ML17037C241

Letter Responding to the March 20, 1974 Letter Requesting Additional Information Concerning the Control Rod Drive Conversion Program

ML17037C241
Person / Time
Site:	Nine Mile Point
Issue date:	04/18/1974
From:	Schneider R Niagara Mohawk Power Corp
To:	Ziemann D US Atomic Energy Commission (AEC)
References
Download: ML17037C241 (10)

Text

AEC D " IBUTION. FOR PART 50'DOCKET 11AT""" .AL (TEMPORARY FORM) CONTROL NO: 3536

'PILE:

PRON: DATE OP. DOC DATE REC'D LTR MEMO "'PT 'THER Niagara Mohawk Power Corp.

Syracuse, N., Y. 13202 4-18-74 4-22-74 R. R. Scheider TO: ORIG CC OTHER SENT AEC PDR X D~ L, Zikmann 1 signed SENT LOCAL PDR X CLASS UNCLASS 'ROP INFO INPUT NO C S REC'D DOCKET'O'0-220 40 DESCRIPTION:1 ENCLOSURES:

Ltr re our 3-20-74, furnishing addi info concerning control rod1.,drive conversion programs at Nine Mile Point 81 DO NOT REMOVE ACZZOWLZDGED PLANT NAME: Nine Mile Point Unit 81 FOR ACTION/INFORMATION 4>>18-74 GC BUTLER(L) SCHWENCER(L) +IBiANN(L) REGAN(E)

W/ Copies W/ Copies W/4 Copies W/ Copies CLARK(L) STOLZ (L) DXCKER(E)

W/ Copies W/ Copies W/ Copies W/ Copies PARR(L) VASSALLO(L) KNXGHTON(E) "

e~ 1 W/

Jh ~

VVPA CO oil W/

r... ~

VVPAE D W/ VVPAVEB W/ VVPA.'VIE KNIEL(L) PURPLE (L) YOUNGBLOOD(E)

W/ Copies W/ Copies W/ Copies W/ Copies INTERNAL DISTRIBUTION PILE A/T IND

~iEC G

PDR TECH REVIEW QKNDRIE DEN TON GRIMES 'IC ASST BRAT TMAN OGC, ROOM P-506A +CHROEDER GAMMXLL v@IGGS (L) SALTZMAN

~NTZXNG/STAFF ~C CARY KASTNER GEARIN (L) B, HURT

~ASE ~XGHT BALLARD GOULBOURNE (L) PLANS GIAMBUSSO ~AWLICKI SPANGLER LEE (L) MCDONALD BOYD ~HA,O MAXGRET (L) DUBE w/Inpu t MOORE (L) (HWR)- ~TELLO ENVIRO" REED (E)

DEYOUNG (L) (PWR) HOUSTON MULLER INFO SERVICE (L)

SKOVHOLT (L) NOVAK DICKER SHEPPARD (L) C. MILES OLLER(L) ROSS KNIGHTON SLATER (E) B. KXNG (E/W-358)

PE COLLINS IPPOLXTO YOUNGBLOOD KLECKER SMITH (L)

DENISE y&DESCO REGAN TEETS (L) EISENHUT EG OPR ~ONG PROJECT LDR WADE (E)

FILE 6 REGXON(3) v4AINAS WILLIAMS (E)

MORRIS MENAROYA HARLESS WILSON (L)

STEELE VOLLMER EXTERNAL DISTRIBUTION

- LOCAL PDR Oswe o N Y.

vl - TIC (ABERNATHY) (1) (2X10)-NATIONAL LAB'S 1-PDR-SAN/LA/NY g 1 NSIC(BUCHANAN)

ASLB 1-ASLBP(E/W Bldg,Rm 529) 1-W. PENNINGTON, Rm E-201 GT 1-GERALD LELLOUCHE BROOKHAVEN NAT. LAB I -

Po Ro DAVXS (AEROJET NUCLEAR) 1-CONSULTANT'S 1-AGMED(Ruth Gussman) 6 CYS ACRS IXKXE SENT TO LXC ~ ASST'EWARK/BLUME/AGBABIAN RM- B-127, GT.

