ML20206D817
| ML20206D817 | |
| Person / Time | |
|---|---|
| Site: | Grand Gulf  |
| Issue date: | 04/29/1999 |
| From: | Hughey W ENTERGY OPERATIONS, INC. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| GNRO-99-00032, GNRO-99-32, NUDOCS 9905040247 | |
| Download: ML20206D817 (5) | |
Text
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Enttrgy rttions, Inc.
Port Gbson. MS 39150 Tel 601437-6470
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W.K.Hughey Drector Nue: ear Safety & Fh9datory April 29, 1999 U.S. Nuclear Regulatory Commission Mail Station P1-37 Washington, D.C. 20555 Attention:
Document Control Desk
Subject:
Grand Gulf Nuclear Station Unit 1 Docket No. 50-416 License No. NPF-29 Plant improvement Considerations identified in the GGNS IPE GNRO-99/00032 Gentlemen:
A letter GNRI-96/00067 from J. N. Donohew, Senior Project Manager, NRR to C. R.
Hutchinson, Vice President, Operations GGNS dated March 7,1996 listed two Plant j
Improvements for implementation and four Plant Improvements for Consideration identified by the GGNS IPE. That letter requested GGNS to inform the staff of the results of these considerations and what has been implemented at the plant when the identified considerations have been completed. The requested information can be found in the
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attachment to this letter.
J We found the effort to be worthwhile and believe that the procedural changes, plant modification and additional training have reduced the probability of core damage or
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minimized the extent of radiological release in the unlikely event that a severe accident occurred. Should you have any questions or comments o' this submittal, please feel free to contact Wayne Russell at (601) 437-2717.
Yours truly, D
Ko i
fOw WKH/ WAR attachment:
IPE Plant improvement Information cc:
(See Next Page) 9905040247 990429 PDR ADOCK 05000416' P
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GNkO-99/00032 Page 2 of 2 cc:
Ms. J. L. Dixon-Herrity, GGNS Senicr Resident (w/a)
Mr. L. J. Smith (Wise Carter) (w/a)
Mr. N. S. Reynolds (w/a)
Mr. H. L. Thomas (w/o)
Mr. E. W. Merschoff (w/a)
Regional Administrator U.S. Nuclear Regulatory Commission Region IV 611 Ryan Plaza Drive, Suite 400 Arlington, TX 76011 Mr. S. P. Seherak, NRR/DLPM/PD IV-1 (w/2)
U.S. Nuclear Regulatory Commission One White Flint North, Mail Stop 13D18 11555 Rockville Pike Rockviile, MD 20852-2378
.t GN'RO-99/00032 Attachment IPE Plant Improvement Information Plant Improvements for Implementation:
1.
IPE Insight Section 6.2.1:
During an SBO event, the Loss of Offsite Power Off-Normal Event Procedure (ONEP) requires the Div 3 diesel generator to be '
cross-tied to Div 1 or Div 2 if the HPCS pump is unavailable. The required circuit
= breaker alignment is not possible if a HPCS initiation signal is present. The ONEP does not allow bypassing the Level 2 signal.
Results:
The Loss of Offsite Power ONEP (05-1-02-1-4) has been revised to include bypassing of the Level 2 initiation signal.
2.
IPE insight Section 6.2.3:
The bypassing of the RCIC turbine trip due to main steam tunnel high temperature is only proceduralized for SBO sequences. For non loss of offsite power sequences, with a failure to recover a secondary containment isolation, Plant Service Water (PSW) is lost and a RCIC isolation may 4
occur due to a high main steam tunnel temperature signal.
Results:
Engineering analysis (XC-Q1E51-98001) indicates that the RCIC steam tunnel high temperature trip would not occur within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> of loss of steam tunnel l
cooling. This will be the basis for a PRA model change in the future. In addition, the revised EOPs and SAPS implemented to nddress Severe Accident Management at 1
Grand Gulf, provide directions for defeating isolation interlocks when RCIC is called for, if necessary.
Plant improvements for Consideration:
1.
IPE Insight Section 6.2.2:
The secondary containment isolation valves close on loss of a Division 1 or 2, AC or DC bus without the capacity of bypassing the isolation signals and re-opening the valves.
Results:
The secondary containment valves in question fait closed on loss of
- either AC solenoid power or loss of DC logic power. Engineering analysis has been unable to provide sufficient justification to support the removal or modification of the loss of AC solenoid power fail closed design feature. Because the valves in j
question are currently designed for manual overriding of the isolation, a design i
modification that removed the automatic close logic, to address the loss of DC logic j
power portion of the insight, was developed. Plant staff review determined that the modification is not cost effective from a perceived risk improvement perspective. No further action is expected on this insight.
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i GN'RO-99/00032 Attachment 2.
IPE Insight Section 6.2.4:
A dependency between Div 1 and Div 3 SSW, through the SSW pump house cooling system, was noted. A separate SSW pump house contains SSW-B pump and has one train of ventilation. Upon failure of ventilation in either SSW pump house, the pump house will heat up such that SSW pump failures could occur in approximately 2.5 to 3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br />. Complete failure of SSW pump house
. ventilation could fail all of the SSW trains and, in a LOSP event, also fail all three onsite emergency diesel generators. The existing control room indication for the SSW pump house ventilation system would not adequately warn operators of the conditions that could lead to SSW pump failures.
- Results:
A modification was made in 1998 that added high SSW pump house temperature alarms to the control room. Alarm Response Instructions 04-1-02-1H13-P870-1 A and -7A have been revised to address these alarms.
I 3.
IPE Insight Section 6.2.5:
The low pressure ECCS pump dependency on SSW
-is included in the GGNS IPE model. The LPCS dependency is through pump room cooling. The failure of this cooler or the SSW supply to the cooler would be expected to result in a LPCS pump failure after approximately 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />. The RHR pumps are dependent on SSW for pump seal cooling. A loss of SSW to the seal coolers could be expected to result in pump seal failure shortly after the suppression pool reaches saturation conditions. Analysis indicates that with loss of all l
containment heat removal the pool will become saturated in abcut 6 to 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br />.
' Under these conditions, the operator may simply alternate operation of the pumps to 1
significantly extend the time available for recovery actions.
Results:
This insight has been addressed by operator training through lesson l
plan OP-LOR-lE-LP-022-00.
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GN'RO-99/00032 Attachment 4.
IPE Insight Section 6.2.6:
A major contributor to the scurce term released to the environment, as identified by the Level 2 results, is the "MSIV Venting" event. This venting is procedurally required by the Containment Flooding portion of the Emergency Operating Procedures (EOPs). If this procedure step was removed or suitably revised, the Level 2 results indicate that the source term release could be reduced.
Results:
As indicated in GNRO-92/00157 dated December 23,1992, Grand Gulf intended to actively pursue this issue through the BWR Owners Group generic Severe Accident Management effort. Those efforts resulted in revisions to both the generic and plant specific Containment Flooding guidance. The Containment Flooding guidance has been relocated to the Severe Accident Procedures (SAPS).
The SAPS establish minimum thresholds for consideration of RPV venting through the MSIVs based on existing plant conditions. Guidance to vent is only provided if venting is expected to mitigate the situation thereby postponing any deliberate release permitting further decay and plateout of fission products.
The SAPS are entered when adequate core cooling cannot not be assured and are implemented through the ERO. The ERO is expected to carefully consider the effects of venting for current and forecasted plant conditions and develop an action plan to implement the SAPS venting guidance that will minimize any impact on public hesth and safety. The Emergency Director must concur with the action plan before any actual venting its performed.
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