ML20134L660
| ML20134L660 | |
| Person / Time | |
|---|---|
| Site: | Grand Gulf  |
| Issue date: | 11/18/1996 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML20134L648 | List: |
| References | |
| NUDOCS 9611210127 | |
| Download: ML20134L660 (7) | |
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UNITED STATES NUCLEAR REGULATORY COMMISSION f
WASHINGTON, D.C. 2006M001
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGVLATION RELATED TO AMENDMENT NO.130 TO FACILITY OPERATING LICENSE N0. NPF-29 ENTERGY OPERATIONS. INC.. ET AL.
GRAND GULF NUCLEAR STATION. UNIT 1 DOCKET N0. 50-416
1.0 INTRODUCTION
By application dated May 9,1996, as supplemented by letter dated August 27, 1996, Entergy Operations, Inc. (the licensee) submitted a request for changes to the Technical Specifications (TSs) for Grand Gulf Nuclear Station, Unit 1 (GGNS). The proposed changes are to Surveillance Requirements (SRs) 3.4.4.3, Safety / Relief Valves (S/RVs), 3.5.1.7, Automatic Depressuri-zation System Valves, and 3.6.1.6.1, Low-Low Set Valves, of the TSs.
The proposed changes would state that the required surveillance of the valves is to verify that the relief-mode actuator strokes when the valve is manually actuated and the frequency of the surveillances would be in accordance with the inservice testing program for the valves. These changes would allow the surveillance of the relief mode of operation of each of the valves to be performed without physically lifting the disk off the seat at power.
In its application of May 9,1996, as supplemented by letter dated August 27, 1996, the licensee also submitted changes to the Bases of the TSs that are associated with the proposed changes discussed above.
In the applications, there was also an associated request for relief from inservice testing requirements in the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code) for the safety and relief valves (S/RVs). This relief is needed to revise the requirements in the GGNS inservice testing program for these valves so that the program does not require stroking of these valves.
These valves were the subject of License Amendment No.123, which increased the safety function lift setpoint tolerances that are listed in SR 3.4.4.1.
The tolerances were increased from plus/minus 1 percent to plus/minus 3 percent, as approved in the staff's letter of June 12, 1996, in response to the licensee's application of February 22, 1996. This amendment approved a new frequency of removing the S/RVs and testing the safety lift setpoints during a refueling outage, beginning with Refueling Outage 8 commencing in October 1996.
The new frequency is in accordance with the ASME Code inservice testing requirements for these valves.
9611210127 961118 DR ADOCK 05000416 PDR
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2.0 BACKGROUND
The proposed changes to the TSs involve the S/RVs which are the overpressure i
protection for the reactor coolant system (i.e., reactor vessel, main steam lines, and associated piping) and are discussed in Section 5.2.2 of the Updated Final Safety Analysis Report (UFSAR) for GGNS. The overpressure protection includes the functions of automatic depressurization and of low-low set.
Each S/RV is a Dikkers, 8 X 10, direct-acting, spring-loaded safety valve with i
an attached pneumatic actuator. There are a total of 20 S/RVs installed on i
the 4 main steam lines. These valves have both a safety mode and a relief mode of operation.
As explained in the application, the S/RVs provide pressure relief based on i
the principle of vertically moving the stem that attaches directly to the 1
valve disk. The force that provides the stem movement is provided by one of two sources:
(1) the vessel pressure directly against the force of the stem j
s) ring (safety mode) or (2) the pneumatic actuator arm against the force of j
tte stem spring (relief mode). The safety mode is never tested while the S/RV is installed in the plant. The testing of the relief mode of operation for a
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direct-acting S/RV provides verification that the control functions of i
electrical and pneumatic connections have been properly reconnected, and that the actuator are will provide the necessary force to operate the S/RV.
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The safety mode is the self-actuating function which is necessary to relieve system overpressure. The relief mode is accomplished by an automatic or j
manual control circuit which applies electric power to solenoids which provide control air to the pneumatic actuator piston.
