ML20045B964
| ML20045B964 | |
| Person / Time | |
|---|---|
| Site: | Zion File:ZionSolutions icon.png |
| Issue date: | 06/14/1993 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20045B724 | List: |
| References | |
| GL-89-04, GL-89-4, NUDOCS 9306210326 | |
| Download: ML20045B964 (34) | |
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NUCLEAR REGULATORY COMMISSION ENCLOSURE 1 e
W ASHINGTON, D.C. 205WOOO1
- ' j SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO THE INSERVICE TESTING PROGRAM RE00ESTS FOR RELIEF COMMONWEALTH EDISON COMPANY ZION NUCLEAR POWER STATION. UNITS 1 AND 2 DOCKET NOS. 50-295 AND 50-304
1.0 INTRODUCTION
The Code of Federal Regulations,10 CFR 50.55a, requires that inservice testing (IST) of certain American Society of Mechanical Engineers (ASME)
Boiler and Pressure Vessel Code (Code) Class 1, 2, and 3 pumps and valves be performed in accordance with Section XI of the ASME Code and applicable addenda, except where relief has been granted or proposed alternatives have been authorized by the Commission pursuant to 50.55a $$(f)(6)(i), (a)(3)(i),
or (a)(3)(ii).
To obtain authorization or relief, the licensee must demonstrate that:
(1) conformance is impractical for its facility; (2) the proposed alternative provides an acceptable level of quality and safety; or (3) compliance would result in a hardship or unusual difficulty without a compensating increase in the level of quality and safety.
Section 50.55a 5(f)(4)(iv) provides that inservice tests of pumps and valves may meet the requirements set forth in subsequent editions and addenda that are incorporated by reference in 5(b) of s50.55a, subject to the limi htions and modifications listed, and subject to Commission approval.
NRC guidance contained in Generic Letter (GL) 89-04, Guidance on Developing Acceptable l
Inservice Testing Programs, provided alternatives to the Code requirements determined to be acceptable to the staff and authorized the use of the j
alternatives in Positions 1, 2, 6, 7, 9, and 10 provided the licensee follow i
the guidance delineated in the applicable position.
When an alternative is proposed which is in accordance with GL 89-04 guidance and is documented in the IST program, no further evaluation is required; however, implementation of the alternative is subject to NRC inspection.
Section 50.55a authorizes the Commission to grant relief from ASME Code requirements or to approve proposed alternatives upon making the necessary findings. The NRC staff's findings with respect to granting or not granting the relief requested or authorizing the proposed alternative as part of the licensee's IST program are contained in this Safety Evaluation (SE).
The staff approved the use of OM-6, Inservice Testing of Pumps in Light-Water i
fluclear Power Plants, and OM-lo, inservice Testing of Valves in Light-Water
//uclear Power Plants, which were incorporated into $50.55a, j(b), through the 1989 Edition of Section XI, by rulemaking effective September 8, 1992.
OM-10 9306210326 930614 PDR ADDCK 05000295 p
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s was approved with modifications related to containment isolation valve leakage testing.
This SE concerns relief requests and supporting information that were submitted in Commonwealth Edison Company's (CECO, the licensee) letter dated January 7, 1993, for the Zion Station, Units 1 and 2, IST Program. The new or revised relief requests which were included in the-submittal are evaluated bel ow.
The Zion Station, Unit 1 and 2, IST Program was developed to the requirements of ASME Section XI, Subsections IWP and IWV, 1980 Edition up to and including the Winter 1981 Addenda.
The IST Plan for Class 1, 2, and 3 Pumps and Valves are applicable for a 120-month interval beginning December 31, 1983, for Unit I and September 19, 1984, for Unit 2 (ending December 31, 1993, for Unit I and September 19, 1994, for Unit 2).
The commercial service date for Zion Station, Unit 1, is December 31, 1973, and September 19, 1974, for Zion Station, Unit 2.
2.0 PUMP RELIEF RE0 VESTS i
The licensee's letter dated January 7,1993, forwarded Revision 11/92 to the IST Plan for Class 1, 2, and 3 Pumps and Valves for Zion Station, Units 1 and 2.
This revision contained two revised pump relief requests, PR-03 and PR-09, and one new pump relief request, PR-ll.
Each of these is evaluated separately below in accordance with the requirements of Section XI of the ASME Code.
It also contained one new pump Technical Approach and Position, PP-08, discussed t
in Section 3 below, and two revised valve relief requests, VR-01 and VR-33, discussed in Section 4 below.
5 2.1 Relief Reauest PR-03 (Anomaly Items 3 and 4)
The licensee requested relief from the requirements of ASME Section XI, Subarticles lWP-3100, IWP-3200, and IWP-4510 and in reference to Table IWP-3100-2, " Allowable Ranges of Test Quantities," that pump vibration be measured in and compared to values expressed in mils displacement.
This relief request applies to the following pumps in the IST Program:
Component Cooling Water (CC), Containment Spray (CS), Auxiliary Feedwater (FW), Residual-Heat Removal (RH), Safety Injection (SI), Service Water (SW) and Charging (VC).
2.1.1 Licensee's Basis for Relief The licensee stated:
The measurement of pump vibration is required so that developing problems can be detected and repairs initiated prior to a pump becoming inoperable.
Measurement of vibration only in displacement quantities, as required by the ASME Code Section XI, does not take into account frequency, which is also an important factor in determining the severity i
i
" of the vibration. Measurements of vibration in mils displacement are not sensitive to small changes that are indicative of developing mechanical problems.
The ASME Code Section XI 1980 Edition, Winter 1981 Addenda minimum
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standards require measurement of the vibration amplitude in mils (displacement).
Zion Station proposes an alternate prrgram of measuring vibration velocity which is more comprehensive.
This technique is an industry-accepted method which is much more meaningful and sensitive to small changes that are indicative of developing mechanical problems.
These velocity measurements detect not only high amplitude vibration, that ir.dicates a major mechanical problem such as misalignment or unbalance, but also the equally harmful low amplitude,. high frequency vibration due to bearing wear that usually goes undetected by simple displacement measurements.
2.1.2 Alternative Testina The licensee stated that:
The allowable ranges of vibration and their associated action levels will be patterned after the guidelines established in ANSI /ASME OMa-1988, Part 6, Table 3a.
These ranges will be used in whole to assess equipment operational readiness.
The acceptable range for the centrifugal and vertical line shaft pumps with speeds >600 rpm (except those for which specific relief has been requested and granted) will be as follows:
Acceptable Ranae Alert Ranoe Reauired Action
<2.5 V,
>2. 5 V, to 6 V,
>6 V, or or
>0.325 in/sec
>0.70 in/sec This relief request does not include any pumps with speeds <600 rpm or reciprocating pumps.
If deviations fall within the established alert range, the frequency of testing shall be doubled until the cause of the deviation is determined and the condition corrected.
If deviations fall within the required action range, the pump shall be declared inoperable until the cause of the deviation has been determined and the condition corrected. When a 1
test shows deviations outside the acceptable range, the instruments involved may be recalibrated and the test rerun.
Vibration measurements for all pumps will be obtained and recorded in velocity, and will be broadband unfiltered (filtered-out (hand held i
analog vibration meter) or total (spectrum analyzer)] measurements.
The
' reference points for vibration analysis will be clearly identified cn the pump to permit subsequent duplication in both location and plane.
The centrifugal pumps in the program will have vibration measureents taken in a plane approximately perpendicular to the rotating shaft in two orthogonal directions e, each accessible pump bearing housing and in the axial direction on each accessible pump thrust bearing housing.
Measurements of vibration in mils displacement are not sensitive to small changes that are indicative of developing mechanical problems.
Therefore, the proposed alternate method of measuring vibration velocity in inches /second and using the allowable vibration ranges and limits established in Oma-1988 Part 6 provides added assurance of quality, safety, reliability and continued operability of the pumps.
2.1.3 Evaluation i
for pumps that operate above 600 rpm, measurement of pump vibration in units of velocity rather than in units of displacement provides a better indication of anti-friction bearing wear and other types of pump degradation; hence, this method can result in more timely repairs.
Pump bearing degradation results in increased vibration at frequencies 5 to i
100 times the rotational speed of the pump.
These high frequency bearing vibrations may not produce a significant increase in pump vibration displacement measurements and could go undetected.
However, the high frequency vibration would result in relatively large changes in pump vibration velocity measurements, which could permit corrective action prior to j
catastrophic bearing failure.
Because of the high frequencies of vibrations associated with the pump bearings, vibration velocity measurements are generally much better than vibration displacement measurements in monitoring mechanical condition of pumps and detecting pump bearing degradation.
