ML17276B643

Forwards NRC Position Paper Closing Out Licensing Review Group II Channel Box Deflection Issue

ML17276B643
Person / Time
Site:	Columbia
Issue date:	09/22/1982
From:	Schwencer A Office of Nuclear Reactor Regulation
To:	Ferguson R WASHINGTON PUBLIC POWER SUPPLY SYSTEM
References
NUDOCS 8210080068
Download: ML17276B643 (8)

Text

p ~P ivy Docket No.:

50:397 Mr. R. L.

Fer.,tl,uson Managing Director Ilashington Public Supply System P. 0.

Box 968 3000,george Washington May Richkand, Hashington 99352

Dear Mr. Ferguson:

DISTRI B UTION:

~k LB¹2 File Local PDR RAuluck NSIC EHylton PRC I'SE

Paton, OELD Region V

ACRS (16)

MTokar

Subject:

Resolution of LRG-II Channel Box Deflection Issue (LRG-II Issue 3-CPB)

In a generic topical report (NEDE-21354)

General Electric descri,bes a

chahnel lifetime prediction mich'od and a backup recommendation for periodic channel deflection measurements that consist of settling friction tests.

Upon consideration of the factors inv'olved, the NRC staff concluded that the settling friction tests or an acceptable alternative (such as, channel dimensional deflection measurements) should be performed.

Basically, the staff accepted a multistep procedure that had been proposed by the Zimmer applicant.

The key ingredient of the ',Zimmer plan was a commitment to:

a) perform some control l."'od settling friction tests, which would provide an exact profile of control rod drive friction versus position at refueling

outages, or b) make some actual'1 channel dimensional measurements.

'llith a 'letter (D. L. Holtzscher, Illinois Power Company, to Howard J.

Faulkner, NRC) dated May 17, 1982, LRG-II submitted a position paper.'on channel box deflection that incorporated sev'eral of the same features as the Zimmer proposal.

The staff has reviewed this:submittal and has prepared a position paper closing out this issue for L~RB-II plants.

A copy of the staff's position paper is enclosed.

To maintain our licens'ing review schedule for IlNP-2, please respondj to the channel box deflection issue for MNP-2 as soon as possible.

Please contact Raj Auluck, Licensing Project Manager, if your desire, any discussion or clarification.

'-Sincerely, f 82i0080068 8209M PDR ADQCK 0500031117 A

PDR

Enclosure:

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R. L. Ferguson Managing Director.

Washington Public Power Supply System P.

0. Box 968

~,3000 George Washington Way

Richland, Washington 99352 CC:

Nicholas Reynolds, Esquire Debevoise 8 Liberman 1200 Seventeenth

Street, N.

W.

Washington, D. C.

20036 Mr. G.E.

Doupe, Esquire Mashington Public Power Supply System P.O.

Box 968 3000 George Washington Way

Richland, Washington 99352 Hicho1 a s Lewi s, Chairman Energy Facility Site Evaluation Council Nail Stop PY-ll Olympia, Washington 98504 Roger Nelson, Licensing Manager Washington Public Power Supply System P.O.

Box 968 Richl and, Mashington 99352 Nr. W.G.

Conn, Sr, N/N Group Supervisor Burns and Roe, Incorporated 601 Milliams Boul evard Richl and, Washington 99352 Nr. Richard Feil U.S.

NRC Resident Inspector MPPSS-2 HPS P.O.

Box 69 Richl and, Washington 99352 Dr. G.D.

Bouchey Deputy Director, -Safety 8 Security Washington Public Power Supply System P.O.

Box 968, MO 650

Richland, Mashington 99352

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ENCLOSURE Resolution of LRG-II Channel Box Deflection Issue (Issue 3-CPB)

BWR fuel channels provide structural stiffness for the fuel assemblies and distribute the coolant flow between the assemblies and channel bypass regions.

The channels are subject to time-dependent, permanent dimensional changes (i.e., deflections) that result from irradiation, creep and stress-relaxation effects.

The resultant bulge (resulting from long-term creep) or bow

( resulting from differential irradiation-induced axial growth) reduces the size of the gap available for control rod insertion.

Channel box deflection is thus a potential life-limiting phenomenon.

