ML20236G758
| ML20236G758 | |
| Person / Time | |
|---|---|
| Site: | Summer  |
| Issue date: | 07/01/1998 |
| From: | SOUTH CAROLINA ELECTRIC & GAS CO. |
| To: | |
| Shared Package | |
| ML20236G745 | List: |
| References | |
| NUDOCS 9807060366 | |
| Download: ML20236G758 (12) | |
Text
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PLANT SYSTEMS SURVEILLANCE REQUIREMENTS (Continued)
(i) manually induced snubber movement; (ii) evaluation of in place snubber piston setting; or (iii) stroking the mechanical snubber 3
through its full range of travel.
d.
Visual Inspection Acceptance Criteria Visual inspections shall verify (1) that there are no visible indica-tions of damage or impaired OPERABILITY and (2) attachments to the foundation or supporting structure are functional, and (3) fasteners for the attachment of the snubbers to the component and to the snubber anchorage are functional.
Snubbers which appear inoperable as a re-sult of visual inspections shall be classified as unacceptable and
,o may be reclassified acceptable for the purpose of establishing the
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next visual inspection interval, provided that (i) the cause for being classified as unacceptable is clearly established and remedied for that particular snubber and for other snubbers irrespective of type that may be generically susceptible; and (ii) the affected snubber is
)l' functionally tested in the as found condition and detennined OPERABLE per Specifications 4.7.7.f.
When a fluid port of a -hydraulic snubber is found to be uncovered the snubber shall be declared inoperable and shall not be determined OPERABLE via functional testing unless the test is started with the piston in the as found setting, extending the piston rod in the tension mode direction. All snubbers found connected to an inoperable common hydraulic fluid reservoir shall be counted as unacceptable and may be reclassified as acceptable for detemining the next inspection interval provided that criterion (i) and (ii) above are met. A review and evaluation shall be performed 9
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and documented to justify continued operation with an unacceptable
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l-snubber.
If continued operation cannot be justified, the snubber l
shall be declared inoperable and the ACTION requirements of 3.7.7 shall be met.
e.
Functional Tests During the first refueling hutdown and at least once per 18 months thereafter Arh; WJtL., a representative sample of either:
(1) At least 10% of the total of each type of snubber in use in the plant shall be functionally tested either in place or in a bench test. For each snubber of a type that does not meet the functional test acceptance criteria of Specification 4.7.7.f, an additional 105 of that type of snubber shall be functionally tested until no l
more failures are found or until all snubbers of that type have been functionally tested, or (2) A representative sample of each type of snubber shall be functionally tested in accordance with Figure 4.7-1, "C" is the total number of snubbers of a type found not meeting the acceptance requirements of Specification 4.7.7.f.
{
The cumulative number of snubbers of a type tested is denoted by l
"N."
At the end of each day's testing, the new values of "N" and "C" (previous day's total plus current day's increments) shall be plotted on Figure 4.7-1.
If at any time the point plotted falls in l
the " Accept" region testing of that type of snubber may be teminated.
y SUP9tER - UNIT 1 3/4 7-17 Amendment No.U.103 f 9907060366 980701 i
PDR ADOCK 05000395 l
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PLANT SYSTEMS SURVEILLANCE REQUIREMENTS (Continued) g.
Functional Test Failure Analysis (Continued)
For the snubbers found inoperable, an engineering evaluation shall be performed on the components to which the inoperable snubbers are attached. The purpose of this engineering evaluation shall be to determine if the components to which the inoperable snubbers are attached were adversely affected by the inoperability of the snubbers in order' to ensure that the component remains capable of meeting the designed service.
If any snubber selected for functional testing either fails to lockup or fails to move, i.e., frozen in place, the cauce will be evaluated and if caused by manufacturer or design deficiency all snubbers of the same type subject to the same defect shall be functionally tested. This testing requirement shall be independent I
of the requirements stated in Specification 4.7..e for snubbers not meeting the functional test acceptance criteria.
7 h.
Functional Testina of Repaired and Replaced Snubbers Snubbers which fail the visual inspection or the functional test acceptance criteria shall be repaired or replaced.