Eight of the S/RVs use the relief mode to perform the Automatic Depressurization System (ADS) function which is necessary for depressurizing the primary system to enable low-pressure injection systems for small-break loss-of-coolant accident (LOCA) 1-scenarios. Also, six S/RVs, two of which are also ADS S/RVs, use the relief mode to perform the low-low set function which is necessary to prevent multiple simultaneous openings of the S/RVs and the associated containment loads. SRs 3.4.4.3, 3.5.1.7, and 3.6.1.6.1 assure the overpressure safety i
mode, ADS, and low-low set function relief modes, respectively, and are concurrently satisfied by performing the required testing of the S/RVs.
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In past refueling outages, all 20 S/RVs were removed, bench tested for the j
safety mode setpoint according to the 1980 Edition of Section XI of the ASME Code through and including the Winter 1980 Addenda, and replaced with recertified S/RVs that had been verified to have zero seat leakage. After j
installation, each recertified S/RV was manually stroked to verify the relief i
mode function of the S/RV. This S/RV stroking was performed to satisfy ASME Code requirements for inservice testing of these Category B valves, as well as for meeting the current requirements in the above SRs.
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, i The licensee stated that meeting the current requirerents in Sr.s 3.4.4.3, 3.5.1.7, and 3.6.1.6.1 required physically lifting tha disk c/f of the valve seat (i.e., the valve is stroked) and passing reactor i,tm through the valve.
The licensee stated that, in order to prevent seat leakage from occurring, it 1
is not desirable to open the S/RVs once they are installed at the plant.
Seat leakage causes undesirable contamination and heating in the containment and i
contributes to further valve seat damage. The licensee also stated that performance trending data show that the S/RVs have an increased probability of j
leaking and experiencing safety mode setpoint drift in the negative direction 4
j (i.e., toward a lower setpoint) each time they are stroked.
3.0 EVALUATION 3.1 Proposed Te'.hnical Specification Changes The licensee 'nas proposed to change SRs 3.4.4.3, 3.5.1.7, and 3.6.1.6.1 to l
(1) allow stroking of only the S/RV actuator to demonstrate operability of the i
S/RVs in the relief mode and (2) conduct the SRs at a frequency in accordance
.with the inservice testing program for.the S/RVs. The licensee proposed to 1
perform the surveillance of the S/RV relief mode function without physically i
lifting the disk off of the valve seat at power. Not requiring the disk to be lifted means that reactor steam pressure is not needed to conduct the surveillances and, therefore, the surveillances do not have to be performed with the plant at power.
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The licensee stated that, during the refueling outage, a sample of the S/RV population would be removed for safety mode setpoint testing in accordance with the plant inservice testing program, as now allowed by Amendment No. 123.
j This sampling provides for testing approximately one-third of the S/RVs during each outage with all being tested within approximately 5 years. The ASME Code also requires that additional valves, beyond the sample, be tested if S/RVs fail the setpoint testing.
i The licensee also proposed that the frequency for the surveillances of the
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S/RV relief mode function would be in accordance with the inservice testing program for the valves and, therefore, following the setpoint testing 1
i discussed in the previous paragraph, the test sample of S/RVs would also be
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tested on the bench in the relief mode to verify that the pneumatic actuators function properly. After this test sample of S/RVs is replaced with recertified valves and the S/RV controls are connected to the newly installed valves (i.e., the valves are reinstalled on the main steam lines), the upper 4
stem nut that couples the valve stem to the relief mode actuator would be i
moved up away from the actuator arm to allow an uncoupled actuation of the i
relief mode actuator (i.e., the disk would then not be coupled to the relief mode actuator and not move when the actuator is operated). The actuator would be remotely operated from the control room, and visual verification would be 4
i performed for proper actuator response and range of motion. After proper i
actuator operation has been verified, the upper stem nut would be returned to j
its operating stem location. Attachment 5 to the application dated May 9, i
1996, showed pictures of an S/RV and where the stem nut is moved to allow an 9
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i uncoup' led actuation. Page 2 of the attachment shows the washer and nut which 4
I are to lock the upper stem nut in its proper location.
i' The licensee further stated that the remaining installed S/RVs, which would not be removed as a part of the above testing sample, would continue to be i
tested for proper system function. As presently required by the plant TSs and l
administrative procedures, proper system function is demonstrated by providing an open signal to each S/RV and a check to verify that the actuator solenoid valve repositions. This test is conducted to meet SRs 3.4.4.2, 3.5.1.6, and 1
3.6.1.6.2 (companion SRs for the S/RVs to the three SRs proposed to be i
changed) to verify each S/RV system actuates on an actual or simulated i
automatic signal. As allowed by the note in the SRs, value actuation may be l
excluded.
