IR 05000413/1988006
| ML20195K439 | |
| Person / Time | |
|---|---|
| Site: | Catawba  |
| Issue date: | 01/20/1988 |
| From: | Lesser M, Peebles T, Vandoorn P NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| To: | |
| Shared Package | |
| ML20195K426 | List: |
| References | |
| 50-413-88-06, 50-413-88-6, 50-414-88-06, 50-414-88-6, NUDOCS 8802040211 | |
| Download: ML20195K439 (7) | |
Text
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UNITED STATES '
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o NUCLEAR REGULATORY COMMISSION
,8 REGION li o
g y
101 MARIETTA STREET,N.W.
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ATL ANTA, GEORGI A 30323 hy.....,/
Report Nos.
50-413/88-06 ano 50-414/88-06 Licensee: Duke Power Company 422 South Church Street Charlotte, N.C.
28242 Docket Nos.:
50-413 and 50-414 License Nos.: NPF-35 and NPF-52 Facility Name: Catawba 1 and 2 Inspection Conducted: January 11-15, 1988
//28/T Inspector:
F. W.
IIn[To n DatM Signec Inspector:
11/1
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'N.~5. tels6r~~
DYte Signed Approved by:
/-10 - J'T T. A. Pe'ebles.'Section Chief Fe' Signed e
Projects Branch 3 r
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Division of Reactor Projects SUMMARY Scope:
This special, unannounced inspection was conducted :n site inspecting in the area of followup of a previously identified item.
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Results:
Of the one (1) area inspected, one apparent violation tuas identified (Failure to Follow TS for Nuclear Service Water System).
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REPORT DETAILS 1.
Persons Contacted Licensee Employees
- H. B. Barron, Operations Superintendent
- M. A. Cote, Licensing Specialist
- J. W. Hampton, Station Manager
- C, L. Hartzell, Compliance Engineer
- G. T. Smith, Maintenance Superintendent
- R. F. Wardell, Technical Services Superintendent
- Attended exit interview.
2.
Exit Interview The inspection scope and findings were summarized on January 15, 1988, with those persons indicated in paragraph 1 above.
The inspector described the area inspected and discussed in detail the inspection findings.
No cissenting comments were received from the licensee.
The licensee did not identify as proprietary any of the materials provided to or reviewed by the inspectors during this inspection. A new violation was l
identified as described in paragraph 3.
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Followup of Nuclear Service Water System Operability (92701)
(CLOSED)
Unresolved Item 413,414/87-10-01: Single Failure Vuinerability of the Nuclear Service Water System.
In late 1935, prior to operation of Unit 2, the licensee recognized the need to develop procedures for two unit operation of the shared Nuclear Service Water System (RN).
In March, 1986 the NRC: SRI observed that RN was being aligned based in part on guidance from a Technical Memorandum.
Concerns were expressed to the licensee that a Technical Memorandum was inappropriate for this activity.
The licensee indicated that additional procedure guidance was being developed and that a Technical Specification Interpretaticn would also be issued.
Special guidance was necessary due to the shared nature of the system and the Technical Specification (TS) 3.7.4 requirement to have two independent RN loops operable per unit.
A general system descrip* ion and the actions required were stated in Licensee Event Report (LER) 86-31 Rev. 1, dated August 29, 1986 as follows:
"The Nuclear Service Water (RN) System contains pumps which are unit designated, i.e.,1A, 2A,18, 2B, yet supply both units through common discharge piping.
All RN pumps receive auto-start signals from a Safety-Signal cn either unit.
Each Diesci Generator (D/G) supplies emergency power to its respective RN pump.
Emergency power is not required for dependent equipment to be operable, unless specifically specified by Technical Specifications (Tech Specs).
If a D/G is inoperable, the dependent RN train is conservatively declared inoperable on both units due to the shared nature of the RN System.
If a station
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blackout and a LOCA on one unit occurs, only three RN pumps can supply sufficient flow for four RN trains, but cannot do so if a single failure occurs, this configuration does not represent two independent RN trains for each unit.
Therefore, with only three RN pumps operable, Tech Spec 3.7.4 action statement for one RN train out of service et be entered for both units or, sufficient inoperal31e RN supplied equipment is isolated to
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ensure adequate flow to operable equipment.
