ML17193B460
| ML17193B460 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 06/01/1981 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML17193B459 | List: |
| References | |
| NUDOCS 8106100514 | |
| Download: ML17193B460 (5) | |
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UNITED STATES NUCLEA.R REGULATORY COMMISSION WASHINGTON, D. C. 20555 S/\\FETY EV/\\LU/\\TION BY TllE OrFICE OF NUCLE/\\R RE/\\CTOR REGULATION SUPPORTING TllE PROPOSED CH/\\NGE TO LICENSE NO. DPR-19 COMf*iONHE/\\L TH EDISON DO~KET NO. 50-237 DRESDEN ST/\\TION UNIT 2 1.0*
Introduction On May 23, 1981, one recirculation loop at Dresden Unit No. 2 was removed from service due to an electrical fault in its motor generator (MG) set.
- By telecopy of a letter dated May 24, 1981, Commonwealth Edison (CECo),
the licensee, requested immediate temporary*changes to Facility Operating License DPR-19 for Dresden Station Unit 2. The requested changes would permit the plant to operate at up to 50% of rated power with one recirculation loop out of service while repairs to the damaged MG set were 5eing completed. Because the NRC staff has not explicitly reviewed single loop operation at Dresden Unit No. 2 the currerit
- . Technical Specifications require shutdown in 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> when operating on one recirculation loop.
The May 24 request was for one loop operation for a period not to exceed seven days.
The May 24 request transmitted a summary of a single loop operation analysis.for Dresden 2 that has been cr,mpleted. by the reactor vendor, Gene~al Electric (GE) but has not yet been submitted for NRC *staff review.
On May 25, 1981, CEC6 determined that the damag~ to the MG set was too extensive to repair within seven days because of. the need to completely.rewind the MG set motor. Therefore, CECo supplemented its May 24, 1981 request for a seven day extension by a letter dated May 27, 1981 that submitted the complete GE analysis in support of operaticin with one reci rcul at ion loop out of service for four weeks.
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' 2 :O *.
Ev a 1 u at ion 2.1 Steady State thermal po1*1er level *will n~t exceed 50%
The licensee proposed to limit ste~dy state thermal power ~6 50% ~f rated power when ~p~rating with one recirculation loop isolated.
The licensee stated that for the Dresden 2 power/flow operating map the 100% flow control l~ne intersects the natural circulation line at 53% power.
Witti power* 1 imited to 50% no fuel°, damage would occur in the.eVeQt of a recirculation pump seizure.:
Oper~ti'rig 'at.50% power with appropriate.T-S changes was approv*ed o~~
a temporarY basis for the Duane Arnold plant and Peach Bottom Units 2
- arid 3 (Safety Evaluation Reports (SER) dated May 6, 1980 and May 15; r'.l 1981_. respectively).* It wa? concluded that for operation at. 59%
.. /:.*-*.:
power transient and accident *bounds \\'mul d not be e.Xceede-d *for these......
pl a*nts.
Since the Dresden 2 is a 1 ower: power density pl ant i:tian>-'
Peach.Bottom we find that the analyses and.concl.usions would also **-
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appJ~.,,t.o_ ~_re~den.~...,
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-* *:.:.': *.2.2 *Minimum Critical* Power Ratio (MCPR) Safety Limit wil 1 be increas'ed by*
- 0. 03 to 1
- l 0
~-~*:~>--r The MCPR Safety dmit will be i~creas~d by 0.03 to.*~ccount for increased
.~.. '.*.. --:.-. uncertafoties *in* core flow and Trav.ersing Incore Plant (TIP) readings.
The 1 icensee has reported that this increase in the MCPR Safety Limit
'* ** was ad.~ress~dJ.n GE repor.ts _specifically for Dresden 2 for one.foop
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oper:a*~.fo*ot C On-'lhe basis 'of*.'previ6~us*_~taff review*s: ror. Duane ArnoJ d
-*.. **------**--*--*-* -*
- and**Peach Bottom and ori our review. of plant comparisons *we find that*
this analysis':is acceptable for Dresden 2.