Advantages of measuring vibration velocity in lieu of displacement for monitoring mechanical condition of pumps, with the exception of low-speed pumps, are widely acknowledged in the industry. Many nuclear licensees measure pump vibration velocity to detect pump degradation and provide advanced. warning of incipient pump bearing failure. Given this advanced warning, the licensee can plan and prepare for maintenance during scheduled outages instead of suffering losses resulting from unplanned outages to repair failed critical equipment.
Because of the increased sensitivity to pump i
degradation,.this test method is superior to earlier Section XI testing methods for pumps that operate at speeds above 600 rpm.
The NRC has approved ANSI /ASME'0M-6, Inservice Testing of Pumps in rulemaking effective September 8, 1992.
OM-6 allows for the use of either pump displacement or pump velocity vibration measurements and provides acceptance criteria for both types of vibration measurements.
When using OM-6'for inservice testing program vibration monitoring, all of the vibration-related requirements must be incorporated into the program.
Licensees may update
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, their programs in accordance with this position without further relief, provided all related requirements of OM-6, Paragraphs 4.6.1, 4.6.4, and 6.1, for vibration monitoring are met.
2.1.4 Conclusion Relief is no longer required for use of this portion of OM-6, pursuant to.
550.55a 1(f)(4)(iv), provided the licensee implement all related requirements.
Whether all related requirements are met is subject to NRC inspection.
2.2 Relief Reouest PR-09 (Anomalv Item 8)
The licensee requests relief from the requirement of IWP-4120 that the full range of each instrument be three times the reference value or less for the flow instruments associated with RHR pumps 1(2)RH001 and 1(2)RH002.
2.2.1 Licensee's Basis for Relief The licensee stated that:
Flow instruments 1(2)fl0 610 / 610A and 1(2)FIC 611 / 611A are diffe rential pressure instruments connected to elbow tap flow elements in the discharge piping of the 1(2) A and B RHR pumps respectively.
The instruments are installed such that there are twc instruments associated with each pump.
For instance, IFIC 610 and IFIC 610A are connected to the elbow tap flow elements in the discharge piping of the 1A RHR pump.
Each of these pairs of instruments are scaled for a low range (0-1500 gpm) and a high range (0-5000 gpm).
Neither of these instruments meets the range requirements stated above when the pumps are tested in the miniflow condition.
These instruments are the only installed flow measuring instruments which are physically within the boundaries of the miniflow recirculation flowpath.
The flow element which supplies the flow induced differential pressure is a 10 inch elbow tap in the discharge piping of the pump (s).
This 10 inch flow element produces a very low (0.8 to 1.42 inches water) differential pressure for the miniflow condition of 300 to 400 gpm.
Based on a hypothetical reference value of 310 gpm, a differential pressure instrument attached to the 10 inch elbow would have to read j
within a band of- 0.82 to 0.89 inches of water d/p in order to indicate flow within i 2% of the reference value. This is an unrealistically
'l tight band of tolerance for an elbow tap instrument.
Miniflow flow rate for the RHR pumps is non-adjustable with the Unit at power.
The 3 inch miniflow control valves MOV-RH610/611, for the A and
' i B pumps respectively, are either open or closed and have no provision 1
for throttling.
The recirculation line is not orificed and as a result the 3 inch line resistance is relied on to regulate flow.
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- Past IST data for 1989 through 1991 was reviewed showing a range of recorded flows as follows
PUMP FLOW SPREAD 1A 375 to 425 gpm IB 350 to 400 gpm 2A 310 to 375 gpm 2B 300 to 400 gpm A 10-inch gate valve on the discharge line of the pump was considered and rejected as a means of throttling miniflow.
The 10-inch gate valve, operated via reach rod, has insufficient throttle control at low flow rates. Attempted throttling was considered to be a hazard to the pump due to minimum flow considerations.
The RWST recirculation line through SI-8735 valve was considered as a means of increasing (and throttling) flow. This flow path was rejected due to single failure concerns.
Per NRC GL 89-04, Attachment 1, Position 9:
"In cases where flow can only be established through a non-instrumented minimum-flow path during quarterly pump testing and a path exists at cold shutdowns or refueling outages to perform a test of the pump under full or substantial flow conditions, the staff has determined that the increased interval is an acceptable alternative to the Code requirements provided that the pump differential pressure, flow rate, and bearing vibration measurements are taken during this testing and that quarterly testing also measuring at least pump differential pressure and vibration is continued.
Data from both of these test frequencies should be trended as required by IWP-6000..."
As discussed previously, flow instrumentation does exist but the accuracy of this flow instrumentation, at miniflow flow rates, is such as to make it unusable for ASME Code testing application.
No other flow path exists during plant operation at power whereby the pump flow rate could be increased such as to make the instrumentation usable.
Therefore, for all practical purposes, flow instrumer,tation does not exist.
Furthermore, no reasonable method exists whereby the pump miniflow rate can be adjusted.
2.2.2 Alternative Testina The licensee proposes the following:
Flow readings will continue to be recorded as an indication of equipment operation, but the acceptance criteria will be a minimum value only and will not be subject to assignment of a reference value or trending during the " normal" quarterly test.
The cold shutdown " substantial flow" test will have reference values assigned to the flow as well as
1
. 1 differential pressure and vibration in accordance with the rules defined in Generic Letter 89-04.
2.2.3 Evaluation As stated in section 2.3.1 of the TER attached to the SER contained in the June 4, 1991, letter, from R.J. Barrett to T.J. Kovach:
With the RHR system in the normal cooldown configuration, the requirements of IWP-4120 can be met when the pump flow rate is >1666 gpm, suction pressure is >200 psig, and the discharge pressure is >233 psig.
When testing the RHR pumps near the upper end of the operating range using the minimum flow recirculation flow lines, the discharge pressure instrument meets the Code range requirement and the flow instrument is only slightly outside this requirement.
The licensee performs testing using the minimum recirculation flow lines on a monthly basis in lieu of the quarterly Code frequency requirement.
Using the currently installed instrumentation, monthly testing performed as high in the pump operating range as practically achievable combined with pump testing during cold shutdowns and refueling outages (in the normal cooldown mode) such that the test parameter indications meet the requirements of IWP-4120 would provide an acceptable level of quality and safety.
Therefore, relief may be granted provided the licensee performs testing of these pumps under these conditions.
Inasmuch as the licensee has now committed to testing the RHR pumps as described in the TER the NRC could grant the licensee's relief request pursuant to G50.55a (a)(3)(i) because the proposed alternative provides an acceptable level of quality and safety.
However, by issuing NRC GL 89-04, the staff has already concluded that if the details of Position 9 are followed, alternative testing is authorized pursuant to 10 CFR 50.55a 1(a)(3)(i).
Therefore, alternative testing, consistent with Position 9 of NRC GL 89-04, does not require specific relief from the Code requirement to test the minimum-flow return line with or without (i.e., including without adequate) flow measuring devices and testing with higher flow, and flow measurement, during cold shutdown.
2.2.4 Conclusion As indicated in NRC GL 89-04, the proposed alternative to the Code requirements is authorized pursuant to 550.55a 1(a)(3)(1) based on the alternative providing an acceptable level of quality and safety.
2.3 Relief Reauest PR-11 (Anomaly items 3 and 4)
The licensee requests relief from the requirements of ASME Section XI, Subarticle IWP-3210, Table IWP-3100-2, for the Containment Spray pumps 1(2)CS003 as modified by PR-03 (use of OMa-1988 Part 6 Table 3a) which specifies allowable ranges of vibration amplitude and relief from the requirements of IWP-3230 which specifies corrective actions based on
9 Table IWP-3100-2 (and IWP-4510 addressed in Pump IST Plan Relief Request, PR-03).
The Containment Spray pumps at Zion Station, Units 1 and 2, are diesel driven centrifugal pumps with a speed >600 rpm.
2.3.1 Licensee's Basis for Relief The licensee stated:
If relief is granted as requested in PR-03 then this basis will be applicable in regard to Table 3a of OMa-1988 Part 6.
The diesel driven CS Pumps have an inherent higher normal vibration level as compared with other pumps by virtue of their having a reciprocating engine as a pump driver.
The reciprocating action of the
' i engine creates vibration transients which are then induced into the pump.
These transients cause vibration levels which frequently place the component in the alert range.
The proposed revision of vibration allowable limits allows trending and observation of the subject component, without unnecessarily declaring a component in the alert or action range. This stance is reasonable in light of the fact that OMa-1988 Part 6, Table 3a assigns different values for positive displacement pumps than for centrifugal pumps.
Reciprocating (positive displacement) pumps are not required to have an absolute limit for vibration assigned.
