ML20248H050
| ML20248H050 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 06/01/1998 |
| From: | Collins S NRC (Affiliation Not Assigned) |
| To: | Del Core D AFFILIATION NOT ASSIGNED |
| Shared Package | |
| ML20248H053 | List: |
| References | |
| NUDOCS 9806080040 | |
| Download: ML20248H050 (9) | |
Text
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UNITED STATES j
NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20666-0001
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Mr. Donald W. Del Core, Sr.
4 Driscoll Drive Uncasville, CT 06382-1808
Dear Mr. Del Core:
I am responding to the letter you sent to Chairman Shirley Ann Jackson of the U.S. Nuclear Regulatory Commission (NRC) dated April 12,1998, in which you expressed your concerns regarding the modification that installed flow-restricting orifices at the recirculation spray system (RSS) pump discharge immediately upstream of the expansion bellows. Your April 12,1998, letter also restates similar concerns raised in your latters of March 26 and April 2,1998. The failure of the expansion bellows was also of concern to the NRC, as evidenced by the public meeting with Northeast Nuclear Energy Company on April 8,1998, to fully explore this issue.
The staff discussed the ren,is of that meeting at a meeting with the public on the evening of April 8,1998, at which you asked, and the staff answered, many of the same questions contained in your letter.
As a result of the staff's concerns about the failure of the RSS bellows, the staff took the following actions, it requested Sargent and Lundy (S&L), as part of the scope of the Independent Corrective Action Verification Program (ICAVP), to review the modification that removed the expansion bellows and installed a spool piece in its place. This review will include an assessment of the analyses that determined the ability of the RSS pump to handle the increased nozzle loads imposed by the connected piping. The S&L review will also include an assessment of the licensee's analysis that concluded that any slivers of the failed expansion bellows liner that might remain in the RSS will not inhibit or degrade the functionality of the RSS. In addition, the NRC staff, as part of the ICAVP corrective action inspection, reviewed the licensee's evaluation of the effect of any remaining liner slivers on RSS functionality. On the basis of its inspection of the licensee's analyses, the staff concluded that the liner slivers, if any exist, would not affect the operability of the RSS, including pumps and motor-operated valves.
Further, prior to the licensee's entry into Mode 4, an operating mode defined by the plant's technical specifications for which the RSS is required to be operable, a staff consultant performed a review of the results of the increased nozzle loads on the operability of the RSS pump and confirmed that the nozzle loads were acceptable. The NRC staff also met with the licensee's staff, including members of Nuclear Materia!s Engineering (involved with the bellows structural analysis and development of the vibrational acceptance criteria), Condition Based Maintenance (resrecible for obtaining the expansion bellows measurements during the flow testing), and Nuo's Oversi % to better understand the role of these organizations in this 9
modification, and the sequence of events that resulted in the failure of the expansion bellows.
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information to demonstrate that the operators are capable of performing the required actions witin the specified time.
I trust that this information will be helpful in showing the staff's perspective on the issues that you raised.
Sincerely, Samuel J. Collins, Director Office of Nuclear Reactor Regulation Distribution:
Docket File (w/originalincoming)
PUBLIC NRR Mailroom (w/ copy incoming)
EDO G980237 SPO R/F SCollins PNorry FMiraglia JBlaha BSheron SBurns BBoger HMiller, RI WTravers JLieberman, OE JRoe KCyr, OGC
- LCallar, AThadani HThompson
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NOTE: This document has been reviewed by the Tech. Editor (4/30/98 DOCUMENT NAME:P:dcore412.ltr *See previous concurrence To receive a copy of this document, Indicate in the box "C" copy w/o attach /enct "E" co ay wlattach/enci"N" no copy OFFICE TA:SPO DD:lCAVP D:SPO D:NRR EDO OCM NAME RPerch/sr" Elmbro 8 WTravers' SCollins
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. Nuclear Oversight appropriately identified the potential for the failure, documenting that concern in a condition report, and placed an administrative hold on the plant's proceeding to Mode 4 until all of its concerns were addressed to its satisfaction. Nuclear Oversight did not object to the continued testing of the original modification as a means to address its concerns regarding the expansion bellows since it recognized that given the complexities of the analysis, testing was the most conclusive way to verify the performance of the expansion bellows.
The fact that the failure of the expansion bellows was only discovered following the testing of the last of the four RSS pumps was a concern to the NRC, as it initially appeared that the discovery of the failure could have been by chance. Our assessment ultimately determined that this was not the case. The staff of the Condition Based Maintenance (CBM) group performing the vibration measurement had been concerned with the vibrations observed during the testing of the previous three pumps. Their concern was that although the testing indicated the expansion bellows were well within the vendor's specified vibrational acceptance criteria, the vendor's acceptance criteria only addressed axial vibrations (along the flowpath of the expansion bellows) and did not include transverse vibrations (at right angles to the flowpath) that CBM had observed during the testing. The CBM group raised this concern with the Nuclear Materials Engineering Group. The vendor was contacted and additional acceptance criteria were developed which addressed the three-dimensional vibration that had been observed. These criteria were not available until the testing of the fourth pump which had been instrumented to measure the tri-axial vibration. As you noted, the fourth pump failed to meet the acceptance criteria. As a result, a decision was made to relocate the flow restricting orifice to a position downstream of the expansion joint. The failure was ciscovered during disassembly of the piping to relocate the flow restricting orifice Again, the reason the failure was detected on the last pump tested was that the acceptance criteria had been refined as a result of concerns raised by the test engineers and the vibrational measurement instrumentation had been augmented to measure the vibration in three directions. At no time was this modification declared to be acceptable for plant operation. Successful completion of the testing program was required before the system could be declared operable.
