ML20101B424
| ML20101B424 | |
| Person / Time | |
|---|---|
| Site: | Prairie Island  |
| Issue date: | 06/01/1992 |
| From: | Eliason L NORTHERN STATES POWER CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 9206040050 | |
| Download: ML20101B424 (3) | |
Text
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Northem Sta'es Power vpany 414 Nrallet Mall Minaeapohs Minnesota 55401 1927 Telephone (612) 330 5500 w
June 1, 1992 10 CFR Part 2 Section 2.201 U.S. Nuclear Regulatory Commission ATTN.*
Document Control Desk Washington, DC 20555 e
FRAIR1E IS1AND NUCLEAR GENERATING PLANT Docket Nos. 50-282 License Nos. DPR 42 50 306 DPR.c0 Reply to a Notice of Deviation NRC Inspection Report No. 306/92009 Loss.nf RHR Flow during Eh111AoyD Pursuant to the provisions of 10 CFR Part 2, Section 2.201, the following is submitted in response to the notice of deviation contained in your letter of April 30, 1992.
Deviation:
In the attachment to your letter of January 6,1989, " Response to Generic Letter 88-17 Loss of Decay Heat Removal", you committed to perform e modification to pcovide two indeperdent reactor coolaut system C
(RCS) level indications, with inctallation to be compieted for Unit 2 durieg the September 1990 refueling outage.
Contrary to the above, on January 3,1990 you issued modification l
package 86Y740, "RCS Loop Level Indication", for Unit 2 which did not prc ide for two independent RCS level indications. The modification, as installed during the September 1990 Unit 2 refueling outage, did not provide twr. independent JCS level indications.
Specifically, both channels of electronic RCS level indication installed by the modification were pressure compensated from the same pressure transmitter.
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s 92060A0050 920601 PDR AmDCK 05000282 O
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USNRC Nodhem States Power Company-June 1. 1992 Page <
Reason for the Deviation Modification 86Y740 "RCS Loop Level Indication" was iscued to install two independent level indicatore for the Reactor Coolant System while in the reduced inventory condition.
Independence was lost when one reactor _ pressure indication (sensed at the Pressurizer Relief Tank) was used to compensate the level instruments for reactor pressure.
The plan to use one instrument to compensate both readings _challengedLthe independence of the design. There was only one suitable reactor pressure indication -the Pressuriner1 Relief Tank pressure instrument--available to provide the information for compensation.
The modification engineers failed to realize that the use of one pressure instrument for compensation would remove the independency at the two level = instruments. This oversight by-the modification engineers is an isolated occurrence, gorrective Actions Taken and Results Achieved Procedures were developed prohibiting the use of nitrogen overpressure during reduced inventory operations for the rest of the February 1992 refueling outage. The pressure compensation from the Pressurizer Relief Tank used in the process computer was defeated. These actions provided indepeno. t instrumentation for the remainder of the February refueling outage an_there 4
was no need for pressurized reduced inventory operations while pressurized Corrective Action To Be Taken To Avoid Further Deviations For future reduced inventory operations, we will assure _that _ndependent level instrumentation is-available.
The long !+cm. solution 1 to add a non-intrusive level indication system on the not leg.
If reduced inventory operations are necessary prior to installation of this modification, the
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reactor coolant system will.be vented to containment atmosphern prior to entry into reduced inventory operations. _lio pressure _ compensation is required in the vented condition where the existing instruments provide independent indication.
The new instrumentation may only provide indication of level in the hot' leg.
We interpret this to comply with the intent of Generic Letter-88-17 even though level above tha hot leg will not be'able to be quantified, p -
Date When Corrective Action Will be Comoleted We will provide non-intrusive hot leg level indication prior to the next planned entry into a Reduced Inventory condition for either unit.
If the hot e
leg level indication Ls needed and not available, the core will be unloaded.
9 Northern States Power Company
,USNRC June 1, 1992 Page 3 1
Please contact us if you have any questions or wish further information 1
concerning this reatter.
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C i
'l Leon R.iason i
Vice President Nuclear Generation c: Regional Ad.ministrator, Region III, NRC Senior Resident Inspector, Monticello Site, NRC NRR Project Manager, NRC J Silberg l
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