ML20209E086

Forwards Branch Review of Natural Circulation Boron Mixing Test Procedure Mods Based on Util 850225 Submittal.Procedure Acceptable.Licensee Committed to Submit post-test Rept for Review

ML20209E086
Person / Time
Site:	05000000, Diablo Canyon
Issue date:	03/14/1985
From:	Sheron B Office of Nuclear Reactor Regulation
To:	Knighton G Office of Nuclear Reactor Regulation
Shared Package
ML082410749	List: ML20209A984 ML20209B531 ML20209B624 ML20209B724 ML20209B847 ML20209B894 ML20209C131 ML20209C225 ML20209C292 ML20209C320 ML20209C516 ML20209C643 ML20209C669 ML20209C675 ML20209C698 ML20209C705 ML20209C710 ML20209C715 ML20209C720 ML20209C836 ML20209C847 ML20209C848 ML20209C876 ML20209C881 ML20209C908 ML20209C921 ML20209C969 ML20209C975 ML20209C981 ML20209C993 ML20209D004 ML20209D012 ML20209D018 ML20209D030 ML20209D038 ML20209D044 ML20209D045 ML20209D071 ML20209D089 ML20209D114 ML20209D127 ML20209D130 ML20209D135 ML20209D139 ML20209D146 ML20209D154 ML20209D211 ML20209D218 ML20209D230 ML20209D235 ... further results
References
FOIA-86-197 TAC-51638, NUDOCS 8503220478
Download: ML20209E086 (4)

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NAR 14 1985 MEMORANDUM FOR:

Licensing Branch - 3 Division of Licensing FROM:

Brian Sheron, Chief Reactor Systems Branch Division of Systems Integration

SUBJECT:

DIABLO CANYON UNIT 1 - NATURAL CIRCULATION PRETEST EVALUATION

References:

1.

Letter, G. Knighton, NRC, to J. Schuyler, PG & E Co.,

September 25, 1984.

2.

Letter, J. Shiffer, PG & E Co., to G. Knighton, NRC, October 26, 1984.

3.

Letter, J. Shiffer, PG & E Co., to G. Knighton, NRC, November 21, 1984.

4.

Letter, J. Shiffer, PG & E Co., to G. Knighton, NRC, February 25, 1985.

The Reactor Systems Branch (RSB) has reviewed the Diablo Canyon, Unit 1 Natural Circulation Boron Mixing Test procedure No. 42.7, and the Natural Circulation Pretest Report.

As a result of that review the RSB has identified several concerns which were, in turn, transmitted to the licensee, Pacific Gas and Electric (PG & E) Company by reference 1.

The licensee responded to the NRC's concerns by references 2 and 3.

With the exception of two items, all concerns were resolved by either procedure modification or by clarification. The two concerns that were not satisfactorily resolved, namely (a) use of the non-safety related Volume Control Tank instead of the safety related Refueling Water Storage Tank, and (b) tripping the Reactor Coolant Pumps as late as 30 minutes after the reactor has been tripped, were further discussed with the licensee.

Reference 4 documents the licensee's response to these concerns.

The staff has reviewed reference 4 and conducted additional discussions with the licensee.* These discussions resulted in further modifications to the test procedure.

• February 28, 1985 telephone conference with the following participants:

Sammy Diab, NRC (Bethesda)

David Sokalsky, PG & E (Bethesda)

Lou Grubmeyer, W (Monroeville)

Mike Norem, PG & E (plant site)

Chuck Coffer, PG & E (San Francisco)

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G. Knighton 2-The test procedure modifications are discussed in the enclosure to this memorandum. The RSB concludes that the Natural Circulation Test procedure is acceptable as modified, i

I We informed the licensee that an RSB representative would like to witness the test, which is tentatively scheduled for the first part of April 1985. The licensee has committed to submit a post test report after the completion of the test to show how it meets the RSB branch position RSB 5-1.

The post test report will be reviewed by the staff. We suggest that DL forward a copy of this memorandum to PG & E for their information.

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Brian W. Sheron, Chief Reactor Systems Branch Division of Systems Integration

Enclosure:

As stated cc:

R. Bernero R. Houston T. Novak H. Schierling C. Graves G. Mazetis D. Langford RSB Section Leaders

Contact:

S. Diab, RSB 3

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ENCLOSURE The Reactor Systems Branch (RSB) has completed its review of the Diablo Canyon Unit 1 natural circulation boron mixing test procedures and pretest report as discussed by the licensee's letters from J. Shiffer, PG & E Co., to G. Knighton, NRC, dated October 26, 1984, November 21, 1984 and February 25, 1985. The licensee was asked to justify (a) the use of the non-safety related Volume Control Tank (VCT) instead of the safety related Refueling Water Storage Tank (RWST), and (b) tripping the Reactor Coolant Pumps (RCPs) as late as 30 minutes after the reactor has been tripped.

In resolving item (a) above, the licensee stated that the RWST water contains high levels of dissolved oxygen.

If this water is injected in the Reactor Coolant System (RCS) while at hot conditions (above 200'F), the licensee argues that it will cause an excessive corrosion to take place at the nozzle connections to the RCS.

The licensee also stated that the use of the RWST will not provide significant additional information beyond that obtainable via the use of the VCT.

In resolving item (b) above, the licensee stated that the RCP operation after reactor trip will enhance achieving stable conditions in the RCS (i.e.

stabilize RCS pressure, temperature, and pressurizer level, and steam generators levels and pressures), and avoid subjecting the plant to a pressure rise transient that would follow a concurrent reactor trip and RCP trip. The licensee states that such a transient would be a dynamic simulation of a loss

6 of flow accident that is not required to satisfy RSB 5-1 criteria. The licensee also argues that RCP trip delay will not significantly affect RCS temperature distribution.

Since the staff's objective is simulation of RCS temperatures, including those in the upper head region, the staff will accept continued operation of the RCPs until RCS stabilization has been achieved subject to the following procedural changes:

1.

Start the magnetic head thermocouples recorder at 2 cm/ min. prior to the reactor trip.

2.

Start recording the readings of the upper head thermocouples at 2 minutes intervals from prior to the reactor trip.

3.

Provide the post scram information recorded by the plant computer.

The licensee, PG & E has accepted implementing the above changes in the test procedure, therefore, subject to implementation of these changes, the staff finds the test procedure acceptable.

The licensee has committed to submit a post test report to show how the test satisfies the RSB 5-1 requirements. That report will be reviewed by the staff to ascertain that cold shutdown can be achieved from the control room using only safety related equipment.

If a component'or a system is found to be j

inadequate the staff will require either upgrading it to safety related or substituting it by another safety related component or system.

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