ML17158B837
| ML17158B837 | |
| Person / Time | |
|---|---|
| Site: | Susquehanna  |
| Issue date: | 10/11/1996 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML17158B835 | List: |
| References | |
| NUDOCS 9610280130 | |
| Download: ML17158B837 (14) | |
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0O UNITED STATES NUCLEAR REGULATORY COMMISSION RELATED TO RELIEF RE U STS NOS.
RRPT-2 AND RRPT-5 I
g WASHINGTON, D.C. 2055&0001 Cy qO
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SA ETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION PENNSYLVANIA POWER 8E LIGHT COMPANY SUS U HANNA STEAM ELECTRIC STATION UNITS 1
AND 2 DOCKET NOS.
50-387 AND 50-388 T,O JNTNOOOOTIIIN The technical specifications for Susquehanna Steam Electric Station, Units 1
'nd 2, state that the inservice inspection of the American Society of Mechanical Engineers (ASHE) Code Class 1, 2, and 3 components shall be performed in accordance with Section XI of the ASME Boiler and Pressure Vessel Code and applicable Addenda as required by 10 CFR 50.55a(g),
except where specific written relief has been granted by the Commission pursuant to 10 CFR 50.55a(g)(6)(i).
As stated in 10 CFR 50.55a(a)(3),
alternatives to the requirements of paragraph (g) may be used, when authorized by the NRC, if (i) the proposed alternatives would provide an acceptable level of quality and safety or (ii) compliance with the specified requirements would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety.
Pursuant to 10 CFR 50.55a(g)(4),
ASME Code Class 1, 2, and 3 components (including supports) shall meet the requirements, except the design and access provisions and the preservice examination requirements, set forth in the ASME
- Code,Section XI, "Rules for Inservice Inspection of Nuclear Power Plant Components,"
to the extent practical within the limitations of design,
- geometry, and materials of construction of the components.
The regulations require that inservice examination of components and system pressure tests conducted during the first 10-year interval and subsequent intervals comply with the requirements in the latest edition and addenda of Section XI of the ASME Code incorporated by reference in 10 CFR 50.55a(b) twelve months prior to the start of the 120-month interval, subject to the limitations and modifications listed therein.
The applicable edition of Section XI of the ASME Code for Susquehanna, Units 1 and 2,, second 10-year inservice inspection (ISI) interval is the 1989 Edition.
Pursuant to 10 CFR 50.55a(g)(5), if the licensee determines that conformance with an examination requirement of Section XI of the ASME Code is not practical for its facility, information shall be submitted to the Commission in support of that determination and a request made for relief from the ASME Code requirement.
After evaluation of the determination, pursuant to 10 CFR 50.55a(g)(6)(i),
the Commission may grant relief and may impose alternative requirements that are determined to be authorized by law, will not endanger life, property, or the common defense and security, and are otherwise in the public interest, giving due consideration to the burden upon the licensee that could result if the requirements were imposed.
9hi0280i30 9hiOii PDR ADQCK 05000387 P
PDR ENCLOSURE
In a letter dated August.28,
- 1996, Pennsylvania Power 5 Light Company submitted to the NRC Requests for Relief Nos.
RRPT-2 and RRPT-5 for Susquehanna, Units 1 and 2.
Additional information was provided by the licensee in its letter dated October 10, 1996.
2.0 V LUATION AND CONCLUS ONS The staff, with technical assistance from its contractor, the Idaho National Engineering Laboratory (INEL), has evaluated the information provided by the licensee in support of Requests for Relief Nos.
RRPT-2 and RRPT-5 for Susquehanna, Units 1
and 2.
Based on the information submitted, the staff adopts the contractor's conclusions and recommendations presented in the Technical Letter Report attached.
The staff concluded for Relief Request RRPT-2, that compliance with the Code requirements to remove Control Rod Drive (CRD) bolting during'ach startup, when leakage is detected would result in a hardship or unusual difficulty without a compensating increase in the level of quality and safety.
The licensee's proposed alternative:
- 1) to visually examine all the accessible bolting in place for corrosion;
- 2) to follow GE SIL 483, Rev 2, as a minimum; and 3) perform a VT-1 visual examination whenever any CRD is disassembled per paragraph IWB-2500 provides reasonable assurance of operational readiness and safety of the CRD bolting.
Therefore, the licensee's proposed alternative contained in RRPT-2 is authorized pursuant to 10 CFR 50.55a(a)(3)(ii) as requested.
