ML20199F405
| ML20199F405 | |
| Person / Time | |
|---|---|
| Site: | River Bend  |
| Issue date: | 11/18/1997 |
| From: | Wigginton D NRC (Affiliation Not Assigned) |
| To: | Mcgaha J ENTERGY OPERATIONS, INC. |
| References | |
| TAC-M83667, NUDOCS 9711240202 | |
| Download: ML20199F405 (6) | |
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t November 18, 1997 t
Mr. John R. McGaha, Jr.
Vice President - Operations Entergy Operations, Inc.
River Bend Station P. O. Box 220 St. Francisv111e, LA 70775 SUNECT: RIVER BEND STATION, UNIT 1 - REQUEST FOR ADDITIONAL INFORMATION ON RIVER BEND INDIVIDUAL PLANT EXAMINATION OF EXTERNAL EVENTS (IPEEE)
SUBMITTAL (TAC NO. M83667)
Dear Sir,
McGaha:
By letter dated June 30, 1995, Entergy Operations, Inc. submitted the IPEEE for iho River Bend Station (RBS).
Based on our ongoing review of the submittai, we have developed the enclosed request for additional information (2A1). The RAI is related to the fire and the high wind, flood, and other external events (HFO) areas of the IPEEE submittal.
The RAI on fire was developed by our contractor Sahdia National Laboratories (SNL):
and the RAI in the H10 area was daveloped by our staff. There is no RAI in the seismic area. The questions were reviewed by the " Senior Review Board" which is comprised of NRC staff and SNL consultants wi' S probabilistic risk assessment expertise in external events.
We request that Entergy Operations, Inc. provide the response by February 15, 1998.
If you have any questions on this matter, please let us know.
Sincerely.
Orig, signed by David L. Wigginton, Senit.r Project Manager Project Directorate IV-1 Division of Reactor Projects III/lV Office of Nuclear Reactor Regulation Docket No. 50-458
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Enclosure:
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November 18, 1997 Mr. John R. McGaha, Jr.
Vice President - Operations Entergy Operations, Inc.
River Bend Station P. O. Box 220 St. Francisv111e, LA 70775
SUBJECT:
RIVER BEND STATION, UNIT I - REQUEST FOR ADDITIONAL INFORMATION ON RIVER BEND INDIVIDUAL PLANT EXAMINATION OF EXTERNAL EVENTS (IPEEE)
SUBMITTAL (TAC NO. M83667)
Dear Mr. McGaha:
By letter dated June 30, 1995 Entergy Operations, Inc. submitted the IPEEE fortheRiverBendStation(RBS).
Based on our ongoing review of the submittal, we have developed the enclosed request for additional information (RAI). The RAI is related to the fire and the high wind, flood, and other external events (HFO) areas of the IPEEE submittal. The RAI on fire was developed by our contractor Sandia National Laboratories (SNL):
and the RAI in the HF0 area was developed by our staff.
There is no RAI in the seismic area. The questions were reviewed by the ' Senior Review Board" which is comprised of NRC staff and SNL consultants with probabilistic rLk assessment expertise in external events.
We request that Entergy Operations, Inc. provide the response by February 15, 1998.
If you have any questions on this matter, please let us know.
Sincerely, s
I l
David L. Wigginton, Senior Project Manager Project Directorate IV-1 Division of Reactor Projects III/IV Office of Nuclear Reactor Regulation Docket No. 50-453 L
l
Enclosure:
As stated cc w/ enc 1:
See next page l
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Mr. John R. McGaha Entergy Operations Inc.
Fiver hnd Station CC:
Winston & Strawn Executive Vice President and 1400 L Street. N.W.
Chief Operating Officer t.'ashington, DC 20005-3502 Entergy Operations, Inc.
P. O. Box 31995 Manager - Licensing Jackson, MS 39786 Entergy Operations, Inc.
River Bend Station General Manager - Plant Operations P. 0.'Dox 220 Entergy Operations, Inc.
