ML20199B235

Safety Evaluation Supporting Amend 90 to License NPF-58

ML20199B235
Person / Time
Site:	Perry
Issue date:	11/04/1997
From:	NRC (Affiliation Not Assigned)
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ML20199B178	List: ML20199B235
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NUDOCS 9711180251
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y* 4 UNITE 3 STATES } NUCLEAR REGULATORY COMMISSION i WASHINGTON, D.c. 30MH001 s, *. * / SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATIOS I RELATED TO AMENDMENT NO. 90TO FACILITY OPERATING LICENSE NO. NPF 58 CLEVELAND ELECTRIC ILLUMINATING COMPANY. ET AL PERRY NUCLEAR POWER PLANT. UNIT 1 DOCKET NO. 50-440

1.0 INTRODUCTION

By letter dated August 14,1997, Centerior Energy Power Generator Group (the licensee), submitted a request for changes to the Perry Nuclear Power Plant (PNPP), Unit 1, licensing basis. The requested change allows for the application of the TORMIS methodology for tornado missile risk analysis of specific plant features that are currently unprotected. Specifically, the licensee proposes to amend its Updated Safety Analysis Report (USAR) for the use of the TORMIS methodology when evaluating the need for positive missile protection of unprotected components or portions of systems. The existing USAR requires tomado missile protection for all equipment required to operate after a tornado in accordance with Regulatory Guide (RG) 1.117, Additional clarifying information was submitted by letters dated September 26 and October 1, 1997. This additionalinformation did not significantly change the f_ederal Reaister notice dated September 16,1997 (62 FR 48674). Standard Review Plan (SRP) Section 3.5.1.4 includes procedures for users to estimate the probability per year of damage to the total of allimportant structures, systems, and components due to a specific design basis natural phenomens capable of generating missiles, if the probability is greater than the acceptable probability stated in RG 1.117, then specific design provisions must be provided to reduce the estimate of damage probability to an allowable level. RG 1.117 states that the likelihood of a creditable tornado strike varies 4 from about 10 per year to values several orders of magnitude higher. SRP Section 2.2.3 4 suppcrts this probability and identifies an acceptance criteria of 10 for the expected rate of occurrence of potential exposures in excess of 10 CFR Part 100 guidelines per year when combined with reasonable qualitative arguments that show that the realistic probability is lower. !n the Safety Evaluation dated October 26,1983, regarding the TORMIS methodology proposed in Electric Power Research Institute (EPRI) Report NP-2005, the staff concluded that the methodology is well conceived, well developed, versatile, and utilizes state-of the art probabilistic Monte Carlo techniques. At the same time, the staff concluded that the methodology had limitations for its use and that applicants and licensees using this methodology must consider five plant specific points and provide appropriate information 9711190251 971104 i PDR ADOCK 05000440 P PDR

2-regarding its use. This evaluation addresses the licensee's response conceming the applicability of the TORMIS code methodology and the licensee's use of the results. In addition to the plant specific information, limitations for the application of the TORMIS methodology were prescribed in the NRC Safety Evaluation. These limitations state ti,at the use of the EPRI PRAs or any tomado missile probabilistic study be limited to the evaluation of specific plant features where additional costly tomado missile protective barriers or attemative systems are under consideration, and that the user demonstrato that the probability of damage to unprotected essential safety related features is sufficiently small The five plant specific points to be considered by applicants and licensees using the EPRI methodology are: 1) Data on tornado characteristics should be employed for both broad regions and small areas around the site. The most conservative values should be used in the risk analysis or justification provided for those values selected. 2) The EPRI study proposes a modified tomado classification, F' scale, for whicn the velocity ranges are lower by as much as 25 percent than the velocity ranges originally proposed in the Fujita, F scale. Insufficient documentation was provided in the studies in support of the reduced F' scale. The F-scale tomado classification should, therefore, be useo in order to obtain conservative results. 3) Reductions in tomado wind speed near the ground due to surface friction effects are not sufficiently documented in the EPRI study. Such reductions were not consistently accounted for when estimating tomado wind speeds at 33 feet above grade on the basis of observed damage at lower elevations. Therefore. users should calculate the effects of assuming velocity profiles with ratios V (speed at ground level)/ Vu (speed at 33 feet elevation) higher than that in the EPRI study. Discussion of the sensitivity of the results to changes in the modeling of the tomado wind speed profile near the ground should be provided. 4) The assumptions concoming the locations and numbers of potential missiles presented at a specific site are not well established in the EPRI studies. However, the EPRI methodology allows site specific information on tomado missile availability to be incorporated in the risk calculation. Therefore, users should provide sufficient information to justify the assumed missile density based on site specific missile courses and dominant tomado paths of travel. 5) Once the EPRI methodology has been chosen, jut,tification should be provided for any deviations from the calculational approach.

