ML20101S894
| ML20101S894 | |
| Person / Time | |
|---|---|
| Site: | Calvert Cliffs  |
| Issue date: | 07/13/1992 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20101S889 | List: |
| References | |
| GL-91-04, GL-91-4, NUDOCS 9207200130 | |
| Download: ML20101S894 (8) | |
Text
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO ' AMENDMENT NO.173 T0 FACILITY OPERATING LICENSE'NO. DPR-53 AND AMENDMENT N0.150 TO FACILITY OPERATING LICENSE NO. DPR-rd-BALTIM0RE GAS AND ELECTRIC COMPANY CALVERT CLIFFS NUCLEAR POWtR PLANT. UNIT-NOS.1 l ANQ),
MCK.ET NOS. 50-317 AND 50-318 K
1.0 'INTRODUCU ON-By letter dated Mar.h 25, 1992, as' supplemented May 28, 1992,- the Baltimore Gas and Electric Conpany-(the licensee). submitted a request for changes to the Calvert Cliffs Nuclear Power Plant, Unit Nos.1 and '2, Technical Specifications (TS).
The-proposed amendments would revise the Calvert-Cliffs TS for both units to provide conditions under-which the steam generator-inspection intervals may-be extended to 30 months in accordance with the guidance provided-in Generic Letter (GL) 91-04.
In addition, a one-time variance (Unit 2 only) is requested from the proposed-TS condition which rer,uires that the last inspection include 20 percent of the-steam generator tubes being inspected with results in the'C-1-Category when. extending the inspection ~ frequency beyond 24 months. The C-1 Category is when-.less than~-5 percent
' the total tubes inspected are degraded tubes-and none of the tabN are dafective.
The GL had not been issued prior to' the last' inspection _of_ the Unit 2 steam generators during which 15 percent of the tubes were tested with results-in the C-1 Category.
l Specifically, the requested changes are for TS 4.4.5.3, 3.4.6.2., 4.'4.6.2, and supporting TS Bases.
The-licensee's submittal identifies and provides just?fication where deviations from the~ guidance provided in GL 91-04 are proposed. The requested variance for Unit.2 inspection.of 20 percent ~of the-tubes tested with results in C-1 Category, as specified in the GL,- is a l
f:otnote -for Unit 2, TS 4.4.5.3,- which states that a 15 percent, sample with results in the C-1 Category is acceptable for the _ unit's current cycle 9 -
oper. tion.
The May 28, 1992,. letter provided supporting information for-the requested Unit 2 one-time variance that did not expand the scope-of the oric!nal-_Notica t
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-or change the initial proposed no significant hazard, consideratiu.
i determination.
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2-I l-2.0 BACVGROUND 4
GL 91-04 was issued on April 2, 1991', to. provide-guidance to licensees for~.
preparing license amendment requests to-modify existing' surveillance intervals to be compatible with 24-month fuel-cycles.- -Improved reactor fuels allow-l licensees to increase the duration of_ fuel cycles from the previous 18-menth L
cycles to 24-month cycles.
The Calvert Cliffs _ units are currently operating-j:
on 24-month cycles.
f The Calvert Cliffs TS require that-the results of the inservice inspections (ISI) of _the steam generator tubes shall be classified into one of the-.
following these categories::
l Oteaory InsDection Result 1 I
C-1 Less than 5% of the total tubes inspected:are degraded' tubes 'and none. of-the p
' inspected: tubes are defective.
C-2 One or more_tubss, hat not-more than 1%'of the total-tubes inspectedcare defective,
- or between 5% and 10% of the total tubes' inspected:are degraded tubes.
C-3 More than'10% of the totali tubes inspected::are degraded' tubes or more than-1% of-the
- nspected tubes;are defecti #
The cv. rent Cal <ert Cliffs TS allow the surveillance; interval for performing the ISI of the steam generators to be: extended to a. maximum of 40 months if the results-from two consecutive inspections!are eachtin.the~C-11 category or if two consecutive' inspections Amonstratee that.previously observed degradation has not. continued and no-additional: degradation has occurred..
-However, if _ either of Me two-previous inspections / yielded inspection results' in the C-2 category, the.next inspection.mustqbe~ performed within-24 months.
Unlike other surveillances, the 24-month inspection period is not subject to-a 25-percent; extension'under TS 4.0.2. :Calvert Cliffs Units'17and 2' operate:on'
-a nominal :24-month' fuel cycir and thel 24-month inspection interval frequently does not coincide.with the next refueling outage,Lparticularly.if there wore.
unplanned outages during the Lfuel cycle or if:there is a;delayjhetween the r
p completion of thel steam generator inspectionsfand plant startup.
