ML19305C337
| ML19305C337 | |
| Person / Time | |
|---|---|
| Site: | Fort Saint Vrain  |
| Issue date: | 02/27/1980 |
| From: | PUBLIC SERVICE CO. OF COLORADO |
| To: | |
| Shared Package | |
| ML19305C332 | List: |
| References | |
| EE-11-0002, EE-11-2, P-80034, NUDOCS 8003260571 | |
| Download: ML19305C337 (15) | |
Text
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l FORT ST. VRAIN INSERVICE INSPECTION AND TESTING PROGRAM SURVEILLANCE REQUIREMENTS REVIEW FOR THE PRESTRESSED CONCRETE REACTOR VESSEL (CONCRETE, PRESTRESSING, LINER, PENETRATIONS) 9' 8003300 G
'E' EE-ll-0002 Rev. 2 February 27, 1980 raJL J
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a' EE-ll-0002 Petr. 2 j
p.2 1.
INTRODUCTION' A review was performed of the current surveillance re-quirements for the Fort St. Vrain prestressed concrete reactor vessel (PCRV).
Additional or modified surveillance re-quirements may be recommended, as a result of this review, to satisfy the criteria established for the Fort St. Vrain inservice
-inspection and testing program as outlined in Ref. 1.
The review included the documents listed in Section 5, and in particular the proposed Draft of ASME Code,Section XI, Division 2.
The proposed Code requirements are identified, and where the current and recommended surveillance differ with these requirements, an explanation is provided.
A review was also performed of Regulatory Guides, which deal with surveillance of prestressing systems for light water reactor containment buildings, to determine the extent of compliance of the proposed surveillance with their requirements.
This review is included as an attachment to this report.
2.
SURVEILLANCE CLASSIFICATION The prestressed concrete reactor vessel (PCRV)- including the-prestressing system, the concrete, the liner, and the primary and secondary closures, provides structural support for the reactor and functions as a major portion of the reactor coolant pressure boundary and'the secondary containment.
The PCRV does not include any active PCRV components,_ except for some instrumentation.
In accordance with the criteria established for the in-service inspection and~ testing program for the Fort St. Vrain nuclear generating station (ref.1), the'PCRV is assigned to
[
surveillance class S3 (criteria 2.lc, 2.2c, and 2.3b of Ref. l?
The following criteria per Ref. 1 are considered when re-viewing the surveillance program of the instrumentation and structures which form the PCRV system.
Instrumentation with an active safety function shall be functionally tested and calibrated at least once each year (criteria 3.2. 3c and 3.2. 3e of Ref. 1).
Structural integrity of the PCRV closures shall be demonstrated by continuous leakage monitoring and by leakage measurement to be performed once each quarter for each penetration group (criteria 3.3.la of Ref. 1).
Structural integrity'of the PCRV shall be verified by surveillance inspections, the frequency of which, as well as the rules and requirements for which will be based on subsection IGK of the Draft ASME Code,Section XI, Division 2, taking into consideration the specific design features of the Fort St.
Vrain PCRV (criteria 3. 3.2a of Ref. 1).
Bolting of maior sarety class 1 equipment, which require disassembly at least once
s a
.t EE-ll-0002 R v. 2 p.3 2.
(cont..)
during each refueling cycle, shall be visually examined for indications of surface damage which could be detrimental to the structura1 integrity of the equipment (criteria 3.3.2d).
3.
OPERATIONAL READINESS 3.1 OPERATIONAL READINESS OF THE SYSTEM Except for some instrumentation, there are no active PCRV components which require that their operational readiness be tested.
i OPERATIONAL READINESS OF INSTRUMENTATION AND CONTROLS 3.2 3.2.1 TENDON LCAD CELLS (a)
Current surveillance requirements:
Technical specification SR 5.2.3 requires that a represen-tative number of tendon load cells be checked for possible shifts in reference points at the end of the first and third years after initial prestressing, and at five year intervals thereafter.
(b)
Recommended surveillance requirements-Surveillance procedure SR 5.2.3-X has been reviewed.