For Relief Request RRPT-5, the staff finds acceptable the licensee's proposed alternative, to implement the alternative to Code requirements contained in Code Case N-498-1, Alternative Rules, for 10-Year System Hydrostatic Testing for Class 1, 2, and 3 Systems.
The staff therefore, concludes that:
1) compliance with the Code requirements would result in a hardship or unusual difficulty without a compensating increase in the level of quality and safety; and 2) the use of Code Case N-498-1 provides reasonable assurance of operational readiness and safety of the plant systems.
The licensee's proposed alternative is authorized pursuant to 10 CFR 50.55a(a)(3)(ii) as requested.
The use of Code Case N-498-1 is authorized for the second 10-year ISI interval or until the Code Case is approved for general use by reference in Regulatory Guide
- 1. 147.
After that time, the licensee must follow the conditions, if any, specified in the regulatory guide.
Attachment:
Technical Letter Report Principal Contributor:
T. McLellan Date:
October 11, 1996
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EC IC L
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E SECOND
- E I SER ICE INSPEC ION INTERVAL E UES S
0 ELIEF RRPT-2 ND RRPT-5
~0 SUS UEK NNA S EA L C RIC STATION UNI S 1
AND 2 PE NS NI POWER LIG CONPANY DOC ET NO. 50-387 AND 50-388 1.0 (RTROORRTIOR By letter dated August 28,
- 1996, Pennsylvania Power
- 5. Light Company (PPBL) submitted Relief Requests RRPT-2 and RRPT-5 for the Susquehanna Steam Electric
- Station, Units 1
and 2.
By letter dated October 10,
- 1996, the licensee submitted a revision to Relief Request RRPT-2.
The Idaho National Engineering Laboratory (INEL) staff has evaluated the subject requests for relief in the following section.
- 2. 0 EVALUATION The Code of record for the Susquehanna, Units 1 and 2, second 10-year inservice inspection (ISI) intervals, which began June 1,
1994, is the 1989 Edition of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code,Section XI.
The information provided by the licensee in support of the requests for relief from Code requirements has been evaluated and the bases for disposition are documented below.
- 2. 1 Relief Request RRPT-2, IWA-5250(a)(2), Corrective Action Resulting from Leakage at Control Rod Drive (CRD) Bolted Connections
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d<<d during a system pressure test be located and evaluated by the Owner for'orrective action.
When the leakage is at a bolted connection, the bolting shall be removed, VT-3 visually examined for corrosion, and evaluated in accordance with IWA-3100.
Licensee's Code Relief Re uest:
The licensee requested relief from the ASHE Section XI requirements for removal and VT-3 visual examination of control rod drive bolting when leakage is detected at these bolted connections.
Licensee's Basis or Re uestin Relief (as stated):
"Leakage from the control-rod-drive-to-housing bolted connection during the system pressure test generally decreases and stops with vessel heatup at operating pressure.
Evaluation of this leakage is done in accordance with the guidelines of the General Electric Co. Control Rod Drive System Operation and Maintenance Instructions GEK-73594 (for Unit 1) and GEK-83270 (for Unit 2).
Should signiFicant leakage from this bolted connection persist, it would be detected by the leakage collection system (drywell sump) serving this equipment, be investigated, and be corrected.
For those cases that do not require 0-ring replacement based on the above evaluation, relief from removal of CRD bolts is requested as explained below.
ATTACHMENT
"Removal of all bolting from a leaking control-rod-drive-to-housing bolted connection beneath a reactor vessel loaded with fuel could cause significant equipment
- damage, as described below.
Disturbing of the seal at the bolted connection could necessitate lowering of the drive for replacement of the special 0-ring seals on the flange.
Lowering of the drive requires it to be uncoupled from its control rod.
With the reactor head on (following completion of the ASHE Class 1 System Leakage or Hydrostatic Test),
the possibility exists that the drive might not recouple to its control rod; and the reactor might then have to be disassembled again to accomplish recoupling.
When attempting to reinsert and recouple the drive to its control rod, three types of damage to the mechanism could occur:
1)
The uncoupling rod in the top of the CRD can become bent; 2)
One or more spud fingers in the top of the CRD can become bent; and 3)
The lock plug in the bottom of the control rod can become bent.
"At the least, significant leakage of contaminated reactor coolant would be created by the act of removing the bolting, lowering the drive, and replacing the special 0-ring seals on the flange.
