
For this moition, the NRC pereits the turbine to be kept in servios il the next schetuled outage, at which time the licensee should
&ke action to
~
reduce _the__ failure probability to the 1E-5 per year ctiterion (Ref.
replacement of both LPA and LFB rotore during the n$14ering 2).
'nia licenses has indicated that they are co the dxt scheduled refuelingoutage,whichisexpectedtobeApril199p 3
concludse that there is no safety concern for norme(k the statf I ased on an anwessment of B
the informationgilab !9peration of f the LPA turnine to the end of the currenQuel gy6le, The SIA
. analysis appears to reduce some of the obvioue ~d66,servatisms used
,in the Gr analysis.
J
~
Jack R.-Stroenider, Chief.I I
Materiale and Chemical Engineering Branch Division of Engineering l'
Enclosure:
- Pilgria Turbine Evaluation Attechsent 2 Beforencee I
cc: B.
D. Liaw l
)
R. Fa *:en J.
Shting i
t
PoO8
,1 PILGRIM UNIT 1: ASSESSMENT OF LOW PRESSURE TURBINE ANALYSIS During the refueling outage in April 1993, General Electric (GE) inspected the rotor in low pressure turbine "A" (LPA) at Pilgrim Unit I and found flaw indications in disks 4, 5, 6, and 7.
GE recommended that the licensee either remove the seventh stage disk on the generator side (disk 7GA) or warm the LPA rotor before starting the turbine.
The licensee later retained Structural Integrity Associates, Inc. (SIA) to evaluate flaw indications in disk 7GA.
On May 12, 1993, the licensee submitted the SIA analysis (Reference 1) to the NRC project manager, who requested that the NRC Materials and Chemical Engineering Branch (EMCB) review the SIA analysis to determine:
whether there were any gross error in the SIA analysis and whether the flaws indications in the turbine disks would have any effect on plant safety.
Pilgrim Unit I has two low pressure turbines, LPA and LPB, with shrunk-on disks.
The flaw indications of the 7GA disk are located in both the hub and web.
Although the fourth and fifth stage disks have more and larger flaws than the 7GA disk has, GE determined that the 7GA disk is the limiting disk 1
based on operating conditions, the fracture toughness of the disk, and.the consequences of a disk failure.
SIA performed parametric studies to determine effects of the fracture appearance transition temperature (FATT), fracture toughness variability, pre-warming, crack growth rate, and stress intensity factors.
The EMCB staff compared key parameters used in both the GE and SIA analyses to our estimates (see Attachment 1).
Parameters used in the.GE analysis were extracted from the SIA analysis because GE's analysis was not available at the time of this assessment.
For the 7GA disk, GE reported one indication of 3.556 mm (0.14 in) in the hub and an indication in the web which GE could not accurately size.
For that indication, GE assumed a crack size of 6.35 mm [0.25 in) based on flaw indications from other power plants' inspection data and laboratory data.
The staff believes that the initial crack size of 6.35 mm (0.25 in) is conservative but could not quantify the uncertainty associated with the assumed size.
GE used a fracture mechanics model of an edge crack in an infinite plate having constant loading. GE's model is conservative because it is more compliant than the actual geometry, which is a radial crack emanating from the keyway.
h.,t
)
P.09 i Moreover, its constant loading does not consider the radial decreas stress with increasing distance from the bore.
oop infinite plate with attenuated loading along the crackSIA's model is a hole in an model of a thick wall cylinder with attenuated loading.
The staff assumed a GE used a crack growth rate of 1.52 mm median value from a statistical study co(0.06] inch each year, which was the rrelating the average crack growth rate with the wheel operating temperature from turbine inspection d BWR and PWR plants.
0.06 in) each year in its studies.SIA used 0.416 mm [0.0164 in), 0.
0.02 in), and 1.52 mm growth ra(te of 0.51 mm (0.02 inch] each year fro i
The staff calcu' ated a crack the LPA rotor.
The staff believes that the actuhl crack growth rate may be between 0.51mm (0.02 in] and 1.52 mm (0.06 in) each year indicate the upper bound growth rate (2 standard deviations) at an oHowe temperature of 78 *C [172 *F] could be as high as 2 03 mm (0 08 in each year.
The critical stress intensity (K ) is an indicator of fracture toughnes the disk material.
The lower the K s of ie themoreconservativetheresultswblbe.used in the fracture mechanics analysis intensity vs. excess temperature (test temperature -
s that the value of 115 HPalm (105 ksilin) is conservative The staff finds GE and SIA calculated the critical crack sizes (depths) of 8 64 m and 13.72 mm (0.54 in), respectively.
n crack length is the length of the keyway bore.SIA conservatively assumed that the crack aspect ratio is known, the critical crack size may be larger thanSIA in 13.72 mm (0.54 in).
about 11.43 mm (0.45 in] for the thick wall cylinder model.SIA's ca Using the above parameters, the staff estimated a end of the current fuel cycle in April 1995 to that of the critical crack size of the cylinder model (see attachment).
The factor of safety for stress root of the safety factor for flaw size. intensity (K ) ranges from 1.1 g
The NRC desires that the turbine disk failure probability be IE-5 each yea
'\\
lower for an unfavorably orientated turbine.
GE's analysi turbine disk failure probability of IE-5 failure per year.s is based on a perform a probabilistic fracture mechanics analysis.
SIA did not judgment, the staff estimated that the turbine disk failure probability for Using engineering the LPA turbine is between IE-5 and IE-4 per year.
turbine in this condition to remain in service until the next scheduledThe NRC would p outage, at which time the licensee should ensure they meet the turbine disk failure probability to the 1E-5 per year criterion (Attachment 2, Ref. 2).
7' ' I '
e.to
.s t Upon assessing tho information available, the staff found no safety concern for normal operation of the LPA turbine to the end of the current fuel cy although the SIA analysis is less conservative than the GE analysis.
e, staff intends to perform a confirmatory review of the GE analysis and its The methodology.
low pressure turbines during the next refueling out be in April 1995.
l
.