The relief-mode of operation involves the actuator solenoid valve repositioning to admit control air to the actuator cylinder which will move 4
j the cylinder piston and, through the actuator arm, the valve disk. This is an acceptable method to demonstrate the solenoid control function. To prevent i
the valve disks from moving during the test, the control air is isolated and the cylinder piston and valve disk do not move. The licensee concluded that the verification of proper actuator solenoid valve operation in the non-removed, remaining installed, S/RVs by conducting SRs 3.4.4.2, 3.5.1.6, and 3.6.1.6.2, and the proper relief-mode operation of the test sample of S/RVs provides assurance that all the S/RVs will perform as expected for relief-mode l
operation.
By plone call on August 16, 1996, the licensee explained why all the S/RVs i
were not tested by the method described above for the test sample of S/RVs
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that are removed from and later re-installed on the main steam lines. The i
licensee stated that there would be about 20 hours2.314815e-4 days <br />0.00556 hours <br />3.306878e-5 weeks <br />7.61e-6 months <br /> of occupaticnal exposure in j
a radiation area that was not needed because'SRs 3.4.4.2, 3.5.1.6, 3.6.1.6.2 are an accepted method to verify the S/Rvs in the relief mode of operation will actuate on a signal.
3.2 Evaluation j
i 3.2.1 Method to Demonstrate Operability of S/RVs The staff has reviewed the licensee's proposed changes to SRs 3.4.4.3, 3.5.1.7, and 3.6.1.6.1, and agrees that the current requirements result in 4
i opening the valves during power operation, which could cause an undesirable j
transient in the reactor coolant system and failure of an S/RV to reclose would result in a LOCA. The licensee proposed the following two methods to demonstrate that the S/RVs meet the three SRs:
The current method in the TSs that is described in the Bases for the a
i three SRs. The manual activation of the valve with verification of the j
response of the turbine control valves or bypass valves, by a change in
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the measured steam flow, or any other method suitable to verify steam flow (e.g., tailpipe temperature or pressure).
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The new method described in Section 3.1 above.
The differences between the current TS testing and that proposed are (1) the i
proposed testing does not verify by actual stroking that the stem is properly coupled to the actuator, (2) the proposed sample testing of one-third of the
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total S/RV population each outage is less than the current testing of all S/RVs each refueling, and (3) the proposed testing does not verify, by successfully discharging the S/RVs, that the attached piping is not blocked.
The second item is addressed in this section in terms of the reliability of the valves and in Section 3.2.2 in terms of the licensee's proposed change to q
the frequency of conducting the surveillances.
The potential concern regarding the first difference is that the stem may not i
be properly coupled to the actuator by the proper position of the stem nut I
after the S/RVs are installed and the actuators are stroked.
This activity would be performed under plant quality controlled procedures which will J
require that the work be independently checked. The licensee has stated that, for the past seven cycles, all of the S/RVs have been removed and installed with only a single relocation failure which resulted in a solenoid valve failing to reposition.
The licensee determined that, for this occurrence, the-failure would have been detected by the proposed testing. The staff agrees that the licensee's good installation history and procedures adequately I
address concerns relative to the necessary repositioning of the stem nut.
The potential concern regarding the second difference is that the S/RVs may not be adequately reliable if they are only setpoint tested and stroked less often than currently performed. However, the 1980 Edition of the ASME Code, i
which is currently applicable to the licensee, requires only that a sample of S/RVs be setpoint tested in any test period.
Further, more recent editions of the ASME Operations and Maintenance Code provide for the stroking of S/RV actuators only when setpoint tests, maintenance activities, or repair activities are performed.
Therefore, the licensee's proposed testing frequency meets the more recent editions of the Code, which the staff has i
agreed are adequate for testing valves of this type. This frequency of testing the S/RVs was addressed by the staff and approved in Amendment No. 123.
l' Regarding the third diVference, the licensee places Foreign Material Exclusion i
(FME) controls on til system openings when each S/RV is removed. The licensee states that the FME controls, as well as the horizontal orientation of the S/RV discharge pipe attachment, provide reasonable assurance that no obstruction will be admitted into the S/RV discharge piping. The licensee further states that, for the past seven maintenance outages, no failures related to line blockage have occurred. The staff agrees that this is acceptable for addressing this concern.
i Using the methods for SRs 3.4.4.2, 3.5.1.6, and 3.6.1.6.2 to verify that the j
S/RVs that were not removed will function correctly for the relief mode of operation is acceptable.