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- _=~~~~-~,"~,,~~*** 2.}:.=;~~-~~*~!p~r~~i1ar:-:~p~wer Ra.tio (~*~PR;*:; i~i**~fog-* c~~nji.~.i~~*~ :~~r J).pera*t~~*
(LCO) will be increased 0.03 to 1.27 and 1.34 for 7 x 7 and 8-x 8
/, fuel respectively.
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.-:~* '"" The staff proposed that the operating 1 im*it MCPR be increased by 0..03 and multiplied by the appropriate two loop KF factors that are in the*
Dresden 2 Technical Specifications.
This will preclude an inadvertent flow increase from causing the MCPR to drop below the safety limit.
MCPR.
Using KF factors derived for two loop operation is *conservative*
for l lopp operation.
The licensee*agreed to the staff's proposal of
- =~*~* multiplying the operating.limit MCPR by the Technical Specification-- -
Kf factor.
This was also approved by the staff for Duane Arnold and
.. *******.-**********--****-------*... Pe.ach Bottom 2 a*nd 3...
.. *~*-**-.. **--~-'-*-~i~-:r~ *tt1e*--r.;*ax-i*ffiliffi.. Av.eri9e *Pfanar 'Cine*ar:***Heat Genera Hon Rate (MAPLHGR) **1 imfts w**-~-*~~*---*~*,,=*-..,.. ~,,,"~- wi 11. be reduced by appropriate multi p 1 i ers *..........,.-.,.. *.. **~-*-**. ' -. --***.,.......
.-.*-y_..........,..,..... -.,.. -.... _, --.. -~.-.:*.-~.---.:..... *_~rtie li*censee proposed.reducing the Technical Specification. MAPLHGR *by 0.87 (7x7 fuel); 0.87 (8x8 fuel) and 0.84 (8x8R/P8x8R fu~l) for single'°.
loop operation.
These reductions were based on analyses by General Electric (GE) in reports NEDE 24011-P-A-l and NEDD 24807.
Since these reports have not been reviewed and approved by the staff for Dresden 2 we applied an additional conservatism by using a reduction factor of
2.4.
' 6. 70.
The Peach Gottom units ~1ere allo1"1cd to operate \\'lith their MAPLllGR values reduced by factors of 0.71, 0.83, and 0.81 for an unlimited period of time for the three types of fuel. Accordingly, the greriter MAPLHGR reduction factor of 0.70 for Dresden 2 for the limited four week period is adequately conservative to assure operational safety while the staff is reviewing CECo's long term single loop request *
- dated May 27, 1981.
The APRM Scram and Rod Block Setpoints and RBM Setpoints will be reduced.
The licensee proposed to modify the two loop APRM Scram, Rod Block and Rod Block Monitor (RBM) setpoints to accoun~. for back flow through half the jet pumps.
The changes were based on plant specific analyses by GE.
These setpoint equation$ will be changed in the Dresden 2 license conditions.
The above changes are si~ilar to the Duane Arnold and Peach Bottom Technical Specific~tion changes*
and are acceptable to the staff.
2~5 The Suction valve in the idle loop is clo~ed and electrically.*
isolated.
The licensee will close the recirculation pump suction v.alve and remove power from the valve.
In the event of a loss of coolant accident this would preclude partial loss of L~CI flow through the recirculation loop degrading the intended LPCI performance. The.
removal of power also helps to preclude a start ~P of an idle loop transient.
2.6 The Equalizer line between the loops will be isrilated.
The licensee will close appropriate ~alves.in the cross-tie (equali~er) line between the loops.
The previously discussed analyses ~ssumed the two loops were isolated therefore, it is required that the *cross-tie valve be closed.
2.7 The recirculation control will be in manual control.
The staff requested that the licens'ee operate the recirculation system in manual mode to eliminate the need for control *system analyses and to reduce the effects of potential flow instabilities. This was also required of Duane Arnold and Peach Bottom.
The licensee agreed to operate in this manner.