- GL 91-04 rovides guidance-for TS which allows extension:of. th'e T nspection i
interval for steam gencrators int the C-2 category from'24 to-30 months, sThis:
l-guidance -includes increasing the number of tubes-inspected based on-the -
l-results of the previous' inspection performing an engineering' analysis of steam generator tube : integrity for operation longer' than 24 months between
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l inspections and reducing the TS limit on leakage between the primary and secondary coolant systems.
3.0 EVALUATION-The event which must be considered when revising the steam generator inspection intervals is the steam generator tube rupture event as discussed in Section 14.15 of the Updated Final Safety Analysis Report (UFSAR) for the Calvert Cliffs facility.
The steam generator tubes provide a haat transfer i
boundary between the primary reactor coolant and the secondary feedwater and steam, and the proposed inspection intervals should provide reasonable assurance that the steam generator tubes wil' have structural integrity until the next inspection.
The integrity of the barrier is signfficant to radiological safety in that a leaking or ruptorcd tube would allow the transfer of reactor coolant into the main steam system with possible release to the environment.
4 The licensee has proposed the TS changes in accordance with the guidance provided in GL 91-04 to maintain an acceptable confidence level in the structural' integrity of the steam generator tubes. Where the licensee deviates from the guidance of GL 91-04, justification is provided. The proposed changes address an increase in sample size, details on the engineering analysis to be used, and the requirements for lower limits on the 4
primary-to-secondary leakage.
4 3.1 Samole Size in relation to the sample size, the licensee notes that the TS for Calvert Cliffs require a minimum of 3 percent of the total number of tubes in each steam generator be inspected during each ISI interval.
The proposed TS allow this inspection interval to be extended beyond 24 months if the last inspection examined at least 20 percent of the tubes and the results were in the C -1 category or at least 40 percent of the tubes were examined and the resuits were in the 0-2 category.
This increasing sample size is a compensating measure to offset the extension in surveillance intervals in accordance with the guidance in Gl. 92-01.
The proposed changes also require an engineering assessment if the ISI results of either of the previous two inspections were in the C-2 category in accordance with GL 91-04.
The proposed wording for TS 4.4.5.3.2 are consistent with the guidance provided in GL 91-04'with the following exception.
The licensee has added "at least" in front of the 20 percent and 40 percent tube inspection statements.
This addition is to clearly state that the percentages are the minimum required in that the licensee frequently inspects 100 percent of the steam generator tubes.
In addition, a footnote is proposed for the Unit 2, TS 4.4.5.3.2.a, which statet that "for Cycle 9, an inspection of 15% of the steam generator tubes with inspection results in the C-1 Category shall be acceptable to extend the
, next inspection up to 30. months-to coincide with the next-refueling outage."
The last ISI of.the Unit 2 steam generators was performed in October of 1990 and 15 percent of the steam g,tnerator tubes were inspected.
This-inspection was performed prior to the issuance of GL 91-04 which was issued on April-2,.
1991, which specified a sample size of 20 percent.
The licensee indicates that 100 percent of the tubes (16,947 tubes) were inspected in both of the Unit 2 steam generators in April of 1989. As the result of the inspection, only 11 of 22 tubes were:found to have indications of imperfections which exceeded the plugging _ limit of 40 percent loss of nominal wall thickness. An additional 11 tches were plugged as a preventive measure.
The results of the ISI were in the C-2 category.
In addition, a Motorized Rotating Pancake Coil (MRPC) examination of the Unit 2 steam generator tubes was performed in July 1990. The tuba-to-tubesheet expansion region was examined on 35%-of the hot leg tubes:and no; flaws were detected.
In October 1990,-15 percent of the tubes in both Unit _2 steam generators were inspected in preparation for the resumption of power operation.following an extended shutdown. No power operation occurred on Unit _2 between the April 1989 and this inspection. During this period steam generator chemistry conditions were maintained consistent-with the recommendations in Electric Power Research Institute (EPRI) Report NP-6239-S405-2, "PWR Secondary Water Chemistry Guidelines," Revision 2.
The ISI resulted in no tubes being plugged and the results were in the C-1 category.