Although S&L's review of the RSS modification is ongoing, the staff's preliminary assessmeat is that the replacement of the expansion bellows with the rigid spool piece is acceptable. Since l
the RSS piping and the spool piece are stainless steel, erosion is not a concern in the RSS l
piping, including the portion immediately downstream of the flow-restricting orifice. As a result of the information obtained at the public meeting with the licensee, and the additional information obtained in subsequent meetings with the groups previously indicated, the staff is of the opinion that (1) the licensee's design control processes functioned in a reasonable manner, l
(2) the line engineering organization did not ignore the concerns raised by Nuclear Oversight, in that testing was being performed as part of the ongoing modification process, and the RSS had not been declared operable, and (3) Nuclear Oversight functioned in an effective manner.
As a result of the failed RSS expansion bellows, the licensee conducted a review of the approximately 195 plant modifications made during the current outage, including a more detailed review of all the RSS-related modifications, to verify that the root causes attributed to the failure of the RSS bellows did not adversely affect any of these modifications. The licensee's assessment concluded that there were no generic issues that impact the other modifications and that overall, the design engineering effort was well conducted. The NRC l
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. recently inspected this licensee-initiated review during the ICAVP corrective action inspection.
The preliminary results of the NRC's review are that the licensee did a thorough assessment and that the conclusions appear to be reasonable.
With regard to your concern as to why this potential failure was not identified by S&L during its review, S&L stated in the meeting on April 8,1998, that it relied on the results of the Westinghouse analysis that predicted only incipient cavitation at the RSS post-accident design conditions. The results of the analyses performed by Westinghouse are not in question. As you may be aware, because of the test configuration and system alignments necessary to perform the flow testing, the test flows were on the order of 2700 gpm, substantially above the 2200-gpm condition analyzed by Westinghouse. The licensee did not anticipate that cavitation would occur at the test conditions (i.e.,2700 gpm) because the water temperature during the test was less than 125 *F, which is significantly lower than the analyzed post-accident condition of 260 'F. The licensee's expectation that cavitation would not occur at the test conditions was based on engineering judgement which ultimately proved inconect.
You also raised a concern regarding the number of calculational errors found by S&L and reported in the ICAVP status meeting you attended on April 7,1998. At that meeting, S&L identified five Level 3 discrepancy reports (DRs) and 158 Level 4 DRs associated with calculational errors. Level 3 DRs have been defined by the NRC staff as issues that do not call into question the ability of the system to perform its specified function even though they represent nonconformances with the licensing or design bases. Alllicensing and design basis issues identified in Level 3 DRs will be corrected prior to restart of the unit. In addition, Level 3 DRs are assessed for possible ICAVP scope expansion as specified in a letter to the licensee from Dr. William Travers, dated January 30,1998. For Level 3 DRs, the staff's decision on whether or not to expand the ICAVP scope is based on the adequacy of the licensee's actions in correcting the identified problem, assessing the potential for the existence of similar errors, and the correcting of those errors. The staff is currently assessing the adequacy of the Gce.nsee's corrective actions as part of the ICAVP oversight inspections. Although the inspedo is ongoing, preliminary results indicate that the licensee's corrective actions have been comr densive. Therefore, the staff does not at this time see a need to increase the scope J, (N ICAVP.
DRs classified as Level 4 have been defined by the staff as errors that do not represent nonconformances with the plant's design and licensing bases. Accordingly, Level 4 DRs, taken individually, do not represent either a safety or a regulatory concern. Nonetheless, to make the ICAVP process comprehensive, the staff decided that Level 4 DRs should be identified in the ICAVP to gain any insight that could be obtained by assessing any trends evidenced by a collective review of DRs. A trend would be indicated, for example, if a proportionately large number of errors appeared in a particular type of calculation (e.g., voltage drop calculations or piping stress analyses). The preliminary indications are that no trends exist within the population of the 158 Level 4 DRs.
The staff disagrees with your view that the corrective action process is ineffective or that DRs in, and of themselves, are necessarily indicative of an inadequate corrective action process, it is the staff's view that insights into the effectiveness of the licensee's corrective actions can be gained from a review of the actions taken to correct problems identified in DRc, rather than the
. number of DRs themselves. The staff has inspected the corrective action program through the recently completed NRC Inspection Procedure 40500 and through the ongoing review of corrective actions in responce to the staff's inspection findings and the S&L DRs. While the overall corrective action program will be assessed as part of the restart assessment process, preliminary results indicate that the licensee has substantially improved its corrective action program and that tha corrective action program is generally effective. However, we share your i
concern regarding the errors identified by S&L in recent calculations related to the installation of the RSS flow orifices. Although these errors do not appear to affect the functionality of the RSS, the staff plans to review this issue and the licensee's corrective actions as part of the ongoing ICAVP corrective action inspection.