St. Francisville, LA 70775 River Bend Station P. O. Box 220 Joint Ownership Manager St. Francisville LA-70775 Cajun Electric Power Cooperative P. O. Box 15540 Director - Nuclear Safety Baton Rouge, LA 70895 Entergy Operations, Inc.
River Bend Station Senior Resident inspector P. O. Box 220 P. O. Box 1050 St. Francisville, LA 70775 St. Francisville, LA 70775 Vice President - Operations Support President of West Feliciana Entergy Operations, Inc.
Police Jury P. O. Box 31995 P. O. Box 1921 Jackson, MS 39286-1995 St. Francisville, LA 70775 Attorney General Regional Administrator, Region IV Etate of Louisiana U.S. Nuclear Regulatory Comission P, O. Box 94095 611 Ryan Plaza Drive, Suite 1000 Baton Rouge, LA 70804 9095 Arlington, TX 76011 Wise, Carter. Child & Caraway Ms. H. Anne Plettinger P. O. Box 651 3456 Villa Rose Drive Jackson, MS 39205 Baton Rouge, LA 70806 Administrator Louisiana Radiation Protection Division P. O. Box 82135 Baton Rouge, LA 70884-2135
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Reguset for Additional intermation (RAl) on River Bond individual Plant Examination of External Events (IPEEE)
F Fire 1.
In the EPRI Fire PRA implementation Guide, test results for the control cabinet heat release rate have been misinterpreted and have been inappropriately extrapolated, i
Cabinet heat release rates as low as 65 Blu/sec are used in the Guide, in contrast, experimental work has developed heat release rates ranging from 23 to 1171 Stu/sec.
i Considering the range of heat release rates that could be applicable to different control-cabinet fitos, and to ensure that cabinet fire areas are not prematurely screened out of the analysis, a host release rate in the mid-range of the currently available experimental data (e.g., 550 Btu /sec) should be used for the analysis.
Discuss the host release rates used in your assessment of control cabinet fires. Please provide a discussion of changes in the IPEEE fire assessment results if it is assumed j
- that the heat release from a cabinet fire is increased to $50 Btu /s.
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s 2.
It is important that the human error probabilities (HEPs) used in the screening phase of the analysis properly reflect the potential effects of fire (e.g., oroke, heat, loss of lighting, and poor communication), even if these effects do not directly cause equipment damage in the scenarios being analyzed, if these effects are not treated, the HEPs may be optimistic and result in the improper screening of scenarios. Note that HEPs which are realistic with respect to en intomal events analysis could be optimistic with respect to a fire risk analysis.
Please identify: a) the scenarios screened out from further analysis whose quantification involved one or more HEPs, b) the HEPs (descriptions and numerical values) for each of these scenarios, and c) how the effects (e g., smoke, heat, loss of lighting, and poor i.
communication) of the postulated fires on HEPs were treated.
i 3.
In general, the fire risk ascociated with a given compartment is composed of contributions from fixed and transient ignition sources. Neglect of either contribution can lead to an underestimate of the compartment's risk and, in some cases, to improper l
screening of fire scenarios. The EPRI Fire PRA Implementation Guide allows the screening of transient ignition sources in compartments where all fixed ignition sources have been screened out. Based on this approach, a cable spreading room or a e,able shaft that does not contain any items other than IEEE 383 qualifed control and instrumentation cables, and access to the compartment is strictly controlled, can be screened out. If such compartments contain the cables for all redundant trains of important plant safety systems, a major vulnerability may be overlooked, without L
sufficient analysis of potential accident sequences and needed recovery actions.
l' The description of Screen 5 modifications to fire frequencies (Section 4.6.3.2, second paragraph) is not clear. Please explain how the scenario specific fire frequency for fixed combustibles was determined and provide an example, in compartments where all fixed ignitions sources have been screened out, has the possibility of transient combustible EleCLOSURE
fires been considered? For each compartment where transient fires have not been considered, please provide th6 justification for this conclusion and provide a discussion on compartment inventory in terms of system trains and associated components (i.e.,
cables and other equipment). Please explain whether or not the conditional core damags probabilities, given damage to all cables and equipment in these compartments, are significant (i.e., cables from redundant trains are present). If the conditional core damage probability for a compartment is considered significant, please provide justification for assigning a very low likelihood of occurrence to transient fuel fires for the compartment.
