ML19309B154

Provides Descriptions of long-term Lessons Learned Changes to Plant Shielding & Modified Sampling Sys to Minimize Personnel Exposure During Worst Case Accident Conditions

ML19309B154
Person / Time
Site:	Arkansas Nuclear
Issue date:	03/31/1980
From:	Trimble D ARKANSAS POWER & LIGHT CO.
To:	Eisenhut D Office of Nuclear Reactor Regulation
References
RTR-NUREG-0585, RTR-NUREG-585 1-030-22, 1-30-22, NUDOCS 8004030209
Download: ML19309B154 (7)

Text

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ARKANSAS POWER & LIGHT COMPANY POST OFFICE BOX 551 UTTLE ROCK. ARKANSAS a33 (501)371-4000 March 31, 1980 1-030-22 2-030-17 Director of Nuclear Reactor Regulation ATTN: Mr. Darrell G. Eisenhut, Acting Director Operating Reactors U. S. Nuclear Regulatory Commission Washington, D. C. 20555

Subject:

Arkansas Nuclear One-Units 1 and 2 Docket Nos. 50-313 and 50-368 License Nos. DPR-51 an, NPF-6 Lessons Learned Implementation Items 2.1.6.b and 2.1.8.a (File: 1510.3, 2-1510.3)

Gentlemen:

Pursuant to our January 31, 1980 letter and in accordance with your March 10, 1980 letter, Arkansas Power and Light Company herein provides descriptions of long-term changes to plant shielding and of a modified sampling system to minimize personnel exposure during worst case acci-dent conditions. These descriptions address Arkansas Nuclear One-Units 1 and 2 (ANO-1 and 2).

Item 2.1.6.b - Plant Shielding We have identified long-term corrective actions which will minimize personnel exposure. These modifications include:

1) Relocation of the clean and dirty liquid waste control panels from elevation 317' to elevation 354' on ANO-1. No access problems of unmanageable magnitudes were found on ANO-2 re-garding access to waste control panels.

2) Installation of an interlock to automatically isolate letdown and seal return on both units when core damage exceeds a point at which radiation levels become a hindrance to access around vital areas. Currently, the dose levels from 1% failed fuel are being considered as the set point beyond which isolation should occur.

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3) Modification of procedures on ANO-1 to warn against use of decay heat removal systems during accidents involving sig-nificant core damage. ANO-2 already has such . warning in the procedures.

Item 2.1.8.a - Post-Audit Sampling We have identified the conceptual design of a modified sampling system to minimize personnel exposure. This conceptual design (including new reactor coolant system sampling points) is described below.

1. Reactor coolant sampling and analysis -

We propose to incorporate an on-line monitoring system as described below and shown in Sketch 1. Liquid samples may be obtained from reactor coolant hot leg, pressurizer steam space, pressurizer surge line and containment sump in Unit 2.

In Unit 1, the reactor coolant hot leg pressurizer steam and liquid spaces, and containment sump may be sampled. New and existing sampling lines will be tapped outside the containment and routed to the respective unit in-line monitoring equipment room in the new sampling facility (see Sketch 4).

Sample coolers, pumps, air conditioning package, reach rod operated or remotely operated isolation and bypass valves, shielding required to ensure uncontrolled access to the com-puter and control panel area and necessary sample piping will be provided. Pressure regulators and orifices are included to permit sampling capability under pr;ssurized and depressurized reactor coolant conditions. The flowing sample effluent will be returned to the containment via the safety injection system piping.

On-line analytical instruments will include a gamma ray spec-trometer consisting of a liquid nitrogen cooled, intrinsic germanium crystal detector with stainless steel collimator and a microcomputer to perform continuous isotopic analysis in-cluding concentration levels.

The detectors will be located within the monitoring equipment room, whereas the computer and other electronics will be located in the shielded uncontrolled access area. Remote display will be provided in the Unit #1 and #2 control room.

Following the isotopic analysis, the sample will be depres-surized and hydroger. released from the liquid sample in an expansion tank. Gaseous hydrogen will be analyzed by a ther-mal conductivity type meter and dissolved oxygen in the liquid sample by an electrochemical cell method. Effluent hydrogen I will be returned to the containment through hydrogen purge system piping. The liquid sample will also pass through a j Boronometer and a chloride monitor before being returned to '

the containment.

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2. Containment Atmosphere Sampling -

We propose to incorporate an on-line monitoring system for radionuclide isotopic analysis. The proposed system to be duplicated for both Unit 1 and Unit 2 is shown in Sketch 2.

The detection system will utilize a nitrogen cooled intrinsic Germanium stainless steel collimated detector similar to the f

one described above. A single computer will be shrred by two detectors (liquid and gas) of both units. Sample lines will be heat traced as required. Containment atmosphere will be analyzed for hydrogen concentration utilizing the existing redundant hydrogen analyzers. To meet the requirement of the increased range, the analyzers will be modified and remote indicators will be added. Remote displays will be provided in the control room.

! 3. The sampling facility will be cooled by a packaged air condition-ing unit with its own exhaust system. The exhause will be monitored in accordance with 10CFR50 Appendix I requirements and the requirements for extended range measurement of noble gases, iodine and air particulates.

4. All equipment will be powered from the normal (non Class lE) power sources. Provisions will be made to connect the equipment 1

to the onsite emergency power source if the normal power source is not available.

Very truly yours, DavidC.Trimblehd#

j Manager, Licensing DCT:DGM:nak 4

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