2.8 Surveillance Requirements The.staff requested. that the licensee perform daily surveillance on the jet pumps to ensure that the pressure drop for one jet pump in a
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loop does not vary from the mean of all jet pumps in that loop by more than 5%.
The licensee stated that this requirement is already incorporated in their technical specifications.*
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- 3.0 Summary of Single Loop Operation In order to ensure an adequate margin of safety the licensee has committed to the following during single loop operation.
A.
The idle loop suction valve is closed and electrical po\\'1er is
- removed.
B.
The recirculation controls will be placed in the manual mode.
- c.
The settings for.the APRM rod block trip, flow bias scram and the rod block monitor will be modified as necessary.
D.
E.
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- G.
MAPLHGR reduction factors will be imposed.
Power level will be limited to 50% of rated.
The cross~tie valve between the recirculation loops will be closed *.
.,Daily surveillance on jet pump operating characteristics will be perfonned.
4.0. Extension of Allowable Outage of Service Interval from Seven Days to Four Weeks CECO' s May 27, 1981 letter has indicated* that they wi 11 require four weeks to re~urn the damaged recircul~tion loop to service and have
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requested an extended out-of-service interval of four weeks.
In support
- Of this extension CECo has submitted a General.Electric Company Report, NEDD 24807, entitled "Dresden Nuclear Power Station Units 2 and 3 and Quad Cities Nuclear Power Station Units l and 2 Single Loop Operation."
. This GE Report has been prepared in support of a planned CECo submittal for single.loop operation for an unlimited time period.
Such an authori-
. zation has oeen issued for Peach Bottom Units No. 1 and 2 by NRC lette.r dated May 15, 1981.
Although the methodology of the analysis is identical to thaf used in**
the Peach Bottom review, and the reactors are similar, both General
___ Electric Boiling Water Reactors; the staff has not been able to com-plete its review of the CECo submittal in time to authorize single loop operation at Dresden for an unlimited time period.
During a period of single loop opf:!ration that occurr'ed at Browns ferry Unit No. 1 in 1978, unexpected variations in jet pump flow and neutron flux were observed.at a power le~el of 59%.
These variations stopped when the power level was reduced below 59% and the reactor operated for
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approximately t\\':O months in single loop operation until the end of cycle.
In October 1978, General Electric suggested that (1) the APRM
- ffux noise should be limited to. 5 percent peak to peak,.(2) that the core plate lip noise should.be limited to 1 psi peak to peak due to fuel channel considerations a~d (3) the pump speed shall be reduced if the above surveillance indicates the presence of ~nexpected internals vibrations.
We have revie\\'Jed the results obtained in the NEDO 24807 review and conclude that the similarities in the analysis, the reactor system, and the conservative limits placed on flow induced internals vibration permit us to authorize a temporary 4 we.ek operation v1ith one loop out of service while the analysis is under review and the recirculation pump MG set is repaired.
Therefore, based upon the above eva.luation, we conclude that single loop operation fo~ Dresden 2, up to a power level of 50% and in accordanc~
with the above proposed license changes, for four weeks will not exceed the bounds of transients and accidents previously found acceptable. by the staff.
5.0 Environmental Constderations We have deterrn'lned that thJs: amendment does not authorize a change in effluent types or total amounts nor an increase in* power level and will not result in any s*1~gni'ficant environmental impact.
Having made this determination, we have further concluded that this amendment involves an action which is insignificant from the standpoint of ~nvironmental impact a.nd pursuant to 10 CFR 951.5(9}(4). that an environmenta*l impact statement, or negative declar~tion and environmental impact appraisal need not be prepared fn connecti~n with the issuance of this amendment.
6.0 Conclu~ion We have concluded, based on the considerations discussed above, that (1) because the amendment does not involve a significant increas*e in.
the probability or consequences of accidents previously considered and.*
does not involve a significant-decrease in a safety margin, the amendment does not involve a significant hazards consideration, (2) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, and (3} s1.1ch activities will be conducted in compliance with the Commission's regulations and the issuance of this amendment will not be inimic*a1 to the common defense and security or to the health and safety of the 'public..
- DATED:
June 1, 1981
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