ML20155G696

Forwards Response to NRC Compliance Bulletin 88-008, Thermal Stresses in Piping Connected to RCS, Requesting Review of RCS to Identify Connected Unisolable Piping Re Unacceptable Thermal Stresses

ML20155G696
Person / Time
Site:	Davis Besse
Issue date:	10/08/1988
From:	Shelton D TOLEDO EDISON CO.
To:	NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM)
References
1585, IEB-88-008, IEB-88-8, TAC-69622, NUDOCS 8810170336
Download: ML20155G696 (6)

Text

TOLEDO

%ss EDISON A Cerura fregy Ccnway DONALD C. SHELTON Docket No. 50-346 License No. NPF-3 Serial No. 1585 October 8. 1988 United States Nuclear Regulatory Commission Document Control Desk Vashington, D. C.

20555

Subject:

Response to NRC Complianet Bulletin No. 88-08 Gentlemen P

Toledo Edison (TE) hereby submits the information requested by NRC Compliance Bulletin No. 88-08, "Thermal Stresses in Piping Connected to Reactor Coolant l

Systems", dated June 22, 1988 (Log No. 1-1855). Additionally, supplements 1 and 2 to Bulletin 88-08 (dated June 24, 1988 and August 4, 1988 respectively) vere revieved. These supplements did not include any new requirements. The subject bulletin requested that licensees review their reactor coolant systems (RCS) to identity any connected unisolable tiping that could be subjected to temperature distributions which result in unacceptable thermal stresses. The bulletin further requested licensees to take appropriate action, where such

(

piping is identified.

The results of the reviev are included in the attached evaluation performed by I

Toledo Edison.

Based on this evaluation it is concluded that the intent of Bulletin 88-08 vill be satisfied upon completion of the items listed in the i

conclusion to this response.

Very truly yours, I

hwA RVG/dlm l

cci P. Byron, DB-1 NRC Resident Inspector l

A. V. dea azio. DB-1 Senior NRC Prcject Manager F

A. B. Davis, Regional Administrator, NRC Region III t

6 o s i

THE TOLEDO EDtSON COMPANY EDtSON PLAZA 300 MADtSON AVENUE TOLEDO. OHIO 43652 I l I

r

-_._---,__-____~._,_..___._._2

Dockot No. 50-346 Liccnse No. NPF-3 i

Serial No. 1585 Page 2 i

t Response to NRC Bulletin No. 88-08 For i

i l

Davis-Besse Nuclear Power Station I

]'

r Unit No. 1 h

i i

1' I

I i

This letter is submitted in conformance with Atomic Energy Act of 1954 Section l

182a, in remponse to NRC Bulletin 88-08 (Log no. 1-1885) "Thermal Stresses in j

Piping Connected to Reactor Coolant Systems".

l 1

By:

D. C. Shelton, Vice President, Nuclear I

l l

Svorn and subscribed before me this 8th day of October. 1988.

i I

l i

l

// {l{

\\.{f'f(

(Rotary Public, State of Ohio l

1 i

LAURIE A NHellt Notary Public. SMe of 0Wo D Camida Egira Mg it,1W1 I

J 1

l v

I 1

Dockot No. 50-346 License No. NPP-3 Ser.ial No. 1585 Page 3 Response to NRC Compliance Bulletin No. 88-08 As discussed in NRC Compliance Bulletin 88-08, thermal fatigue of unisolable piping connected to the RCS can occur when the connected piping is isolated by a leaking block valve, the pressure upstream of the block valve is higher than RCS pressure, and the temperature upstream is significantly lover than RCS temperature. The actions requested in this bulletin should provide assurance that unisolable sections of piping connected to the RCS vill not be subjected to stresses that could cause fatigue failure.

The following sections provide Toledo Edison's response for each of the applicable actions requested in Bulletin 88-08:

NRC Item 1:

1 Reviev systems connected to the RCS to determine whether unisolable sections of piping connected to the RCS can be subjected to stresses from temperature stratification or temperature oscillations that could be induced by leaking valves and that vere not evaluated in the design analysis of the piping.

If none are identified no further action 's required.

TE Response The following connections / penetrations vere reviewed to determine whether i

unisolable sections of piping connected to the RCS could be subjected to temperature stratification or temperature oscillations that could be induced by leaking valves:

1.

Pressurizer surge line (1) 2.

Pressurizer spray / auxiliary spray line (1) 3.

Core Flood /Lov Pressure Injection (2) 4.

High Pressure Injection (4) 5.

Letdown (1) 6.

Reactor Coolant drains / vents (several) 7.

Decay heat drop line (1) 1 8.

Sample line (1) 1 9.

Pilot operated relief valve, PORV (1)

Wote: Numbers shown in parenthesis are the number of penetrations into the RCS f

The direction of flov for the Letdown line, Reactor Coolant Drain / Vent lines, Sample Line, and PORV connections is out of the RCS.

Therefore, these penetrations vill not be exposed to the thermal stress failure mechanism described in Bulletin 88-08.

The High Pressure Injection (HPI), Lov Pressure Injection (LPI), Core Flood (CF) Systems, and the Decay Heat d op line all have a lover operating pressure i

than the RCS, hence the e vill be no leakage into the RCS from these l

penetrations.

Hovever, one HPI penetration which is being used for normal makeup vill have in-flov to the RCS cold leg. The makeup system normal i

Dockat No. 50-346 Liecnso No. NPF-3 S:;rici No.1585 Attachment Page 4 operational discharge path to the RCS is through the HPI line to the loop 2-1(A) cold leg (Figure-1).

Cross-connection to loop 2-2(A) HPI is through normally closed containment isolation valves HP2A and HP2B.