The reasoning parallel may be easily drawn between pumps and drivers; specifically a reciprocating engine driver (with its reciprocating linear motion and the attendant power strokes) that would generate significantly more vibration than a motor or turbine driven pump.
A detailed study of the vibration and maintenance history of this driver / pump combination has been performed, and no detrimental vibration a
characteristics have been observed in the pump.
Bearings, impeller, shaft and body have displayed no undesirable conditions which can be attributed to vibration.
In an effort to mitigate the effects of the diesel engine on the pumps, flexible couplings have been installed but observed vibration levels remain in excess of the alert range absolute value.
While observed vibration levels were reduced slightly, no significant improvement was noted.
During the evaluation of frequency spectrum plots, the diesel engine displays certain component type-specific frequency characteristics.
These characteristics, also appearing in the pump spectrum plot, are unlike those generated by a motor-driven pump of this design. The-frequency plot can discriminate between discrete frequencies, so that engine-generated vibration may not mask the vibration characteristics generated by a degraded pump, i
The high observed pump vibratien levels display frequency character-istics identical to those observed on the diesel engine.
The engine s
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. supplier has indicated that the current engine vibration amplitudes are acceptable.
In addition, the engine shares a common rigid mounting base with the pump.
These engine frequency characteristics are attributable to installation-specific driver-induced vibration, and are not considered to be detrimental to proper component or system operation for the following reasons.
While high vibration is certainly a condition to be avoided in any installation, the recorded maintenance and vibration. history of this component shows no indication of any induced adverse effects.
The
~
observed vibration predominant peak is at a frequency normally associated with misalignment.
But this vibration is not attributable to misalignment, since this component has been aligned satisfactorily as evidenced by maintenance records.
The possibility of temperature effects on alignment have been addressed.
The pump has proven to consistently operate at its normal vibration level independent of component temperature.
The other possible causative condition for this type of frequency characteristic is the pump's structural coupling with the diesel engine driver.
The frequency characteristics demonstrate that the engine is clearly inducing vibration into the pump.
Vibration levels of a constant amplitude are less detrimental to rotating equipment at lower frequencies than those at higher frequencies. Any vibration thus generated by the diesel engine would be considerably less detrimental to the pump than the high frequency of vibrations normally associated with pump rotating element degradation because of the naturally lower frequency of incidence of the engine vibration. Any incidences of unbalance, misalignment or other detrimental condition could be detected by spectral analysis and corrected.
A physical solution to the high vibration was explored, that of physically splitting the pump / driver base to structurally isolate the pump from the driver. Aside from the physical challenge presented by this modification, significant mechanical and structural reanalyses would be necessitated.
These analyses would be prohibitively expensive without a corresponding increase in quality, safety or reliability.
2.3.2 Alternative Testina The licensee proposes:
A rigorous preventative maintenance program is proposed whereby the flexible coupling rubber blocks would be removed, examined, compared to previous removals to detect significant changes, and replaced each
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refueling outage.
This particular item is proposed because the flexible coupling is the power transmission link between the diesel engine and the pump, and would generally be the first physical indication (exclusive of observed vibration levels) of any detrimental engine-induced vibration effects.
' Zion Station recommends, for the reasons given in the basis above, that the alert and action range absolute values be deleted and the-multipliers of V,be, reduced to define reasonable allowable ranges (ie.
(V - vibration reference value) which determine the allowable ranges Alert >l.2 V, to 1.5 V,; Action: >l.5 V,) for the diesel driven CS Pumps.
Additionally, pump vibration spectrum plots would be recorded each time the required quarterly test is performed.
The resultant spectra would be compared to spectra previously obtained and a thorough analysis would be performed on deviations identified.
Thus, a realistic trending _
effort would be undertaken whereby minute changes to pump performance could be evaluated far in advance of any actual degradation.
This vibration trending methodology would provide confidence in equipment reliability and exceeds the requirements addressed by OMa-1988, Part 6 Section 5.2.d.
2.3.3 Evaluati:n IWP-3100 requires that pump vibration amplitude be measured and compared with reference values of vibration amplitude.
IWP-3400 requires that an inservice test be run on each pump nominally every 3 months during normal plant operation.
Table IWP-3100-2 specifies the allowable ranges for the various test quantities (including vibration amplitude).
IWP-3230 states (in part):
(a) If deviation falls within the Alert Range of Table IWP-3100-2, the frequency of testing specified in IWP-3400 shall be doubled until the cause of the deviation is determined and the condition corrected.
(b) If deviations fall within the Required Action Range of Table IWP-3100-2, the pump shall be declared inoperative and not returned to service until the cause of the deviation has been determined and the condition corrected.
(c) Correction shall be either replacement or repair per IWP-3111, or shall be an analysis to demonstrate that the condition does not impair pump operability and that the pump will still fulfill its function.
A new set of reference values shall be established after such analysis.
l The NRC has approved ANSI /ASME OM-6, Inservice Testing of Pumps in rulemaking effective September 8, 1992. OM-6 allows for the use of either pump displacement or pump velocity vibration measurements and provides acceptance criteria for both types of vibration measurements.
Relief is no longer required for use of OM-6, pursuant to s50.55a j(f)(4)(iv),
provided the licensee implement all related requirements. Whether all related l
requirements are met is subject to NRC inspection. However, the licensee's j
request is a variation from OM-6; therefore, relief from OM-6 is required.
j
! OMa-1988, Part 6, Section 6.1, Table 3a, establishes acceptance criteria for pump displacement vibration (i.e., V,) and velocity vibration (i.e., V ) as y
follows:
Table 3a' Pump Pump Test Acceptable Alert Required Type Speed Parameter Range Range Action Range Centrifugal
<600 V or V, d. 5 V, 2.5 V, to
>6 V, or o
and vertical rpm 6 V, or
>22 mils line shaft
>10.5 mils
[ Note (2)]
Centrifugal 2600 V, o r V, d. 5 V,
- 2. 5 V, u
% V, w _
and vertical rpm 6V or
>0.70 line shaft
>0.525 in./sec
[ Note (2)]
in./sec Reciprocating V w V,
- d. 5 V,
>2. 5 V, to
>6 V, o
6 V, GENERAL NOTE: lhe subscript r denotes reference value.
NOTES: (1)
Vibration parameter per Table 2. V, is vibration reference value in the selected units.
(2) Refer to Fig. I to establish displacement limits for pumps with speeds 2600 rpm or velocity limits for pumps with speeds <600 rpm.
Even though the Containment Spray pump is a centrifugal type pump (with speed 2600 rpm), because the driver is a reciprocating engine, it may be more appropriate to use the limits for reciprocating pumps, which does not include an absolute limit.
International Standard 150-2372, " Mechanical vibration of machines with operating speeds from 10 to 200 rev/s - Basis for specifying evaluation standard," 1974 Edition, provides guidance for several classes of machines.
For Class VI, machine and mechanical drive systems with unbalanced inertial effects (due to reciprocating parts), root-mean-square " velocities of 20 to 30 mm/s (~.8 to 1.2 in/sec) and higher may occur without causing trouble.
In addition, if couples are acting, large displacements may be caused at points which are at some distance from the center of gravity.
Resiliently mounted [ Class VI machines) permit a greater tolerance in this respect." Therefore, the pump / engine unit may operate at a higher level of vibration with no detrimental effects.
The licensee indicated that a detailed study of the vibration and maintenance history of this driver / pump combination was performed, and no detrimental vibration characteristics were observed in the pump.
Bearings, impeller, shaft, and body displayed no undesirable conditions which could be attributed to vibration.
In an effort to mitigate the effects of the diesel engine on the pumps, flexible couplings were installed, but observed vibration levels remain in excess of the alert range absolute value.
While observed vibration levels were mduced slightly, no significant improvement was noted.
, The licensee's proposal, to have a rigorous preventative maintenance program (that includes flexible coupling removal, inspection, and replacement each refueling outage) coupled with quarterly spectrum analysis of the diesel-p driven CS Pumps, with an alert range defined as >l.2 V, to 1.5 V, and a required action range defined as >l.5 V,, may be as conservative and informative as the vibration testing required by OM-6.
Quarterly spectrum i
analysis of the CS Pumps where this data is recorded, analyzed, and trended with reduced allowable ranges', will provide a comprehensive and sensitive j
l technique of assessing pump condition and early indication of degradation, and J
will provide an adequate monitoring technique.
f The licensee considered a physical solution to the high vibration condition, i
that of physically splitting the pumn/%er base to structurally isolate the pump from the driver.
The licensee stated that aside from the physical challenge presented by making such a modification, it would necessitate significant mechanical and structural reanalyses.
To impose the Code limits, these modifications and analyses would be required, presenting a hardship without a corresponding increase in quality, safety or reliability.
