ML20010D694
| ML20010D694 | |
| Person / Time | |
|---|---|
| Issue date: | 07/24/1981 |
| From: | Advisory Committee on Reactor Safeguards |
| To: | Advisory Committee on Reactor Safeguards |
| Shared Package | |
| ML20010D695 | List: |
| References | |
| ACRS-1877, NUDOCS 8108310022 | |
| Download: ML20010D694 (8) | |
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DATE ISSUED:
7/24/81 p
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MEETING MINUTES OF THE gggy
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U ACRS ECCS SUBCOMMITTEE MEETING
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h *i.h JULY 7,1981 POR &/G/8I g
WASHINGTON, D.C.
g On July 81981 the ECCS Subcommittee held a meeting in Washington, D.C.
The purpose of the Meeting was to review the NRC RES Programs in the areas of LOCA and Transient Pesearch and LOFT for the Committee's annual Reports to the Comission and Congress.
Dr. Plesset Subcommittee Chairman, con-vened the meeting at 8:30 a.m.
Attendees:
Principal attendees are listed below.
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ACRS NRC s
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- d FC Tlesset, Chairman H. Sullivan, RES j
NgSgg\\#b D. Ward D. McPherson, RES
/ 4, C. Mark (part-time)
S. Bassett, RES G
P. Boehnert DFE L. S. Tong, RES E
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F. Odar, RES fj/
INEL W. Beckner, RES
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s 'C Golbrig W. Lyon, RES
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B. Tolman R. Landry, RES N. Zuber, RES B. Sherson, NRR N. Lanbin, NRR Meeting Highlights, Agreements, and Requests 1.
Dr. H. Sullivan reviewed the RES budget expenditures for the LOCA and Trasient Research and LOFT Program elements. The LOCA and transient r.
element is continually decreasing through FY-84 ($31.0M - FY-83,
$30.3M - FY-84) and no provisions have been made for inflation. LOFT l
is budgeted at $40.6M fc,r FY-83 decreasing to $14.lM for FY-84.
In response to Dr. Plesset's question, RES said a compromise between the Senate and House versions of the NRC FY-82 budget bill for LOFT (House version - $30.0M, Senate version - $45.5M) should be completed no later i
than mid-August.
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2.
The status and planned development of the RELAP-5 code was discussed l
by W. Lyon. RELAP-5 is an advanced system code designed to model LOCA
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and opvational transients.
It is being used by NRC to support LWR experiments and in development of rulemaking and operator guideline ac tivi ty.
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8108310022 810724 PDR ACRS 1077 PDR L
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ECCS Meeting July 7,1981 Accomplishnents for FY-81 include release of the 710D-1 version of RELAP plus 1 number of model improvements. For FY-82, the modeling required for PWR transient capability is scheduled to be completed. The code
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will also be used to support the PBF severe core damage experiments.
In response to a question from Dr. Plesset, RES r.oted that one of the f
most difficult problems is modeling of two-phase flow. RES hope to get access to some air-water and air-steam data to aid this effort.
In FY-83 the completed PWR version noted above should be released for E
public use and the BWR version should be completed.
bi Mr. Lyon showed comparisons of code predictions vs. data. He emphasized L
that RES strives to obtain consistent predictions and not tune the code I
to each spacific test facility. NRR commented, at the Chairman's request, that their, experience with RELAP-5 has been good. They also said that Exxon Nuclear and Yankee Atomic plan to use RELAP in support of their EM licensing codes in the near future.
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3.
Mr. Odar (RES) discussed the status of the TRAC BWR code development.
The TRAC code is designed to be a detailed best-estimate BWR system
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code for modeling of design basis LOCAs and operational transients.
h The BD1 (BWR - Detailed) version was released for public use in February 1981. Presently a BD1 - MOD-1 version is under development, r
MOD-1 will extend the code's capability to model operational transients and ATWS. BD1 model development is scheduled to be complete by October 1982.
t Dr. Plesset inquired as to the status of the COBRA / TRAC code link designed to model UHI plants. NRC said this code is complete and should be released to the National. Software Center in 1-2 months,.
4 In response to a question from Mr. Ward, Mr. Odar said TRAC-BD1 runs 10 times as fast as RELAP-4/ MOD-6.
4.
Mr. Odar discussed the status of the code assessment program.
