ML20141F705

Forwards Request for Addl Info Re 841231 & 851024 Repts Documenting Assessment of Risk from Tornadoes & cost-benefit Evaluation of Plant Upgrades.Questions Included Re Winds & tornado-related Risk Assessment & Underlying Assumptions

ML20141F705
Person / Time
Site:	Yankee Rowe
Issue date:	04/17/1986
From:	Clifford J Office of Nuclear Reactor Regulation
To:	Papanic G YANKEE ATOMIC ELECTRIC CO.
References
NUDOCS 8604230134
Download: ML20141F705 (5)

Text

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' APR 171986 Docket No.50-029 Mr. George Papanic, Jr.

Senior Project Engineer-Licensing Yankee Atomic Electric Company 1671 Worcester Road Framingham, Massachusetts 01701

SUBJECT:

REQUEST FOR ADDITIONAL INFORMATION - TORNADO WIND COST-BENEFIT EVALUATION Re: YANKEE NUCLEAR POWER STATION By letters dated December 31, 1984 and October 24, 1985, you submitted reports documenting your assessment of the risk from tornadoes and a cost-benefit evaluation of plant upgrades.

Preliminary questions relating to the structural capacity analysis were issued to you on March 14, 1986. The enclosure to this letter provides staff questions on the winds and tornado related risk assessment and some of its underlying assumptions, including some further questions on the structural analysis. These questions are based on our completed review of the wind and tornado issue, except for (1) the assumption of no tornado missiles, and (2) for~ resolution of issues relating to either the cost-benefit study or structures and systems that may result.from your responses to these questions.

The staff suggests a meeting be held to discuss resolution of these issues before you provide a formal response. We further suggest that such a meeting take place no later than the May 19, 1986 meeting being held on SEP seismic issues.

This information request affects fewer than ten respondents and, therefore, an OMB clearance is not required in accordance with P. L.96-511.

James W. Clifford, Project Manager Project Directorate #1 Division of PWR Licensing-A cc: See next page 8604230134 e60417 PDR ADOCK 05000029

• SEE PREVIOUS CONCURRENCE Office: ISAP:DPL-B ISAP:DPL-B ISAP:DPL-B PM/P y PD/P .,

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Mr. George Papanic, Jr.

Yankee Atomic Electric Company Yankee Nuclear Power Station cc:

Mr. James E. Tribble, President Yankee Atomic Electric Company 1671 Worcester Road Framingham, Massachusetts 01701 Thomas Dignan, Esquire Ropes and Gray 225 Franklin Street Boston, Massachusetts 02110

. Mr. N. N. St. Laurent Plant Superintendent Yankee Atomic Electric Company Star Route Rowe, Mass,achusetts 01367 Chairman Board of Selectmen Town of Rowe Rowe, Massachusetts 01367 Resident Inspector Yankee Nuclear Power Station c/o U.S. NRC Post Office Box 28 Monroe Bridge, Massachusetts 01350 Regional Administrator, Region I U.S. Nuclear Regulatory Commission 631 Park Avenue King of Prussia, Pennsylvania 19406 Robert M. Hallisey, Director Radiation Control Program Massachusetts Department of Public Health 150 Tremont Street, 7th Floor Boston, Massachusetts 02111

Enclosure QUESTIONS ON YANKEE TORNADO HAZARD STUDY

1. The random failure rate in the risk analysis for the safe shutdown system, 0.01 for a 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> period, was based on the preliminary design information available at the time the study was performed. Yankee Atomic Electric Company (YAEC) is requested to reevaluate the failure rate for the safe shutdown system based on the as-built design. The human factor evaluation should explicitly address the time requirements on remote manual actions and the associated stress levels.

2. The report states that top event LG (and 0F), that i:, failure of steam removal via the atomosphere dump valves or safety vaives, is negligible.

. YAEC is requested to clarify the basis for this assumption crnsidering the range of possible windspeeds.

3. The development of top event LE, failure of the recirculation mode, in section 6.3 does not include the possibility of the operator failing to initiate the realignment process in time. Further justification for this logic development is needed.