Three out of 27 tendon load cells are tested at the end of each specified interval, i.e. 10 percent of the load cells, which is considered to be a representative number.
The current surveillance requirements are adequate to assure that the measurements performed by the load cells will reflect or can be corrected to reflect actual tendon load with acceptable accuracy.
A difference exists with criteria 3.2.3c of Ref. 1 which require that a calibra-tion test be performed annually.
The very slow evolu-tion of the PCRV prestressing, as well as the difficulty of access to the load cells are acceptable justifications for the lesser frequency of calibration based on sampling.
There are no current surveillance requirements concerning the common high/ low tendon load alarm circuit between the PCRV concrete data acquisition system and the control room.
In accordance with criteria 3.2.3c of Ref.
1, it is recommended that this circuit be functionally tested annually, including verification that the load cell (s) which initiate the alarms are properly identified.
9 JE EE-ll-0002 Rav. 2 p.4 3.2 1 (cont. )
(c)
Proposed ASME Code requirements:
Tendon load cell surveillance is not addressed by the propose'd ASME Code,Section XI, Division 2, Draft.
3.2.2 PCRV EMBEDDED INSTRUMENTATION The PCRV embedded sensors, such as strain gauges, moisture ga ges and thermocouples, have no safety functions.
Therefore, u
there are no current surveillance requirements nor is any recommended concerning this instrumentation.
3.2.3 PCRV PENETRATION INTERSPACE PRESSURE AND FLOW INSTRUMENTS The corresponding instrumentation and controls are part of the PCRV auxiliary systems and the su: reillance requirements are discussed as part of the review of that system (see Ref. 2).
4.
STRUCTURAL INTEGRITY 4.1 PCRV CONCRETE STRUCTURE (a)
Current surveillance requirements:
The basis for' technical specification SR 5.2.4 states that PCRV structural response is monitored by installed sensors and deflection measurements as outlined in 1
section 5.13.4 and appendix E.17 of the FSAR.
Section 5.13.4.8 of the FSAR requires that vessel deformations and deflections be measured on the first, third and fifth year following initial power operation.
Continuation of the measurements thereafter will be dependent upon the assessment of the results following the fifth year recording.
(b)
Recommended surveillance requirements:
It is recommended that a requirement be added to techni-cal specification SR 5.2.4 to monitor overall deformations and deflections at vessel midheight and at the center of the top head during a vessel pressurization from atmospheric to operating pressure prior to initial power operation and during the first scheduled PCRV depressurization after the end of the first, third and fifth year following initial power operation, and at about 5 year intervals _thereuSar, to verify that the PCRV response is elastic and that no significant permanent strains exist.
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EE-11-0002.
Rev. 2 Pago 5 4.1 (cont.)
of PCRV concrete structure degradation in excess of normal behavior evolution predicted and incorporated j
in the design, a continuation of such a test is recommendr.d since it is the best indication of the overall PCRV structural performace.
(c)
Proposed ASME Code requirements:
Paragraph IGK 3320 and table IGK 3400-1 require overall deformations and deflections at vessel mid-height and center of the top head to be measured during a vessel pressurization from atmospheric to operating pressure, on the 1st, 3rd, and 5th year following commercial service and every 5th year thereafter.
(d)
The recommended surveillance meets the proposed Code l
requirements, and criteria 3.3.2a of Ref. I which require that the surveillance be based on these requirements.
4.2 PCRV CONCRETE (crack mapping)
(a)
Current surveillance requirements:
Technical specification SR 5.2.4 requires that cracks which exceed 0.015 inches in width shall be recorded during the initial proof test (IPTP), and be assessed for any changes in length during subsequent inspections and that any new cracks found during subsequent inspections be recorded.
Such visual inspections are to be performed at the end of the first and third years following initial power operation, and at ten year intervals thereafter.
(b)
Recommended su rveillance requirements:
The surveillance procedure SR 5.2.4c-X has been reviewed and found adequate to verify structural integrity by assessing surface cracking patterns and sizes.
(c)
Proposed ASME Code requirements:
Table IGK 2500-1, i tems A, B, and C, define the requirements for crack mapping of the PCRV top head, bottom head and side wall respectively.