Furthermore, continuing to test the diesel-driven CS Pump at twice the Code-required frequency (i.e., because the normal vibration levels frequently place this component in the alert range specified by the Code) may cause unnecessary wear to the pump's diesel and thereby make the diesel-driven pump less reliable.
2.3.4 Conclusion Based on the review of the licensee's relief request as evaluated by this SE, the staff concludes that imposition of compliance would result in an undue burden on the licensee without a compensating increase in the level of quality and safety and, therefore, the licensee's alternative is authorized pursuant to 10 CFR 50.55a(a)(3)(ii).
2.4 Relief Reauest PR-10 Request for relief from the requirements of ASME Section XI, IWP-3100, that require annual measurement of bearing temperature, for the auxiliary feedwater pumps.
The Operations and Maintenance Code Committee did not require bearing temperature to be measured.
Bearing temperature increases rapidly until bearing failure, but only for those bearings outside of the pump fluid flow path (bearings in separate housings).
The main reason for deleting this requirement was that it is unlikely that bearing failure would be detected by a yearly test.
The parameter is only indicative of pending pump bearing failure when it is continuously monitored which is not applicable for standby pumps.
Therefore, the deletion of measurement of bearing temperature for the auxiliary feedwater pumps at Zion is approved pursuant to 10 CFR 50.55a (f)(4)(iv) based on the 1989 Edition of Section XI, which 1 In lieu of having less restrictive allowable' ranges using displacement or vibration analysis and alert and action range absolute values.
4
. references OM-6 for inservice testing of pumps, no longer requiring this quantity to be measured.
3.0 PUMP TESTING POSITIONS:
Pump Test Development Usino Reference Values PP-08 (Anomaly Items 1 and 2 1 The licensee's letter dated January 7, 1993, forwarded Revision 11/92 to the IST Plan for Class 1, 2, and 3 Pumps and Valves for Zion Station, Units 1 and 2.
This revision contained one new pump Technical Approach and Position, PP-08.
This position is evaluated below.
The licensee stated:
Zion has, in the past, performed periodic testing of Emergency Core Cooling System (ECCS) and Engineered Safety Features (ESF) pumps in strict compliance with, or conservatively in excess of, Technical Specifications requirements.
These periodic tests required the pump operating parameters of flow and differential pressure to be within a band of 10% of the accepted pump head curve.
The accepted pump head curve is either the manufacturer's supplied curve or in some cases a preoperational test curve.
This methodology results in essentially an infinite number of reference values of flow and differential pressure and therefore does not meet the intent of testing per the requirements of ASME Section XI Code (IWP). A Technical Specification change approved May 12, 1992 eliminates the previous Technical Specification specific testing requirements in lieu of general reference to Section XI of the applicable edition and addenda of the ASME Code.
Consequently, the following three Code requirements have been clarified:
1)
Reference Value determination [see section 3.1 of this SER]
2)
Inservice Test Procedures, and [see Section 3.2 of this SER]
- 3) Analysis of Results.
[see section 3.3 of this SER]
The licensee's proposed position would apply to the following pumps 'in their IST Program:
Residual Heat Removal Pumps Centrifugal Charging Pumps Safety Injection Pumps Auxiliary Feedwater Pumps Containment Spray Pumps Component Cooling Water Pumps Service Water Pumps 3.1 Reference Value Determination IWP-3110 states:
Reference values are defined as one or more fixed sets of values of the quantities shown in Table IWP-3100-1 as measured or observed when the
t.
equipment is known to be operating acceptably. All subsequent test results shall be compared to these reference values or with new reference values established in accordance with IWP-3111 and IWP-3112.
Reference values shall be determined from the results of an inservice test which may be run during preoperational testing, or from.the results of the first inservice test run during power operation.
Reference values shall be at points of operation readily duplicated during subsequent inservice testing.
3.1.1 Licensee's Position The licensee stated:
At this time, Zion feels it is inappropriate to utilize (early 1970's era) preoperational test data or data from the first inservice test run during Power operation.
Therefore, reference values will be established based on past testing where possible.
These reference values will be determined from recent inservice test data of pumps known to be operating accaptably.
Where permanently installed instrument range or accuracy is not in compliance with Code requirements, a special test will be performed using suitable temporary instrumentation p. ior to establishment of the reference values.
Similar temporary instrumentation will then be used in performance of the periodic testing.
Vibration reference values will be established either during this special test or during the first execution of the test procedures which incorporate this reference value testing methodology.
-i 3.1.2 Staff Evaluation of Position in a letter from T.K. Schuster to T.E. Murley dated September 16, 1991, the licensee stated that:
The pump performance curve consisting of multiple data points will not be used as a reference pump curve for Inservice Testing / Code requirements.
Instead, Zion will set a reference value for flow and differential pressure at a point of operation readily duplicated during subsequent IST for the required IST pumps.
This does not require a relief request.
Zion will determine flow and differential pressure reference values for the IST Pumps by December 17, 1991.
Pump Technical Approach and Position, PP-01, was revised to remove the discussion on reference values.
i In a letter from T.K. Schuster to T.E. Murley dated December 17, 1991, the licensee stated that-1 I
'9
. Zion has determined the reference values and limits for the pump hydraulic test parameters, particularly flow and differential pressure.
Due to the large scope of procedure changes required to implement this new method of testing, Zion must simulate and validate the tests and train the operators on the new testing method.
Currently, the tests are being revised by Technical Staff and will be introduced as a group (all IST pump test procedures) to be implemented by the end of the next refueling outage scheduled to begin March 1992.
IWP-3112 allows for the establishment of an additional set of referens values.
Specifically:
If it is necessary or desirable for some reason other than stated in IWP-3111 [i.e., following pump replacement, repair, or routine servicing] to establish an additional set of reference values, an inservice test shall first be run at the conditions of an existing set of referer values and the results analyzed.
If operation is satisfactt ;, a second test run at the new reference conditions shall follow as soon as practical. The results of this test shall establish the additional set of reference values. Whenever an additional set of reference values is established, the reasons for so doing shall be justified and documented in the record of tests (IWP-6000).
The most recent submittal from the licensee (dated January 7, 1993) indicates that " reference values will be established based on past testing where -
possible.
These reference values will be determined from recent inservice test data of pumps known to be operating acceptably." Provided that these reference values are established and documented consistent with-IWP-3111, this aspect of the licensee's position does not require relief from the Code and is acceptable.
The NRC's June 4, 1991, SER indicates that "the licensee's instruments used for pump testing, whether they be the normal installed instruments or temporary ones, should meet the accuracy and range requirements of IWP-4110 and -4120 for the measured pump test parameters.
These points should be addressed in the relief request."
The licensee's commitment to use suitable temporary instrumentation to establish reference values, where permanently installed instrument's range or accuracy is not in compliance with Code requirements, adequately addresses this staff concern.
Similar temporary instrumentation will then be used in performance of the periodic testing.
No further NRC action is required and IST Program anomaly #1 is considered resolved.
- t 3.2 Inservice Test Procedure A requirement of the Code is to establish a reference' value of _ flow, differential pressure, and vibration as measured and observed.when the
. equipment is known to be operating acceptably.
Then, for each subsequent.
test, the system resistance is varied until the flow or differential pressure equals the corresponding reference value at which p. 'nt the other parameters of operation can be measured.
The licensee contends that:
Even though a singia reference value or set of reference values can easily be chosen or established, returning to " EXACTLY" the same operating characteristics is not possible, or at.least very unlikely.
For this reason, the system resistance must be varied such that the pump is operating at the reference value plus or minus some tolerance.
3.2.1 Licensee's Position The licensee stated:
At Zion, the pumps.will be adjusted by ' varying system resistance-(as necessary) to obtain the reference values of flow or differential-pressure plus or minus this pre-established _ tolerance.
This_ tolerance will be dependent upon the flow throttling capability of the individual systems and/or the accuracy and readability of the instrumentation.
3.2.2 Staff Evaluation of Position The Code does not address an allowable variance from a fixed reference value.
It simply states "[t]he resistance of the system shall be varied until either-the measured differential pressure or the measured flow rate equals the i
corresponding reference value." For designs that do not facilitate establishing and maintaining flow at an exact value, achieving a steady flow rate or differential pressure approximately the set value, as close as is achievable, does not require relief from the Code. However, if a particular system design does not facilitate setting flow essentially at the reference value, for example,'due to limitations in instrumentation and controls or due to piping system characteristics, then the licensee could submit a relief request to establish a range of values, but with a very narrow band.
For example, another licensee's relief request proposed "to use a reference curve (i.e., a loci of values located either side of a specific value)" with the
- tolerance around the selected value will be i 2%." ' Plant implementing t
procedures or training may provide instruction to " set flow to '1500 gpm."