3 i Based on the results of the TORMIS analysis and the revised licensing basis, the licensee proposes not to provide tomado missile protection for the unprotected components or poitions of the systems required to operate after a tomado. l 2.0 EVA1.UATION The limitation that the TORMIS methodology be used for specific plant features where additional costly tomado missile protective barriers or attemative systems are under consideration was addressed by the licensee in its September 26,1997, letter. The licensee identified that the questionable systems under review are the emergency service water system, the Division 1 motor control center switchgear room, the diesel generators, the control room, Division 1 and 2 cable chases, and the spent fuel pool. The licensee states that these systems may have short portions of piping located outside of the Seismic Category I building, or are located near a doorway or a pipe penetration. To be in compliance with its existing licensing basis, additional tomado missile protection would need to be added. The licensee committed to include the specific components or portions of systems in its USAR. Two items associated with the condensate storage tank (CST), the level instrumentation, and a suction line were identified in a recent NRC inspection as not being appropriately missile-protected. The licensee did not propose to include these items in its total plant configuration probability. Rather, the licensee will use administrative controls that require the suction for the reactor core isolation cooling and high pressure core spray systems be transferred from the CST to the suppression pool when a tomado waming is initiated in a letter dated. October 1,1997, the licensee committed to revise its procedure for tomado or high winds to reflect these actions upon initiation of a tomado waming. Also, the USAR, including Table 3.5-7, will be revised for the piping and instrumentation portion that is.1ot protected for iomado missiles. To meet the criteria that the user demonstrate that the probability of damage to unprotected essential safety related fea.ures is sufficiently small, and to meet the acceptance criteria of 4 SRP Section 2.2.3 that identifies an acceptance criteria of 10 for the expected rate of occurrence of potential exposures in excess of 10 CFR Part 100 guidel.~,es per year when combined with reasonable qualitative arguments that show that the real stic probability is lower, the licensee provided qualitative arguments that the probability w is conservative. These arguments included, in part, that a failure was assumed when co nponents are simply struck by a tomado missile and any damage resulted in release values in excess of 10 CFR 4 Part 100 guidelines. The staff finds the acceptance criteria of 10, when combined with the licensee's qualitative arguments, to be acceptable. The licensee will ensure that both the total probability of tomado missiles striking each target and the total probability of to,nado missiles striking all of the targets for the entire plant will 4 remain below 10, in its September 26.1997, letter, the licensee states that the total plant

4 probability value is calculated by determining specific system or component probabilities using TORMIS and then summing all of the probabilities together. This summation must be 4 below the acceptance criteria of 10. The licensee's proposed change to the USAR includes the statement that the plant configuration equali, or exceeds PNPP's 10* seceptance criteria. The staff finds the licensee's use of the TORMIS results to be acceptable. The licensee addressed the five plant specific points for the application of TORMIS in ito submittal. Point 1 The NRC Safety Evaluation for TORMIS specifies that broad and local regions near the site be evaluated and to use the most conservative value, in the original submittal, the licensee states that it uses the most consevative value of two possible values. These values were the plant's USAR tomado probability value, using local data, and a TORMIS generated value, 4 using broad regional data. The USAR value is 3.11x10 per year. The TORMIS value was d determined to be 4.25x10 per year. In its September 26,1997, letter, the licensee includes d another value,5.8x10 per year, from WASH.3i,, ' Technical Basis for Interim Regional d Tomado Criteria.' The licensee will use the value of 5.8x10 for its analysis. The staff finds this to be conssrvative and, therefore, acceptable. Point 2 The licensee uses the F scale tomado classification for the FO through FS intensities, and a wind speed range of 313 to 360 mph for the F6 intensity. The staff finds this to be acceptable. Point 3 To address the reductions in tomado wind meed near the ground due to surface friction effects that are not sufficiently docum v w 1 the EPRI study, the licensee states that for PNPP potential missiles are injected into the tomado windfield using a height range where the lower end of the height range corresponds to rotational wind speeds greater than or equal to 246 mph. This provides V/Vu ratio = 246/300 = 0.82. The ratio of 0.82 was previously approved for another plant in the same tomado intensity region. The staff finds this to be acceptable, Point 4 The licensee performed a site walkdown to identify the type and number cf missiles for the plant. The walkdown included the contents and construction of warehouses, office buildings, sheds, trailers, parkin0 ots, and switchyards. Additionally, conservaiisms such as assuming l a full parking lot and adding 10 percent to account for increased missiles during outage periods were included. The ficansee will use approximably 74,000 missiles in its TORMIS