Additional justification for the requested one-time variance was rrovided in the May 28, 1992, submittal. The Unit I steam generators were_ controlled to the same chemistry requirements during jhe 1989-1990 shutdown as were in the Unit 2 steam generators. An ISI of the Unit I steam generators just completed during the current Unit I refueling-outage revealed little degradation.- Only 18 of the 16,861 tubes inspected full: length with the bobbin coil were_ plugged as result of eddy current indications.
In addition, a'3-coil MPPC examination war conducted on 25% of the_ hot leg tube-to-tube-sheet expansion zone region-in each steam generator and no cracks were detected.
The proposed changes to the TS wordi.'9-in TS 4.4.5.3;a, 4.4.5.3.b and a new 4.4.5.3.d reflect the guidance in GL 91-G?.
Specifically, if the criteria in L
TS 4.4.5.3.a is met the ISI interval can be extended to a maximum of once per 30 or 40 months, as applicable, -and the provis' ions of TS 4.0.2 do not apply' L
for extending the frequency of ISI as specified in TS 4.4.5.3;a and ~ b.
i The staff has determined that the proposed changes to TS 4.4.5.3;a, 4.4.5;3.b, l
the addition of 4.4.5.3.d, and-the one-time _variancetfrom the 20 percent-sample size are acceptable.. The use of "at_ least" in the wording of the TS provides clarification that the percer,t specified are minimum percentages,.the rest of the proposed TS are consistent with GL 91-04; adequate justification, as discussed above, has been provided for the requested-one-time variance from-tM 20 percent sample size for Unit 2 during the remainder of cyCe 9 operation.
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.. 3.2 [noineerino Asse m ent GL 91-04 provided guidt.ce for modifying the TS Bases Section to clarify the intent of the engineering assessment of steam generator _ tube integrity included in the r oposed changes to TS 4.4.5.3.a.
The guidance provided'in GL 91-04 provides. ee elements to be considered ~in an engineering assessment..
The licensee proposes inclusion of the three elements ~with one exception. The proposed element two does not _ include an assessment of the: maximum flaw size.
Tne ISI of the steam generator tubes is' to. provide reasonable assurance that the structural integrity of this-' portion of the reactor coolant system boundary is maintaired. The purpose of the engineering assessment is to demonstrate that the steam generator tubes maintain adequate structural-capability against burst between inspections.-
The licensee's justificath, & not including.the requirement to assess the maximum flaw size is that pressurized water reactor (PWR) steam generator tube inspections are typically conducted using an eddy current _ bobbin coil device.
While this device is capable of determining the' depth of a tube defect,-_it is not capable of determining the length or width.of the defect. Therefore,.
there is insufficient information to determine the size of-a detected flaw or :
the maximum flaw size that can be expected before the next inspection.- This information is not necessary in ' order to determine the structural margins-r:lative to Regulatory Guide (RG) 1.121, " Bases for Plugging Degraded:PWR Generator Tubes." This determination is currently made using only depth information from eddy current testing.
The licensee further staH thn if the results of either:of the previous two ISI were in the C-2 category classification,' an engineering assessment _would be required prior to operation beyond 24 months. This assessment would-determine whether all tubes 'will. retain adequate structural. margins against burst throughout norma 1' operating, transient, and accident conditions until the end of the fuel cycle or 30-months, whichever occurs first. The assessment would include a review of the flaws found during the previous inspection and a comparison of the structural margins to the_ criteria in RG -
1.121. Also, the assessment model would be updated, as appropriate, based on comparison of the' predicted results of the steam generator tube integrity assessment with actual results from inspections.
The staff has determined that the-proposed changes to TS~ Bases 3/4 _4.5 are-acceptable.
As noted above,-the licensee states:and the staff agrees, that an-assessment of the maximum flaw size Is not necessary to determine the structural-margin relative tc the criteria of RG 1.121.- In add _ition, recent ISI of:the steam generator tubes at the Calvert Cliffs units. have resulted in-a small number of tubes with flaw indications (22 of 16,947'and:18 of _16,861) which required-plugging.
Thus, there is reasonable assurance that the structural integrity will be maintained for.the proposed increase.in the interval between lil.
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m 3.3 Leakaae Limits GL 91-04 specifies a reduced primary-to-secondary leakage limit for any steam generator not isolated from the Reactor Coolant System to allow plant operation beyond 24 months. The guidance provided in GL 91-04 reduces the current standard TS leakage limit of 500 gallons-per-day for each steam generator to 100 gallons-per-day for each_ steam generator.
