ML20033F304
| ML20033F304 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 03/02/1990 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20033F303 | List: |
| References | |
| NUDOCS 9003190344 | |
| Download: ML20033F304 (5) | |
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UNITED STATES
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NUCLE AR REGULATORY COMMISSION
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, ENCLOSURE 3 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION SUPPORTING AMENDMENT NO.131 TO FACILITY OPERATING LICENSE NO. DPR-77 AND AMENDMENT NO.118 TO FACILITY OPERATING LICENSE NO. DPR-79 TENNESSEE VALLEY AUTHORITY SEQUOYAH NUCLEAR PLANT, UNITS 1 AND 2 DOCKET NOS. 50-327 AND 50-328
1.0 INTRODUCTION
By letter from the Tennessee Valley Authority (the licensee), signed by M.J. Ray on January 12, 1990, the licensee requested a change to Section 3.6.5, Ica Condenser, of the Sequoyah, Units 1 and 2, Technical Specifications (TSs).
The purpose of the TS Change was to revise the surveillance requirement to extend the current 12-month ice weighing interval to 18 months, lower the mini-mum ice basket weight from 1,200 pounds to 1,155 pounds and extend the surveil-lance requirement for the ice condenser inlet doors from 12 months to 18 months.
Thelicenseehasalsorequestedthat(1)aone-timeextensioncontainedina footnote to SR 4.6.5.1.b and (2) certain text in SR 4.6.5.1.b. 4.6.5.3.1.b and 4.6.5.3.2.b regarding test milestones that were previously completed during the first two years of Sequoyah operation, be deleted for each unit because they are no longer applicable.
This is the licensee's TS Change Request 90-05 By letters dated November 28, 1988 and September 19, 1989, the staff modified SR 4.6.5.1.b.2 to allow a one-time extension of the ice weighing surveillance to the next refueling outage for Unit 2 (Amendment 80) and Unit 1 (Amend-ment 126), respectively. These are the one-time extensions for each unit discussed above.
This extension was based on the sublimination rate of the ice in the ice condensers for the units.
2.0 EVALUATION The operability of the ice beds in the ice condenser requires that the ice inventory be distributed evenly throughout the ice condense bays in contain-ment and contain sufficient heat removal capability to condenser the reactor system volume released during a loss-of-coolant accident (LOCA).
Sufficient pressure suppression capability from the ice in the ice condenser is necessary to limit the containment peak pressure transient during a LOCA. The ice inventory is contained in 1,944 ice baskets throughout the ice condenser.
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2 The ice condeaser is an insulated cold storage room in which ice is maintained in an array of vertical cylindrical columns.
The columns are formed by per-
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forated metal baskets with the space between columns forming the flow channels i
for steam and air.
The ice condenser is contained in the annulus formed by the containment vessel wall and the crane wall circumferential1y over a 300* arc.
1 The ice columns are composed of four baskets approximately 12 feet long, each filled with flake ice.
The baskets are assembled into the lattice frames to form a continuous column of ice 48 ft. high. The bottom wire mesh is designed to allow water to flow out of the basket.
Surveillance Requirement (SR) 4.6.5.1.b.2 currently requires that each basket contains at least 1,200 pounds of ice and that the average ice weight for each bay and each group-row combination is not to be less than 1,200 pounds per j
basket at a 95 percent level of confidence at the start of the surveillance interval.
Sequoyah's current 1,200 pound TS limit is based on a containment analysis that assumes an even distribution of 1.080 pound baskets throughout the ice condenser at the time of the LOCA. The margin of 120 pounds of ice allows for a 10% loss of ice through sublimation and a 1% margin for instrument error. The above limits ensure, at a 95 percent level of confidence, a minimum l
total ice weight of 2,333,100 pounds at the conclusion of ice weighing which is required by the Limiting Condition for Operation (LCO) 3.6.5.1.
The current containment analysis using the 1080 pound ice weight per basket yields a peak containment pressure of 11.09 pounds per square inch (psi) following a design basis LOCA.
The design pressure is 12.0 psi.
l New mass and energy releases were incorporated into the containment analysis which resulted in a net decrease in the current peak containment pressure even with a reduced TS ice weight.
This is Westinghouse report WCAP-10325-P-A.
The new containment mass and energy releases during a LOCA were approved by the staff in the Safety Evaluation Report contained in the NRC staff letter from i
Charles E. Rossi to William J. Johnson dated February 17, 1987.
The calculation of the containment response to the revised mass and energy release was done using the LOTIC 1 Code, which is the same code used in the original containment analysis for Sequoyah that is described in the Sequoyah Final Safety Analysis Report.
The LOTIC 1 Code is specified as a staff-approved code for ice condenser containments in Standard Review Plan 6.2.1.1.B, Ice Condenser Containments, of NUREG-0800 dated July, 1981.
The calculation with the revised mass and energy release resulted in a containment pressure of 10.9 psi for an ice weight per basket of 993 pounds.
Since the basket ice weight of 993 pounds was derived using an acceptable mass and energy model in the original containment analysis, we conclude that a basket ice weight of 993 pounds at the time of the LOCA is acceptable.
With the 16% allowance for ice loss due to sublimation (i.e.,15%) and instrument error (i.e.,1%), the acceptable ice basket weight at the time of weight measurement will be 1155 pounds.
This proposed weight of ice with the 16%
margin for en ice basket is acceptable.
SR 4.6.5.1.b.2 currently establishes the time interval between ice weighings at 12 months.
The SR is based on a 10% ice loss due to sublimation during the 12 month interval.
The licensee proposes to extend the ice weighing time interval from 12 months to 18 months, allowing a 15% ice loss due to
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3 sublimation and the 1% margin for instrument error. This 15% ice loss allowance is based on the 10% loss for 12 months and the conservative assumption that sublimation is a linear function for the 18 month interval.