Replacement snubbers and snubbers which have repairs which might affect the functional test result shall be tested to meet the functional test criteria before installation in the unit. These snubbers shall have met the acceptance criteria subsequent to their most recent service, and the functional test must have been performed within 12 months i
before being installed in the unit.
1.
Snubber Seal Replacement Procram The seal service life of hydraulic snubbers shall be monitored to ensure that the seals service life is not exceeded between surveil-lance inspections. The maximum expected service life for the various j
seals, seal materials, and applications shall be determined and
-established based on engineering information and the seals shall be replaced so that the maximum service life will not be exceeded J
during a period when the snubber is required to be OPERABLE. The i
seal replacements shall be documented and the documentation shall be retained in accordance with Specification 6.10.2.
.1 SUMMER - UNIT 1 3/4 7-19
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POWER DISTRIBUTION LIMIT BASES 3/4.2.2 and 3/4.2.3 HEAT FLUX HOT CHANNEL FACTOR and RCS FLOWRATE AND NUCLEAR ENTHALPY RISE HOT CHANNEL FACTOR f
i The limits on heat flux hot channel factor, RCS flowrate, and nuclear i
enthalpy rise hot channel factor ensure that 1) the design limits on peak local power density and minimum DNBR are not exceeded and 2) in the event of a LOCA the peak fuel clad temperature will not exceed the 2200 F ECCS acceptance criteria limit.
Each of these is measurable but will normally only be oetermined periodically as specified in Specifications 4.2.2 and 4.2.3.
This periodic surveillance is sufficient to insure that the limits are maintained provided:
a.
Control rods in a single group move together with no individual rod I
insertion differing by more than steps, indicated, from the group demand position.
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l b.
Control rod groues are sequenced with overlapping groups as described in Specification 3.1.3.5.
c.
The contrei rod insertion limits of Specifications 3.1.3.5 and 3.1.3.6 are maintained.
d.
The axial cower distribution, expressed in terms of AXIAL FLUX DIFFERENCE, is maintained within the limits.
1 F
will be maintained within its limits provided concitions a. through H
- d. above-are maintained. As noted on the RCS Total Flow Rate Versus R figure in the CORE OPERATING LIMITS REPORT (COLR),.RCS flow rate and power may be f-7 "tracec off" against one another (i.e., a low measured RCS flow rate is acceptable if core power is also low) to ensure that the calculated DNBR p
N will not be below the design DNBR value.
The relaxation of F as a function of THERMAL POWER allows changes in the radial power shape for all permissible rod insertion limits.
R, as calculated in 3.2.3 and used in the RCS Total Flow Rate Versus R figure in the CCLR. accounts for F less than or equal to the FfH II*it H
I specifigdintneCOLR. This value is used in the various accident analyses wnere F influences carameters other than DNBR, e.g., peak clad temperature
,gg and thus is the maximum "as measured" value allowed.
Margin is maintained between the safety analysis limit DNBR and the design limit DNBR. This margin is more than sufficient to offset any rod bow l
penalty and transition core penalty. The remaining margin is available for I
plant design flexibility.
When an F measurement is taken, an allowance for both experimental error g
and manufacturing tolerance must be made.
An allowance of 5% is appropriate for a full core map taken with the incore detector flux mapping system and a 3% allowance is appropriate for manufacturing tolerance.
SUMMER - UNIT 1 B 3/4 2-3 Amenoment No./3, SS l
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PLANT SYSTEMS
. SURVEILLANCE REQUIREMENTS (Continued)
(i) manually induced snubber movement; (ii) evaluation of in-place snubber piston setting; or (iii) stroking the mechanical snubber through its full range of travel.
1 d.