Generally, the requirements consist of visual examination during each inspection interval (defined in IGA 2400) of 100 percent of selected control areas and 25 percent of the uncontrolled areas for cracks 0.015 inch wide or wider.
Paragraph IGK 2410 requires that 25 to 33 percent of the examinations be completed by the expiratirn of one-third of the inspec'.on interval, 50 to 66 percent by the expiration of tr.e second third, and the remaining by the expiration of the interval.
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EE-ll-0002 Rsv. 2 p.6 4.2 (cont.)'
(d)
The current surveillance exceeds the proposed Code re-quirements, since 100 percent of the accessible concrete surface is visually examined during each inspection in-terval.' A difference exists with the Code scheduling requirement.
This is acceptable considering the larger extent of examination than required by the proposed Code.
Generally, the current surveillance exceeds criteria 3.3.2a of Ref. 1.
4.3 PCRV CONCRETE (permeation)
(a)
Current surveillance requirements:
Technical specification SR 5.2.13 requires that the permeability of the PCRV concrete to helium be measured at the end of the third year after initial power opera-tion, and at five year intervals thereafter.
(b)
Recommended surveillance requirements:
The current surveillance is adequate to provide additional information concerning the continued integrity of the PCRV.
i (c)
Proposed ASME Code requirements:
i There are no requirements related to concrete per-
^
meation in the proposed ASME Code,Section XI, Division 2, Draft.
(d)
Therefore, the current surveillance exceeds the proposed Code requirements, and criteria 3.3.2a of Ref. 1.
4.4 PCRV SUPPORT STRUCTURE (a)
Current surveillance requirements:
None.
(b)
Recommended surveillance requirements:
It is recommended that the support structure be visually examined for signs of structural deterioration at the same time the PCRV is examined.
Significant cracking patterns or sizes should be investigated with respect to their impact on the integrity of the PCRV.
..e EE-11-0002 Rav. 2 p.7 4.4 (cont.)
(c)
Proposed ASME Code requirements:
Table IGK 2500-1 item D states that the requirements are in course of preparation.
(d)
The recommended surveillance is. assumed to meet the intent of the proposed ASME Code, and criteria 3.3.2a of Ref.
1.
4.5 PCRV PRESTRESSING TENDONS (a)
Current surveillance requirements:
Technical specification SR 5.2.2 requires that corrosion-protected wire samples, inserted with the tendons with load cells,be inspected for corrosion and that samples of the atmosphere contained in a representative number of tendon tubes (with as well as without load cells) be drawn and analyzed for products of corrosion.
Such inspection and sampling are to be performed at the end of the.first and third calendar
- year after prestressing and every five years thereafter.
(b)
Recommended surveillance requirements:
Review of the surveillance procedures SP 5.2.2.a-X SR 5.2.2.b-X and of applicable sections of the FSAR has revealed no need for additional surveillance to assure that there is no significant corrosion of the prestressing tendons.
However, since it is not practical to perform this surveillance with the plant in operation, it is recommended that the technical specification be modified to allow operation until the first scheduled PCRV de-pressurization following the specified intervals, to provide some operating flexibility without impairing plant safety since tendon corrosion is a slow evolving phenomenon.
Technical specification SR 5.2.2 requires that the wire sample be of " sufficient length (at least 15 feet)".
FSAR Section 5.13.8 provides an exception for those wire samples in the bottom cross head tendons.
Further, each wire is reinserted after testing, but a 4 foot section may have been cut off.
It is therefore recommended that the reference to a minimum 15 foot length be modified to take into account the wire samples which are half the tendon length in the bottom crosshead tendon tubes.
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iJ EE-11-0002.R:v. 2 p.8 4.5 (cont.)
(c)
Proposed ASME Code requirements:
Paragraph IGK 3330 requires that visual examinations be performed of a random sampling of anchcrs and that unstressed sample wires be examined for corrosion.
Un-stressed wire samples are allowed when it has been de-monstrated that the wire material is not susceptible to stress corrosion.
