ML20138F363
Text
. -.
SEP 121996 MEliORANDUM TO:
Frederick J. Hebdon, Director Project Directorate II-3 Division of Reactor Projects I/II FROM:
Jack R. Strosnider, Chief Materials and Chemical Engineering Branch Division of Engineering
SUBJECT:
SECTION 2.206 PETITION OF THOMAS J. SAPORITO AND THE NATIONAL LITIGATION CONSULTANTS REGARDING THE ST. LUCIE NUCLEAR STATION (TAC M95758)
By a letter dated June 12, 1996, Thomas J. Saporito, Jr. petitioned the staff on behalf of himself and the National Litigation Consultants (petitioners) requesting staff action under 10 CFR 2.206 regarding operation at the St.
Lucti Nuclear Station, Units 1 and 2.
The petitioner requests the NRC (1) to issue a confirmatory order requiring that the licensee not operate Unit-1 above 50% of its power level capacity, (2) to require the licensee to spe.'fically identify the root cause for the premature failure of the steam generator tubing, and (3) to require the licensee to specifically state what corrective measures will be implemented to prevent reoccurrence of steam generator tube failures in all the steam generators in Unit-1 and Unit-2.
The attachment contains the input from the Materials and Chemical Engineering Branch.
This completes our effort for TAC number M95758.
Docket No. 50-335
Attachment:
As stated Distribution:
CENTRAL FILE EMCB RF LWiens BSheron Glainas DOCUMENT NAME: G:\\STLUCIE.NEM, \\STLUCIE.R2 To receive a copy of this doctment, indicate in the box C= Copy w/o attachmehe[$losure E= Copy with attachment / enclosure N = No copy 0FFICE DE:EMCB 6
DE:EMCB E
DE:EMCk C
NAME JTsao:jt N f ESu111vand JStrosher DATE 9 //4/96
'l //i)/96 7 //c /N OUICIAL RECORD COM us_ $7 g _ u3 gg 0bO'illc0 3/C A"
s NRC FM.E CENTER COPY
i 3Ep 1219 9
MEMORANDUM T0:
Frederick J. Hebdon, Director i
Project Directorate II-3 i
Division of Reactor Projects I/II FROM:
Jack R. Strosnider, Chief Materials and Chemical Engineering Branch Division of Engineering 1
SUBJECT:
i SECTION 2.206 PETITION OF THOMAS J. SAP 0kITO AND THE NATIONAL LITIGATION CONSULTANTS REGARDING THE ST. LUCIE NUCLEAR STATION (TAC M95758)
By a letter dated June 12, 1996, Thomas J. Saporito, Jr. petitioned the staff i
on behalf of himself and the National Litigation Consultants (petitioners) requesting staff action under 10 CFR 2.206 regarding operation at the St.
j Lucie Nuclear Station, Units I and 2.
The petitioner requests the NRC (1) to issue a confirmatory order requiring that.the licensee not operate Unit-1 above 50% of its power level capacity, (2) to require the licensee to specifically identify the root cause for the i
premature failure of the steam generator tubing, and (3) to require the licensee to specifically state what corrective measures will be implemented to i
prevent reoccurrence of steam' generator tube failures in all the steam l
generators in Unit-1 and Unit-2.
The attachment contains the input from the Materials and Chemical Engineering Branch.- This completes our effort for TAC number M95758.
t Docket No. 50-335 J
Attachment:
. As stated i
Distribution:
i CENTRAL FILE EMC8 RF LWiens i
BSheron 4
Glainas 4
i DOCUMENT MAME: G:\\STLUCIE.NEM,\\STLUCIE.R2 a r csiv.. cos, of thi. enca ne. insie.e. in th. non e c.w of.. e.ch ebeest ur.
c.or with et chment/eneto ur m u c.pv 0FFICE DE:EMCB 6
DE:EMC8 E.
DE:EMCb d
l NAME JTsao:jt l'f ESullivanN JStros[ider l
DATE
'//B/96
'///0/96
'7 //c /96 u
o 0FFICIAL RECORD COPY 4
?
l i
?
.d,.
4 Attachment RESPONSE TO SECTION 2.206 PETITION j
0F THOMAS J. SAPORITO REGARDING i
THE ST. LUCIE NUCLEAR STATION, UNITS 1 AND 2 Petitioner Reauest h
(a)
Issue a confirmatory order requiring that the licensee not operate Unit-j I above 50% of its power level capacity.
NRC Resnonse 1
The NRC staff has concluded that the operation of the Unit I steam generators at full power poses no undue risk to public health and safety.
The inspections and repairs performed by the licensee on the steam generators 4
j during the 1996 outage provide reasonable assurance that the tubes having structurally significant flaws have been identified and removed from service.