VisualInspection Acceptance Criteria Visual inspecuens shall verify (1) that there are no visible indications of damage or impaird OPERABILITY and (2) attachments to the foundation or supporting l
structu., are functional, and (3) fasteners for the attachment of the snubbers to the component and to the snubber anchorage are functional. Snubbers which appear inoperable as a result of visualinspections shall be classified as unacceptable and may be reclassified acceptable for the purpose of establishing the next visual inspection interval, provided that (i) the cause for being classified as unacceptable is clearly established and remedied for that particular snubber and for other snubbers irrespective of type that may be generically susceptible; and (ii) the affected snubber is functionally tested in the as found condition and l
determined OPERABLE per Specifications 4.7.7.f. When a fluid port of a hydraulic snubber is found to be uncovered the snubber shall be declared inoperable and shall not be determined OPERABLE via functional testing unless the test is started with the piston in the as found setting, extending the piston rod in the tension mode direction. All snubbers found connected to an inoperable common hydraulic fluid reservoir shall be counted as unacceptable and may be reclassified as acceptable for determining the next inspection interval provickd that criterion (i) and (ii) above are met. A review and evaluation shall be performed and documented to justify continued operation with an unacceptable snubber, if continued operation cannot be justified, the snubber shall be declared inoperable and the ACTION requirements of 3.7.7 shall be met.
e.
FunctionalTests During the first refueling shutdown and at least once per 18 months thereafter, a j
representative sample of either: (1) At least 10% of the total of each type of 8
snubber in use in the plant shall be functionally tested either in place or in a bench test. For c.-l. onubber of a type that does not meet the functional test acceptance criteria of Specification 4.7.7.f, an additional 10% of that type of snubber shall be functionally tested until no more failures are found or until all snubbers of that type ~
have been functionally tested, or (2) A representative sample of each type of snubber shall be functionally tested in accordance with Figure 4.7-1, "C" is the total number of snubbers of a type found not meeting the acceptance requirements of Specification 4.7.7.f. The cumulative number of snubbers of a type tested is denoted by "N". At the end of each day's testing, the new values of "N" and 'C" (previous day's total plus current day's increments) shall be plotted on Fgure i
4.71. If at any time the point plotted falls in the " Accept" region, testing of that I
type of snubber may be terminated.
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SUMMER - UNIT 1 3/4 7-17 Amendment No. 41,103, I
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4ep.
PLANT SYSTEMS SURVEILLANCE REQUIREMENTS (Continued)~
g.
Functional Test Failure Analvsis (Continued)
For the snubbers found inoperable, an engineering evaluation shall be performed on the components to which the inoperable snubbers are attached. The purpose of this engineering evaluation shall be to determine if the components to which the inoperable snubbers are attached were adversely affected by the inoperability of the snubbers in order to ensure that the component remains capable of meeting the designed service.
If any snubber selected for functional testing either fails to lockup or fails to move, i.e., frozen in place, the cause will be evaluated and if caused by manufacturer or design deficiency all snubbers of the same type subject to the same defect shall be functionally tested. This testing requirement shall be independent of the requirements stated in Specification 4.7.7.e for snubbers not meeting the l
functional test acceptance criteria.
h.
Functional Testino of Repaired and Replaced Snubbers Snubbers which fail the visual inspection or the functional test acceptance criteria shall be repaired or replaced. Replacement snubbers and snubbers which have repairs which might affect the functional test result shall be tested to meet the functional test criteria before installation in the unit. These snubbers shall have met the acceptance criteria subsequent to their most recent service, and the functional test must have been performed within 12 months before being installed in the unit.
i.
Snubber Seal Replacement Prooram The seal service life of hydrau'lic snubbers shall be monitored to ensure that the seals service life is not exceeded between surveillance inspections. The traximum expected service life for the various seals, seal materials, and applications shall be determined and established based on engineering information and the seals shall be replaced so that the maximum service life will not be exceeded during a period when the snubberis required to be OPERABLE.
The seal replacements shall be documented and the documentation shall be retained in accordance with Specification 6.10.2.
9 SUMMER - UNIT 1 3/4 7-19
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' POWER DISTRIBUTION LIMIT BASES 3/4.2.2 and 3/4.~2.3 HEAT FLUX HOT CHANNEL FACTOR and RCS FLOWRATE AND NUCLEAR ENTHALPY RISE HOT CHANNEL FACTOR-
)
The limits on heat flux hot channel factor, RCS fbwrate, and nuclear enthalpy rise hot channel factor ensure that 1) the design limits on peak local power density and minimum DNBR are not exceeded and 2) in the event of a LOCA the peak fuel clad temperature will not exceed the 2200*F ECCS acceptance criteria limit.
l Each of these is measurable but will normally only be determined periodically as specified in Specif.c iions 4.2.2 and 4.2.3. This periodic surveillance is sufficient to insure that the limits are maintained provided:
a.