The Code requires that a minimum of 5 percent of the linear prestressing members be selected for corrosion surveillance.
Table IGK 3400-1 requires that at least two prestressing members.be examined at the end of the first year and one at the end of the third and fifth year, then a minimum of 1 percent during each inspection interval.
(d)
Fort St. Vrain has 448 prestressing members, all of them of the linear type.
Wire samples are provided in 27 of them (i.e. 6 percent).
Of those, a minimum of 4 (i.e.
about 1 percent) are examined at intervals as specified in (a) above.
Experimental tendon corrosion testing has been performed and reported in Appendix E.19 of the FSAR.
The current surveillance exceeds the code require-ments, even though no examination is performed at 5 years, since about 2 percent of the wire samples are examined during the Code inspection interval as defined in IGA-2400.
Therefore, the current surveillance also exceeds criteria
- 3. 3. 2a of Ref. 1:
4.6 PRESTRESSING ANCHOR ASSEMBLIES 6
i (a)
Current surveillance requirements:
About 0.5 percent of the prestressing anchor assemblies are visually examined at the end of the first and third year after initial prestressing, and every 5 years there-after, when performing the tendon corrosion wire inspection required by technical specification SR 5.2.2.
This corresponds to 1 percent of the tendons where only one j
end anchor is 'xamined.
j
- (b)
Recommended surveillance requirements:
i It is recommended that the number of anchors scheduled l
for visual examination be increased by a factor of about l
10, so that 5 percent of the PCRV tendon end anchors are examined during the first scheduled PCRV depressurization following the end of each subsequent 5 year interval.
This number may include the anchor assemblies which can be visually examined while performing tendon wire inspection and tendon tube atmosphere samj~.ing.
4
EE-ll-0002 Rev. 2 P9 4.6 (cont.')
(c)
Proposed ASME Code requirements:
Tables IGK 2500-1 and IGK 2600-1 item E require that 25 percent of the tendon end anchor assemblies be visually examined, as scheduled per IGK 2410 during the inspection interval' defined in IGA 2400.
(d)
The proposed surveillance requirements imply that 10 percent of the anchor assemblies are examined during the Code in-spection interval and that the examinations are scheduled so that half of them are performed by the expirar. ion of half of the Code inspection in'erval.
These requirements t
are considered to meet the intent of the proposed ASME Code and provide an adequate representative sample to determine the integrity of the anchor assemblies.
There-fore, the recommended surveillance meets criteria 3.3.2a of Ref. 1.
4.7 PCRV LINER (a)
Current surveillance requirements:
Technical specification SR 5.2.5 requires that three sets of.12 specimens of the PCRV liner and weld materials, previously installed in the PCRV, he tested for Charpy V-notch toughness.five years following initial power operation, and that additional specimen testing be con-ducted at 10 year intervals thereafter.
Technical specification SR 5.2.14 requires that the i
liner be examined for corrosion induced thinning, using ultrasonic inspection techniquas, at the end of the third and fifth years following initial power operation, and at 10 year intervals thereafter.
(b)
Recommended surveillance requirements:
The current surveillance requirements are adequate to assure that there are no acceptable changes in liner material toughness and subsequent NDTT shift due to irradiation, nor is there unacceptable liner thinning due to corrosion.
However, it *s recommended that tecnnical specification SR 5.2.5 be modified so that the surveillance intervals are based on refueling cycles rather than calendar years since the change in Charp y V-notch toughness is a function of fluence and not of time alone.
't.
EE-11-0002 Rev. 2 p.10 4.7b (cont.)
It is also recommended that technical specification SR 5.2.14 be modified to provide some flexibility in scheduling the examination since it requires that the reactor be shutdown and the PCRV depressurized, and since the corrosion thinning is a slow process.
It is recommended that plant operation be continued until the next scheduled PCRV depressurization when the specified surveillance interval may have' elapsed.
This is also consistent with Section 5.13.5 of the FSAR which states that the plant will not be shut down to perform the liner corrosion inspections if such inspection is the sole reason for the shutdown.