The current Calvert Cliffs TS do not include the 500 gallons-per-day leakage limit, however, the licensee imposes an administrative limit of an 100 gallons-per-day leakage for each steam generator.
The proposed change to'TS 3.4.6.2.c will include the 100 gallons-per-day leakage limit through any one steam generator as specified in GL 91-04.
The staff has determined that the proposed change to TS 3.4.6.2.c is consistent with the primary-to-secondary limit specified in GL 91-04, is a conservative limit for allowing plant operation beyond 24 months, and is acceptable.
In addition, the current surveillance TS 4.4.6.2.c states 'that the leakage is determined by performing a " water inventory balance." While the leakage measurement for comparison to the 1 gallon-per-minute limit is determined using a water inven+ory balance, the leakage measurement for comparison to the 100 gallor -per-day pr steam generator limit will be determined using an analysis of seandary coolant radiochemistry. This analysis cannot be considered a " water inventory balance." Therefore, the licensee proposes to revise the surveillance requiremant to state, " Determining Reacter Coolant System leakage." The proposed cliange does not alter the surveillance requirement, but allows the different measurement technique to be used.
The staff has determined that the proposed change to TS 4.4.6.2.c is acceptable in that the surveillance requirement is not changed = and other measurement techniques are available for meeting the required surveillance.
The changes to TS Bases 3/4.4.6.2 to reflect the new primary-to-secondary leakage are also acceptable.
4.0 ':UMMARY 3ased on the above evaluation, the staff has determined that the ISI intervals for the Calvert Cliffs, Units 1 and 2, steam generators may be extended to 30 months and that a one-time variance, for Unit 2 only, from the proposed TS requirement that the last inspection include 20 percent of the steam generator tubes having been inspected when extending the-ISI interval beyond 24 months.
This one-time variance is only applicable for the remainder of cycle 9 operation-for Unit 2 which is scheduled to be comp 1.eted in the spring of 1993.
Therefore, the proposed changes to TS 4.4.5.3.a, 4.4~.5.3.b, 3.4;6.2.c, 4.4.6.2.c, B3/4.4.5, B3/4.4.6.2, and the addition of 4.4.5.3.d are acceptable and provide reasonable assurance that the steam generator tubes will maintain structural integrity between the allowed ISI intervals.
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5.0 STATE CONSULTATION
In accordance with the Commission's regulations, the' Maryland State official was notified of the proposed issuance of the amendments.
The State official had no comments.
6.0 ENVIRONMENTAL CONSIDERATION
The amendments change a requirement with respect to installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20 and changes to the surveillance requirements.
The NRC staff has determined that the amendments involve no significhht increase in the amounts, and no significant change in the types, of any effluents that may be released offsite, and that there is no significant increase in individual or cuulative occupational radiation exposure.
The Commission has-previously issued-a proposed finding that the amendments involve no significant hazards consideration, and there has been no public comment on such finding
.(57 FR 18170). Accordingly, the amendments meet the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9).
Pursuant 19 10 CFR 51.22(b) no environmental impact statement or environmental assessment need be prtpared in connection with the issuance of the amendments.
7.0 f_0NCLUSION The Commission has concluded,-based on the considerations discussed above, that:
(1) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, (2) such aethities will be conducted in :ompliance with the commission's regulations, acu (3) the issuance of the amendments will not be inimical to the common Jefense and security or to the health and safety of the public.
Principal Contributors:
D. Mcdonald H. Conrad Date: July 13, 1992
.c DATED: July 13,1992 AMENDMENT NO 173 TO FACILITY OPERATING 1 JCENSE NO. DPR-53-CALVERT CLIFFS i
VNIT 1 4
AMENDMENT NO.150T0 FACILITY OPERATING LICENSE N0. OPR-69-CALVERT CLIFFS UNIT 2
- Docket File i
NRC & Local PDRs PDI-l Reading S. Varga, 14/E/4 J. Calvo,14/A/4 R. Capra C. Vogan D. Mcdonald 0GC D. Hagan, 3302 MNBB C. Liang, 8/E/23 G. Hill (8), P-137-4 Wanda Jones, P-130A i
C. Grimes, ll/F/23 ACRS (10)
OPA OC/LFM8 PD plant-specific file C. Cowgill, Region I T. Dunning, 11/E/22 M. Fields, 13/Hil5 K. Wichman, 7/D/4 H. Conrad, 7/0/4 cc:
Plant Service list i
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r 1'16001
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