ML20079H489
| ML20079H489 | |
| Person / Time | |
|---|---|
| Site: | Hatch  |
| Issue date: | 10/02/1991 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20079H487 | List: |
| References | |
| NUDOCS 9110110151 | |
| Download: ML20079H489 (4) | |
Text
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UNITED sT ATES
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'i NUCLE AR REGULATORY C'OMMISSION
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- SAFETY EVALUATION DY THE _OFF1(E OF NitCLEAR REACTOR REGttLATION
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ret ATEDJO AMENDMENT NO.174 TO QCILITY OPERATING LICENSE DPR-57 AND AMfNDMF'lT NO.114 TO FACILITY OPERATING LICENSC NPF-5 GEOPGIAp0WERCOMPANY,ETAb EDWIN 1. HATCH NUCLEAR PLANT, UNITS 1 AND 2 00CKET N05. 50-3?! AND 50-366 0
1.0 INTRODUCTION
By letter dated January 26, 1990, as supplemented January 15, 1991, the Georgia Power Company, et al. (the licensee), submitted a request for changes to the Edwin 1. Hatch Nuclear Plant, Units 1 and 2. Technical Specifications (TSs).
The requested changes would revise-Technical Specification (TS) 3/4.7 for Hatch Unit 1 and TS 3/4.6.2.1 for Hatch Unit 2.
The TS Bases for both units are also revised. The proposed changes incorporate into the TSs a means fnr determining the suppression pool bulk temperature. This value vill be used to show compliance with existing TS operational limits. The licensee's proposal, originally described in a January ?6,1990 submittal and revised per the subject letter, describes the prefetred method of using an average of all 15 temperature elements as read from the Safety Parameter Display System (SPDS) to determine the bulk pool temperature. The licensee also proposed preplanned alternate methods of temperature monitoring when the preferred method is unavailable due to inoperab"e temperature elements of SPDS.
2.0 EVALUATION Temperature limits have been placed on the suppression pool for BWRs with Mark I containments to minimize the potential for high amplitude plant loads during transient or accident events.
Because the suppression pool is the intermediate heat sink for this plant design, it is important that its water temperature be monitored during normal operations as well as during transient / accident conditions.
The NRC's requirements are based on " local" pool temperature responses. Correlations are used to relate " local" to " bulk" conditions. Today, the " bulk" or average water temperature in the suppression pool is used as the initial condition for many safety antlyses, and as such, it is an important plant parameter which must be monitored during normal, abnormal and emergency conditions.
The existing Plant Hatch TSs makcs no reference to " average" or " bulk" temperatures and does not describe any methods used to monitor them. The licensee's proposal specifies that the " bulk" pool temperature will be used to show compliance with existing TS limits.
Furthermore, the TS change describes the preferred method for obtaining this critical parameter as the average of all 15 temperature elements (e b en N300 series upper sensors, four N009 series lower sensors) in each unit. The new TS Bases will describe the preplanned alternatives for measuring the " bulk" pool temperature during periods when more than two of the upper temperature elements (TEs) are inoperable.
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-P-in its submittal, the licensee stated that the N300 (upper) series sensors feed into a single-point recorder and are not single-failure proof. Also, plant Hatch's SPDS, from which the bulk pool temperature is usually monitored, is neither single-failure proof nor subject to TS requirements for operability. Therefore, Georcia Power postulated the failures of more than two of the upper ils during normal and abnormal operating conditions and provided alternative methods for conservative suppression pool temperature monitoring.
The proposed alternatives to usirg the SPDS for various operating conditions are as follows:
(a) Normal Operation! Torus cooling not operating; No high pressure coolant injection-(HPCI) testing; No leaking safety relief valve (s) (SRV(s))
In the event that more than two of the eleven N300 seriet sensors become inoperable, the licensee proposed to add 5 degree Fahrenheit correction factor to the average of the four operable N009A-D elcments, For the above plant condition, the licensee's 1989 study demonstrated that while suppression pool water is not being circulated, thermal stratification caused only minor temperature variances between the upper and lower regions of the pool.
The largest temperature differential observed in either unit during the surveillance checks was 3.5 degrees fahrenheit with the average being about 2 degrees.
This is bounded by the 5 degree correction factor the licensee has proposed for normal operation with no significant heat energy being added to the pool, Based en the above, the NRC staff finds the licensee's proposed suppression pool monitoring alternative for this plant condition to be acceptable.
(b) Normal Operation; With or without torus cooling operating; HPC1 testing on; with or without leaking SRV(s)
Should more than two of the upper suppression pool temperature sensors be deemed inoperable, the licensee has proposed that HPCI testing during this plant condition be administrative 1y limited to assure the bulk pool temperature does not exceed 105 degreet Fahri.nheit, Pool temperature data should still be recorded each 5 minutes as instructed by the TSs, but the HPC1 run time should be administratively controlled by the following equation:
Max Run Time in Minutes = (105 - T initial) x ?, where T initial is the pool temperature taken prior to the test with torus cooling operating.