If less than three RN pumps are operable, both units must enter Tech Spec action statement 3.0.3 until sufficient RN supplied equipment is isolated to assure that at least one RN train per unit or two trains on the same i
unit, will receive the required post accident RN flows.
Tech Spec 3.0.3 requires that within 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />, action will be initiated to place the unit in a mode in which RN is not required.
RN is required in Mode 1, Power Operation; Mode 2, Startup; Mode 3, Hot Standby; and Mode 4, Hot Shutdown.
l Operation with less that 4 RN pumps requires RN System realignment to l
ensure sufficient post accident flow in the event of any single failure.
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Procedure OP/0/A/6400/06C, RN System procedure, provides guidelines to realign the system in the event that one or more RN trains becomes inoperable."
The licensee issued the additional guidance and upon further review the NRC: SRI had additional questions.
An Inspector Followup Item was opened l
in NRC Report 413/86-30, 414/86-33.
Documentation in this report was as l
'ollows:
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"On August 25, 1986, the inspectors held detailed discussions with
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licensee management relative to alignment of the Nuclear Service Water System. Due to an apparent design error sufficient flow cannot be assured
from only one pump to support an operating unit.
Therefore, special alignments must be performed when cne or more of the four available pumps the applicable procedure (9 pears to the inspectors that the enclosures to are out of service.
It a 0P/0/A/6400/06C) could be clarified relative to which action statements are to be entered, use of human valve operators and, further, to assure that all operability scenarios are covered.
The licensee agreed to review these enclosures for clarification.
This is Inspector Followup Item 413/86-30-01, 414/86-33-01: Followup of Clarification of Nuclear Service Water System Procedure."
The inspectors continued to review procedure changes and discuss RN alignment with operators and otter licensee personnel.
In March, 1987 the licensee informed the inspectors that a Station Problem Report (SPR) had been generated to request evaluation of a scenario in which RN may not meet single failure criteria.
The previous open item was upgraded to an Unresolved Item in NRC Report No. 413,414/87-10 issued on May 14, 1987 and documented as follows:
"(CLOSED)
Inspector Followup Item 413/86-30-01, 414/86-33-01: Followup of Clarification of Nuclear Service Water System Procedure.
The inspector reviewed change 47 to OP/0/A/6400/06C, Nuclear Service Water System.
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Initial concerns, regarding the assurance that all operating scenarios had been covered in the procedure, have been adequately addressed, however, additional concerns with the operation of the system have arisen.
The Nuclear Service Water System (RN) consists of two, train specific pumps per unit for a total of four pumps.
Under normal operating-conditions only one of the four pumps is required to supply loads on both units and does so through common discharge piping.
Technical Specification (TS) 3.7.4 requires two independent RN loops per unit to be operable while the applicable unit is in Modes 1 tnrough 4.
Licensee Event Report 414/86-31 Rev. 1 of August 29, 1986, identified that the RN system could not be considered two independent loops when a diesel generator or a Nuclear
~ Service Water pump from either unit became inoperable.
This is because assuming a LOCA and a station blackout,- three RN pumps would theoretically-be available to effectively supply 4 RN trains, however a single failure would leave only two RN pumps.
Duke design engineering has shown this condition would result in inadequate flow to heat exchangers.
Procedure OP/0/A/6400/06C, Nuclear Service Water System, was revised to include special RN system lineups when one or more RN pumps or diesel generators were inoperable for greater than 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />. These special alignments would ensure adequate RN flow to heat exchangers on the operating unit.
The inspector identified areas where clarification was required and documented concerns under IFI 413/86-30-01, 414/86-33-01.
Upon review of various procedure changes up to change 47 it was noted that under certain conditions RN would be isolated to a Component Cooling Heat Exchanger on
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the unit shutting down to ensure adequate RN flow for the opposite unit, thus allowing continued operation. Although not specifically addressed by Technical Specifications, isolation of a Component Cooling Heat Exchanger for the sole purpose of keeping an opposite unit operating does not appear to be prudent as it removes a redundant safety system.
Additional concerns on the use of human valve operators under various conditions remain open.
On January 21, 1987, Station Problem Report #CNPR-2530 was generated identifying a postulated different single failure of the RN system and requested evaluation from desiga engineering.