4.
Qualitative screening steps in approved methodologies, such as fire induced vulnerability evaluation (FIVE), typically include the potential to cause a shutdown demand before screening the area. The submittal notes that the potential for fire.
Induced loss of offsite power (LOSP) was considered, but that only *most likely areas where a LOSP could occur" were not screened. The turbine building was qualitatively screened based on the absence of safe shutdown analysis (SSA) equipment alone.
Please reexamine all qualitatively screened (Screen 1) areas for shutdown demand initiators, including LOSP. Include a discussion if there are any changes in the Screen 1 results and the reasons why LOSP is not a concern in the turbine building.
5.
From the submittal it is not clear whether the licensee has considered hot shorts as a failure mode for control or instrumentation cables. In particular, hot short considerations should include the treatment of conductor to-conductor shorts within a given cable. Hot shorts in control cables can simulate the closing of control switches leading, for example, to the repositioning of valves, spurious operation of motors and pumps, or the shutdown of operating equipment.
The potential for loss of control power for certain control circuits as a result of hot shorts before transferring control from the main control room (MCR) to remote shutdown locations needs to be assessed. The spurious actuation of one or more safety related to safe shutdown related components as a result of hot shorts leading to component damage, LOCA, or interfacing systems LOCA, prior to taking control from the remote shutdown panel, nesds to be assessed. This assessment also needs to include the spurious starting and running of pumps as well as the spurious repositioning of valves.
Provide an evaluation of whether loss of control power due to hot shorts could occur prior to transferring control to the remote shutdown location and identify the risk contribution of these types of failures (if these failures are screened, please provide the basis for ths screening). Finally, provide an evaluation of whether spurious actuation of components as a result of hot shorts could lead to component damage, a LOCA, or an interfacing systems LOCA prior to taking control from the remote shutdown panel (considering both spurious starting and running of pumps as well as the spurious repositioning of valves).
6.
The probability of manual suppression before damage is a function of both the probability of fire damage as a function of time, and the probability of successfully 2
completing fire suppression activities which is also a function of time. For example, the FIVE methodology suggests that if a critical combustible loading la present, then the j
time to damage, t-crit, is calculated. The probability of non suppression depends on the relationship between t-crit and the demonstrated fire brigade response and extinguishment times. In contrast, Section 4.6.4 appears to simply have assigned a numerical value for the probability of failure of manual suppression of several fires.
l Please provide sn explanation of the analysis performed to develop the manual non suppression probabilities, and demonstrate that the values used (0.15,0.65) are a realistic' estimate. Include the time from ign} tion to suppresalon corresponding to the values of the failure to suppress.
7.
The submittal notes that the SSA fire area definitions were used in the IPEEE The boundaries defining fire areas are not discussed in the submittal. The plant maps supplied seem to indicate a variety of boundaries between fire areas. Please discuss the requirements on fire area boundaries, as used in the IPEEE Are open hatches, doorways, and other penetrations explicitly modeled, and if so, how? How was failure of rated barriers modeled with COMPBRN in your analysis?
9 High Wind, Flood and Other External Events (HFO) 1.
With respect to LER g2 005, the IPEEE submittal stated that *lt is possible that the wind gust that damaged the Turbine Building was over 75 mph since the building is designed to withstand a wind gust of 100 mph measured at 30 feet above the ground.* Since this event caused plant damage and a reactor trip, please show that the core damage frequency associated with high wind at River Bend is less than 10 4/ reactor year.
b Selsmic There is no RAI in the selsmic area.
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