This operation would challenge the reactor internal control-rod-to-housing metal-to-metal water seal, which has the potential to become a significant leak for draining the reactor vessel if proper seating does not (automatically) occur.
Also, this additional control rod drive 0-ring replacement operation beneath the reactor vessel contradicts the need to keep personnel radiation exposure As Low As Reasonably Achievable.
"Removal, VT-3 visual examination, and reinstallation of all 8 bolts in any CRD flange exhibiting leakage or seepage would result in a minimum expenditure of 0.6 person rem per CRD under the optimum condition of restraining the CRD in position if lowering of the drive were not necessary.
The hardship of this personnel radiation exposure is without any compensating increase in nuclear safety because the CRD flange bolted connection is designed with considerable safety margin.
(Total capacity of all 8 bolts is established by Susquehanna FSAR paragraph 4.6.2. 1.2.2.3 as 118,400 pounds; compared with total load of 45,000
- pounds, at the 1,250 psi. reactor design pressure.
Accordingly, the capacity of 5 of the 8 bolts is in excess of the load requirements for the connection, when at design pressure.)
"This CRD flange bolting must receive VT-1 visual examination whenever any CRO is disassembled, per paragraph IWB-2500 and the recommendations ot Gt SIL 483,
'CRD Cap Screw Crack indications.'atisfaction of this periodic inspection requirement ensures periodic monitoring of this bolting for evidence of corrosion; and replacement, whenever warranted, as CRD's are regularly changed out during refueling outages.
These CRD changeouts are done at the rate of approximately 20 (of the total 185)
CRD's per outage.
Thus, approximately 160 CRD flange bolts have been VT-1 visually examined in each of the past outages.
In this way the proposed alternative provides an acceptable level of quality and safety."
ice see's ro osed Alternative Ex minatio (as stated):
"If leakage occurs at a control-rod-drive-to-housing bolted connection, the bolting shall be examined in place under tension.
All accessible surfaces of the bolting shall be VT-3 visually examined for corrosion, and evaluated in accordance with IWA-3100.
"The recommendations of GE SIL 483 Rev.
2 will be followed as a minimum.
A VT-I visual examination will continue to be done whenever any CRD is disassembled per paragraph IWB-2500."
~vu~ory:
The 1989 Edition of the Code requires that the source of leakage detected during the conduct of a system pressure test be located and evaluated for corrective measures.
When leakage occurs at a bolted connection, all bolting shall be removed, VT-3 visually examined for corrosion, and evaluated in accordance with IWA-3100. It has been documented'hat an inherent characteristic of General Electric CRD housing designs is that bolted CRD flanged connections leak slightly during startup, prior to full operating pressure.
Leakage typically does not occur during operation.
The licensee is requesting relief from the requirement to remove the bolting at leaking CRD housing connections when leakage occurs.
Requiring the licensee to remove bolting in a CRD assembly when leakage occurs could result in CRD equipment damage.
Considering that the licensee is removing CRDs during each refueling outage for exchange or maintenance and performing a VT-I visual examination of the bolting when removed, it can be concluded that general degradation, if occurring, would be detected.
As a result, the INEL staff believes that requiring the licensee to remove bolting when leakage is detected during each startup pressure test would result in a considerable burden.
The commitments included in the licensee's proposed alternative; to perform a
VT-3 visual examination and evaluation of CRD bolting in place when leakage occurs; perform periodic VT-I visual examinations as CRDs are normally disassembled for maintenance or exchange; and to follow the recommendations of GE SIL 483, Rev.
2, will provide reasonable assurance of the CRD bolting integrity.
Requiring the licensee to remove all bolts at a
CRD joint when leakage is detected will result in a burden without a compensating increase in the level of quality and safety.
Therefore, it is recommended that the proposed alternative be authorized pursuant to 10 CFR 50.55a(a)(3)(ii).
CRD Operation and Haintenance Guidelines by N. J. Biglieri, General Electric Co., Nuclear Energy Division, San Jose, CA. 8/30/70.
2.2 Relief Request RRPT-5, 10-Year Hydrostatic Test Requirements for Code Class 1, 2, and 3 Systems C~
Th qi
- t. f yt hyd tti t tig contained in Table IWB-2500-1, Category B-P, Items B15.11, B15.51, B15.61, and B15.71 (for Class 1 systems);
Table IWC-2500-1, Category C-H, Items C7.20, C7.40, C7.60, and C7.80 (for Class 2);
and Table IWD-2500-1, Categories D-A, D-B, and D-C, Items Dl. 10, D2. 10, and D3. 10 (for Class 3).