Part 1 of Design Study (CNDS-080/00) of March 27, 1987, concluded that an unanalyzed condition exists and needs to be addressed.
The scenario involves a diesel generator or RN pump on either unit inoperable for greater than 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, requiring shutdown of that unit.
Under LOCA conditions of the operating unit and station blackout RN suction and discharge would automatically shift from Lake Wylie to the Standby Nuclear Service Water Pond (SNSWP),
the seismically qualified ultimate heat sink.
A single failure of a SNSWP supply valve would block cooling water to two RN pumps.
Since one RN pump was already inoperable, the fourth RN pump would alone be left to supply cooling to both units.
With one unit in a LOCA condition and one unit shutting down, one RN pump is inadequate to cool all heat exchangers including remaining operating diesel generators.
This would result in eventual loss of all diesel generators, AC power, and cooling water for both unit _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
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Various solutions have been proposed including: installation of redundant parallel SNSWP supply valves or eliminatioa of the requirement to swap RN suctions to the SNSWP on a LOCA (Sp signal). The lictnsee has stated that should a diesel generator or RN pump become inoperable on one unit for greater than 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, manually shifting Rd suction and discharge to the SHSWP wou'sd eliminate the single failure vulnerability and justify -
continued operation of the other unit. -It was noted that there are no I
l provisioW3 to monitor ShiWP temperature during all months of the year.
The' licensea is contineing part 2 of the Design Study which includes a Probabilistic Risk Assessment of the problem. The licensee has generated Problem Investigation Report (PIR) 0-C87-0097 to determine if this ur, analyzed condition is reportable. This is identified as Unresolved Item 413/87-10-01, 414/87-10-01: Single Failure Vulnerability of the Nuclear Service Water System pending licensee resolution and further review by the NRC."
The above documentation was based on Part 1 of the referenced Design Study.
This study appears to have been a preliminary engineering judgement without benefit of a complete analytical review.
In addition the licensee's problem report failed to recognize that accidents which challenge the SNSWP Supply valves also result in automatic loop isolation resulting in a flow to two essential headers from the remaining operable pump, i.e., one RN train in each unit would be supplied by the operable pump.
Upon recognition of the possible single failure vulnerability, the licensee made plans to change procedures to require aligrments to remove the single failure vulnerability.
This in part consisted of aligning to the SNSWP and failing the supply valve open whenever a Diesel Generator (D/G) was out of service for more that 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />.
These plans were described to the inspectors at the time the single failure vulnerability was explained in February. A procedure change for the SNSWP alignment was actually issued on March 5, 1987 since a D/G was approaching being out of service for 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />.
The licensee failed to recognize that power should have been removed from the SNSWP valve at this time but did so later and made the additional procedure change on April 3, 1987.
l The following is an excerpt from LER 413/87-36 dated October 30, 1987 and further describes the sequence of events relative to the RN system:
"On March 27, 1987, Design Study CNDS 080/00, Part 1 was completed.
On April 10 Problem Investigation Report (PIR) No. 0-C87-0097 was originated, and the evaluation was assigned to Design Engineering to detennine operability (response was requested by April 20,1987).
Per a telephone conversation held with Design Engineering personnel on April 16, the situation addressed in the PIR was not an operability problem in the near future because the RN valves could be manually prealigned to the SNSWP to remove the potential for their failure and more information would not be available until Design Study CNDS 080/00, Part 2 was completed.
On May 13, 1907, Design Study CNDS 080/00, Part 2 was completed.
On May 28, 1987, Design Engineering completed the operability evaluation for PIR No. 0-C87-0097, which stated that the unanalyzed condition is not a
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condition which significantly compromises plant safety.
On June 4, a meeting was held between Design Engineering and Nuclear Production
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personnel to discuss the outstanding RN questions and possible solutions.
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On July 13, 1987, the NRC began a two week Quality Validation Inspection Audit at Catawba Nuclear Station.
During this audit, the NRC staff reviewed the RN System design,
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i On July 21, 1987, Compliance originated a letter-requesting written confirmation from General Office Licensing personnel concerning reportability.