Control rods in a single group move together with no individual rod insertion differing by more than i12 steps, indicated, from the group demand position.
l b.
Control rod groups are sequenced with overlapping groups as described in l
Specification 3.1.3.6.
c.
The control rod insertion limits of Specifications 3.1.3.5 and 3.1.3.6 are maintained.
d.
The axial power distribution, expressed in terms of AXIAL FLUX DIFFERENCE, is maintained within the limits.
)
F will be maintained within its limits provided conditions a. through d. above are maintained. As noted on the RCS Total Flow Rate Versus R figure in the CORE OPERATING Lliwii S REPORT (COLR), RCS flow rate and power may be " traded off" against one another (i.e., a low measured RCS flow rate is acceptable if core power is also low) to ensure that the calculated DNBR will not be below the design DNBR value. The relaxation of F as a function of THERMAL POWER allows changes in the radial power shape for all permissible rod insertion limits.
R, as calculated in 3.2.3 and used in the RCS Total Flow Rate Versus R figure in the N
RH COLR, accounts for F less than or equal to the F limit specified in the COLR. This AH AH l:
value is used in the various accident analyses where F influences parameters $her than
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N DNBR, e.g., peak clad temperature and thus is the maximum "as measured" value allowed.
Margin is maintained between the safety analysis limit DNBR and the design limit DNBR. This margin is more than sufficient to offset any rod bow penalty and transition core penalty. The remaining margin is available for plant design flexibility.
When a Fo _ measurement is taken, an allowance for both experimental error and
~ manufacturing tolerance must be made. An allowance of 5% is appropriate for a full core map taken with the incore detector flux mapping system and a 3% allowance is appropriate for manufacturing tolerance.
SUMMER - UNIT 1 B 3/4 2-3 Amendment No. E881 l
Document Control Desk
' Attachment ll TSP 980004 RC.-98-0126 Page 1 of 3 SAFETY EVALUATION FOR REVISING THE SNUBBER FUNCTIONAL TESTING FREQUENCY IN THE VIRGIL C. SUMMER NUCLEAR STATION TECHNICAL SPECIFICATIONS DESCRIPTION OF AMENDMENT REQUEST I
This license amendment request proposes to revise Surveillance Requirement 4.7.7.e to remove the " situational" qualifying condition of "during shutdown" from the specified test interval. This change is in conformance with recommendations and guidance presented in Generic Letter 91-04, Enclosure 1, industry experience, and the forthcoming issuance of ASME OM Code, Subsection ISTD.
An administrative change is proposed to Surveillance Requirement 4.7.7.g and to BASES 3/4.2.2 and 3/4.2.3 to correct typographical errors.
SAFETY EVALUATION Snubber installation, removal, repair, and functional testing at VCSNS is procedurally implemented and controlled. Removal for maintenance or testing is subject to engineering evaluation prior to unpinning. The evaluations consider system availability, plant configuration, and current operational mode.
The surveillance practice implemented at VCSNS usually allows only one snubber on a piping train to be removed at a time. This practice precludes significant dynamic effects on the associated piping system should an event occur while the snubber is unpinned.
This process is within general industry practice and is supported by the results of NUREGICR-6027 (EGG-2697), Preliminary Evaluation of Snubber Single Failures, April 1993. This NUREG utilized snubber history experience gained from utilities of varying reactor types to analyze the sensitivity of a system response to a single inoperable snubber resulting from an event outside the bounds of the analyses performed by the licensees to establish the licensing basis of their plants. The NUREG presented in the Conclusion section that only the PWR ice condenser main steam line penetration was judged to be potentially vulnerable to the failure of a single snubber under blowdown and/or seismic loads. Also the NUREG notes, "The piping systems assessed can withstand several times the design safe shutdown earthquake before rupture, based en recent tests of piping systems that have shown them to have significant reserve safety margin when subjected to earthquake loads.". The Conclusion ended with
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I Docum:nt Control Desk Attachment ll TSP 980004 RC.-98-0126 Page 2 of 3 the statement, "The overall risk from the potential single failure of most piping snubbers appears to be low.".
