ML19031A914

LER 1976-004-01 for Salem, Unit 1 Regarding 1A Vital Instrument Bus Transfer, 1RH2 Closed Resulting in a Loss of RHR Flow to RCS

ML19031A914
Person / Time
Site:	Salem
Issue date:	02/17/1977
From:	Schneider F Public Service Electric & Gas Co
To:	O'Reilly J NRC/IE, NRC Region 1
References
LER 1976-004-01
Download: ML19031A914 (4)

Text

Frederick W. Schneider Public Service Electric and Gas Company 80 Park Place Newark, N.J. 07101 201/622-7000 Vice President Production 1*,

' February 17, 1977 Mr. James P. O'Reilly Director of USNRC Off ice of Inspections and Enforcements Region 1 631 Park Avenue King of Prussiar Pennsylvania 19406

Dear Mr. O'Reilly:

LICENSE NO. DPR-70 DOCKET NO. so~272 REPORTABLE OCCURRENCE 76-04/3L SUPPLEMENTAL REPORT Pursuant to the requirements of Salem Generating Station Unit No. 1 Technical Specifications, Section 6.9.1, we are submitting.

a Supplemental Report to 76-04/3L dated 9/15/76.

Sincerely yours, 2076 CC: Director, Office of Inspectibri and Enforcement (30 copies)

Director, Office of Management Information and Program Control (3 copies)

SUPPLEMENTAL REPORT TO

- - - _a LER 76-04/3L 9/15/76 -

LICENSEE EVENT REPOA f9 _ - --- -_

CONTROL BLOCK 6

UCENSEE L.ICENSE EVENT NAME L.ICENSE NUMBER' TYPE . TYPE

@l!J!N tJt S !GI S 111 150101-10101010101-101qJ Js4lll ll ll 1Jo 10 111

~

- . ~

CATEGCRVR~~..:T :~~~~~ . CCCKET NUMBER EVENT DATE . REPORT CATI!

IOTt1 CON'Tt.RJ..Qj

~ 57 68 L9

. 59

~

60 I 0 I 51 0 I -I 0 I 21 71 2J 61 .

I 0 I 91 0 I 21 71 61 69 74 I 0 I 11 21 81 71 75 id-EVENT DESCRIPTION _

.@Ell During Mode 6 operation, RHR System-in service. the 1A Vfral 7 8 9

@1!11 Bus was being transferred to an alternate source of power to allow 7 89

@El the lA Vital Instrument Bus Inverter to be deenergized. Durin the

• j0 15j I lA Vital Instrument Bus transfer, 1RH2 closed resulting in a: loss of ,. - *.

7 8 9 so

~I rum. flow to. the RCSU. No-redundant system was available during this 1*

7 8 9 CAUSE PRIME COMPONENT COMPONENT so SYSTEM CODE* CODE COMPONENT CODE SUPf'L.IER MANUFACTURER" VIOL.ATIOH*

--@mtE 1B I - U2J IZ IZ IZ IZ IZ.IZ r LLl - I zl 919 I9 I l~. J 7 8 9 10 11 12 17 43 44 47 48 CAUSE DESCRIPTION

~I The 115 VAC vital instrument busses are nomaJJy fed through their

~{associated inverters. These inverters* are eguipped with automatic 7 8-9

[ilfil I load transfer.switches which trans£ er the load to the -backup power 7 8 9 FACILITY METHOD OF

- STATUS .. ___ ;_"°'POWER-* - - - --OTHE-RSTATUS* --OISCOVER*Y* -- _-- DISCOVERY DESCRIPTlON

[fil ~. --- I O! Q 01 I NIA - . I l..aJ N&

I~46=---".!..'-"-'1---------------;......;----"----~so J*

1 a g 10 _ 12 13 44 45 FORM OF- - .

ACTIVITY CONTENT

[lfil 7- 8 w

REL.EASED OF RELEASE.

