ML20148F496

Summary of 780201 Meeting W/Util in Bethesda,Md Re Environ qualified,safety-related Terminal Block Replacement Inside Containment

ML20148F496
Person / Time
Site:	Yankee Rowe
Issue date:	02/03/1979
From:	Burger A Office of Nuclear Reactor Regulation
To:	Office of Nuclear Reactor Regulation
References
TASK-03-12, TASK-3-12, TASK-RR NUDOCS 8011050667
Download: ML20148F496 (7)

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ket No. 50-29

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(:f LICENSEE: YANKEE ATOMIC ELECTRIC COMPANY (YAEC) ie.)

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FACILITY: YANKEENUCLEARPOWERSTATION(YANKEE-ROWE)

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SUMMARY

OF MEETING HELD ON FEBRUARY 1,1978 CONCERNING

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YANKEE-ROWE On February 1.1978, during a meeting at the NRC offices in Sa' hesda, t

Maryland, YAEC briefed the staff on actions they have taken in con-2 nection with the replacement of safety related terminal blocks inside f

the Yankee-Rowe containment, with ones that are environmentally qua.lified.

As a matter of background, the mcent replacement of connectors inside containment at the Haddam Neck Plant with teminal block / boxes identified a generic safety concern with respect to the environmental qualification of unprotected (exposed) teminal blocks inside con-

~y tainment for safety related electrical equipment that would have to be capable of withstanding the adverse conditions during and following H

the most limiting design basis accidents. Connecticut Tankee Atomic Power Company (CY) the licensee for the Haddam Neck Plant performed M

. conservative screening tests on January 25 and 26,1978 ta determine if an existing exposed terminal block (Marathon, Model 6012), and a potential replacement teminal block (Westinghouse, Model f542247) 4 would perfom as intended in a containment accident environment at r H the Haddam Neck Plant.

In the tests, the Marathon blocks did not hH survive for the full exposure time (one faileri after 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> following

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an unplanned temperature-pressure excursion in excess of intended

'd values and the other failed after 21 hours2.430556e-4 days <br />0.00583 hours <br />3.472222e-5 weeks <br />7.9905e-6 months <br /> of the planned 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> 1

exposure period). The Westinghouse teminal block passed the full 1

24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> test. Concurrent with CY's actions and briefing of NRR in j

a meeting on January 29,1978, (described in a meeting summary on Docket No. 50-213 dated January 30,1978), D0R conducted a telephone survey of all licenseess to determine whether any unprotected (exposed) safety related terminal blocks are installed inside containment of operating reactors. On January 30, 1978, YAEC advised the staff that Yankee-Rowe had several safety related exposed teminal blocks inside containment, which t)ey had decided to replace with environmentally qualified teminal blocks before resumption of operation.

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b Meeting Summary for Yankee-Rowe

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At the February,1977 briefing YAEC provided oral infomation to the NRC staff on the safety evaluation YAEC had perfomed for the terminal block replacement at Yankee-Rowe. The highlights of that briefing are summarized below.

h For perspective, on January 26, 1978, the plant had tripped because n

of an instrumentation malfunction and thus was in a shutdown mode when YAEC learned about the terminal block problem. YAEC established that there were several exposed safety related terminal blocks inside containment at Yankee-Rowe. YAEC obtained a sufficient number of the new Westinghouse terminal blocks which passed CY's screening test to implement their decision to replace safety related terminal blocks inside containment with environmentally qualified Westinghouse terminal 1

block prior to returning Yankee-Rowe to power.

The terminal block a

replacement was completed and carried out as a design change based on YAEC's assessment under the provisions of 10 CFR 50.59.

This change was reviewed and approved by YAEC's onsite and offsite safety review i

committees.

j YAEC established that there are a total of 76 safety related terminal j

blocks inside the Yankee-Rowe containment. About 6 terminal blocks N

are installed in the location of the reactor coolant loops between 1

the primary shield and the biological shield. These tendnal blocks are enclosed and thus are not directly exposed to the containment atmosphere.

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The balance of these terminal blocks are outside the biological shield.

About 17 are at the biological shield wall in enclosures and the remainder are in enclosure boxes at the containment penetration amas.

ED The covers on the boxes at the penetration areas were, prior to the

'O January 26, 1970 shutdown, not installed. The licensee has located d

all of these covers and stated they will be in place prior t*) return s

to power. Of the total of 76 teminal blocks replaced, about 6 were States, Hodel M25015, the others were Marathon, Model 6012 (the type that failed the CY screening test). The teminal blocks located between the primary shield and the biological shield which were already enclosed in boxes were replaced as a precautionary measure, YAEC presented information on its plant specific evaluation to demon-strate that the new Westinghouse teminal block would perfom as intended during accident conditions.