4-22-74 DIGGS 1-GERALD ULRIKSON...ORNL 1-RD..MULLER..F-309 G

.1-B 6.M,SWINEBROAD,.Rm E-201.GT

~ ~

NIAGARA MOHAWK POWER CORPORATION NIAGARA "+j MOHAWK lPgggt 300 ERIE BOULEVARD WEST SYRACUSE. N. Y. 13202 IIA ~A)'ORI bofg- ~'C~0O April 18, 1974 .'~

Mr. Dennis L. Ziemann, Chief Operating Reactors Branch ¹2 Directorate of Licensing Division of Reactor Licensing United States Atomic Energy Commission i'washington, D. C. 20545 Re: Provisional Operating License: DPR-17 Docket No: 50-220

Dear Mr. Ziemann:

Your letter of March 20, 1974 requested additional information concerning the control rod drive conversion program at Nine Mile Point Nuclear Station, Unit ¹1. In particular, the enclosure to your letter specified three question areas. The response to those questions is as follows:

1. The proposed conversion program consists of the repositioning of a filter to place this filter in the flow path. for reactor water to the stop piston seals and not in the scram path.

(Figure 1) The fine mesh filter was originally mounted on the traveling portion of'the drive and early in plant life, prior to changing the mesh size, was responsible for deteriorating scram times. However, with the repositioning,t;the filter is mounted on top of the stop piston and is provided to filter reactor water flowing to the stop piston seals, removing foreign, particles or abrasives matter that could result in internal damage to the seals. This modification has been recommended by General Electric Company, the nuclear steam supplier, and is the design incorporated on later plants . Based upon testing results of all control rod drives, criteria has been established in determining the scheduled modifi-cation of all control rod drives. A withdrawal stall leakage flow test was performed on all control rod drives.

Continued

t

>r

The result of this testing showed that those drives stopping at position 02 following a scram'. ~'. had the highest stall leakage flows. Therefore, using this test method a schedule for modification was derived as follows:

1. Modify all drives that have clear indication of stop piston seal deterioration, (those that stopped at position 02 on a scram) .

2. "

Modify all drives with withdrawal stall leakage flows equal to or greater than 4 gpm.

3. Modify the remaining drives in decreasing stall leakage flow order time permitting.

Part three (3) of the criteria indicates that all drives may not be modified this refueling outage. An attempt will be made to modify all 129 control rod drives, however, this modification becomes critical path for the outage and some low stall leakage flow drives may not be modified until the next annual outage.

Eighty control rod drives will be modified this outage as a minimum (this is the 4 gpm cut off point). The outage is scheduled to end May 26, 1974.

2. As described in the response to question 1, the appropriate test to use in determining the amount of leakage from the upper set of stop piston seals is the withdrawal stall flow leakage test. This is conservative as stall flow leakage is the sum of collect seal and stop piston seal leakage.

As a weekly requirement during power operqtion,. control rod drive exercising is done. This test verifies that all control rods are capable of movement. It has been practical to incorporate a withdrawal stall leakage test in this procedure,

'for control rods at position 48. This can be used as a method of determining the extent if any of deterioration of upper stop piston seals.

During the previous operating cycle, 22 control rod drives experienced stop piston seal deterioration to the extent that flow past the upper set of stop piston seals to the discharge (the discharge is common to flow thru the buffer holes) was enough to prevent the drive from latching at position 00. Thru analysis, it has been shown that:

1. The drive would settle only to position 00 (normal) or 02 (high leakage) and no higher withdrawn position,

2. The reactor would be shutdown under these conditions.

3. The control rod drives that settled to position 02 could in all cases be inserted to 00 using the manual control system.

4. Approximately 20'o of the drives (all without modification) failed to insert to position 00.

Continued

~k lt

Therefore, it can be concluded that if those unmodified control rod drives during the next cycle experienced the stop piston failure in the same percentage, the result would be more conservative than the previous cycle.

A single drive where the upper set of stop piston seals are leaking greater than 6 gpm presents a reasonable probability of latching in tto position 02 instead of position 00. Thru testing with all stop piston seals removed the stop piston leakage was slightly greater than 6 gpm and the drive did.,

settle to position 02. This would be the maximum deterior-ation condition. If the deterioration of all seals is present the control rod drive would be difficult to withdraw from the fully inserted position and could settle to position 02 following a scram.

3. The process computer monitors certain vital parameter enabling a "post mortum" study following a reactor scram.

One point monitored is scram dump volume (SDV) hi hi level.

The time to reach the SDV hi hi level can be obtained from the computer. On November 20, 1973,2eleven drives failed to insert to position 00. They settled into position 02.