When this step is performed, the operator is expected to set the flow as close as possible to 1500 gpm. -In reality, it may not be set at exactly 1500 gpm; however, it should be essentially steady at approximate 7y 1500 gpm.
The allowed tolerance for setting the fixed parameter must be established on a case-by-case basis including the instrument accuracy and the readability of i.
r t
- the instrument.
This may require verification of the affect of readability on accuracy as factored into the instrument / gauge design.
In no case is a total tolerance of greater than i 2% of the reference value allowed without relief.
If a total tolerance of less than i 2% of the reference value is achievable, relief is not required, but the variance and the method for establishing the variance must be documented in the IST program.
The basis for the 2% of the reference value is from Section XI, IWP-4150, which provides the requirements for instrument fluctuations.
IWP-4150 allows symmetrical damping devices or averaging techniques to reduce instrument fluctuations to within 2% of the observed reading.
The use of i 2% of the reference value in this position is to allow the licensee to specify the values in the implementing procedures.
Because the licensee's pump test methodology (i.e., to set the flow rate to a value within some tolerance band close to the reference flow value) is not in accordance with the Code, the licensee should submit relief request (s) to the NRC for the specific pumps that require relief from the Code required pump test methodology. The licensee's relief reTiests(s) should clearly describe the impracticality of performing the test in accordance with the Code for each pump or group of pumps (e.g., that the pump operator actually can not set the reference flow at the reference flow value, and that even though the procedure directs the operator to set the flow at this value, the flow rate can only reasonably be set within some small, defined band close to the reference flow rate).
The basis for the specified tolerance band should be clearly stated in the relief request (s).
3.3 Analysis of Results The licensee stated that:
The basis of the previous Technical Specification ( 10% of pump head curve) was to verify that the pumps remain within the ECCS analysis.
Therefore, Zion will retain these limits in addition to the limits imposed by the Code.
In some cases, this combination of limits will restrict the limits of acceptable operation to less than that specifically required by the Code, but all limits will be equal to or conservative relative to the Code requirements.
3.3.1 Licensee's Position The licensee stated that:
Due to Zion imposing dual requirements (i 10% from the pump head curve and specified percentages above and below chosen reference values per 1
the Code), and due to establishment of tolerances on pump flow, Zion has established two methods for analysis of hydraulic data.
Vibration data analysis will be discussed separately as a relief request.
j i
> I
- 1) Pumps which are tested with flow through a fixed flow limiting orifice such as a miniflow or recirculation line orifice, or for pumps which are tested in a low flow condition, the values transitioning the analysis ranges of " Acceptable," " Alert," and
" Required Action" will be in accordance with the limit requirements of Table IWP-3100-2 0_B conservative relative to those limits if restricted by the ECCS flow analysis. These limits will be represented by a fixed value of differential pressure.
j
- 2) Pumps which are tested near the design flow condition, OR where the throttling capability is substantially limited, will be i
evaluated by means of curved lines above and below the reference point which are parallel to the pump head curve.
These curved lines will be defined as follows:
a) The differential pressure reference value will be defined as a point (at the reference flow value) which lies on a' curve segment parallel to the pump head curve.
b) The curve segment will be limited in the X (flow) dimension by the established flow tolerance discussed previously.
c) The boundaries of the " Acceptable," " Alert," and " Required Action" ranges will be parallel curved line segments calculated as percentages above and below this reference curve.
d) The percentages above and below this reference curve will be
[
those of Table IWP-3100-2, or conservative relative to those percentages if confined by the ECCS flow analysis limits.
The difference between #1 and # 2 is that the analysis range in #2 will follow the shape of the pump head curve while #1 uses fixed values as boundaries between the analysis ranges.
3.3.2 Staff Evaluation of Positi2D The Coda does not address the possibility that a flowrate or differential pressure can not be controlled to an exact value.
However, the limits for flowrate and differential pressure do not both apply for monitoring the condition of pumps. When the Code specifie: that the system resistance be varied until either the flow or differential pressure equals the corresponding reference value, it does not intend that the set value have-an acceptable range per Table IWP-3100-2 (oms 6 Table 3b).
Licensees have recognized that for certcin pumps, the reference value can only be achieved within an approxinate value.
The staff has determined that the licensees should set the repeatab?e parameter as close as possible during each test rather than consider that any variance in the value must be treated with a pump curve.
If, as a result of trending data, the licensee determines that the set
~ parameter varies so much that the measured readings are outside the allowable ranges, consideration should be given to establishing allowable ranges based on a combination of reference values and pump curves and requesting relief for the specific pump (s).
Additionally, the use of OM-6 15.2(c) requirements for systems where resistance can not be varied may be used pursuant to Section 50.55a(f)(4)(iv).
Related requirements do not apply, other than that the flow and pressure are to be compared to limits of Table IWP-3100-2, or 0M-6 Table 3b if using OM-6 limits.
The licensee should ensure that pumps tested on mini-flow lines-are tested in accordance with the guidance provided in GL 89-04, Position 9.
In addition, any relief request (s) for such pumps should address the provisions of this position.
Based on a telephone conversation between the NRC and the licensee on March 8, 1993, the licensee's position and procedures used to define allowable ranges based on reference values of flow and differential pressure and pump curves, appear to be similar to positions and procedures that other licensees have described to the NRC in relief requests to justify the impracticality of complying with the Code.
However, because the licensee's methodology is not in accordance with the Code, within six months, the licensee should submit relief request (s) to the NRC for the specific pumps that require relief from the method for establishing allowable ranges as specified in the Code.
The staff considers the subject pumps to be operable under the licensee's.
alternate testing methodology and would be favorably disposed toward granting relief to the licensee from the restrictive Code requirements if the licensee proposed alternate testing similar to that described in its position.
The licensee's relief requests (s) should clearly describe the impracticality of performing the test in accordance with the Code for each pump or group of pumps.
Furthermore, the staff encourages the licensee to ask the Code Committee to modify the Code in a fashion similar to that which is described in its submittal.
4.0 LAjVE RELIEF RE0 VESTS The licensee's letter dated January 7, 1993, forwarded Revision 11/92 to the IST Plan for Class 1, ?, and 3 Pumps and Valves for Zion Station, Units 1 and 2.
This revision contained two revised valve relief requests, VR-01 and VR-33.
Each of these are evaluated separately below in accordance with the requirements of Section XI of the ASME Code.
4.1 Relief Reouest VR-01 (Anomalv Item 16)
The licensee requests relief from the requirements of ASME Section XI, Subarticles IWV-3521, " Test Frequency" and IWV-3522, " Exercising Procedure."
IWV-3521 states that "[c] heck valves shall be exercised at least every 3 months, except as provided by IWV-3522."
IWV-3522 states, in part, that:
Check valves shall be exercised to the position required to fulfill their function unless such operation is not practical during plant
H operation.
If only limited operation is practical, during plant operation the check valve shall be part-stroke exercised during plant operation and full-stroke exercised during cold shutdowns.
Valves that cannot be exercised during plant operation shall be specifically identified by the Owner and shall be full-stroke exercised during cold shutdowns.
This relief request is applicable to the containment spray chemical additive supply check valves: 1(2)CS0016, 1(2)CS0021, and 1(2)CS0026.
These valves must open to supply NaOH to spray down containment and close to prevent diverting pump suction.
4.1.1 Licensee's Basis for Relief The licensee stated that:
Full stroke exercising of check valves in the spray additive system with normal flow will add sodium hydroxide into the spray system and cause the RWST chemistry to exceed acceptable levels for chloride concentration.
4.1.2 Alternative Testina The licensee states and proposes the following:
To disassemble and remove each valve requires breaking the valve bonnet.
With this consideration, one valve will be disassembled and inspected each refueling outage.
Results of the inspection will be reviewed and if the valve f ails the other two will be inspected.
A partial flow test will be performed before the return to service following disassembly and inspection as outlined in Generic Letter 89-04, Attachment 1, Position 2.
This alternative will provide adequate assurance that operational readiness and safety will be maintained.
Currently, the non-intrusive diagnostic technique is only used on certain valves in the Check Valve Preventive Maintenance Program.
Acoustic monitoring will be investigated for these valves in the future.
The frequency of obtaining data could only be used in conjunction with disassembly at this time.
As of 11/92, Zion will attempt a partial flow test after Z2R12. Any necessary changes will be made to the IST Plan and procrdures prior to the next disassembly of these valves in 1993.
This relief request was previously evaluated in NRC -Safety Evaluation dated June 4,1991.
Zion will test these valves in accordance with Generic Letter 89-04,, Position 2.
