ML19345A701
| ML19345A701 | |
| Person / Time | |
|---|---|
| Site: | Yankee Rowe |
| Issue date: | 02/19/1975 |
| From: | Heider L YANKEE ATOMIC ELECTRIC CO. |
| To: | Office of Nuclear Reactor Regulation |
| References | |
| WYR-75-23, NUDOCS 8011240585 | |
| Download: ML19345A701 (3) | |
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Cffice of !!uclear Reactor Regulation
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Subject:
Yankee Rowe Low Coolant Flow Trip
Reference:
1)
License tio. DPR-3 (Docket No. 50-29) 2)
Letter from R. A. Purple, !!RC to Yankee Atomic Electric Company, Attn: Carl Andognini, January 30, 1975.
3)
Proposed Change No. 120, "Iow Main Coolant Flow Technical Specification Change", dated January 13, 1975
Dear Sir:
The Yan';ee Atomic Electric Company hereby submits the following g) additional information in response to your request of g uary 30, 1975 to enable you to complete your review of our submittal While performing the Cycle X loss of coolant flow analyses it was decided to irpreve the reactor protection system by modifying the low main coolant flew trip. Previously, a reactor trip signal was generated when flow in any loop was reduced below 80% of normal. Thus, a delay associated with the ti.e required for flow to drop below 80% of normal always occurred before a reacter trip signal was generated. The new low flow trip corpletely eliminated this time delay by basing the reactor trip signal on high or low pump current which is assumed to be part of the initiating event in the loss of flev transient.
A comparison of the sequence of events during the four out of four For less purp loss cf flow transient is shown in the attached table.
severe loss of flow transients, the time delay associated with the previously existing low flow trip is larger and the improvement in reactor protection is even greater.
l It is concluded that the revised low flow trip represents a sub-stantial increase in the margin of safety provided by the reactor protection system.
Respectfully submitted, YANKEE ATOMIC ELECTRIC COMPANY 1
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h.#[I.!1 L. H. Heider Manager of Operations MLO10
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SEQUENCE OF EVENTS LEADING TO REACTOR TRIP DUltING TiiE 4/4 PUMP LOSS OF FLOW TRANSIEhT Event Time (seconds)
Revised Low Flow Previously Existing Low Trip Flow Trip Less of power to 0.0 0'.0 pumps Reactor trip signal 0.0 cencrated by low pump cu. rent Reactor trip signal 0.27 generated by low flow Control rods begin 0.60 1.27 to drop into core e
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NRC DIST' UTION FOR PART 50 D7CKET MA
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CONTROL NO:
2041 FILE:
FRO.*.i:'lankee Atomic Elec. Cc.
DATE OF DOC DATE REC'D LTR TWX RPT OTHER
' estborough, P. css. 01581 TO:'
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2-19-75 2-22-75 xx ORIG CC OTHER SENT AEC FDR XX DRL 3 siened 37
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CLASS UNCLASS PROPINFO INPUT NO CYS REC'D DOCKET NO:
xxx 40 50-29 DESCRIPTION:
Ltr submitting addl info re ENCLOSURES:
Sequeme of Events Leading to our request of 1-30-75 re addl info to Tech Specs Reactor Trip During the h/4 Pu=p Loss of :
& trans the following:
Flow Transient....
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