ML20217C556

Submits Test Rept for Oregon State Univ,Test Dates 940719 & 940721

ML20217C556
Person / Time
Site:	05200003
Issue date:	09/06/1994
From:	Bessette D, Dimarzo M NRC OFFICE OF NUCLEAR REGULATORY RESEARCH (RES)
To:	Mcpherson G NRC (Affiliation Not Assigned)
Shared Package
ML20217C479	List: ML20217C474 ML20217C501 ML20217C508 ML20217C514 ML20217C522 ML20217C544 ML20217C550 ML20217C556
References
NUDOCS 9803270061
Download: ML20217C556 (5)

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1. E'4 p 't UNITED STATES j j NUCLEAR REGULATORY COMMISSION

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%".....,/ Seotember 6,1994 MEMORANDUM FOR: G. Donald McPherson, Senior T/H Expert Division of Systems Ssfety & Analysis Office of Nuclear Reactor Regulation THRU: Louis M. Shotkin, Chief Reactor and Plant Systems Branch " " /p,)[fdn.

Division of Systems Research Office of Nuclear Regulatory Research FROM: Marino diMarzo Thermal / Hydraulic Testing Section Reactor and Plant Systems Branch Division of Systems Research 80b([t/ d([P -

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i Office of Nuclear Regulatory Research ' .

David E. Bessette, Section Leader Thermal / Hydraulic Testing Section i,5 p O 6 '

4 Reactor and Plant Systems Branch Division of Systems Research Office of Nuclear Regulatory Research

SUBJECT:

TEST REPORT FOR OSU (Test dates 071994 and 072194)

Referonces: 1. J.N. Reyes, Scaling Analysis for the OSU AP600 Integral System and Long Term Cooling Test Facility, H Report OSU-NE-9204

2. M. diMarzo, Request for Additional Information on Friction Number Assessment for the OSU AP600 Facility, Memo to M.J. Virgilio on July 18, 1994

3. M. diMarzo,- Request for Additional Information Concerning the Behavior of the SPES Test Facility During SBLOCA Transients, Memo to M.J. Virgilio on August 8, 1994 We (D. Bessette and M. diMarzo) visited the OSU test facility on July 19-21, 1994. During our visit, we had the opportunity to: a) witness two tests; b) browse through data collected during previous tests; and c) discuss some of our thoughts with the crew that operates the facility.

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G. Donald McPherson 2 September 6, 1994 Activities in Prenaration to the Visit We reviewed the draft scaling report listed in reference 1. The issue of total losses ratio [f(L/D)+K] was raised in the single and two-phase scaling >

procedure described in the document. A request for additional information was forwarded through NRR to M (see reference 2).

Additional concerns were raised about the pressure scaling rationale. Two potential problems were identified: a) the pressure scaling is based on a quasi-steady state analysis which is not applicable during rapid depressurization transients such as ADS 1 through 3; and b) the facility experimental data are extrapolated to plant conditions in terms of an absolute pressure ratio. This is unrealistic since the system has no notion of a zero

.reforence pressure.

The concerns about the scaling rationale have implications on the timing of.

the accumulators discharge because their gas pressure.is set in terms of scaled pressure. In some of the transients, CMT draining is resulting from a very delicate balance of flashing and condensation. This balance may be l_

. altered when pressure is scaled due to properties variation.

We reviewed the overall system behavior based on tests conducted with the ,

ROSA-AP600 facility. Several potential atypicalities of the ROSA-AP600 l facility due to the cold leg geometry and to the elongated aspect ratio were i considered in. light of the more. prototypic configuration of the OSU facility. l Consideration was given to the test program that NRC intends to perform at the OSU facility beginning in Fall 1994. In particular, we intended to assess the j L level of OSU personnel training and their data analysis capability. We also reviewed the instrumentation placement and density in relation to the phenomena that were observed in the ROSA-AP600 facility.

On-Site Observations The OSU facility is built to the highest standards. The crew of operators is most capable and extremely well trained. We were impressed by the level of professionality of the personnel. Time prevented an in-depth review of the Q/A documents and implementation. However, the handling of a mechanical problem on the test conducted on July 21, 1994, revealed a meticulous care for the details and an outstanding technical capability of the crew.

The conduct of the tests and .the facility housekeeping in general was outstanding. The documentation was readily.available, updated and very clear.

Prior to the initiation of-each test, the operating procedures were carefully )

reviewed, the personnel and the visitors were instructed as how to act during 1 Lthe test,lwhat to expect, who.to ask questions of and when, etc. Clearly.

. defined lines of authority were established and firmly respected.