On August 5, General Office Licensing personnel issued a letter to Station Compliance referencing a meeting held on July 29, 1987, at which Design Engineering and Nuclear Production personnel discussed the RN situation and reportability concerns.
The outcome of the meeting was that a heat load review would be necessary to confirm that the postulated-situation would have provided adequate cooling and would not have prevented fulfillment of the RN System safety function.
On August 7,1987, the NRC issued a letter requesting justification for continued operation for Catawba Nuclear Station with one D/G out of service. - On August 8,1987, Operations Management personnel issued an Operations Technical Memorandum to inform Operations personnel of NRC notification requirements upon removal of a D/G from service and subsequent alignment of RN to the SNSWP. This notification was requested by NRC during a telecon on August 7, 1987.
On August 14, 1987, Duke Power issued a response to the NRC request for justification of continued operation'.
The response concluded that the design of the RN System meets General Design Criteria (GDC) 5 ar.d 44 and
that operating procedures adequately address operation with a D/G removed from service.
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While preparing the August 14 response, the RN crossover supply valve
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positions required with one 0/G or RN pump inoperable for extended periods l
were reviewed. A telephone conversation with Design Engineering confirmed that the valve lineup was incorrect if a single RN pump was required to supply both units.
On August 18, 1987, the D/G and RN Operating Procedures were revised to incorporate the correct RN crossover supply valve alignment for this situation.
On August 31, 1987, Duke Power personnel decided to submit this LER as a voluntary report for information purposes.
Submittal of this LER was accordingly scheduled for September l
30, 1987.
On September 10, 1987, a heat load analysis was completed which provided acceptance criteria for an RN System flow balance which would not require isolation or rethrottling of RN to the component cooling system (KC) when one unit is shutdown with a D/G inoperable.
On September 27, 1987, Performance completed the RN flow balance which confirmed the capability of one RN pump to supply adequate RN flow to both units.
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On September 30, 1987, the NRC issued a Safety Evaluation Report which confirmed the adequacy of the RN System design and operating procedures.
This report also concurred with modification to delete the swap of RN to the SNSWP on a Sp signal.
Also on September 30, 1987, submittal of this LER was delayed to October 30, 1987 per a letter from H.8. Tucker to the NRC Document Control Desk.
On October 12, 1987, Operations personnel determined as a result of this investigation that a Technical Specification violation had occurred due to the incoreset RN crossover supply valve alignment between September 4, 1986, and September 8, 1986."
Although the licensee felt that interim actions after the single failure question was recognized were adequate, a historical review of previous alignments was necessary for reportability determination.
The licensee indicated in LER 413/87-36 that Design Engineering instructions for realignment during September 1986, while Unit 1 was shutdown and Unit 2 was in Mode 1, were inadequate.
Assuming the failure scenario previously described occurred, a single RN pump would have been left to support one essential header on each unit and a non-essential header.
The lineup should have isolated the non-essential header.
Insufficient flow would have resulted. A D/G had been out of service for greater than 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> on September 4, 1986, thereby making one train of RN inoperable greater than 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />.
Since TS 3.7.4 requires shutdown after 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> if two loops of RN are not available and one loop was essentially degraded greater than 72
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hours from September 4-8, 1986, the TS was violated.
The licensee has l
shown via a revised heat load analysis and RN flow balance verification that one RN pump is sufficient to supply post-LOCA loads on one unit and shutdown loads on the other unit.
The licensee also claims that the abnormal procedure for loss of RN would have resulted in operators regaining adequate flow with the degraded RN System.
The licensee has submitted a TS change for approval which more adequately addresses the shared aspects of the RN System and has further requested that the design bases be changed by deleting the assumption of a simultaneous LOCA and seismic event.
The licensee has considered the seismic event credible in the past and continues to do so via the present procedure requirements.
The situation in September 1986, appears to be a violation of TS's which requires NRC:RII management review for consideration of escalated enforcement.
Therefore a Notice of Violation is not being issued with this report but will be issued upon completion of an Enforcement Conference.
This item is assigned as Violation 413,414/88-06-01: Failure to Follow TS for Nuclear Service Water System.
Additional documentation of this issue is contained in NRC reports 413,414/87-25, 87-30 and 87-33 and licensee LER 413/87-36.
One violation was identified as described above.
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