During that scram the amount of time necessary to reach SDV hi hi level was over 60 seconds indicating that even with high leakage the effect was not seen in SDV. Following each reactor scram this parameter would be monitored to assure that the times to fill to hi hi level are greater than the average scram time. lilith the modification to limit deterioration of the stop piston seals it is expected that times to reach SDV hi hi level will increase.

Very truly yours, R. R. Schneider Vice President Electric Operations

1. JAFNPP 50-333

2. AOR 73-11-20

3. AOV 73-11-29

I

'6 4 4

2 RING FLANGE c3 , SOCKET HEAD CAP SCREW (RING FLANGE MOUNTING)

<<4 .

FILLISTER HEAD SCREW (POSITION INDICATOR PROBE MOUNTING)

• 5 LOCKWASHER (FOR PART 4)

"8, 7 5 PISTON TUBE 29 72 80 71 25 61 23 12

<<9 71 66 28 0-RING (PISTON TUBE) 10 NUT (PISTON TUBE)

-12 STOP PISTON

'13 SPLIT BUSHING (STOP PISTON) 14 SEAL RING (STOP PISTON)

'15 SPRING WASHERS

'16 COTTER PIN (STOP PISTON)

P17 INDEX TUBE

<<18 BAND

<<19 COLLET AND PISTON 20 SEAL RING (COLLET PISTON INTERNAL)

'21 SEAL RING (COLLET PISTON EXTERNAL)

'23 FILLISTER HEAD SCREW (GUIDE CAP PLUG-MOUNTING) 0 RILLED FILLISTER HEAD SCREW (OUTER FILTER aaaaa

-I

'25 aa ea e e ae e a e a aadpeaedc aaaaa dc dp a a e ee aeaedp OUNTING) ooe eo eeoc oo dcd>adcdpe ooooooooooeodcpoeo ceo eeoc oee e a ooooo

~ FLAT HEAD SCREW (INNER FILTER MOUNTING) eeoc ooo doe oe oo eecp deuce e

'29 BAND

<<34 DRIVE SCREW (NAMEPLATE MOUNTING)

"35 BALL RETAINER

'36 BALL (CHECK VALVE)

• 37 0-RING (BALL RETAINER) 70 38 0-RING SPACER 16 49 P41 POSITION INDICATOR PROBE

'49 PLUG (GUIDE CAP)

<<50 0-RING (INSERT AND WITHDRAW PORTS)

<<51 0-RING (CRD FLANGE FACE)

<<55 SET SCREW PLUG (COOLING WATER ORIFICE)

'57 SCREW (0-RING SPACER MOUNTING) (NOT SHOWN)

<<59 COLLET SPRING

'60 BARREL ,2E G 1 Zy )P

• 61 GUIDE CAP

• 63, 74 NAMEPLATE

• 64 FLAT HEAD SCREW (STRAINER MOUNTING)

'65 STRAINER OUTER FILTER DRIVE PISTON SPUD ROD

<<72 TUBE

'73 CYLINDER, TUBE,"AND FLANGE

<<77 DOWFL (ALIGNMENT) PIN 78 COLLET HOUSING (PORTION OF OUTER TUBE) 79 SPACER (PART OF CYLINDER, TUBE, AND FLANGE)

<<80 INNER FILTER aaaaaa aaeaaaa ea&ae edc 81 82 POSITION INDICATOR SWITCHES INDEX TUBE NOTCH a O a e O e e Oee ooe O o eeeooooooeodeoeoeoeoo e aC'ae e o e e o e Cp o e dce e dce dpo dco ae eo Oe ee Cpd' a

OUTER TUBE (PART OF CYLINDER, TUBE, AND ceo o ooo oo oooo CP eoeeeoee e 83 FLANGE) ccc e cp o cpcDcp cDe ecp Ocp CDe eed CP CP CP CP O PP O e e ecp oe cD CP CD CP O O O cD CP 84 INNER CYLINDER (PART OF CYLINDER, TUBE, AND FLANGE) 85 THER>MOCOUPLE (PART OF POSITION INDICATOR PROBE) 70 86 ST(h) (PORTION OF PISTON TUBE) 87 COLLET FINGER (PART OF COLLET AND PISTON) 88 11(DICATOR TUBE (PART OF PISTON TUBE) 89 INNER SEALS {DRIVE PISTON BUFFER SEALS) 90 Seal 1<ing Inner 1:ilter

iZ P~~

~ ~

i 'yP

'I