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.i G. Donald McPherson 3 September 6,1994 The tests were performed to the highest standards. The test conduct is fully i automated. The number of operators was more than adequate, the procedures were followed strictly, logs were promptly updated, the control room was quiet, well organized, and all interactions were to the highest professional standards. Data recording was carefully monitored and any anomaly was promptly noted. Recording frequency was of about 7-8 seconds (0.13 Hertz).

This frequency may turn out to be insufficient to record events which will be described in the following.

The personnel were composed of a highly trained W operator acting as test coordinator while the system console operator and the DAS console oparator were OSU personnel. The OSU personnel are well trained to run the facility but may need some limited supervision from a senior facilities engineer (e.g.,

INEL personnel) when the facility will be used by NRC.

Post-Test The data were carefully qualified. Each instrument trace was plotted in a long-term comprehensive format and in a 45 minute initial transient format.

l These formats are not adequate for the observation of some important phenomena which may occur after 45 minutes (e.g. in some tests ADS 4 actuation occurs after the initial 45 minutes).

There are phenomena observed within the first 45 minutes which also require a higher data acquisition frequency (i.e. 1-10 Hertz). The objectives of using these data are for: a) code assessment; and b) to understand the behavior of the facility. Therefore, we suggest that NRR should ask M to consider changing data acquisition frequency and data report forn.ats as appropriate to each specific test.

The number of instrument channels is redundant (800) in many regions of the system while it is lacking in others. It is recognized that an a priori ideal placement of the instrumentation cannot be achieved without the knowledge of the significant phenomena to be observed. Therefore, a flexible approach to instrumentation placement and acquisition frequency is highly desirable and, in this particular case, is necessary.

In particular, the OSU facility lacks significant density of instrumentation (i.e., TCs) in the cold legs and in the upper plenum. This lack of instrumentation prevents quantification of the saturated water layer and in general of the thermal stratification. Additional instrumentation would greatly enhance ti.c assessment of the impact of the observed condensation phenomena on the structural integrity of the upper plenum components. We suggest that NRR should discuss with M appropriate modifications of the-instrumentation placement consistent with the significant phenomena observed

.during the tests.

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G. Donald McPherson 4 SeDtember 6,1994 Comments l Two major observations resulted from this visit: a) the facility is built and

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operated to the highest standards; b) the data analysis feedback to the-experimental program is not effective. 1his second observation stems from the findings concerning data acquisition frequency and instrumentation placement' previously discussed. In general, we suggest that a faster feedback is needed

>etween the. analysis team and the crew at the facility In our view, NRR should suggest to M an upgrade of their internal procedures to review the data and to modify the test matrix and/or the facility based on the information gathered.from the experiments already performed.

i This suggestion is most important because the apparent lack of feedback between the analysis and the test matrix could limit the outcome of an otherwise outstanding experimental program. While the data are processed at the OSU site, the data analysis is performed in Pittsburgh. To this effect, consider that there is little understanding of the observed phenomena and of ,

the apparent anomalies associated with the instrumentation by the crew. A cursory review of some of the data revealed that, during the later portion of the transients, the steam generators on the primary side were full of superheated steam, while differential pressure level measurements indicated  !

that .they were full of liquid. This apparent discrepancy is probably due to a vacuum effect at the upper tap of the pressure differential cell reference leg.- No apparent knowledge or consideration of this issue was given by the crew. Rather, it was accepted that the steam generators were full of liquid.

s Another example of the problem that may arise from the lack of rapid feedback from the analysis team to the crew at the facility is provided by the finding ,

that condensation events similar to the ones observed in the ROSA-AP600 l facility were being experienced in the OSU facility. Unfortunately, the crew had little er no knowledge of them or of their implications. Reportedly, several' operators attributed the clanging associated with these events with the reactor vessel upper plate being loose. In fact, the plate was bolted down more securely in the hope of eliminating the phenomena.

f-The occurrence of the condensation pheromena in the OSU facility confirms the possibility of large vapor space collapses in the upper plenum for the AP600 design. The extent of these phenomena has to be carefully considered. - Note to this;effect that the ROSA-AP600 facility is significantly elongated and thus tt.e saturated liquid layer (that acts as a buffer between the vapor and the subcooled liquid) is morel stable. In the OSU facility, the saturated liquid layer aspect ratic is close to prototype. However, the reduced operating pressure suggests that a lower temperature differential (i.e.,

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G. Donald McPherson 5 September 6, 1994 subcooling) is present. In both cases, the phenomena observed will be amplified in the plant according to these considerations. We suggested that NRR discuss this issue with H in a recent memo (reference 3).

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