In your letter of March 26,1998, you also raised a concern regarding the licensee's submittal of February 16,1998, regarding its comrnitment that, prior to the next refueling outage, operator crews will be tested to show that they can accomplish transfer from the injection mode to the recirculation mode in less than 25 minutes. During a publicly observed meeting on February 19,1998, the staff discussed the licensee's February 16 submittal and, as part of that discussion, the staff questioned the licensee on training for the operating crews, specifically, whether all the operating crews had been through a simulator walk-through since the simulator was upgraded to include the modifications made to the RSS. During that meeting, the licensee committed to provide additionalinformation concerning the training. In a letter dated March 5, 1998, the licensee provided additionalinformation on operator training issues. The licensee stated that all the crews had received a combination of classroom and simulator training that addressed the modifications and procedure changes. The licensee further stated that as of February 11,1998, the shift crews had been fully trained on the recent changes made to the RSS and if any additional changes are made, the licensee will evaluate the potential effect of the training impact on operator actions.
On March 6,1998, the staff discussed the licensee's letter of March 5,1998, with the licensee during a telephone call and asked additional questions regarding the training associated with the RSS modifications. The staff specifically questioned the change in the operator action time (10 to 25 minutes) required to perform the transition between cold-leg injection and cold-leg recirculation following a loss-of-coolant accident (LOCA). During the call, the licensee stated that in late 1996, the training department collected simulator data from the six operating crews that showed that the operator action time required to perform the transition averaged 15 minutes. The licensee further stated that the only change with respect to the transition procedure was that the operators no longer had to close the two spray header isolation valves.
On the basis of the operator response times documented in 1996, the reduction in operator I
actions necessary for the transition, the classroom training given to the operating crews, and the simulator walk-through, the licensee determined that formal operator action time testing did not need to be performed during the current outage. The licensee also determined that the transition between cold-leg injection and cold-leg recirculation following a LOCA should be included in the formal operator requalification training program. The licensee committed to perform the formal timed testing prior to refueling outage 6. The NRC staff has reviewed the
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change in operator action time and the associated licensee training and commitments and has determined that the licensee has provided adequate justification for the change and sufficient
information to demonstrate that the operators are capable of performing the required actions within the specified time.
I trust that this information will be helpful in showing the staff's perspective on the issues that you raised.
Sincerely, Original Sipod by ;
Samuel J. Collins, Director Office of Nuclear Reactor Regulation Distribution:
Docket File (w/originalincoming)
PUBLIC NRR Mailroom (w/ copy incoming)
EDO G980237 SPO R/F SCollins PNorry FMiraglia JBlaha BSheron SBurns BBoger HMiller, RI WTravers JLieberman, OE JRoe KCyr, OGC l Callan AThadani HThompson
)
NOTE: This document has been reviewed by the Tech. Editor (4/30/98 DOCUMENT NAME:P:dcore412.ltr *See previous concurrence To receive a copy of this document, Indicate in the box "C" copy wIo attach /enci "E" cosy w/ attach /encI "N" no copy OFFICE TA:SPO DD:lCAVP D:SPO D:NRR EDO OCM d
NAME RPerch/sr Elmbro
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,v EDO Principal Correspondence Control FROM:
DUE: 05/06/98 EDO CONTROL: G980237 DOC DT: 04/12/98 FINAL REPLY:
Donald W.
DelCore, Jr.
Uncasville, Connecticut
- ' TO
Chairman Jackson FOR SIGNATURE OF :
ROUTING:
MILLSTONE Callan Thadani Thompson Norry Blaha Burns DATE: 04/15/98 Miller, RI Cyr, OGC ASSIGNED TO:
CONTACT:
Bell, OIG NRR g llins SPECIAL INSTRUCTIONS OR REMARKS:
Add EDO and Chairman on for concurrence.
Chairman's office to review response prior to dispatch.
R3f. G980188.
NRR ACTION:
SPO: Travers NRR RECEIVED: April 15, 1998 3
NRR ROUTING: Collins /Miraglia
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PAPER NUMLER:
CRC-98-0331 LOGGING DATE: Apr 14 98 i
l ACTION OFFICE:
EDO AUTHOR:
DONALD DEL CORE AFFILIATION:
CONNECTICUT ADDRESSEE:
CHAIRMAN JACKSON LETTER DATE:
Apr 12 98 FILE CODE: IDR 5 MILLSTONE
SUBJECT:
MILLSTONE #3 1
ACTION:
Direct Reply DISTRIBUTION:
CHAIRMAN, COMRS SPECIAL HANDLING: SECY TO ACK l
CONSTITUENT:
1 NOTES:
CHAIRMAN SHOULD REVIEW PRIOR TO DISPATCH DATE DUE:
Apr 30 98 SIGNATURE:
DATE SIGNED:
AFFILIATION:
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