(c)
Proposed ASME Code requirements:
Paragraph IGK 3340 requires Charpy V-notch specimens cf the liner material to be positioned in the vicinity of the maximum radiation exposure experienced by the liner.
Requirements for the number of specimens and for surveillance intervals are stated to be in course of pre-paration.
There are no Code requirements related to liner examination for corrosion.
(d)
The current surveillance exceeds the intent of the pro-posed Code requirements since UT inspection is performed which is not required by the proposed Gode.
Therefore, the current surveillance meets criteria 3.3.2a of Ref. 1.
4.8 PCRV PENETRATIONS AND CLOSURES (a)
Current surveillance requirements:
Technical specification SR 5.2.16 requires that the penetration interspace leak rate, for primary and second-ary closures, be determined once per month to monitor and verify the integrity of the penetrations and closures.
(b)
Recommended surveillance requirements:
The primary closure is not subject to a high pressure differential due to pressurization of the interspace.
The secondary closure, although pressurized, is not subject to significant temperature transients.
Therefore, the operating conditions are r.ot expected to degrade the strength of the penetrations and closures.
Limit stops are installed as appropriate to limit the shock on the secondary closure in case of failure of the primary closure, so that the secondary closure remains intact.
Simultaneous failure of both primary and secondary closures is considered an incredible event.
,1 1,
EE-11-0002 Rnv. 2
- p. 11
- 4. 8bL (cont. )
The interspace-between primary and secondary _ closures is~ filled with purified helium at a pressure slightly higher than primary pressure, so that.any leak which.
could occur would be of purified helium.-
Further, the leak rate is continuously monitored, and alarmed if ab-normal, to provide additional assurance of integrity.
It is recommended, as in part C of Ref.
2, that the test frequency be decreased from monthly to quarterly, which is adequate to assure the integrity and leak tight-ness of the penetration closures, as specified by criteria 3.3.2a of Ref. 1.
With respect to the bolting for the penetrations and closures, no surveillance is recommended as per criteria 3.3.2d of Ref. 1, since any one refueling penetration is disassembled about every sixth refueling shutdown for re-fueling of the corresponding core region, and the other penetrations are disassembled at several year intervals for maintenance or repairs or may not require disassembly.
However, it is recommended that the refueling penetration hold down plate bolting be visually examined for indications of surface damage which could be detrimental to the structural integrity of the hold down plates, as per criteria 3.3'.2d of Ref.
1, since the hold down plates are major components to be removed at each refueling shutdown.
(c)
Proposed ASME Code requirements:
Previous paragraphs above address the PCRV features covered by subsection IGK of the proposed ASME Code Section XI, Division 2, Draft.
However, paragraph IGK 1100 specifies that metal sections of the pressure boundary that are not backed by concrete sha.ll meet the inspection re-quirements under subsection IGB, IGC, or IGD as appropriate.
The primary closures are considered equivalent to j
Code class 1 and their surveillance is specified by subsection IGB.
The secondary closures are considered equivalent to Code class 2 and their surveillance is specified by subsection IGC.
Both primary and secondary closures are exempted from volumetric and surface examinations by IGB 1220 and IGC 1220, respectively, since they are not utilized for shutdown heat removal, or chemical ingress detection or control, and a failure of the component would not result in a primary coolant system depressurization which exceeds the rate established for the design basis depressurization accident, since simultaneous failure of both closures is an incredible event.
However, IGB-1220 and IGC 1220, require a visual examination during the system leakage and pressure test required by IGB 5000 or IGC 5000.
)
-r EE-11-0002 Rev. 2 p.12-4~. Sc (cont. )'
For PCRV penetrations (IGB 5410 or'IGC 5410), the re-quirements.for inservice pressure testing and examina--
tion for leakage are met by performance of IGA 5440 which requires that a test for detection of reactor coolant leakage be conducted after each fueling outage while the reactor is operating at the power level permitted by the Regulatory Authority.
(d)
The recommended surveillance exceeds the proposed Code re-quirements since leakage is determined quarterly.