J analyds. This is a higher missile density co",ipared to some other plants (25,000 - 69,000) that use the TORMIS methodology, however, many plants have a more limited application of the TORMIS methodology. The staff considers this missile density to be acceptable. Point 5 The licensee states that no deviations occur from EPRI NP-2005, except as noted in Points 1 through 4 above. The staff finds this to be acceptable. The staff concludes that the licensee's use of the methodology and its results are appropriate. Additionally, the staff concludes that the licensee includes qualitative conservatism such that the acceptance criteria of 10 for all tomado missiles striking all 4 unprotected systems or components required to operate following a tomado is appropriate. Based on the above, the staff concludes that the use of TORMIS to analyze tomado m!ssiles for limited portions of the plant that are unprotected and are identified by the licensee in its USAR meets the acceptance criteria of SRP Sections 3.5.1.4 and 2.3.3 for tomado missiles and sclisfactority addresses the items in the NRC Safety Evaluation related to the TORMIS methodology. The staff further concludes that the proposed changes to the licensing basis meet the requirements of General Design Criteria 2 and 4, with respect to protection against tomado-generated missiles for specific plant equipment. As described in the licensee's letter dated August 14,1997, following NRC approval, the licensee will update the USAR to change the design basis as describsd in the USAR by adding a description of the methodology utilized for determining the systems and components that are considered to require protection from tomado missiles, as authorized by this amendment and in compliance with 10 CFR 50.71(e). 3.0 S_ TATE CONSULTATION In accordranca with the Commission's regulations, the Ohio State official was notified of the proposed issuance of the amendment. While the State official had no formal comments, clarification was requested in two specific areas. The first area focused on the licensee's long-term use of the TORMIS methodology. The licensee's submittal was prompted by recent NRC inspection findings that identified safety-related components that do not have tomado missile protection as described in the USAR. While the methodology will be immediately applied to the identified components, the licensee is authorized to incorporate this methodology with future applications provided the summation 4 of the probabilities remain below the acceptance criteria of 10, i The second area focused on the following statement made on page 5 of 7 of Attachment 1 to l the licensee's letter of August 14,1997: There are no missiles that can directly impact on irradiated fuel, even on the spent fuel stored in the Fuel Handling Area of the intermediate Building. Any missiles i y y

6-postulated to enter this area either miss the pools entirely, are stopped by intomal walls, or stnke the for side of the pool above the level of the fuel. The State omcial asked whether the NRC had verified the above statement. The State was informed that an NRC inspector had closely examined this issue and concurred with the licensee that any missile entering the Intermediate Suilding via the metal roll-up doors would not directly impact irradiated fuel. i

4.0 ENVIRONMENTAL CONSIDERATION

This amendment involves a change to a requirement with respect to the hetallation or use of i a facility component located within the restricted area as defined in 10 CFR Part 20. The staff has determined that the amendment involves no significant increase in the amounts, and no significant change in the types, of any emuent that may be released offsite and that there is no significant increase in individual or cumulative occupational radiation exposure. The Commission has previously issued a proposed finding that this amendment involves no i significant hazards consideration and there has been no public comment on such finding (62 l FR 48674) Accordinr',, iis amendment meets the eligibility criteria for categorical exclusion set forth in 10 CFR 51.24)(g). Pursuant to 10 CFR 51.22(b), no environmental impact statement or environmental assessment need be prepare:I in connection with the issuance of this amendment. i

5.0 CONCLUSION

The staff has concluded, based on the consider 61ons discussed above, that: (1) there is reasonable assurance that the health and safe'.y of the public will not be endangered by operation in the proposed manner, (2) such activities will be conducted in compliance with the Commission's regulations, and (3) the issuance of this amendment will not be inimical to the common defense and security nr to the health and safety of the public. l Principal Contributor: Diane Jackson Date: November 4, 1997 rq y,---v4y. .-e-w,+- e e%r=m.y9+, yru w-------.# w. y -..we,,,mwei,,.e,m-,,y ..w,,_,,, y,,--w.-~w e-+-c-r.-. ...--w..w.-- ...w-- =<-- - +.. - *.}}