ML19270G528

Forwards Responses to NRC 790518 Questions.Loss of Main Feedwater Pumps Occurred Twice in Past Three Years.Unit Has Automatic Isolation Actuation Sys.Appropriate Pumps Used to Remove Liquid Waste

ML19270G528
Person / Time
Site:	Fort Calhoun
Issue date:	05/31/1979
From:	Short T OMAHA PUBLIC POWER DISTRICT
To:	Reid R Office of Nuclear Reactor Regulation
References
NUDOCS 7906130011
Download: ML19270G528 (5)

Text

. e -g. ..

1 f: '

~~#

Omaha Public Power District 1623 HARNEY a OMANA. NEBRASMA 68102 e TELEPHONE 536 4000 AREA CODE 402 May 31, 1979 Director of ITuclear Reactor Regulation ATTII: Mr. Robert W. Reid, Chief Operating Reactors Branch Iio. 4 U. S. Iluelear Regulatory Commissicn Washington, D. C. 20555

Reference:

Docket Ilo. 50-285 Gentlemen:

Please find attached, responses to questions received frca you via teleccpy on May 18, 1979 Sincerely, T. E. Short Assistant General Manager TES/KJM/3JH:j=m Attach, cc: LeSceuf, Lamb, Leiby & MacRae 1333 IIew Ha.:pshire Avenue Suite 1100 Washington, D. C. 20036 2327 A5 sl o 7906180s\\ TII

NRC Questions Received May 18, 1979 Question 1:

Provide the- total positive displacement charging pu=p capacity (maxi-mum capacity /gpm per pu=p). How many charging pu=ps?

Response

Number of charging pu=ps: 3 Maximum capacity per pu=p: 40 gpm Question 2:

Describe all events that resulted in a complete loss of =ain feedvater over the last three years of operation. Include as a mini =um the follcv-ing information:

a. Date

b. Initiating event

c. Power level

d. Consequences (one palagraph description)

e. Safety significance of event Each event which occurred during a startup need not be described separately.

Restense:

The following events resulted in a co=plete loss of main feedvater during the last three years. Normal shatdown of the main feedvater sys-tem due to routine unit shutdown has not been included.

I. a. Date: February 21, 1976

b. Initiating ' event : Loss of 161 K7 supply to house service buses followed by failure to fast transfer,

c. Power level: 71%

d. Consequences: See footnote (1) <

e. Safety significance of event: None II. a. Date: August 22, 1977

b. Initiating event: Mc=entary loss of 16? K7 supply to house ser-vice buses followed by failure to fast transfer.

c. Power level: 97%

d. Consequences: See footnote (1)

e. Safety significance of event: None Footnote (1): In both cases, following loss of the main feedvater pu=ps, the auxiliary feedvater system actuated and functioned per design.

Question 3.a.:

For all lines penetrating contain=ent that are automatically isolated in the event of an accident, identify the parameters that are associated with automatic contain=ent isolation. Also, indicate the and/or logic associated with these parameters.

Resconse:

The Fort Calhoun Station Unit No.1 reactor containment building is provided with an automatic isolation actuation system which cperates con-tainment penetration isolation valves (both to the open and to the cicsei position) to mitigate the consequences of an accident. The automatic sys-te=s are the Containment Isolation Actuation Signal (CIAS) and the Ventila-tion Isolation ~ Actuation Signal (VIAS). It should be noted that VIAS is redundant to CIAS in that it also ginerates a valve closure signal for sc=e isolation valves closed by CIAS; specifically, the containment purge and relief lines and containment sa=ple lines to and frem EM-050/051.

The CIAS is generated if either a Pressurizer Pressure Lcv Signal (PPIS which actuates at 1600 psia) er a Centainment Pressure High Signal (CPHS which actuates at 5 psig) is generated by an accident condition in the primary system and/or centainment building. The actual mechanism of isolation is designed to meet single failure criteria. The CIAS sys-tem consists of two redundant isolation channels (or trains) which are actuated by sensors, in a two out of four logic, monitoring the primary system and containment pressure. When the actuation logic is satisfied, a signal is then generated which actuates the PPLS or CPES "86" lockout relay which =echanically seals in the accident signal. The accident signal in turn actuates the emergency ccre cooling system and CIAS via an "86" lockout relay which mechanically seals in the CIAS control func-tion. In addition, the Fort Calhoun Station Engineered Safety Feature System is provided with an additional control relay whereby channel A controls may " reach ecross" and actuate channel 3 equipment and vice versa. This provides increased availability of safety equipment. The CIAS train separation is maintained at the line isolation valves; channel A vill operate the A valve and channel 3 the 3 valve.