', 9 . -

LI 10 . - - 11 I

AMOUNT OF ACTIVITY N/A 44 I -1.,..,,____

45 L.OCATION OF REL.EASE N._/=A_ _ _ _ _ _ _ _ _-...:1 so -

PERSONNEL EXPOSURES

. NUMBER TYPE DESCRlllTION * - .

1010101 1..[JI~-~--~N~/~A:...----~~-~~------~-~-dJ 1 -s 11 12 13 - iiO

- ---- PERSONNEL INJURIES -

NUMBER DESCRIPTION (IE] I 0 10 I 0itI

7. a 9 12_

• ,.....-_ _ _ _ ....;N=/....;;;A=*-------------------=' ao OFFSITE CONSEQUENCES l'"ilsl 1 N/A 74 9.

LOSS OR DAMAGE TO FACU..ITY TYl'tt' DESCRIPTION-i ls! t;J.

1 .,,,110.-----....--~.;;;NL../:.:A~----...,.----------------------zi(J PUBUCITY Gfilt NIA r.

- -------_- 7 8c9 so AODITIONAl. FACTORS ITJ!)t Supplemental Report to 76-04/3L 1 a g

[ill] ""'__E_VE_N_T_D_E_s_c_R_I_P_T_I_ON_&_c_A_u_s_E_DE_s_c_R_I_P_T_I_o.....N...._;,(C_o_n_t_i_n_u_e_d_o_n_P_a_:g;:..e_2...:;)_ _ _ _ _.'=:!,

7 89 ~

NAME=*~----~T~*~L~**;,.......:S~p~e~n~c~e~r--_______________ PHONE: (609) 365-7000 .Ext*. Salem- 5

• __.L~cense Event Report 76-04/31 Page 2 EVENT DESCRIPTION (Continued) occurrence. Corrective action* for* this event was to establish administrative controls as follows*:

A. When operating at or below 10% reactor power:

1. Will not allow maintenance or calibration of the lA-lD inverters.

B. When operating above 10% reactor power:

1. Will not transfer lD Vital Instrument Bus as a reactor trip signal will result due to the "General Warning" trip in the* SSPS.

c. At any reactor power level, will not transfer any vital bus if* another protective channel bistable is. in a tripped condition since the protective_... :**

logic. for the function would then be complete.

This is the first occurrence of this type. (76-04/3L).

CAUSE DESCRIPTION (Continued) source only when both the inverter output voltage and current are zero (0).

• However, due to NRC requirements, the supply breakers for the backup source for the vital. instrument busses must be tagged open.

PROBLEMS:

A. When transferring the IA vital instrument bus to back-up power, 1RH2 valve closes due to an. erroneous HIGH pressure signal caused by an 8-cycle* (approx.)

loss of voltage during .the transfer. Also, a P-7 reactor trip signB.l is generated if the reactor is below 10% power due to de-energization of turbirie

• first stage pressure bistables.

B. When transferring*the lB vital instrument* bus,* the-loss of-voltage due .to*

the switChing causes the lRHl*valve to close, also, one source range channel is lost, resulti.ng in a reactor trip signal - "HIGH neutron flux-source-range."

C. When transferring the lC vital instrument bus, the Reactor Protection Channel III trips, initiating a P-10 permissive and a resultant de-energization of both No.* 31 and 32 source range channels.

- ~~ - --- - - - - - *- - - - : - ' " . -

i: '

" - -License Event Repqrt 76-*L Page 3 CAUSE DESCRIPTION (Continued)

ANALYSIS OF PROBLEMS:

On September 23, 1976, a test was made on the lA vital instrument bus transfer switch. It was shown that there exists an 8 1/2 - 9 cycle loss of voltage from the instant the 1A inverter's output breaker was opened to the time the transfer switch's contacts closed on the backup supply. After investigation, it is apparent that modification of the transfer switch to obtain a minimal loss of voltage period is not feasible. Because of the 1-2 millisecond operating time of the.bistable comparators used in the protection racks, even the 1/4 cycle transfer time of static switches would.still trip these bistables. Therefore, administrative control is necessary to minimize the- impact of vital instrument bus transfers on the plant.