This equation assumes a 30 degree / hour rise in bulk pool temperature.
In its submittel, the licensee stated that T initial can be determined by using only the lower TEs, if necessary, since the PHR system will be aligned in the sup-pressionpoolcooling(SPC)modepriortorunningHPCI.
On that basis, the lower TEs' accuracy would be offset by an effective thermal mix in the suppression pool l
caused by running RHR in SPC mode. Worst case data taken during the licensee's l
1989 surveillence runs indicate that since the HPCI system has a large capacity l
for steam flow, thermal stratification may be significant during HPCI testing.
From Figure 2 in the licensee's January 1991 submittal it is shown that the calculated bulk pool temperature rose at an estimated 22.5 degrees / hour during HPCI. This rate of temperature increase is bounded by the 30 degree / hour rate assumed in the proposed equation for administrative 1y controlling HPC1 testing.
Based on this review, the NRC staff finds the above alternative nethod for suppression pool temperature monitoring to be acceptable during normal operations with HPCI testing,
. (c) Normal Operation; Torus cooling operating; No HpC1 testing; With or without leaking SRV(s)
In the event that more than two of the eleven N300 series sensors become inoperable, the licensee proposed to use the average of the four operable N009 elements with no correction factor.
The licensee maintains that a correction factor would not r
be necessary due to at least one RHR pump being in the SpC mode and providing enough flow to effect thermal mixing during normal operations, testing of SRVs, or testing of the RCIC System.
Results from the 1989 study indicate that the temperature differential between the average of the N009 Series elements and the bulk pool temperature is on the order of I degret fahrenheit or less during these conditions.
Based on the NRC staff's review of the subject submittal, it finds the above defined method for monitoring suppression pool temperature during normal operations with no significant heat addition to the pool to be acceptable.
(d) Abnormal Operation; With or without torus cooling operating; Significant heat addition to the suppression pool Based on a telephone conversation with the licensee of July 22, 1991, the licensee has agreed to withdraw this paragraph. TechnicalSpecification(TS) paragraphs 3.7.A.1 for Unit 1 and 3.6.2.1.G for Unit 2 address the suppression pool temper-ature monitoring during(normal power operation with or without HpCl surveillance in process. paragraph d) of the licensee's letter dated January 15, 1991, addresses an abnormal plant condition with significant heat addition to the suppression pool. This would be, as a minimum, a condition where a single SRV (or more SRVs) is (or are) discharging to the pool potentially under ATWS conditiont.
Therefore, for the licensee to be in a postulated condition similar to paragraph (d), the licensee would have already entered or be about to enter other action statements on high suppression pool temperature and the plant operators would be in process of dealing with the primary cause of the event such as an ATWS or open SRV. The TS paragraphs in question here are monitoring requirement which assure that the suppression pool is operable and capable of receiving the heat input from the postulated transient.
If the N300 series sensors, and Sp0S become inoperable, and a significant heat addition to the pool was postulated to occur, other TS LCOs would be exceeded requiring a shutdown on the reactor.
On the basis of the above evaluation, the staff concludes that the licensee employed a sound methodology in analy:ing suppression pool temperature surveillance data to develop m servative alternative methods for determining this critical parameter. Therefore, the licensee's proposal to change the TSs to specify that a "bu',k" temperature be used to show compliance with existing TS limits is i
acceptable as described in paragraphs (a), (b), and (c) only of the licensee's l
1etter dated January 15, 1991.
In addition, the proposed revision to the TS Bases for both units, describing the " preferred method" of using 15 TEs as l
well as the alternative methods for the various operating conditions, is also acceptable. The licensee's proposal in paragraph (d) of Enclosure 1 to the t
l January 15, 1991, letter was withdrawn by the licensee.
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4-3.0 STATE CONSl!LTATION In accordance with the Conmission's regulatinns, the Georgia State official was notified of the proposed issuance of the amendments. The State official had no comments.
4.0 ENVIRPNMENTAL CONSIDERATION The amendments change requirements with respect to instellation or use of a facility component located within the restricted area as defined in 10 CFR Part 20.
The NRC staff has determined that the amendrents 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 ne significant increase in individual or cumulative occupational radiation exposure. The Conmission has previously issued a proposed finding that the amendments involve no significant hazards consideration, and there has been nn public comment on such finding (56 FR 27044). Accordingly, the amendments meet the eligibility criteria for categ(orical exclusion set forth in 10 CFR 51.22(c)(9).
Pursuant to 10 CFR 51.?? b), no environmental impact statement or environmental assessment need be prepared in connection with the issuance of the amendments.
5.0 CONCLUSION
The Commission 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 (?) such activities will be conducted in compliance with the Commission's regulations, and (3) the issuance of the amendments will not be inimical to the common defense and security or to the health and safety of the public.
Principal Contributors:
D. Roberts, SPLB/ DST A. Angelo, SPLB/ DST F. Rinaldi, PDil-3/0RP Date: October 2, 1991
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