4. Section 6.5 states that the turbine building west staircase was not modeled explicitly because failure of this area does not directly impact any system credited in the analysis. Section 3.4.2 indicates that cabling for operation of vital equipment, such as the non-return valves and atmospheric steam dump valves, passes through this area. Please clarify this situation.

5. It does not appear that the consequences of failure of the " upper level primary auxiliary building south wall" was explicitly addressed in the risk analysis. Please provide the basis for exclusion or an assessment of its wind capacity and consequences of failure.

6. The failure of the " lower level primary auxiliary west wall" was excluded from the analysis because it is bordered by an adjacent room, the hydrogen storage room. Please provide an assessment of the potential for a hydrogen explosion from wind-induced damage to this area.

7. Section 6.5 states that failure of the south and/or west walls of the safety injection building could cause damage to the fire water tank heater, a potential flooding hazard. Please provide a discussion of the effects of failure of this tank on equipment in the area credited in the risk analysis and not already assumed to be failed by failure of the south and west walls.

i

8. During the plant site visit on February 4, 1986, YAEC verbally agreed to upgrade the wind capacity of the upper level primary auxiliary building west wall. Please provide the details of the modification and what wind capacity will be afforded by the proposed upgrades.

9. The term ULPAB is used to represent location failure of the blowdown header either in the upper level primary auxiliary building or non-radioactive pipe tunnel. From an examination of the logic expression used to represent failure to supply feedwater assuming no off-site power, ULPAB will, by itself, lead to the failure of safety injection and safe shutdown system supply to the feedwater lines, but that an additional failure (e.g. LLPAB) is needed before electric emergency feedwater and charging pump supply to the feedwater lines would be lost.

Since electric emergency feed and charging feed paths are also located I in the upper level primary auxiliary building, an explanation is needed I for the logic expression used in the model.

10. Wind / tornado loads for interior walls and systems have not been assessed I in general. However, in selected areas, a more detailed evaluation of l the possible loading and wall capacity, is needed, given that the exterior l wall has failed. For instance, the wind capacity for the diesel generator I building west wall is significantly lower than the wind capacity for the diesel generator building north wall. This disparity in wind capacities was not found to be significant in the risk study because the failure of the west wall was assumed to damage only one diesel generator while the failure of the north wall results in the loss of all three emergency diesel generators. The staff will need further assurance that the interior diesel generator building walls will not fail given that the l west wall has experienced failure.

Furthernore, the licensee is requested to address the above staff concern about the interior walls near by the following walls:

Auxiliary Boiler Room South Wall T1J2 Lower Level Primary Auxiliary Building Walls PIE 1 and PIE 2 Upper Level Primary Auxiliary Building Walls P2F1 and P2F2 Safety Injection Building south walls D1Z1 and D1Z2 Safety Injection Building West Walls D11051 and D11052 Safety Injection Building North Wall D1XI Diesel Generator Building West Wall D11053 Diesel Generator Building North Walls D1V1, DIV2, and D1V3 These walls were chosen because their failure under wind loads may have a significant impact on the core melt frequency.

11. Please provide an assessment of the wind capacity of the main steam /

main feedwater lines and their support structures.

12. The failure under wind loads for some components and/or structures may have a significant impact on the core melt frequency. Therefore, the licensee is requested to provide more detailed information concerning the analytical technique and criteria to confirm the adequacy of the wind capacities of the following items listed in Table 5-2 of the licensee's September 1984 report (October 24, 1985 submittal):

a) Tanks - TK-1, TK-28, and TK-39 b) Non-radioactive pipe tunnel c) Safe Shutdown System Pump House d) Cable Spreading Room w/fix.

APR 17 1986 DISTRIBUTION.m.

7., Docket Files

.POR" ~ ~

Local PDR G. Lear J. Clifford OELD E. Jordan P. Chen B. Grimes J. Partlow NSIC F. Miraglia E. McKenna P. Anderson C. Grimes ACRS (10)

PD#1 r/f PD#1 s/f 1