. 4.1.3 Evaluation Based on a telephone conversation between the licensee (Mr. S. Stimac) and the NRC (Mr. C. Shiraki) dated March 5,1993, the valves for which relief is being requested are similar valves used in similar applications-(i.e., they have the same design (manufacturer, size, model number, and materials of construction) and have the same service conditions including valve orientation.
During a telephone conversation between the NRC and the licensee dated March 8, 1993, the licensee indicated that one of the containment spray chemical additive supply check valves in Unit I was changed and now has a different kind'of stop. The licensee evaluated this difference and has concluded that this stop would not effect valve performance and should not require that it be excluded from that unit's three-valve disassembly sample group (i.e., put in a separate disassembly sample group).
GL 89-04, Position 2, " Alternate to Full Flow Testing of Check Valves" states:
The NRC staff position is that valve disassembly and inspection can be used as a positive means of determining that a valve's disk will full-stroke exercise open or of verifying closure capability, as permitted by IWV-3522.
If possible, partial-valve stroking quarterly or during cold shutdowns, or after reassembly must be performed.
Since these check valves are included in the licensee's disassembly program (which the licensee says meets the guidance of NRC GL 89-04) and since these check valves will be at least partially-stroked open before the return to service following disassembly and inspection, the staff concludes that Position 2 of NRC GL 89-04 has been met.
Implementation of the licensee's check valve disassembly program and compliance with NRC GL 89-04 are subject to NRC inspection.
By issuing NRC GL 89-04, the staff concluded that if the details of Position 2 are followed, alternative testing is authorized pursuant to 10 CFR 50.55a
$(a)(3)(i).
Therefore, alternative testing, consistent with Position 2 of NRC GL 89-04, does not require specific relief from the Code requirement of l
quarterly full-stroke exercising safety-related check valves.
4.1.4 Conclusion I
As indicated in NRC GL 89-04, the proposed alternative to the Code requirements is authorized pursuant to 650.55a j(a)(3)(i) based on the alternative providing an acceptable level of quality and safety.
4.2 Relief Reouest VR-33 (Anomalv Item 15)
The licensee requests relief from the requirements of ASME Section XI, Subarticles IWV-3521, " Test Frequency" for the check valve between the Refueling Water Storage Tank (RWST) and the Residual Heat Removal (RHR) pumps
- suction, i.e., valve 1(2)SI8958.
=
i,
4.2.1 Licensee's Basis for Relief The licensee stated that:
These check valves cannot be full-stroke exercised open during unit operation as the shutoff head of the pumps is lower than reactor coolant system pressure.
The valves cannot be partially stroked during normal operation when testing the RHR Pumps on mini-flow recirculation. Alternative flow paths were investigated and evaluated.
The eight-inch recirculation line (51003-8") to the RWST utilizing the RHR return' valve, S18735, didL not prove to be a prudent method to partial-stroke exercise this valve quarterly and during cold shutdowns. The following are the reasons for this determination:
1.
This is the only valve on the line that provides isolation between the RHR System and the RWST.
Failure of this valve (single failure) to close would render the RHR System inoperable and not able to fulfill its design basis function during an i
accident.
2.
Manual operation of this valve would require-closure within 25 to 27 seconds which is not possible due to the valve size and -
operator action requirements.
Full-stroke exercising of the check valves with the reactor coolant system depressurized but intact could lead to an overpressurization of the system.
The alternative method of providing a surge volume by partial draining of the reactor coolant system is not considered a safe practice due to concerns of maintaining adequate water level above the reactor core.
In addition, the injection of potentially cold water into the reactor core could adversely affect shutdown margins.
Lastly, the RHR pumps are operating during shutdown taking suction from the RCS hot legs and discharging to the RCS cold legs while isolating the RWST suction check valve.
Therefore, exercising this valve during cold shutdown is not possible.
t 4.2.2 Alternative Testina The licensee proposes the following:
Full-flow exercising of the suction check valve will be demonstrated by total pump discharge flow during refueling while the reactor vessel head is removed.
This condition is required to establish suction from the RWST and provide system flow conditions similar to design flow.
4.2.3 Evaluation IWV-3521 states that "[c] heck valves shall be exercised at least every 3 months, except as provided by IWV-3522."
IWV-3522 states, in part, that:
Check valves shall be exercised to the position required to fulfill their function unless such operation is not practical during plant operation.
If only limited operation is practical, during plant operation the check valve shall be part-stroke exercised during plant operation and full-stroke exercised during cold shutdowns.
Valves'that cannot be exercised during plant operation shall be specifically identified by the Owner and shall be full-stroke exercised during cold 1
shutdowns, i
Section 3.3.2 of the TER attached to the SER contained in the June 4, 1991, letter, from R.J. Barrett to T.J.Kovach stated:
When full-stroke exercising a check valve is impractical during power operation or cold shutdowns, a part-stroke exercise should be performed if possible. The licensee has not demonstrated the impracticality of part-stroke exercising this valve quarterly and during cold shutdowns.
using the eight inch recirculation line to the RWST.
Therefore, a part-stroke exercise should be performed.
Full-stroke exercising this valve at a refueling outage frequency combined with a part-stroke exercise quarterly and during cold shutdowns would provide reasonable assurance of operational readiness.
Significant system design changes, such as the addition of a substantial flow test loop, would be necessary to enable full-stroke exercising of this valve at the Code-required frequency.
The necessary modifications would be burdensome for the licensee due to the costs involved.
l Based on the determination that compliance with the Code requirements is
)
impractical, and considering the burden on the licensee if the Code l
requirements were imposed, relief may be granted provided the licensee J
part-stroke exercises this valve quarterly and during cold shutdowns.
- i The licensee has now adequately addressed the impracticality of partial-flow testing quarterly and during cold shutdowns and has reiterated its commitment i
to do full-flow testing each refueling outage.
Therefore, relief could now be granted pursuant to s50.55a $(f)(6)(i) based on the impracticality of performing testing in accordance with the Code requirements, and in consideration of the burdtn on the licensee if the Code requirements were i
imposed on the facility.
However, in rulemaking to 10 CFR 50.55a effective September 8, 1992 (See 57 Federal Reaister 34666), the 1989 Edition of ASME Section XI was incorporated in $(b) of $50.55a.
The 1989 Edition provides that the rules
- l for inservice testing of valves are as specified in OM-10.
The staff imposed no limitations to OM-10 associated with exercising check valves.
l OM-10, Paragraph 4.3.1.i (e) states:
"if exercising is not practicable during plant operation or cold shutdown, it may be limited to full-stroke during refueling outages."
The staff's endorsement of this provision of OM-10 is consistent with the provisions of the regulation which allow the staff to grant relief from'the Code based on impracticality.
Section 50.55a 1(f)(4)(iv) provides that inservice tests of valves may meet the requirements set forth in subsequent editions and addenda that are incorporated by reference in $(b) of f 50.55a, subject to the limitations and modifications listed, and subject to Commission approval.
Portions of editions or addenda may be used provided that all related requirements of the respective editions or addenda are met.
As stated above, OM-10 has been approved by the NRC staff as providing an acceptable level of safety.
4.2.4 Conclusion The requisite approval is provided pursuant to 1(f)(4)(iv) for implementing the requirements of OM-10, Paragraph 4.3.2.2 (e) for check valve inservice testing frequency for valve 1(2)SI8958.
Therefore, relief is no longer required for compliance with OM-10 provided all related requirements are met.
Whether all related requirements are met 'for implementation of the test frequency for 1(2)SI8958 is subject to NRC inspection.
4.3 Relief Reauest VR-34 The licensee evaluated a variety of pressure tests, vacuum tests, and special system alignments to perform check valve full stroke capability of a number of check valves.
None of the tests proved to be a practical method of verification the capability of the valves to close.
Alternatively, a disassembly and inspection program has been implemented in accordance with GL 39-04, Attachment 1, Position 2.
The valves are grouped such that one of four is inspected each refueling outage on a rotating basis except for valve RC-8079 which requires a core off-load.
RC-8079 will be disassembled and inspected each time the core is defueled. The licensee should ensure that a basis for the extreme hardship is documented for on-site review during any IST' inspection.
GL 89-04 approves the implementation of Position 2 guidance.
4.4.
Relief Reouest VR-35 Relief'is requested from the test frequency requirements of IWV-3520 for check valves in the main steam supply to the turbine driven auxiliary feedwater pump which are required to open to supply steam and close to isolate steam flow in the event of a failure of one of the steam lines.
- i 4.4.1 Licensee's Basis for Relief The licensee states:
" Zion has investigated methods.of testing these valves I
for closure as required by the Code.
The Plant piping configuration does not-provide a positive way to verify valve closure.
