IR 05000263/1977021
| ML20024G566 | |
| Person / Time | |
|---|---|
| Site: | Monticello  |
| Issue date: | 11/23/1977 |
| From: | Little W, Maura F NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| To: | |
| Shared Package | |
| ML20024G565 | List: |
| References | |
| 50-263-77-21, NUDOCS 9102120674 | |
| Download: ML20024G566 (5) | |
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S U.S. NUCLEAR REGUIATORY COMMISSION OFFICE OF INSPECTION AND ENFORCl>iDiT
REGION III
Report No. 50-263/77-21 Docket No. 50-263 License No. DPR-22 Licenseet Northern Stat es Power Cotepany 414 Nicollet Hall Hinneapolis, MN 55401 Facility Names Monticello Noelcar Generating Plant Ins,pection att Monticello site. Monticello, MN Inspection Conducted: November 5-8, 1977 Inspector:
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Approved by:
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[8_d Nuclear Support Branch I_nspection Summay
,1nspection_on No_vember 5-BulE7,Refo,r,t_No._ 50-263/77-21)_
A r,e s In sp,e,c t ed :
Routine, announced inspection to review the procedure, witness the test, and review the results of the containment integrated Icak rate test. The inspection involved 41 inspector-hours onsite by one NRC inspector.
Re_sul_t s : No items of noncompliance or deviations were found.
9102120674 771120 PDR ADOCK 05000263 o
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DETAILS,
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1.
Persons Contacted
- L.
Eliason, Plant Manager
- H. Clarity, Superintendent, Plant Engineering and Radiation Protection
- D. Antony, Plant Engineer, Operation H. Shamla, Plant Engineer, Technical
- D. Goranson, Engineer H. Theobalt, Computer Engineer The inspector also talked with and interviewed several other licensee employees including shift supervisors, reactor operators, instrumentation personnel, plant engineers and student engineers.
- denotes those present at the exit interview.
2.
T_est Procedure Test procedure $3016, Rev. 3 approved November 4, 1977, was reviewed prior to the performance of the test and found to comply with the requirentcts of the Technical Specifications and 10 CFR t
50 Appendix J.
In general the procedure also complied with pro-posed ANS N274, Rev. 3.
Procedure changes required during the test were processed in accordance with Technical Specification require-ments. Among the items discussed with the licensee prior to the test were:
a.
The acceptance criteria did not specifically require the upper confidence limit to be within.075 Lt. however, the licensee stated their policy has always been to include the upper confidence limit, b.
The procedure permits the subtracting of local Icakage rates f rom the ILRT results in case penetrations leak excessively during the tests and require repairs following the ILRT. The inspector discussed with the licensee the problems created by allowing this practice. This item was further discussed at the exit ir:terview.
c.
The valve alignment checklist for the instrument air, nitro-gen, and service air lineups depended on one closed valve to-2-(
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prevent the air or nitrogen from leaking into the contaitvoent during the test. After discussing the problem with the Ifeensee the procedure was revised to include at least two closed valves in series with the line between both valves vented to the reactor building. The inspector verfied dur-ing the test that the agreed upon valve lineup had been implemented.
The inspector verified that a copy of the procedure and changes to it were being utilized by the personnel perform-ing the test.
Sign offs to indicate completion of specific steps were being observed.
No items of noncompliance or deviations were identified.
3.
Test Instrumentation Twenty RTD's and six dewcells were used to measure temperature and dewpoint of the five subvolumes into which the containment was divided. Each sensor was calibrated, separate from its trans-mitter, and the 3 point calibrations were traceable to NBS standards.
The transmitters were calibrated separately to match the utandard model curve which had been entered in the computer.
(Model 104 (
heavy duty curve for the RTD's, and Foxboro NR-226 and DI-2 curves
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for the deweells) While this is not the prefered method to cali-brate this equipment, the inspector, by comparing the results of each sensor calibration to the standard curve to which the trans-I mitters were calibraa.d; determined that the largest deviation for t he temperature sensors was 10.2r and for the deweells of i 0.6T.
The inspector discussed with the Itcensee the desirability'
of having the sensors and transmitters, as a unit, calibrated to the curve entered in the computer.
A pressure gauge (0-60 psig) with a readibility of 0.01 psi was used to monitor containment pressure. Another pressure gauge with a readibility of 0.1 psi monitored reference system pressure. An inclined manometer (0-20 inches of water) with a readibility of 0.01 inch was used to measure the A p between the reference system and t he containment. A digital manometer (0-60 inches of water) with a display to 0.01 inches was used as backup to the inclined manometer.
For the superimposed leak rate test a flowrator rotameter (0.5 to 4.5 scfm at 14.7 psia and 70F) with a resolution of i 0.005% was utflized.
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Calibration traceable to NES exist for all of the above pressure gauges, differential pressure devices and the flovmeter.
No items of noncompliance or deviations were identified.
4.
Integrated Leak Rate Test The ILRT was performed during the period of November 6-8, 1977.
Temperature and vapor pressure data was printed by the process confiter every 10 minutes. All other readings were recorded manually every 30 minutes. Data was reduced every 30 minutes in accordance with the point to point and total time methods described in ANSI N45.4-1972 and the mass plot method described in ANS N274, Rev. 3.
The upper confidence Ifmit was based on the T-distribution function with N-1 degrees of freedom for the point to point and total time methods, and N-2 degrees of fre? dom for the mass plot method. The obtained 95% confidence band is more restrie-tive than the requirements of ANS N274.
A stabilization period of, -6 hrs was observed. By 2000 hrs on November 6,1977, the stabilleation criteria of ANS N274 was met. The test commenced at 2100 hrs on November 6, 1977. At the end of 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, the results in vt%/ day, were as follows:
Licensee's Inspector's 1, Reference Vessell LAbsolute Pressurel Point to Point 0.2582 1 0.0246
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Total Time 0.3108 1 0.0139
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Mass Plot 0.2488 1 0.0069 0.3795 1 0.0092 It should be noted that the equations used by the inspector are those of ANS N274 which give a 90% confidence band.
The Technical Specifications limit. 0.75 Lt. is 0.90 wt%/ day.
Following completion of the ILRT the licensee introduced a leak rate of 4.63 scfm (approximately 60% Lt) or the equivalent of 0.71 wt%/ day. The measured leak rate in wt%/ day as determined by the licensce's data reduction method af ter 6 hrs was:
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Point to Point - 0.9697 1 0.0342 Total Time
- 0.9883 1 0.0205 Mass Plot
- 0.9996 1 0.0089 The results were well within the acceptance criteria of 10 CFR 50 Appendix J.
No items of noncompliance or deviations were identified.
Exit Interview
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The inspector met with licensee representatives (denoted in Paragraph 1)
at the conclusion of the inspection on November 8.1977. The inspector summartred the scope and findings of the inspection and praised the outstanding job done by the station personnel in the performance of the integrated Icak rate test. The licensee made the following remarks in response to certain of the items discussed by the inspector:
A permanent procedure revision will be made to ensure all systems which could introduce air or nitrogen into the containment during the test are isolated by two valves and the volume between the two valves is vented; and that the acceptance criteria vill state that the upper con-I fidence limit shall be f.0.75 Lt.
(Paragraph 2)
If they ever have to use the subtraction of leakages, enough testing will be performed and the documentation will be available to show that the subtracted leakage rate did not include IcakaSe into the contain-ment.
(Paragraph 2)
In the future, the calibrafit..i of the RTD's transmitters and deweells converters will be performed to match their respective sensors calibra-tion to the standard curve entered in the computer.
(Paragraph 3)
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