In a generic topical report (NEDE-21354 ) General Electric describes a

channel lifetime prediction method and a backup recommendation for periodic channel deflection measurements that consist of settling friction tests.

Upon consideration of the factors involved, the NRC staff concluded that the settling friction tests or an acceptable alternative

( such as, channel dimensional deflection measurements) should be performed, and in a memo-randum (L.S. Rubenstein to R.

L. Tedesdo) dated September 18, 1981, the staff outlined a method for resolving the channel box deflection issue for several near-term BWR operating license applications, which included

LaSalle, Shoreham, Susquehanna, Zimmer, Feei 2; Grand Gulf, Clinton, WHP-2, Perry and Riverbend.

Basically, the staff accepted a multistep procedure that had been proposed by the Zimmer..applicant.

The key ingredient of the Zimmer plan was a commitment to: a)

~ perform some control rod settling friction tests, whichwould provide an exact profile of control rod drive friction versus position at refueling outages, or b) make some actual channel dimensional measurements.

Plants that agreed to the Zimmer proposal and for which we were able to close out the issue completely included: (in addition to Zimmer) LaSalle, Fermi-2, Grand Gulf, and, with a slight modification, Clinton.

With a letter (D. L. Holtzscher, Illinois Power Company, to Howard J.

Faulkner, NRC) dated May 17,

1982, LRG-II submitted a position paper on channel box deflection that incorporated several of the same features as the Zimmer proposal, viz:

a)

Records will be kept of channel locations and exposure for

'ach operation cycle.

b)

. Channels shall not reside in the outer row of the core for more than two operating cycles (because flux gradients are largest near the core periphery and, therefore, differential irradiation-induced growth and bowing will be greatest at those locations.)

c)

At the beginning of each fuel cycle, the combined outer row residence time for any two channels in any control rod cell shall not exceed four peripheral cycles.

In addition, LRG-II stated that channels that reside in the periphery (outer row) for more than one cycle shall be situated each successive peripheral cyle in a location which rotates the channel so that a different side faces the core edge.

Me believe that this should help to reduce uni-directional irradiation-induced

growth, and should thus lessen channel

bowing, and that the other measures outlined above would also help to reduce the magnitude of channel deflection.

Like the Zimmer proposal, the LRG-II position statement contains a descrip-tion of a control rod drive friction test that would be performed for those core cells exceeding the above general guidelines or containing channels with exposures greater than 30,000 Mwd/t (associated fuel bundle exposures).

'n the LRG-II position paper, the control rod drive settling friction test is described in considerable detail.

For instance, it is stated that after reload and again before: reaching 40'5 thermal

power, a friction test shall be performed (for those cells exceeding the above general guidelines), in which each control rod will be allowed to settle a total of two notches, one notch at a time, from the fully inserted position.

Total control rod drive friction would be acceptable if the rod settles, under its own weight, to the next notch within approximately ten seconds.

The settling friction test described by the LRG-II is sai'd to provide an equivalent level of test to that described in NEDE-21354.

To be precise, the LRG-II test is equivalent to a so-called "screening-type" test (described in NEDE-21354) to identify any control rod drive where the force required to insert is greater than approximately 250 lbs. '(equal to the settling pressure times the piston area).

But whereas in NEDE-21354, it is indicated that rods failing the screening test would be given another settling friction test to obtain an exact friction-versus-position profile, the latter type of test is not mentioned by LRG-II.

The LRG-II position is that failure of the proposed settling time test would "prompt an investigation," which, if necessary, would lead to corrective action.

While we believe that a commitment to perform an exact settling friction profile test (or actual dimensional measurement) i s preferable (because it would provide an estimate of the margin and physical state of the system in an unambiguous way), the LRG-II and General Electric Company (in NEDE-21354 ) have stated that the control rod drives will tolerate a

relatively large increase in driveline friction (~350 lbs.) while still remaining within technical specification limits.

The screening-type test proposed by LRG-II would, thus, provide assurance of the scram function.

Therefore, we accept the LRG-II position that the proposed actions will preclude excessive channel bowing in the LRG-II plants (i.e., River Bend and Perry).

We are continuing our review of this phenomenon (and the GE report), however, and should our review indicate that a modification to the proposed steps is necessary, thd licensees will be so notified.

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