ML20097E042
| ML20097E042 | |
| Person / Time | |
|---|---|
| Site: | LaSalle  |
| Issue date: | 09/04/1984 |
| From: | John Marshall COMMONWEALTH EDISON CO. |
| To: | Harold Denton Office of Nuclear Reactor Regulation |
| References | |
| 9129N, NUDOCS 8409180083 | |
| Download: ML20097E042 (2) | |
Text
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\\ Commonwealth Edison
/ One First Natiorul Ptna. Chicago, lihnois
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] Address Reply to. Post Othca Box 7M N
,/ Chicago.illknois 60690
-September 4, 1984 Mr. Harold R. Denton, Director Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Washington, DC 20555
Subject:
LaSalle County Station Unit 2 Reactor Scram on Low Control Rod Drive Pump Discharge Pressure Modification NRC Docket No. 50-374 References (a):
NPF-18 License Condition 2.C.(7) Low Pressure in Pump Discharge of the Control Rod Drive.
(b):
FSAR Section 4.6.2 pages 4.6-9, 26, 31.
(c):
FSAR Section 7.2 pages 7.2-8, 10, 65, 65a, 65n, 65c, 92, 93, Figure 7.2-5.
(d):
SSER #2 4.6.2, Control Rod System.
(e):
SSER #7 7.2 Control Rod Drive Low Changing Pressure Scram.
(f):
Telecon with Dr. A. Bournia et. al. on August 15, 1984.
Dear Mr. Denton:
The following is in response to a discussion between the NRC and CECO in the conference call of August 15, 1984 (reference (f)), and provides clarification on the subject of automatic reactor scram from Control Rod Drive low charging pressure.
The purpose of the CRD low charging pressure scram is to assure that there is adequate pressure in the charging header to accomplish CR0 rod insertion into the core.
An automatic reactor scram from CRD low charging pressure has been interlocked with the reactor mode switch.
The reactor mode' switch activates this interlock when the mode switch is placed into the refuel or start-up position only.
A new alarm has been installed on the main control room annunciator (Hathaway) indicating CRD charging water pressure - low.
With the mode switch in refuel or start-up, a reactor scram will occur within 10 secs. of this alarm, should the header charging pressure remain below the setpoint.
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H. R. Denton September 4, 1984 2
The automatic reactor scram on CRD low charging pressure is not activated when the reactor mode switch is placed into the run position t
because the accumulators are not necessary for rod insertion at vessel Z
operating pressure.
The auto-scram is also not activated in the shutdown mode since no control rods may be withdrawn in this mode.
?
Should vessel operating pressure decrease when in the run mode, MSIV closure will initiate at greater than or equal to 854 psig and within 1 second of the beginning of closure of these valves, reactor scram and control rod insertion will occur.
At this point, assuming low accumulator or header pressure exists, there will be sufficient vessel pressure for4 control rod insertion.
7 From the above discussion, it has been shown that the automatic scram on CPD^10w header pressure is not a necessary function when operating in the run mode.
Portions of IEEE-279 require that if a g.
f protective action has been bypassed or deliberately rendered inoperative, E
this fact should be indicated in the control room.
Since the auto-scram E
function on low CRD header pressure is not a required action in the run mode, we believe there is no need to annunciate in the main control room s
when this function is not active.
}
E During our review of this subject in the LaSalle FSAR, we determined that the installation description of the four new pressure transmitters needs clarification.
The FSAR presently indicates that the
=
four new pressure transmitters are attached to two pressure taps on header downstream of the CRD pumps.
The actual plant installation of these four new pressure transmitters is connected to individual process taps (four separate process taps to the charging header).
Applicable portions of the LaSalle FSAR will be revised to correct and clarify the interlocks and annunciation associated with this r.
SCRAM logic at the next annual update.
L:
-g Please direct any questions you may have concerning this matter to this office.
D One signed original and fifteen copies of this letter are 7
provided for NRC use.
y Very truly yours, b
NM J. G. Marshall Nuclear Licensing Administrator 1m r
cc:
A.
Bournia - NRR
_jl Resident Inspector - LSCS hy 9129N c-1 l
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