Removal of the situational requirement, "during shutdown", will allow VCSNS to accomplish TS surveillance testing on-line.
In addition, TS 4.0.2 would be applicable to the "specified surveillance interval".
VCSNS TS Surveillance Requirement 4.7.7.e denotes snubber functional testing to be performed "at least once per 18 months during shutdown".
Industry experience since this TS was developed has led to an ongoing evaluation and restructuring of the standards regulating snubber examinations and testing. The NRC has actively participated with utility groups, standards committees and manufacturers throughout the evolution of snubber surveillance development.
The issue of on-line examination and testing will be addressed by the ASME OM Code in Code for Operation and Maintenance of Nuclear Power Plants, Subsection ISTD, Preserwce and Inserwce Examination and Testing of Dynamic Restraints (Snubbers) in Light Water Reactor Power Plants.
On-line examination and testing of snubbers was ISTD Working Group Action item 961. This item was approved by the Main Committee and by the Board on Nuclear Codes and Standards. The change to allow on-line snubber testing will be published in the 1998 edition of the ASME OM Code.
Additionally, the NRC has issued interpretations and Generic Letters in regards to TS surveillance requirements which recognize industry experience and has modified surveillance requirements which presented hardships or unnecessary restrictions on utilities with no corresponding benefit to nuclear safety. This has resulted in recommendations for improving TS through allowable changes or by providing guidelines to adopt industry practices.
The NRC (USNRC - Technical Specifications Interpretations; Fermi, 5/18/88) noted that a " regular surveillance interval" is an interval " characterized by the wording 'at least once per' a specified time interval. A ' situational' surveillance requirement is characterized by the wording 'within' a specified time interval and is followed by a certain condition or situation (i.e., prior to startup, after control rod movement, after taking a sample, etc.)." As TS 4.7.7.e utilizes both a
" regular surveillance interval" ("at least once per 18 months") and a " situational"
("during shutdown") surveillance in the same sentence; it would seem prudent, based on the technical justification described herein, to delete the " situational" requirement.
' Docum:nt Control Desk Attachment ll l
TSP 980004 RC.-98-0126 Page 3 of 3 Also, Generic Letter 91-04, (CHANGES IN TECHNICAL SPECIFICATION SURVEILLANCE INTERVALS TO ACCOMMODATE A 24-MONTH FUEL CYCLE, 4/2/91) notes that "the added restriction to perform certain surveillance during shutdown may be misinterpreted". It also states "This restriction ensures that a surveillance would only be performed when it is consistent with safe plant i
operation.". Enclosure 1 recommends that licensees desiring to adopt a 24 month fuel cycle submit a TS change to define the nominal frequency for surveillance that are specified to be performed each refueling interval. The NRC additionally states that licensees may omit the qualification of "during l
shutdown". Even though this generic letter was primarily issued to address-adoption of a 24 month fuel cycle, the safety considerations discussed for adhering to surveillance activities are soplicable for any length fuel cycle and should be permitted for allowing on-line snubber surveillance testing.
In addition, the NRC has approved at least one TS change allowing on-line testing of snubbers (reference TAC #M92804, March 4,1996).
' CONCLUSION On line performance of surveillance testing has been demonstrated through industry experience and NRC evaluations (e.g., GL 91-04) to be appropriate and acceptable with proper consideration to plant safety and public risk.
In particular, NUREG/CR-6027 allows that the risk for loss of a single snubber (e.g., on-line snubber testing) is low.
Pursuant to the preceding information, the proposed TS amendment request does not create any potential degradation in the ability of the associated piping systems to perform their design functions under postulated environmental or seismic conditions.
Docum::nt Control Desk
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Attachment lll TSP 980004 RC-98-0126 Page 1 of 2 NO SIGNIFICANT HAZARDS DETERMINATION FOR REVISING THE SNUBBER FUNCTIONAL TESTING FREQUENCY IN THE VIRGIL C. SUMMER NUCLEAR STATION l
TECHNICAL SPECIFICATIONS DESCRIPTION OF AMENDMENT REQUEST This license amendment request proposes to revise Surveillance Requirement l
4.7.7.e to remove the " situational" qualifying condition of "during shutdown" from l
the specified test interval. This changs is in conformance with recommendations and guidance presented in Generic Letter 91-04, Enclosure 1, industry experience, and the forthcoming issuance of ASME OM Code, Subsection ISTD.