The preliminary results from the licensee's in-situ pressure testing of the steam generator tubes during the refueling outage in 1996 demonstrate that the j
most severely degraded tubes had adequate structural integrity after a full cycle of operation.
to determine whether the tubes need to be inspected again prior to 1
i refueling outage.
The licensee stated that based on the preliminary results
)
of its analysis, it expects the results will support the tube inspection interval of 15 months for the current cycle that started in July 1996.
NRC will review the adequacy of this evaluation.
The g.
In addition, the licensee has implemented defense-in-depth measures in both units to protect public health and safety in the unlikely event that tube integrity is compromised.
leakage monitoring program and emergency operating procedures.These m j
The leakage j.
monitoring program provides early warning of tube leakage.
The amount of leakage is limited by the plant technical specifications beyond which the unit
.is required to be shutdown.
1 1he emergency operating procedures specify operator actions to mitigate consequence of the potential tube rupture events and to. bring the unit to a safe shutdown.
On the basis of the licensee's actions licensee, not operate Unit I above 50% of its power level capaci Petitioner Reauest (b)
Require the licensee to specifically identify the " root cause" for the premature failure of the steam generator tubing.
NRC Resnonse 1
Each of the St. Lucie units uses two Combustion Engineeric.; Model 67 steam generators.
Each steam generator has 8,519 tubes which are fabricated with j
mill annealed nickel-based Alloy 600 material.
l There have not been any steam generator tube ruptures at St. Lucie.
Many of j
the tubes in the Unit I steam generators have degraded as a result of j
corrosion and/or mechanical conditions.
The root cause of the corrosion and i
3
.q.
! d. -
i 2
mechanically induced damage is the interaction of water chemistry, thermal-j hydraulic design, materials selection, fabrication methods, and operating-t conditions. The basic causes of tube degradation are well understood by the 4
industry and are documented in the public record.
4 The licensee has identified to the NRC modes of degradation that have affected the steam generator tubes in both units. The degradation modes includes j
intergranular attack / stress corrosion cracking, and denting.
Intergranular i
attack / stress corrosion cracking is the uniform corrosion attack of grain boundaries over the surface of the tubing, resulting from the interaction of i
stress, corrosive environment, and the tube material. Denting is the j.
accumulation of corrosion products at the tube-to-tube support plate that l
causes phstic deformation of the. tube.
The licensee has identified locations of these degradations in the tubes.
They include eggerate and drilled tube support plates, free spans, expansion transition regions, and sludge pile areas.
In every case the root cause can be attributed to material selection,
)
water chemistry, or residual stresses at the affected location.
i Because the causes of tube degradation are well understood and the licensee 4
i has identified the areas of degradation, the petitioner's request to require L
the licensee to specifically identify the " root cause" for the premature j
failure of the steam generator tubing is denied.
j Petitioner Reauest
{
(c)
Require the licensee to specifically state what corrective measures will i
be implemented to prevent recurrence of steam generator tube failures in j
all the steam generators in Unit-1 and Unit-2.
j NRC Response As mentioned above, the degradation of the steam generator tubing is caused by the interaction of water chemistry, thermal-hydraulic design, materials i
selection, fabrication methods, and operating conditions.
In general, the causes of tube degradation are directly related to the fundamental design of i
the steam generator and are not reversible.
In some cases, preventive i
measures are able to reduce the rate of tube degradation.
For example, the rate of tube degradation may be reduced through improvements in water i
i chemistry. The licensee follows the Electric Power Research Institute j
guidelines on secondary water chemistry for both units which represent a j
significant improvement over the guidelines followed when Unit I was put into j
service. Replacement steam generators having improved design, e.g., material selection and tube support configuration, have had much better operating experience than the earlier designed steam generators such as those at St.
Lucie. The licensee plans to replace the Unit I steam generators in October i
1997.
1 Because of the limited actions available to prevent further tube degradation, regulatory interest is focused on ensuring adequate tube integrity between steam generator inspections. NRC regulations and plant technical i
specifications require that steam generator tube degradation be managed j
through a combination of inservice inspection, repair of tubes exceeding the i
i
=
') * *.
3 plugging criteria, primary-to-secondary leakage monitoring, and analyses to ensure safety objectives are met.
In addition, the NRC provides oversight to ensure that licensees satisfy the regulations and technical specifications as they apply to steam generator tube integrity and that licensees use appropriate inspections method and repair criteria to address specific forms j
of degradation.
Furthermore, region-based inspections of licensee steam generator program are performed periodically.
The combination of the
)
regulations, technical specification requirements, and oversight activities 4
provide assurance that licensees are implementing appropriate measures to i
ensure steam generator tube integrity.
Therefore, the petitioner's request for requiring the licensee to specifically state what corrective measures will j
be implemented to prevent recurrence of steam generator tube failures in all the steam generators in Unit-1 and Unit-2 is denied.
l 1
1 4
1
-