The differences with the proposed Code requirements concern-ing visual examination are con,sidered justified for the reasons outlined in paragraph (b) above and since, in addition, most of the penetration closures are not accessible during reactor operation.
5.
LIST OF REFERENCES
References:
1.
_PSC Report EE-SR-0001 - Surveillance inspection and test
~
criteria for the Fort St. Vrain' nuclear generating station.
2.
PSC Report EE-ll-0001 - Fort St. Vrain inservice inspec-tion and testing program.
Surveillance requirements review for the PCRV auxiliary systems.
3.
Fort St. Vrain FSAR Section 5 and Appendix E 4.
System descriptions SD-ll-1, SD-ll-2, SD-11-3, SD -ll-6 5.
Technical specifications LCO 4.2.9, SR 5.2.2, SR 5.2.3, SR 5.2.4, SR 5.2.5, SR 5.2.13, SR 5.2.14, SR 5.2.16.
6.
Surveillance procedures SR 5.2.2a-X, SR 5.2.2b-X, SR 5.2.3-X, SR 5.2.4c-X, SR 5.2.4d-X, SR 5.2.5-X, SR 5.2.13-X, SR 5.2.14-X.
7.
ASME Code Section XI, Division 2, Draft.
8.
FSV C&I diagram IC-ll-6
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4 EE-ll-0002 Rsv 2-
. P 1-ATTACHMENT 1 TO EE-SR-1102 REVIEW OF NRC' REQUIREMENTS FOR CONTAINMENT P_ESTRESSING SYSTEMS INTRODUCTION NRC Regulatory Guide 1.103 provides design requirements for post-tensioned prestressing systems for concrete reactor vessels and containments.
Regulatory Guide 1.35 provides inservice inspection requirements for ungrouted tendons in prestressed concrete containments.
These regulatory guides have been reviewed and the applicable requirements have been compared with the recommended surveillance requirements for the Fort St. Vrain PCRV prestressing system to identify and assess any differences regarding the intent of these requirements.
DISCUSSION-REGULATORY GUIDE 1.103-Reg. Guide 1.103 simply recognizes the prestressing system used for the Fort St. Vrain PCRV (BBRV system with 169-wire tendons) as a. system approved by the NRC staff.
There are no additional design requirements specified for approved systems.
DISCUSSION-REGULATORY GUIDE 1. 35 Reg. Guide 1.35 applies to ungrouted tendons in pre-stressed concrete containment structures, for which "an inservice inspection program is necessary'because generally there is no permanent instrumentation installed in the containment that could continuously monitor its structural behavior".
Even though the PCRV at Fort St. Vrain is continuously monitored for prestressing, and even though there is abundant instrumentation permanently installed in the PCRV that could monitor its structural behavior, the requirements of Reg. Guide 1.35 have been reviewed, to de-termine the extent to which the Fort St. Vrain tendon sur-veillance requirements comply with containment tendon in-spection requirements.
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EE-11-0002 Rov. 2 p.2 1.
The Reg. Guide requires that inservice inspections be per-formed 1, 3, and 5 years after the initial structural integrity test and every 5 years thereafter.
These are approximately the same intervals as scheduled for inspection at Fort St.
Vrain, which'are 1 and 3 years after prestressing and every five years thereafter.
2.
The Reg. Guide requires that the tendon population be divided in homogeneous groups and that 2 percent of the popu-lation of each group with a minimum of 3 tendons be selected for'each inspection.
The Fort St. Vrain prestressing system has 90 longitudinal tendons, 310 c,ircumferential tendons and 48 cross head tendons.
Twenty-seven of these tendons are continuously monitored for prestress, of which 6 are longitudinal (i.e. 6.7 percent), 17 are circumferential (i.e. 5.5 percent),
and 4 are cross head tendons (i.e. 8.3 percent).
It has been further recommended at Fort St. Vrain that 5 percent of the tendon end anchor assemblies b~e visually examined at each inspection.
3.
Section 3 of Reg. Guide 1.35 requires that the concrete surface be visually examined for widespread cr cking, spilling and grease leakage, and that visual examination be performed on selected tendon anchorage assembly ha'rdware, without dis-mantling load-bearing components of the anchorage (2% of tendons).
