ML20093G555

Final Deficienciency Rept,Item 111 Re Design Defect on RHR Reservoir Freeze Over.Initially Reported on 840104.Procedure Being Developed to Ensure Operability of safety-related Pumps During Cold Weather

ML20093G555
Person / Time
Site:	Fermi
Issue date:	07/05/1984
From:	Jens W DETROIT EDISON CO.
To:	James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
References
111, EF2-69272, NUDOCS 8407240280
Download: ML20093G555 (3)

Text

-s g

mmh Wayne H. J;ns Vice President Nudcar Orweens Detroit

"-2 6400 North Dme H <3h43y ISOn (Newport.%c p1 48I66 313;5864150 July 5, 1984 EF2-69272 Mr. James G."Keppler Regional Administrator U.S.

liuclear Regulatory Commission Region III 799 Roosevelt Road Glen Ellyn, Illinois 60137

Reference:

(1) Fermi 2 11RC Docket flo. 50-341 (2) Letter, D.

A.

Wells to J.

G.

Feppler February 6, 1984, QA-84-0079

Subject:

Final Report of 10CFR50.55(e) Item 111 " Design Deficiency on the RilR Reservoir Freeze Over" This is Detroit Edison's final report concerning the design deficiency on the Residual lleat Removal (RilR) reservoir freeze over.

Item 111 was originally reported as a poten-tial deficiency on January 4, 1984, and subsequently documented in Reference (2).

Description of Deficiency On December 28, 1983, water in the RilR reservoir, which serves as the ultimate heat sink, froze to a depth of two to three inches.

Safety-related Diesel Generator Service Water, Emergency Equipment Service Water and Residual IIcat Removal Service Water deep draft pumps take suction from these reservoirs.

Ice formed around the column of these pumps and could have potentially made the pumps inoperable if a plug of ice formed inside the column, or if the pumps' column alignment was affected.

The RilR complex design did not provide an adequate method to prevent freezing of the reservoirs for the period between the end of construction and initial plant operation.

For this period, the reservoirs were full of water and no heat was added to the reservoirs during cold weather.

8407240200 840705 PDR ADOCK 05000341 S

pyg JUL1656(

7547 s\\0

_-;*' i s

..s

'Mr. James,G. Keppler

. July-5,-1984 JEF2-69272 I

Page 2 Analysis of Safety Implications

.The - RilR complex, as designed, ' minimizes. excessive heat loss f rom the reservoirs even though the. reservoirs' surface is partially exposed to outside' ambient temperatures.

Based on the. design of the RIIRicomplex and the heat which will. be supplied tof the reservoirs, it is estimated-that the reservoirs will not freeze'during a normalswinter.

In the event of a isevere' cold period,,or a. winter ' colder than t

normal, additional heat may be required :to be ~added to the reservoirs.

~

~

C Cxcessive' freezing'of the ultimate' heat sink 1could prevent safety-related deep draft pumps from operating.

These pumps-are required for the operation of safety-related systems 4

which are used for core cooling and cooling of safety-3 i

related equipment.

The walls of the reservoir were not damaged.by the ice and a 3

design calculation determined that ice could. form in the i-reservoirs up:to a thickness of 18 inches without exceeding the maximum allowable loading on the walls.

J 1

Corrective' Action-1 Af ter ice was observed,' action was taken to eliminate ice from around the pump columns to protect them from potential-

~

7 damage.

This was accomplished by installing-temporary _. air-i bubblers and submersible -circulating ' pumps in 'the reservoirs 1

around the pump. columns.-

No' damage to the pumps'has been

~.

identified asLa result of the reservoirs. freezing.- -

I Detroit-Edison is developing a' procedure to ensure.that the-safety related pumps in the RilR complexiwill be. operable (for -

all cold weather periods.- ThisLwillibe-accomplishedLby d

a'dding heat <to'theireservoirs, and/or~ verifying thatithe'.

pumps are' operable.

The; temperature of both reservoirs'will:

~

be monitored by~thermocouples with an alarmJin/the-' control' room if the. temperature' drops to 43*F.

The amount of' heat that was. originally designed to be Lsent to' the reservoirs -is -

estimated'to be-sufficient to" keep:the reservoirs above 43*F a-

.J

.-4 6

Y 3

A ya

,+ ~;

i Mr. James G.-Keppler July 5, 1984

)

EF2-69272 Page 3 during a normal winter.

During severe cold periods or dur-ing colder.than normal winters, additional heat can be added to the reservoir to maintain the water temperature above 43*F.

The source of this heat, while the unit is operating,

-will be from running the Emergency Equipment Cooling' Water system and/or Emergency Diesel Generators.

While the unit is not operating, the decay heat from the reactor core will supply an ample amount of heat.

In the unlikely-event that heat cannot be added to the reservoir before the temperature drops to 41*F, a visual inspection of the reservoirs by an operator during normal rounds to the RilR complex would be required to verify that no ice has formed.

If ice is observed and the reservoir temperature is below 41*F, the operability of each safety related pump in that reservoir will be verified every eight hours.

This is considered Detroit Edison's final report on this item.

If you have questions concerning this matter, please contact Mr. Lewis P.

Bregni, (313) 586-5083.

Sincerely, cc:

Mr.

P. M.

Byron

/

Mr.

R.

C.

DeYoung Mr.

D. A.

Ferg (Cygna Corp.)

Mr.

R.

C.

Knop Mr. M.

D.

Lynch v

__