View source for L-75-237, Response to Request for Information on Capability of ECCS to Provide Adequate Cooling in Case of Loss of Coolant Accident When Operating Plant with One Idle Loop

{{Adams
| number = ML18227B025
| issue date = 05/19/1975
| title = Response to Request for Information on Capability of ECCS to Provide Adequate Cooling in Case of Loss of Coolant Accident When Operating Plant with One Idle Loop
| author name = Uhrig R
| author affiliation = Florida Power &amp; Light Co
| addressee name = Rusche B
| addressee affiliation = NRC/NRR
| docket = 05000250, 05000251
| license number = DPR-031, DPR-041
| contact person = 
| case reference number = L-75-237
| document type = Letter type:L, Response to Request for Additional Information (RAI)
| page count = 5
}}

=Text=
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FLORIDA POWER 5 LIGHT COMPANY May 19, 19.75";
L-75-237,                     "--'-'-'.'.L, REGULATORY DOCKIiTPILE COPM                                                                       I" Mr. Benard C. Rusche Office of Nuclear Reactor Regulation U. S. Nuclear Regulatory Commission washington, D. C. 20555

==Dear Mr. Rusche:==

Re:   Turkey Point Units     3 & 4 Docket Nos. 50-250     & 50-251 ECCS  'Anal 'sis'or   Two Loo
                                     '
erato.'on This is in response to a request by your Staff that we supply information on the capability of the Turkey'oint Emergency Core Cooling System (ECCS) to provide 'adequate cooling in case of a Loss of Coolant Accident (LOCA) when operating the plant with one idle loop.
On loop March  ll, 1975 operation at we   submitted to you the 'ECCS analysis for. 3 design .power. The'onsequences of a LOCA when operating this plant, which has no isolation valves, with one idle reactor coolant pump at a maximum of 60% of full power will not be as sevexe as those of a LOCA occurring with 3 loop operation.
at full power. Reasons 'for this become "clear by considering the comparison of the various phases of the accident transient for thxee 'loop and two loop operating      conditions.'.
Blowdown: In comparing three 'loop and two loop LOCA's 'the predominant factor influencing the blowdown'ransient is the effect=of reduced core powex required during)CAN                      two loop any given break size, including the "limiting" break, the operation.'or core mass flow transient      vill  remain essentially the same for the cases because the energy and driving forces in the reactor coolant system, i.e. pressure and .temperature, are similar.
The idle reactor coolant pump may cause a slight t'ime shift in the 'core 'flow charact'er'istics,'ut 'the trends will remain the Thexefore, be'cause 'of, the reduced core power', coolant                                        . 'ame.
quality in the core during bl'owdown'ill be significantly lower for two loop operation and the 'clad and pellet temperatures will be 'lower at the 'end of blowdown.
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Mr. Benax'd C, Rus ch.e                                                      May 19, 1975
: 2. Refill: Since the blowdown hydraulic transients are similar                              is   the and emergency. core cooling syst'm performance for the                            two   cases same, lower plenum                refill  and bottom of core recovery will not be altered significantly.
: 3. Reflood: One important factor that influences                             .the reflood transient is. the containment pressure. The                          conservatively        calculated ECCS containment pressure 'transient will be only                           slightly      affected because the'CCS'ass, RCS energy and rate of ezplusion                                  of the primary coolant to containment'ill be calculation              about  the  'same    for   the two cases'. Another factor in the reflood                                      that   must   be is, again, core            powe'r'.       Sensitivity    studies'er'formed K ECCS evaluation model show that
                                                                                               'onsi,der'ed with 'the westinghouse 'Appendix 'heat decreasing core 'poorer'nd core                            release in the '.reflood calculation res'ult in a more effective                'core     'reflood   transient with 'res'pect to core cooling.. The decrease in. core 'power for two loop operation will, therefore,"'mprove''the 'reflood transient.
In summary, since the 'core 'conditions at the 'end and                    of blowdown will be 'improved for the two loop                  'oper'ation     analysis           the, refill/reflood transient -ia, at worst, the                's'arne   'for  three 'loop   and    two loop operation, a LOCA postulated to occur. during                      two  loop  operation      will'esult in lower calculated peak clad                 t'emperatures''than        for   100%   power'.
For additional conservatism                  it   is proposed that the pres'ent echn'al Specifications be amended so that fox two loop operation the 'permissible maximum peaking factor, Fq, be'educed to 80% of the value permitted by Section 3.2.,6a of the Turkey Point Technical Specifiations, This would lower the peak linear heat rate 'during two loop oper'ation to 10.9 kw(ft,'ompared to the '13".62 .kw/ft 'value used in the.'3 loop .
ECCS analysis.                  According to sensitivity studies described zn WCAP-8340, the''peak 'clad temperature following a LOCA would be lowered another'. 360oF as a result of this reduction in heat rate, bringing the.'clad temperature 'we'l below 1840~F.
.Very   truly yours, E. Uhrig
                   )girl'obert.
Vice Presi,dent REU:nch
           'c:
Mr. No'rman Moseley Jack R. Newman, Esquire}}