Compliance with the Code-exercising requirements could only be achieved after a significant redesign of the system.
Any modification would require cooling to vent main steam.
The modification would also require engineering to prevent flooding.
These modifications would be burdensome due to the costs involved.
As an example, in the same lines, motor-operated valves are provided as isolation in the event of a steam line break. A test could be developed during normal operation where the motor-operated valve could be used to isolate the check valve while supplying steam flow to the upstream side of the disk which would cause the valve to close fully.
If the test could be performed, permanent or temporary instrumentation would be needed to detect steam flow or pressure and the piping design at Zion is not set up for this methodology.
These check valves are a Crane / Chapman 623A W.E. tilting disc type.
The valve disc is on one half and the valve seat is on the other half of the valve.
Valve disassembly and inspection is not an option for these valves because I
there are r herent risks involved with this sort of disassembly.
In order to get a good seating match of valve disc and seat, the valve must be assembled while removed from the pipe to visually accept its seating ability.
These 6-inch valves would require their welds cut out, and the valve itself removed for disassembly / reassembly and then welded back in place.
The cost and
(
critical path time during an outage would be extensive and a burden for the Station."
4.4.2 Alternative Testina The licensee proposes: "The Station is currently pursuing acoustic monitoring as a potential method of determining valve closure. This testing could only be done during a refueling outage. However, until sufficient baseline data can be obtained, there will not be enough conclusive evidence to determine valve degradation, if any, in a timely manner.
The valves are tested quarterly for fall flow. The valves have had an excellent Inservice Testing record. This test is sufficient to detect valve degradation for the required open stroke. However, valve closure cannot be verified quantitatively.
The Station believes that the current testing and development of acoustics for these valves would provide reasunable assurance to maintain valve operational i
readiness."
. 4.4.3 Eval uat iori The subject valves have a safety function to close, and are required to be inservice tested to verify their capability to fulfill the safety function.
It is impractical to perform closure verification with the current design limitations unless a nonintrusive technique is utilized.
Disassembly and inspection is not a viable option. The acoustics method proposed by the licensee could be developed to ensure that valve closure is verified using the guidance for qualifying such techniques provided in GL 89-04, Attachment 1, Position 1.
The initial qualification may need to be supplemented by a second nonintrusive method, because disassembly and inspection is not practical, such as radiography or boroscope inspection. To impose the Code requirements would be a hardship in that design modifications would be required.
To meet GL 89-04, Position 2, guidance the valves would have to be cut-out, inspected, and rewelded into the piping system, also creating a hardship.
The nonintrusive methods used by licensees are proving to be acceptable for verifying full stroke movement and for indicating degrading conditions.
Provided the licensee's method (currently under development) is capable of verifying the closure capability of these valves, and degradation of this capability, a nonintrusive method can meet the Code requirements as an "other method" of indicating disc movement and relief is not required to employ this method.
The test frequency proposed by the licensee is based on refueling outages.
The latest approved edition in 10 CFR 50.55a(b), the 1989 Edition, of Section XI, refers to OM-10 for inservice testing requirements.
OM-10, Paragraph 4.3.2.2, provides that tests may be deferred to refueling outages when testing is not practical more frequently.
The licensee's proposal, therefore, is in accordance with the requirements of OM-10, j 4.3.2.2.
The staff may approve the use of portions of later Codes, provided all related requirements are met, pursuant to 10 CFR 50.55a 1 (f)(4)(iv).
Related requirements include 4.3.2.4 and 4.3.2.6.
4.4 4.
Conclusion The alternative frequency proposed is approved pursuant to 10 CFR 50.55a (f)(4)(iv) provided all related requirements are met and relief is not required for implementation.
Whether all related requirements are met is subject to NRC inspection.
4.5 Relief Reauest VR-36 The licensee has requested relief from the test frequency requirements of ASME Section XI, IWV-3521, for the primary water (PW) supply line to the isolation valve seal water (IVSW) tank check valves (one per unit).
These valves are required to close to maintain IVSW tank pressure in the event of a line break on the non-safety related PW piping.
.. 4.5.1 Licensee's Basis for Relief The licensee states:
"The IVSW piping configuration does not provide a positive way of verifying valve closure.
Valve closure can be confirmed when an adequate pressure differential is applied to the valve disk.
The piping upstream of the check valve would require venting to provide the differential pressure.
In order to vent the upstream side of the check valve, portions of the PW system piping would need to be drained to provide a vent path.
The IVSW system is required to be operable during normal operation of the Plant.
In order to test this check valve during normal operation, the IVSW system would need to be taken out of service.
This would put the Plant into a Limiting Condition of Operation in Zion's Technical Specifications.
Zion does not consider this a prudent practice.
Significant system design changes would be needed to comply with the Code required frequency.
These modifications would be burdensome to the Station due to the costs involved.
In order to test this valve at cold shutdown, the available method of testing would require draining, isolating, and instrumenting the system.
To enable exercising the valve as required by the Code, a significant amount of time would be required and likely cause a delay of startup from cold shutdown.
The delay in return to power would be burdensome to the Station due to the costs involved."
4.5.2 Alternative Testing The licensee proposes:
"The valves will be tested during a refueling outage when portions of the Primary Water System piping can be drained.
After the piping is vented upstream of the check valve, a higher air pressure downstream will close the valve and can be verified.
The check valve will be tested in accordance with IWV-3522(a) and corrective action will be taken in accordance with IWV-3523.
This alternative will provide adequate assurance of the required level of safety and that operational readiness is maintained."
4.5.3 Evaluation Though entry into a Limiting Condition for Operation is not, by itself, justification for an impracticality of testing during power operations, it appears that the testing would be quite extensive.
It may not, however, be practical to perform the testing during power operations because of the time period the IVSW system would be out-of-service.
The same concern exists for performing testing during cold shutdowns, possibly delaying startup due to the set-up, testing, and restoration of the system.
The test frequency proposed by -the licensee is based on refueling outages.
The latest approved edition in 10 CFR 50.55a(b), the 1989 Edition, of Section XI, refers to OM-10 for inservice testing requirements.
OM-10, Paragraph 4.3.2.2, provides that tests may be deferred to refueling outages when testing is not practical more frequently.
The licensee's proposal, therefore, is in accordance with the requirements of OM-10, 1 4.3.2.2.
The staff may approve 1
. the use of portions of later Codes, provided all related requirements are met, pursuant to 10 CFR 50.55a 1 (f)(4)(iv).
Related requirements include 4.3.2.4 and 4.3.2.6.
4.5.4 Conclusion The alternative frequency proposed is approved pursuant to 10 CFR 50.55a (f)(4)(iv) provided all related requirements are met and relief is not required for implementation.
Whether all related requirements are met is subject to NRC inspection.
4.6 Relief Reouest VR-38 The licensee requests relief from the test frequency requirements of ASME Section XI, IWV-3521, for the check valves in the charging flow lines to each of the reactor coolant pump seals.
4.6.1 Licensee's Basis for Relief The licensee states:
"These valves cannot be exercised closed during normal operation.
Flow to the reactor coolant pumps (RCP) seals needs to be isolated during this check valve closure test.
Isolating the RCP seal water flow could potentially damage the seals.
Therefore, this test is impractical to perform at normal operation.
The methodology used in these valves would require the RCPs to be secured and backseated. A blank flange would be installed to facilitate testing.
Test equipment would also need to be installed on the system to perform a leakage type test.
To set up and perform this test as required by the Code would be burdensome to perform at cold shutdown due to the costs involved in remaining shutdown even if the RCPs were secured."
4.6.2 Alternative Testina The licensee proposes:
"These check valves will be tested at reactor refueling."
4.6.3 Evaluation The licensee has described the impracticality for extending the test interval from quarterly, or during cold shutdown conditions, to a refueling outage frequency. The latest approved edition in 10 CFR 50.55a(b), the 1989 Edition, of Section XI, refers to OM-10 for inservice testing requirements. OM-10, Paragraph 4.3.2.2, provides that tests may be deferred to refueling outages when testing is not practical more frequently.
The licensee's proposal, therefore, is in accordance with the requirements of OM-10, j'4.3.2.2.
The staff may approve the use of portions of later Codes, provided all related requirements are met, pursuant to 10 CFR 50.55a T (f)(4)(iv).
Related requirements include 4.3.2.4 and 4.3.2.6.
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4.6.4 Conclusion The alternative frequency proposed is approved pursuant to 10 CFR 50.55a-(f)(4)(iv) provided all related requirements are met and relief is not required for implementation.
Whether all related requirements are met is subject to NRC inspection.