The recommended surveillance exceeds the regulatory guide requirements since crack mapping of the PCRV requires recording of cracks on the concrete surface and since it is recommended that 5 percent of the anchor assemblies be visually examined.
4.
Section 4 of Reg. Guide 1.35 requires that liftoff tests be performed to monitor the prestress of selected tendons.
At Fort St. Vrain, liftoff is performed to determine if the load cell reference points have shifted on about one percent of the selected tendons at each inspection.
All selected tendons (about 6 percent) are continuously monitored for pre-stress, which exceeds the requirement of Reg. Guide 1.35 to monitor 2 percent of the tendors at each interval.
- However, changing the sample selection for each inspection would lead to a greater total percentage of tendons to be tested th' are currently monitored Section 4 of Reg. Guide 1.35 also_recuires that one tendon in each group be completely detensioned to identify broken or damaged wires.
No systematic complete detensioning of tendons is performed at Fort St. Vrain, nor is it recommended since prestress forces are monitored as described above.
In addition, the potential degradation of the prestressing system due to dismantling of the components for the purpose of inspection, is a recognized risk as stated in section 3 of the value/ impact statement for revision 3 of Reg. Guide 1.35.
Section 5.13.8 of the FSAR only requires complete detensioning and detailed exami-nation of a monitored tendon af ter a prestress alarm and af ter verification of the deterioration of the corresponding wire
'r EE-ll-0002 Rsv. 2
- 1. -
p.3 specimen with. regard to corrosion and mechanical properties.
5.
Section 5'of Reg. Guide 1.35 requires that one full length previously stressed wire be removed from one tendon in each group at each inspection for testing and examination, with 3 samples (one at each end and one at mid length) cut for tensile tests.
At Fort St. Vrain, at least 4 wire specimens are examined at each inspection but not necessarily one from each group; although this requirement is fulfilled in most cases.
The wire specimens are neither prestressed nor full length, since it was demonstrated by testing that there is no unacceptable stress corrosion.
Samples are cut for tensile testing only if corrosion is observed during the visual inspection of a wire specimen.
6.
Section 6 of Reg. Guide 1.35 deals with the method for in-specting the filler grease installed in containment tendon tubes.
At Fort St. Vrain, there is no filler grease; however, a film of corrosion protection compound is applied to the prestressing tendons.
Integrity of the film is verified on the wire specimens removed for corrosion inspection.
The corrosion protection compound is also examined, when removing the anchor assembly protective cap, for signs of degradation, change in aspect, etc. Further, tendon tube atmosphere sampling and analysis provide additional corrosion monitoring.
7.
Section 7 of Reg. Guide 1.35 addresses criteria for evalua-ting and reporting inspection results.
The effects of prestress losses and tendon failure on the behavior of the Fort St. Vrain PCRV have been thoroughly investigated as outlined in Section 5.6.3 of the FSAR.
Sdction 5.13.8 of the FSAR specifies the actions to be taken, which may involve replacement of a faulty monitored tendon.
In-service inspection of adjacent tendons is not required since overall deflections and deformations of the PCRV are measured at regular intervals and since permanent instrumentation is installed in the PCRV which can be used to monitor the overall structural integrity of the PCRV, should there be signs of abnormal degradation reflected by the load cells which continuously monitor the prestress.
Therefore, it is considered that the acceptance criteria for the PCRV should be somewhat different from those of Reg. Guide 135 which apply to structures not continuously monitored for integrity.
CONCLUSION The recommended inservice inspection program for the PCRV prestressing system generally meets or exceeds the requirements a
of Reg. Guide 1.35.
In some instances, such as wire corrosion surveillance, the requirements of Reg. Guide 1.35 are more
- S EE-ll-0002 Rev. 2 P.
4-Conclusion (cont..)
stringent than the recommended surveillance.-
However, when taking into-consideration the continuous monitoring of PCRV prestress forces, the a'ssurance of integrity for the PCRV is deemed to be as good or better than that obtained by the compliance with the requirements of Reg. Guide 1.35.
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