An administrative change is proposed to Surveillance Requirement 4.7.7.g and to BASES 3/4.2.2 and 3/4.2.3 to correct typographical errors.
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BASIS FOR NO S!GNIFICANT HAZARDS CONSIDERATION DETERMINATION SCE&G has evaluated the proposed changes to the VCSNS TS described above against the Significant Hazards Criteria of 10 CFR 50.92 and determined that the changes do not involve any significant hazard for the following reasons:
1.
The probability or consequences of an accident previously evaluated is not significantly increased.
The proposed change will not affect system operation or performance, nor do they affect any Engineered Safety Features actuation setpoints or L
accident mitigation capabilities.
NUREG/CR-6027 supports the determination that piping failure due to a snubber single failure is l
considered low. Therefore, the proposed changes will not significantly increase the consequences of an accident or malfunction of equipment j
important to safety previously evaluated in the FSAR.
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Docum nt Control Desk 11 TSP 980004 RC-98-0126 Page 2 of 2 2.
The possibility of an accident or a malfunction of a different type than any previously evaluated is not created.
The changes to the situational testing requirements will not affect the method of operation of any system to which a snubber is attached. The proposed changes only address the plant mode at which a surveillaree activity may be performed.
No new or different accident scenar os, transient precursors, failure mechanisms, or limiting single failures will be introduced as a result of these changes. Therefore, the possibility of a new or different kind of accident other than those already evaluated will not be created by this change.
3.
The margin of safety has not been significantly reduced.
This proposed change will not have an impact on the overall reliability of the snubber population. This is due, in part, to the fact that the snubber J
test plans are self correcting. As functional test failures are identified, additional snubbers are required to be tested. Thus, the reliability of the I
snubber population is maintained. The proposed change does not alter the intent or method by which the surveillance are conducted, does not involve any physical changes to the plant, does not alter the way any structure, system, or component functions, and does not modify the manner in which the plant is operated. Therefore the proposed change will not degrade the ability of the snubbers to perform their safety function or significantly decrease the margin of safety.
Based on the above discussions, it has been determined that the requested l
technical specification changes do not involve a significant increase in the probability or consequences of an accident or other adverse condition over previous evaluations; nor create the possibility of a new or different kind of accident or condition over previous evaluations; nor involve a significant reduction in a margin of safety. Therefore, pursuant to 10 CFR 50.91, the preceding analysis provides a determination that the proposed TS amendment request poses no significant hazard as delineated by 10 CFR 50.92.
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7 Docum:nt Control Desk Attachment IV TSP 980004 RC.-98-0126 Page 1of 1 ENVIRONMENTAL IMPACT DETERMINATION FOR REVISING THE SNUBBER FUNCTIONAL TESTING FREQUENCY IN THE VIRGIL C. SUMMER NUCLEAR STATION TECHNICAL SPECIFICATIONS This amendment request meets the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9) as specified below:
1.
The amendment involves no significant hazards determination.
As demonstrated in Attachment IV, the proposed change does not involve any significant hazards consideration.
2.
There is no significant change in the types or significant increase in the amounts of any effluents that may be released offsite.
The proposed changes 'do not involve a change to the facility or operating I
procedures which would create new types of effluents. The change to allow on-line snubber testing will not affect system performance or operation. This change will not compromise the recognized effluents.
l The limits of 10 CFR 100 and 10 CFR 50 Appendix A, GDC 19 are not impacted.
3.
There is no significant increase in individual or cumulative occupation radiation exposure.
l The proposed change will not create a significant increase in radiation i
exposure due to the required surveillance activity, rather, performing on-line surveillance on accessible systems should result in lower exposures l
than if the surveillance were to be deferred until shutdown when certain systems generate more radioactivity and result in potentially more radiation exposuro risk to plant personnel.
Based on the above, it is concluded that there will be no impact on the environment resulting from the proposed changes and that the proposed i
changes meet the criteria specified in 10 CFR 51.22 for a categorical exclusion from the requirements of 10 CFR 51.21 relative to requiring a specific environmental assessment by the Commission.