4.7 Relief Reouest VR-39 The licensee has requested relief from the test frequency requirements of ASME Section XI, IWV-3520, for the inboard containment isolation check valve on the _
reactor coolant loop fill line from the chemical and volume control system,'
valve 1/2-VC-8224 (one valve per unit).
4.7.1 Licensee's Basis for Relief The licensee states:
"The loop fill system is used during refueling outages to fill the reactor coolant piping between the steam generators and the reactor coolant pumps.
The loop fill system is isolated from the reactor coolant system during normal operation.
Cycling this valve with flow would require an abnormal charging line-up resulting in a reactor coolant inventory transient and possibly a subsequent reactor trip.
The loop fill line outboard containment isolation manual valves are supplied with isolation valve seal water (IVSW).
These normally locked closed valves would need to be opened to perform testing.
Also, the IVSW system would need to be isolated from this line. This is not considered a prudent or safe practice at Zion during normal operation and some shutdowns.
The setup for this test would require venting and draining the loop fill line prior to testing.
The test would require a longer duration of most cold shutdowns. This would be burdensome to the station due to the costs involved in remaining shutdown and the draining would be a burden on the radwaste system.
The only method available during a cold shutdown that would verify the valve is closed would not meet IWV-3522, which requires verification that the valve disk travels to its closed position.
The function of this valve is to close, however, the valve must be opened prior to performing the closure exercise."
4.7.2 Alternative Testina The licensee proposes:
"The valve closure test will be performed during a refueling outage."
4.7.3 Evaluation The licensee has described the impracticality of performing the testing of the applicable valves (1/2-VC-8224) during power operations and during cold shutdowns. The latest approved edition in 10 CFR 50.55a(b), the 1989 Edition, r
. of Section XI, refers to OM-10 for inservice testing requirements.
OM-10, Paragraph 4.3.2.2, provides that tests may be deferred to refueling outages when testing is not practical more frequently.
The licensee's proposal, therefore, is in accordance with the requirements of OH-10, 1 4.3.2.2.
The staff may approve the use of portions of later Codes, provided all related -
requirements are met, pursuant to 10 CFR 50.55a 1 (f)(4)(iv).
Related requirements include 4.3.2.4 and 4.3.2.6.
4.7.4 Conclusion The alternative frequency proposed is approved pursuant to 10 CFR 50.55a (f)(4)(iv) provided all related requirements are met and relief is not required for implementation.
Whether all related requirements are met is subject to NRC inspection.
Attachment:
Table 1 Principal Contributor:
David Fischer Dated:
June 14, 1993
Table 1 Table of Anomalies and Action Items in NRC Safety Evaluation dated June 4,1991 Zion Nuclear Power Station, Ur.its 1 and 2 Commonwealth Edison Company's Response dated January 7, 1993 Description of Actions Taken to Address Status of Item Anomaly /
Description of item in NRC SE Ittw; as Descritrd in Jaruary 7 1993, and Action item
Response
Remaining Action Dated Jurr 4, 1991 1
Ptry h ydr aul ic por i m manc e p e + er em o values witi be established baced nn past Fetief f r om t he tc.de i s no t r egu r ed, ref ereeve values, rP 01 testir": whn e p u ible.
T h ew ictetence values wilt te no further NRC action is required, and dc!cen' w l frte recent inwav$te test dita cf pumps IST Program anomaly #1 is considered know, t o be eper a t ing ac c ep t abl y.
resolved.
Zion has determined the ref erence values and Iimits f or the punp hydraulic test parameters, particularly flow and differential pressure (PP-08).
2 Ptyp performance limits, The boundaries of the " Acceptable," " Alert," and The licensee's punp test methodology PP-01
" Required Action" ranges will be determined by one of (i.e., to set the flow rate to a value two methodologies:
within some tolerance band close to the reference flow value and the licensee's For puts which are tested with flow through a fixed method for defining alloweble ranges i
flow limiting orifice such as a niniftow or based on reference values of flow and recirculation line orifice, or for pums which are differential pressure and ptrp curves) tested in a low flow condition, the values transitioning is not in accordance with the Code.
the analysis ranges of " Acceptable," " Alert," and Therefore, the licensee shculd submit "Rtquired Action" will be in accordance with the limit relief request (s) to the NRC for the requirements of Table IWP-3100-2 2 conservative specific pums that require retlef from relative to those limits if restricted by the ECCS flow the Code required purp test methodology analysis. These timits will be represented by a fixed (See section 3.0 of the SER).
value of differentist pressure (PP-08).
Pumps which are tested near the design flow condition, g where the throttling capability is substantially limited, will be evaluated by means of curved lines above and below the reference point which are parattet to the ptmp head curve (PP-08).
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- i Description of Actions Taken to Address Status of Iten Arunaty/
Description of item in WRC SE Items as Described in January 7 1993, and Action Item
Response
Remaining Action Dated Jme 4,1991 3&4 Vibration reference values for the centrifugal and vertical line shaft putps with Relief is no longer required for use of and program wthodology, speed >600 rpm, measurements of vibratton in mits this portion of OM-6, pursuant to PR-03 displacement are not sensitive to smalt changes that are 550.55a 1(f)(4)(iv), provided the indicative of developing mechanical problems.
Lice.isee inplements at t related Therefore, the proposed alternate method of measuring requirements. Whether all related vibration velocity in inches /second and using the requirements are met is subject to NRC allowable vibration ranges and limits established in inspection.
OMa-1988 Part 6 provides added assurance of quality, safety, reliability and continued operability of the purps (PR-03).
For the dieset-driven containment spray pump, the the licensee's proposed alternatives licensee proposes to have a rigorous preventative would provide an acceptable tevel of maintenance program (that includes flexible coupling quality and safety and irposition of removal, inspection, and replacement each refueling conpliance would result in an undue outage) coupled with quarterly spectrum analysis of the burden on the licensee without a dieset-driven CS Purps, with an alert range defined as compensating increase in the level of
>1.2 V, to 1.5 V, and a required action range defined as quality and safety and therefore the
>1.5 v. (PR-11) ticensee's alternative is authorized pursuant to 10 CFR 50.55a(s)(3)(ii).
8 RHR punp instrument full-Flow readings will continue to be recorded as an As indicated in NRC Generic Letter scale range requirement, indication of equipment operation, but the acceptance 89-04, the proposed alternative to the PR-09 criteria will be a minimum value only and will not be
' Code requirements is authorized subject to assignment of a reference value or trending pursuant to $50.55a 1(a)(3)(i) based on during the " normal" quarterly test. The cold shutdown the alternative providing an acceptable
" substantial flow" test will have reference values level of quality and safety.
assigned to the flow as well as differential pressure and vibration in accordance with the guidance contained in Generic Letter 89-04, Attachment 1, Position 9.
15 Stroking RHR punp suction full flow exercising of the RHR punp suction check valve The requisite approval is provided check valves, VR-05 will be demonstrated by total pump discharge flow during pursuant to 1(f)(4)(iv) for inplement-refueling while the reactor vesset head is removed ing the requirements of OM-10, (VR-33).
Paragraph 4.3.2.2 (e), for check valve inservice testing. Whether all related requirements are met is subject to WRC inspection.
Description of Actions Taken to Address Status of Item Antenaly/
Description of Item in NRC SE Items as Described in January 7 1993, and Action Item
Response
Remaining Action Dated June 4,1991 16 Containment spray additive One contairvnent spray additive check valve will be As indicated in NRC Generic Letter check valve disassembly, disassembled and inspected each refueling outage.
89-04, the proposed alternative to the VR 01 Results of the inspection will be reviewed and if the Code requirements is authorized valve faits the other two will be inspected.
pursuant to 150.55a 1(a)(3)(i) based on the alternative providing an acceptable A partial flow test will be performed before the return level of quality and safety.
to service following disassembly and inspection as outlined in Generic Letter 89-04, Attachment 1, Position 2.
Acoustic monitoring will be investigated for these valves in the future (VR-01).
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I Description of Actions Taken to Acifress Status of Item Arummat y/
Description of item in NRC SE Itums as Described in January 7 1993, and Actiert Itcen
Response
Remaining Action bated Jtne 4,1991 l
16 Containment spray additive One containment spray additive check valve will be As indicated in NRC Generic Letter l
check valve disassembly, disassembled and inspected each refueling outage.
89-04, the proposed alternative to the VR-01 Results of the inspection witt be reviewed and if the Code requirements is authorized valve faits the other two will be inspected.
pursuant to 650.55a 1(a)(3)(l) based on the alternative providing an acceptable A partial flow test will be performed before the return level of quality and safety.
to service following disassembly and inspection as cuttined in Generic Letter 89 04, Attachment 1, Position 2.
Acoustic monitoring will be investigated for these valves in the future (VR-01).
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