Makeup flov leakage to the loop 2-2(A) cold leg must pass through these two valves.

If HP2A leaked, pressure svitch PS2883A on the manifold between these valves vould alarm computer point PAH P465.

Prassure indicator PI2883A vould then I

alert operating personnel of the leakage so that corrective action can be initiated. Therefore, inadvertent makeup leakage into loop 2-2(A) HPI line can be adequately detected.

The Makeup and Purification System was modified during the current (fifth) refueling outage to enhance feed and bleed cooling capability following a loss of all secondary side cooling.

An additional HPI nozzle on the loop 1-2(B)

HPI line is being utilized to inject makeup vater in conjunction with the norms 1 makeup HPI nozzle on loop 2-1(A) to achieve this enhancement. This flow path is currently planned to be normally isolated and would require leakage through two closed valves (either HU 6419 and HU 6421 or HU 6421 and HU 6423B) for any makeup sater to reach RC loop 1-2(B).

An alternative method of operation utilizes a minimum bypass flov path which has been provided to allov operation vith the new line unisolated.

In this case, the minimum bypass flov vould protect loop 1-2(B) connection from thermal stresses.

The piping, computer alarm configuration and instrumentation for the installed modification are identical to that described for the normal makeup flovpath such that inadvertent leakage into the loop 1-1(B) HFI line vould be detected.

In addition, a makeup flow path into the ECCS injection line exists through normally closed isolation valves HU208 HP26 and HP2C or HP2D.

This leakage path requires three normally closed valves to leak by for makeup vater to reach the loop 1-1(B) or loop 1-2(B) HPI line.

Detection of inadvertent leakage through this path vould be accomplished by the same instrumentation described above, i

The prersurizer surge line and the spray line vere also considered in the review of RCS connected piping.

A continuous flov of reactor coolant into the pressurizer is maintained via the spray line. The pressurizer surge line is i

always filled with reactor coolant, however, due to temperature stratification experienced on the surge line at the Vest German Huelheim-Kaerlich (B&V) plant, the B & V Ovner's Group Haterials Committee has been assigned a task to review the generic concern and recommend appropriate actions to determine if similar conditions exist at plants in the United States.

Toledo Edison vill implement applicable recommendations from this reviev.

NRC Item 2:

For any unisolable sections of piping connected to the RCS that may have been subjected to excessive thermal stresses, examine nondestructively the velds, heat-affected zones and high stress locations, including geometric discontinuities, in that piping to provide assurance that there are no existing 11avs.

l

~

1 l

Dockot No. 50-346 i

Licens No. NPF-3 Serial No. 1585 Attachment J

Page 5 h

i TE Respong A thermal sleeve in the HPI nozzle assembly for RCS normal makeup is utilized l

to provide a thermal barriet between cold HPI/HU fluid and the hot HP! nozzle.

]

The purpose of the thermal sleeve is to reduce thermal shock and fatigue of l

the nozzle. A minimum bypass flow is provided via MU 58A and MU 588 (See

]

Figure 1) to prevent temperature stratification in the thermal sleeve.

During the current refueling outage, it was discovered that the thermal sleeve j

had experienced a failure which appeared to have been the result of high cycle thermal fatigue.

An investigation of the incident was conducted and a letter i

4 was transmitted to the NRC (Serial 1580, dated September 14, 1988) to document this occurrence. The results of nondestructive examinations (NDE) performed t

1 during the investigation vere presented in that correspondence.

Recommendations from the investigation and a schedule for implementation vere also included in the Toledo Edison letter. Although not due to valve leakage, this is the only area which is known to have been subjected to excessive thermal stresses.

NRC Item 3:

{

I Plan and implement a program to provide continuing assurance that piping I

identified in NRC Item 1 do not experience unacceptable thermal strerses by:

l A.

Redesigning and modifying these sections of piping, 3

J or i

i l

3.

Instrumenting this piping to detect adverse temperature 1

distributions and establishing appropriate limits on

)

temperature distribution

'i

)

or i

I c

C.

Providing means for insuring that pressure upstream from block

(

valves which might leak is monitored and does not exceed RCS l

pressure, f

l l

TE Response i

]

As previously stated in Toledo Edison response to NRC Item 1, current instrumentation installed upstream of the HPI line isolation valves vould i

j detect any inadvertent makeup leakage into the RCS. Therefore, inadvertent 4

leakage into the HPI line can be adequately detected and action can be takan I

to prevent unacceptable thermal stresses.

[

Conclusion f

l Based on Toledo Edison's evaluation of the actions requested in the bulletin, f

i the following action vill be taken j

l i

1.

Irplement applicable recommendations f rom the BW Ovner's Group review i

of potential surge line concerns r

i I

i l

DAVIS-BESSE HPI/MUP Qw L.

2 2

r-,

r, c

M16421 3 f N MJ6419 M kw y

E ' l-l y

&A Vm O

MU208 M

C) i l

MJ6422 NU32

$7 l e 1-2 i

mwe L.

2

$$b K

a, N6420 aaa

=

=

x,z

=

y 2

"E%*

~

s *; t E i

a.u g

10 LO'JP

~

t L2-2-1(A)

IfiORMAL PATH)

}F2 2893A 2883A 8 i

3 T

l C

l b%

TO LOOP _

k-2 8

HPI l-2 J (g 2-2(A) ~

r-,

-l 8.,

1928 8

c s

N (P465}

-i\\

I#

10 LOOP _

b d

b2 i

!-2(B) r-7 J (&

llP2C g

j i

2883B 2883(I i

3 l

C l

l TO LOOP _

'--4 HPI l-1 1-1(0) r-,

HP2D l

---