The staff approved extensions to the ice weighing surveillance based on the sublimination rate data provided by the licensee in its letters dated September 21,1988 (Unit 2) and June 20, 1989 (Unit 1).
The extensions were 4.5 months for Unit 2 and 6.5 months for Unit 1, which are comparable to the six-month extension requested by the licensee.
Therefore, the sublimination rate at Sequoyah has been significantly less than 10% per 12 months.
This change is, therefore, acceptable.
SR 4.6.5.3.1.b currently requires that ice condenser inlet doors be tested once per year to verify that each door meets a minimum torque requirement of 675 inch-pounds (in-lb) and that the door is not impaired from opening by ice, J
frost or debris.
In addition, a test sample of at least 25% of the inlet doors must be verified to have a " door opening torque" of less than 195 in-lb and a
" door closing torque" of greater than 78 in-lb when the door is open 40 degrees.
The 25% sample must be selected so that all inlet doors are tested at least l
once during four test intervals. The " door opening torque" and the " door closing torque" are made up of two components: a nominal door torque and a frictional torque.
The frictional torque component for each door tested under the 25% sampling is required to be less than or equal to 40 in-lb.
The licensee's proposed change to extend the surveillance frequency for inlet doors to once every 18 months is based on historical inlet door test results and the licensee's proposed revision to eliminate the 25% sample to include all inlet doors for the opening / closing torque test. A review of past perfonnance of the inlet door test since the commencement of operation (i.e., 1979 for Unit 1 and 1981 for Unit 2) indicates that these doors consistently meet their criteria for opening / closing torque and the inspections for unimpaired door movement. The licensee has included a change to SRs 4.6.5.3.1.b.3 and 4.6.5.3 '
.4 to test all inlet doors (opening / closing torque) every 18 months.
This et provides an increased level of testing for the lower inlet doors since ar t requirement would only require that a 25% sample undergo testing
.ery. months.
Under this proposal, the lower inlet doors will be tested more than twice as often.
Based on the history of these surveillances and the increased ice door testing at the 18-month test interval, the staff concludes that extending the test interval from 12 to 18 months is acceptable.
Every door will now be tested at an 18-month period as opposed to a 48-month peri od.
The licensee has also proposed to delete certain parts of the SRs on the ice condenser which it considers no longer applicable.
The staff modified SR 4.6.5.1.b.2 to add a footnote to allow a one-time extension of the ice weighing surveillance to the next refueling outage for each unit. This will no longer be applicable with the approval of the 18-month interval for ice weighing.
The text in SRs 4.6.5.1.b 4.6.5.3.1.b. and 4.6.5.3.2.b refers to six-month intervals during the first two years following initial critical-ity and to three-month intervals during the first year after the initial ice bed loading.
Both of these intervals refer to schedule requirements which are no longer applicable to Sequoyah.
Therefore, these proposed changes are acceptable.
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Based on the above, the staff concludes that the licensee's TS Change i
Request 90-05 is acceptable.
3.0 ENVIRONMENTAL CONSIDERATION
These amendments involve a change to a requirement with recpect to the instal-lation or use of a facility component located within the restricted area as defined in 10 CFR Part 20 and changes to the surveillance requirements. The staff has determined that the amendments involve no significant increase in the amounts, and no significant change in the types, of any effluents that may be released offsite, and that there is no significant increase in individual or cumulative occupational radiation exposure.
The Comission has previously issued a proposed finding that these amendments involve no significant hazards consideration and there has been no public coment on such finding. Accord-ingly, the amendments meet the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9).
Pursuant to 10 CFR 51.22(b), no environmental impact statement nor environmental assessment need be prepared in connection with the issuance of these amendments.
4.0 CONCLUSION
The Comission made a proposed determination that the amendment involves no significant hazards consideration which was published in the Federal Register
-(55 FR 2457) on January 24, 1990, and consulted with the State of Tennessee. No public coments were received and the State of Tennessee did not have any coments.
The staff has concluded, based on the considerations discussed above, that:
(1) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, and (2) such activities will be conducted in compliance with the Comission's regulations, and the issuance of the amendments will not be inimical to the comon defense and security nor to the health and safety of the public.
5.0 REFERENCES
1.
Letter from M. J. Ray to V. S. Nuclear Regulatory Comission dated January 12, 1990, entitled, "Sequoyah Nuclear Plant - Technical Specifica-tion Change 90-05."
2.
Letter from Charles E. Rossi (NRC) to Westinghouse Electric Corporation, dated February 17, 1987, entitled, " Acceptance for Referencing of Licens-ing Topical Report WCAP 10325, ' Westinghouse LOCA Mass and Energy Release Model for Containment Design - March 1979 Version.'"
Principal Contributor:
P. Hearn Dated: March 2, 1990
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AMENDMENT NO.131 FOR SEQUOYAH UNIT NO. 1 - DOCKET NO. 50-327 and AMENDMENT NO.118 FOR SEQUOYAH UNIT NO. 2 - DOCKET NO. 50-328 DATED:
March 2 1940 l
O'STRIBUTIO_N:
abetAtet file.,
NRC PDR Local PDR SQN Reading ADSP Reading DCrutchfield BDLiaw SBlack Licensing Assistant JDonohew(2)
RPierson BWilson, Region II LWatson, Region 11 BGrimes 9-A-2)
MNBB-3701)
EJordan DHagan
.MNBB-3206)
TMeek(8)
P1-37)
WJones P-522)
JCalvo 11-F-23)
ACRS (10)
P-315)
GPA/PA 2-G-5)
GPA/CA 17-A-3)
ARM /LFMB MNBB-4503)
OGC 15-B-18)
PHearn EMarinos
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