. 1 When the "86" CIAS relay is actuated, relays in CIAS panels AI-h3A and AI h3B are de-energized, causing the isolation valves to assume their accident position.

Question 3.b_: ,

2:327 ':47 For lines penetra-ing the containment that are used to transfer fluids to the vaste handling system outside containment, describe the action (automatic or =anual) that is required to initiate fluid transfer. If

fluid transfer occurs auto =atically, describe the provisions that have been =ade to ensure that any demand or fluid transfer vill be overridden and that these lines vill be automatically isolated in the event of an accident. Furthermore, describe the provisions which will assure that the lines vill remain isolated, even after resetting of the engineered safety features actuation signal. Identify the lines involved.

Response

At present two lines, the containment sump pu=ps' discharge to the radioactive vaste disposal system and the rer.ctor coolant drain tank pu=ps' discharge to the radioactive vaste disposal system, are used to re=ove liquid vaste from the reactor containment building.

Both sets of pu=ps, WD-3A and WD-3B (containment sump pumps), and WD-2A and WD-23 (reactor ecolant drain pu=ps), are capable of autcmatic or manual operation. To initiate operation of the containment sump pumps ,

the containment isolation valves, HCV-506A and HCV-5063, must be manually opened via control switch. The pumps =ay then be operated =anually or in autc=atic. In the automatic =cde of operation, one of the pu=ps is selected as a lead pump, the other as a standby pump. Cn high level, the lead pump is started; if the level goes higher the second pump is started. Both pu=ps trip en lov su=p level in automatic or manual operatien.

On initiatien of the emergency core ecoling system, both containment su=p pump isolatica valves vill close and, in addition, the energency core cooling system vill trip both sump pumps as part of the h80 V lead shed system. At such time when the accident signal lockout relays are reset, the containment isolaticn valves vill remain in the closed pcsition and must manually (via centrol switch) be repositioned. If in automatic, the pumps vill restart if the level is high. However, as stated above, the containment isolation valves are closed.

WD-2A and 'a?-23 are similar in operation to the. containment sump pu=ps. Ecvever, to pu=ps will act independently in automatic. No lead-standby system exists. To initiate flow, the centainment isolati'on valves ,

HCV-500A and HCV-5003, must be manually, via control switch, cpened and the pumps then operated .anually or automaticaJ.ly en high tank level.

On initiation of the emergency core cooling system (of which centainment isolation is a part), the penetration isolation valves close and the pumps are tripped as part of the 480 volt load shed. On the resetting of ;he accident lockout relays tt s nu=ps, if in autc=atic, may start depending on tank level. McVever, the containment penetration isolation valves will remain closed until manual, via a control switch, repositioning.

Question 3.c.:

Identify the essential lines penetrating the containment; i.e., lines which do not have a post-accident safety function, yet are important to plant safety. These lines typically do not receive an autc=atic isolation signal or, if they do, their isolation is deferred until subsequent signals are received that confirm the existence of an accident ecndition. Describe and justify the isolation actuation provisicns for these lines. (Exclude 2327 243

~

_h_

lines associated with the engineered safety features and the lines which are nor= ally closed during operating modes requiring containment integrity and remain closed following an accident. )

Response

Fort Calhoun Station has only one penetration which, although not required for safe plant shutdown, enhances plant operation. This pene-tration is the instrument air supply to containment. This penetration and its associated isolation valve, PCV-1849, are so arranged that on contain-ment isolation a circuit is enabled such that the air header remains sup-plied during the accident. Ecvever, en lov header pressure tne supply line is isolated. The isolation setpoint is above the maximum design basis accident, thus insuring no radioactive leakage.

2327 ;49 h

a