The Code requires system hydrostatic testing once per 10-year interval at or near the end of the interval.
Lice see's Code Relief Re uest:
The licensee requested relief from ASHE Section XI hydrostatic test requirements for Code Class 1, 2, and 3 systems.
Licensee's 8 s'or Re uestin Relief (as stated):
"ASHE Code Case N-498-1, which is identical to the Alternate Provisions
- below, has been issued by the ASHE to provide an alternative rule to the 10-year System Hydrostatic Tests required by the 1989 Edition of Section XI.
Licensee's Pro osed Alternative Examination (as stated):
"(a) As an alternative to the 10-year system hydrostatic test required by Table IWB-2500-1, Category B-P, the following rules shall be used:
(1)
A system leakage test (IWB-5221) shall be conducted at or near the end of each inspection interval, prior to reactor startup.
(2)
The boundary subject to test pressurization during the system leakage test shall extend to all Class 1 pressure retaining components within the system boundary.
(3)
Prior to performing the VT-2 visual examination, the system shall be pressurized to nominal operating pressure for at least 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> for insulated systems and 10 minutes for noninsulated system.
The system shall be maintained at nominal operating pressure during performance of the VT-2 visual examination.
(4)
Test temperatures and pressures shall not exceed limiting conditions for the hydrostatic test curve as contained in the plant Technical Specifications.
(5)
The VT-2 visual examination shall include all components within the boundary identified in (a)(2) above.
(6)
Test instrumentation requirements of IWA-5260 are not applicable.
(b)
As an alternative to the 10-year system hydrostatic test required by Table IWC-2500-1, Category C-H, the following rules shall be used:
A system pressure test shall be conducted at or near the end of each inspection interval or during the same inspection period of each inspection interval of Inspection Program B.
(2)
(4)
(5)
The boundary subject to test pressurization during the system pressure test shall extend to all Class 2 components included in those portions of systems required to operate or support the safety system function up to and including the first normally closed valve, including a safety or relief valve, or valve capable of automatic closure when the safety function is required.
Prior to performing the VT-2 visual examination, the system shall be pressurized to nominal operating pressure for a minimum of 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> for insulated systems and 10 minutes for noninsulated systems.
The system shall be maintained at nominal operating pressure during performance of the VT-2 visual examination.
The VT-2 visual examination shall include all components within the boundary identified in (b)(2) above.
Test instrumentation requirements of IWA-5260 are not applicable.
(c)
As an alternative to the 10-year system hydrostatic test required by Table IWD-2500-1, Categories D-A, D-B, or D-C, as applicable, the following rules shall be used:
A system pressure test shall be conducted at or near the end of each inspection interval or during the same inspection period of each inspection interval of Inspection Program B.
(2)
The boundary subject to test pressurization during the system leakage test shall extend to all Class 2 components included in those portions of systems required to operate or support the safety system function up to and including the first normally closed valve, including a safety or relief valve, or valve capable of automatic closure when the safety function is required.
Prior to performing the VT-2 visual examination, the system shall be pressurized to nominal operating pressure for a minimum of 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> for insulated systems and 10 minutes for noninsulated systems.
The system shall be maintained at nominal operating pressure during performance of the VT-2 visual examination.
(4)
The VT-2 visual examination shall include all components within the boundary identified in (c)(2) above.
(5)
Test instrumentation requirements of IWA-5260 are not applicable."
valu t'o The Code requires a system hydrostatic test to be performed once per interval in accordance with IWA-5000 for Class 1, 2, and 3 pressure-retaining systems.
In lieu of the Code requirements, the licensee proposes to implement the alternatives to Code requirements contained in Code Case N-498-1, Alternative Rules for 10-Year System Hydrostatic Testing for Class I, 2,
and 3 Systems, dated May 11, 1994..
The system hydrostatic test stipulated in Section XI is not a test of the structural integrity of the system but rather an enhanced leakage test.
Hydrostatic testing only subjects the piping components to a small increase in pressure over the design pressure; therefore, piping dead weight, thermal expansion, and seismic loads present far greater challenges to the structural integrity of the system.
Consequently, the Section XI hydrostatic pressure test is primarily regarded as a means to enhance leak detection during the examination of components under pressure, rather than as a method to determine the structural integrity of the components.