These valves were previously tested, or will be a
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. tested in the future, by moving the upper stem nut when they are removed from the main steam line. When they remain in place, they will be tested by an accepted method to verify the S/RVs in the relief mode of operation will actuate on-a signal. Also, the upper stem nut is locked in its proper location to prevent any movement of the nut while the valve is in place on the steam line.
The staff notes that, in the Bases for the proposed TS changes, the licensee retains the option to perform stroke testing of the S/RVs by actual manual actuation of the valve disks and observing indications of flow through the valves. This is also acceptable to the staff as a testing option.
3.2.2 Change Frequency of Surveillances The licensee proposed to perform the three surveillances for the relief mode actuator in accordance with the ASME Code inservice testing program for the S/RVs. The purpose of this change is to have agreement between the TSs and the inservice testing program for these valves and to have the same sample size requirements for testing the S/RVs by the new relief-mode method as in the associated request for relief from the ASME Code inservice testing requirements for these valves. The request for relief was also in the application of May 9, 1996.
The request for relief was approved in the staff's letter of November 18, 1996.
In that approval, the staff agreed that the ASME Code Category C setpoint testing, combined with stroking of the S/RV actuators was an acceptable alternative test method. The frequency for the Category C setpoint testing is once per five years which is consistent with the testing frequency approved for the safety function lift setpoint testing of the S/RVs in Amendment No. 123.
The licensee's proposed testing frequency meets the more recent editions of the Code, which the staff has agreed are adequate for testing valves of this type.
Therefore, the licensee has proposed a testing frequency for the S/RVs that meets the ASME Code inservice testing requirements and is consistent with Amendment No. 123. Approving the proposed change will then have the TSs consistent with the ASME Code inservice testing frequency requirements for these valves. Based of this, the staff concludes that the proposed changes in frequency are acceptable.
3.3 Conclusion Based on the above evaluation, the staff concludes that the licensee has demonstrated the adequacy of the proposed changes to SRs 3.4.4.3, 3.5.1.7, and 3.6.1.6.1 of the GGNS TSs. The proposed changes provide for testing of the S/RVs to demonstrate proper relief mode function without the need for actually 1
stroking of the valve disks off of the valve seats while the plant is at power and the frequency of the surveillances would be in accordance with the ASME j
Code inservice' testing program for the valves. Therefore, the staff concludes that the proposed changes to SRs 3.4.4.3, 3.5.1.7, 3.6.1.6.1 are acceptable.
4 The changes to the Bases of the TSs for the SRs being revised were also reviewed, and the staff concludes that they are correct and are proper. for the l
Bases of these SRs.
4.0 STATE CONSULTATION
1 In accordance with the Commission's regulations, the Mississippi State official was notified of the proposed issuance of the amendment. The State
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official had no comments.
5.0 ENVIRONMENTAL CONSIDERATION
1 The amendment changes a requirement with respect to installation or use of a j
facility component located within the restricted area as defined in 10 CFR Part 20 and changes surveillance requirements. The NRC staff has determined that the amendment involves no significant increase in the amounts, and no i
significant change in the types, of any effluents that may be released offsite, and that there is no significant increase in individual or cumulative 1
occupational radiation exposure. The Commission has previously issued a l
proposed finding that the amendment involves no significant hazards i
consideration, and there has been no public comment on such finding l
(61 FR 47971) accordingly, the amendment meets the eligibility criteria for categoricai exclusion set forth in 10 CFR 51.22(c)(9).
Pursuant to 10 CFR 51.22(b), no environmental impact statement or environmental assessment need be prepared in connection with the issuance of the amendment.
6.0.CBCLUSION i
The Commission has concluded, based on the considerations discussed above, j
that:
(1) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, (2) such activities will be conducted in compliance with the Commission's regulations, and (3) the issuance of the amendment will not be inimical to the common l
defense and security or to the health and safety of the public.
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Principal Contributors: Charles G. Hammer Jack N. Donohew i
Date:
November 18, 1996 1
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