For environmental qualification of the new terminal blocks installed at Yankee-Rowe YAEC bases its evaluation, in part, on the qualification records developed for these same blocks by the Connecticut Yankee Atomic Power Company. With s.

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o Meeting Summary for

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FEBRUARY 3 19N Yankee-Rowe regard to the calculated Yankee-Rowe LOCA environment YAEC presented the attached graph (Containment Temperature Versus Time) which demonstrates that the above mentioned screening tests envelopes the calculated Yankee-Rowe LOCA transient.

YAEC has determined that because

.of the high elevation where the terminal blocks are installed there is no flooding problem. With regard to potential rad

,i has calculated a total integrated dose of 4.4 x 10{ation damage YAEC rads for the p

terminal block in the most exposed location.

YAEC indicated that E

l" thisprovidesanacc9ptablemargintothetotalintegrateddose raos for the new terminal blocks as established L

'l capability of 2 x 10 by Westinghouse (based on resistance characteristics). With regard y

f to ability to withstand seismic acceleration, YAEC indicated that

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Westinghouse information shows that the new terminal blocks can withstand significant g values (in excess of 1 g).

With respect to considerations of potential adverse effect of a p

steam line break on the new terminal blocks, YAEC indicated they had looked into this safety concern. The terminal block enclosures at A.-

the penetration locations are in the vicinity of two of the four main

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_ steam lines.

YAEC indicated that they considered this to be an acceptable risk taking into account separation by distance, low 4

O probability of occurrence of a steam line break in the area of con-cern and other means to bring the plant to a cold shutdown.

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YAEC stated that puttiag the 1/4 inch thick steel cover plates back on these enclosures eliminates the concern for direct steam jet impingement on the terminal blocks.

YAEC also stated that the enclosures' have drain holes to allow drainage of condensation.

1 With regard to the concern of superheated steam potentially causing a more severe temperature transient than previously considered, YAEC indicated that preliminary calculations have shown temperatures at the enclosures would not exceed 2750F except for a peak of short duration.

YAEC indicated that this temperature exposure would be less severe than the capability of the new blocks to withstand 340 F for 5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> without loss of function. YAEC was also aware that a test at Haddam Neck showed ability of the new blocks to withstand a 400 F temperature transient for 15 minutes.

With regard to plant conditions during the change of the terminal blocks YAEC confirmed that the reactor was shutdown in Mode 4, with the reactor coolant borated, and with a steam bubble in the pressurizer.

All applicable quality assurance requirements were implemented for this field design change.

Further, components were satisfactorily functionally retested after installing the replacement terminai blocks.

Documentation of the evaluation of all relevant safety considerations and the conclusions of the appropriate review committees will be completed prior to resumption of Yankee-Rowe operation which was expected by February 2,1978.

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Meeting Summary for '

p Yankee-Rowe FEBRUARY 3 1979 I

Subject to the above. YAEC's briefing confirmed that all safety

' considerations associated with the teminal block replacement have been appropriately addressed to meet the Commission's regulations and to provide reasonable assurance that Yankee-Rowe can continue to be operated safely.

It should be noted that, upon return to operatiori, there will be no unprotected (exposed) safety related tencinal blocks

l inside containment at Yankee-Rowe. All will be protected by enclosures.

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Original Signed By,

l A. Burger, Project Manager p 5 Operating Reactors Branch fl

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q Division of Operating Reactors Attachments:

1.i Attendeed List 2.: Graph-Containment Temperature

- e :. Versus Time cc's: See page 5 DISTRIBUTION Subje'ct File p

(All other cc's on Page 5) t N

ORB #1 ORB #1h\\f 3,,,,,

x27433 tsb,

ABurger.

WTRussell 2/3/78Q 2/ 3 /78 Nnc rGPO! 318 (9 76) NRCM 0240 Y u. s. oOVERNM ENT PRINTING OF FICEr 1979 - 6364 24

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i Meeting Summary for 5-1

i Docket NRC PDR LOCAL PDR t::

ORB #1 Reading HRR Reading E. G. Case V. Stello K. R. Goller D. Eisenhut A. Schwencer a

D. Davis G. Lear R. Reid L. Shao g..

B. Grimes W. Butler

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R. Baer

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Project Manager h:

Attorney, OELD

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Licensing Assistant Each NRC Participant Licensee T. B. Abernathy J. R. duchanan i..

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ATTENDEE LIST

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EETING WITH d!

YANKEE _ ATOM.I.C ELECTRIC COMPANY g..,

FEBRUARY 1,19_78

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NRC YAEC D urger A. Autio J. W. Reece F. D. Baxter D. G. McDmald G. Tsouderos K. R. Golier P. F. Laind b A. DiBenedetto S. E. Bryan A. SciNencer D. Ziemann t

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SURNAMEM DATE&

NRCTORM 518 (9 76) NRCM 0240 W ua s. GovsRNMENT PRINTING OFFICEt 1978 = e3M&4

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