In addition, the industry experience indicates that leaks are not being discovered as a result of hydrostatic test pressures causing a preexisting flaw to propagate through the wall - in most cases leaks are being found when the system is at normal operating pressure.
In lieu of 10-year hydrostatic pressure testing at or near the end of the 10-year interval, Code Case N-498-1 requires a VT-2 visual examination at nominal operating pressure and temperature in conjunction with a system leakage test performed in accordance with paragraph IWA-5000 of Section XI.
The requirements of Code Case N-498-1 for Class 1 and 2 systems are the same as those of Code Case N-498, Alternative Rules for 10-Year System Hydrostatic Testing for Class 1 and 2 Systems, which was previously approved for general use on Class 1 and 2 systems in Regulatory Guide 1. 147, Rev. 9.
For Class 3
- systems, N-498-1 specifies requirements identical to those for Class 2
components.
Class 3 systems do not normally receive the amount and/or type of nondestructive examinations that Class 1 and 2 systems receive.
While Class 1
and 2 system failures are relatively uncommon, Class 3 leaks occur more frequently and are caused by different failure mechanisms.
Based o~
a review of Class 3 system failures requiring repair during the last 5 years, the most common causes of failures are erosion-corrosion (EC), microbiologically-induced c~rrosion (MIC), and general corrosion.
In general, licensees have Documented in Licensee Event Reports and the Nuclear Plant Reliability Data System databases.
implemented programs for the prevention, detection, and evaluation of EC and MIC; therefore, Class 3 systems receive inspections commensurate with their functions and expected failure mechanisms.
System hydrostatic testing entails considerable time, radiation dose, and dollar resources.
The safety assurance provided by the enhanced leakage detection gained from a slight increase in system pressure during a
hydrostatic test may be offset or negated by the necessity to gag or remove Code safety and/or relief valves (placing the system, and thus the plant, in an off-normal state),
erect temporary supports in steam lines, and expend resources to set up testing with special equipment and gages.
Therefore, performance of system hydrostatic testing represents a considerable burden.
Giving consideration to the minimal amount of increased assurance provided by the increased pressure associated with a hydrostatic test versus the pressure for the system leakage test, and the hardship associated with performing the hydrostatic test, the INEL staff finds that compliance with the Section XI hydrostatic testing requirements results in hardship and/or unusual difficulty without a compensating increase in the level of quality and safety.
Compliance with the Code's hydrostatic testing requirements results in hardship and/or unusual difficulty without a compensating increase in the level of quality and safety.
Performing the hydrostatic pressure test in accordance with the alternative to hydrostatic test requirements contained in Code Case N-498-1 will provide reasonable assurance of operational readiness.
Therefore, it is recommended that the licensee's proposed alternative, to implement the pressure test rules contained in Code Case N-498-1 for Code Class 1, 2, and 3, be authorized for Susquehanna, Units 1 and 2, pursuant to 10 CFR 50.55a(a)(3)(ii).
This alternative should be authorized for the current interval or until such time as the Code Case is published in a future revision of Regulatory Guide 1. 147.
At that time, if the licensee intends to continue to implement this code case, the licensee is to follow all provisions in Code Case N-498-1, with limitations issued in Regulatory Guide 1. 147, if any.
- 3. 0 CONCLUSION The INEL staff has evaluated Relief Requests RRPT-2 and RRPT-5.
For Relief Request RRPT-2, it has been determined that the removal of CRD bolting when leakage is detected will result in a burden without a compensating increase in the level of quality and safety.
Therefore, it is recommended that the licensee's proposed alternative; to perform a VT-3 visual examination and evaluation of CRD bolting in place when leakage occurs; perform periodic VT-1 visual examination when CRDs are disassembled for maintenance or exchange; and to follow the recommendations of GE SIL 483 Rev.
2, be authorized pursuant to 10 CFR 50.55a(a)(3)(ii).
For Relief Request RRPT-5, it is concluded that the Code required 10-year hydrostatic test results in a burden without a compensating increase in quality and safety.
The licensee's alternative, to implement the alternative to Code requirements contained in Code Case N-498-1,
Alternative Rules for 10-Year System Hydrostatic Testing for Class 1, 2, and 3
- Systems, provides reasonable assurance of operational readiness.
Therefore, it is recommended that the licensee's proposed alternative to the Code requirement be authorized pursuant to 10 CFR 50.55a(a)(3)(ii).
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