In FY-82 there is wS2.69M budgeted for assessment of RELAP-5/ MOD-1 and the TRAC PD2, PF1, and BD1 versions. TRAC-PD2 assessment is scheduled
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ECCS Meeting July 7,1981 to be completed in March 1982 with the remaining codes' assessment
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complete in October 1982.
In response to a question from Dr. Plesset, RES said that the report detailing the assessment process (NUREG-0676) should be available to the ACRS within a week or so.
Some preliminary results of TRAC-PD2 assessment were discussed. RES said PD2 shows good improvement over PD1 in calculation of multi-
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dimensional phenomena but that numerical consequence problems (calcula-tion of 2-phase phenomena) still exist for some cases (vapor fraction predictions).
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Dr. N. Zuber briefly outlined the content of the code assessment report -
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He noted that the most important aspect of code assessment involves comparisons of code predictions with tests in full scale plants
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and various US and foreign test facilities. Dr. Zuber said the code assessment process involves making many choices among alternative approaches i
and that dialogue will drive the evolution of r. ode accuracy.
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In response to a question from Mr. Ward, RES said Code Review Groups and the solicitation of comments on 0676 from the technical community will r
drive the dialogue noted above. RES is aiming for a consensus in the technical community as to what is acceptable and sufficient accuracy
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and detail for these codes.
' f; 5.
Mr. L. Shotkin (NRC-RES) discussed the TRAC-PWR status and planned improvements. TRAC-PD2 was released in July 1980, PF1 should be re-leased July 1981. The MOD-1 version of PF1 is scheduled for release in July 1982 and the last release (TRAC-PD3) is scheduled for December 1983.
Details t.f the improvements made to the PWR TRAC versions were noted (Figurds 1&2).
It is planned to extend the code's capabilities to all currently conceived accidents, except seve:e core damage, by the end of CY 1983. The codes will then go to a maintenance status and be improved as neCessary.
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ECCS Meeting July 7,1981 6.
An overview of the LOFT test program was presented by D. McPherson.
In response to Commission' direction, some of the ancillary tasks (human factors studies, electrical / nuclear heater comparison, etc.)
have been reduced in scope or deleted. The current proposed test schedule was also reviewed (Fig. 3).
i-Mr. C. Solbrig discussed the objectives of some of the planned LOFT tests in response to concerns expressed by the ECCS Subcommittee at its meeting on March 27, 1981. The L5-1 (intermediate break) test is designed to investigate the ECCS effectiveness E~ breaks between tra large break (accumulator injection) and small break (high pressure inj ec tion). The L8-1 (slow core uncovery) test whicn has suffered two unsuccessful attempts, will be piggybacked on a small-break test sched-uled for late 1982. The objective of this test is to determine if the core can be cooled by restarting the pumps after partial or complete uncovery (steam cooling). The ATWS tests (L9 series) will try to determine if the codes can predict maximum ATWS pressure, phenomena
~k occurring at this pressure, and how to recover the plant. The uncer-tainties in moderator temperature coefficient and boron distribution will also be investigated. The large-break experiments (L2 series)
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are designed to investigate, among other things, whether with pumps-off no core rewet will occur.
Results of the latest LOFT test, loss of all feedwater and delayed reactor scram (L9-1/L3-3) were discussed. This test attempted to simulate the early portions of the TMI-2 accident. Af ter loss of feed and reactor scram on high pressure, the relief valve was allowed to cycle open and closed. The valve was then locked open and the pumps were tripped. There was little mass loss from the primary system and no core uncovery. The pre-test code predictions showed poor.esults when compared to the data. The main reason for the poor comparison was due to incorrect heat transfer, particulary the modeling of secondary side i
heat sinks.
1 ECCS fleeting July 7,1981 o.
Dr. McPherson said that RES had discovered that commerical plant models had similar model deficie'ncies which when corrected are believed to give' the operator more time to take action in a transient similar to the one above.
Mr. R. Landry (RES) discussed the details of various research informa-tion letters (RILs) resulting from the LOFT program (Fig. 4).
Important results include:
(1) ATWS tests showed improvements are needed in code predictive capab.'ity, (2) for small break LOCA, natural circulation readily occurs in single and two-phase modes and that RCPs should be tripped early in a SB LOCA, (3) for LB LOCAs - small scale electric experiments are adequate for separate effect studies but are not ade-quate to assess nuclear core thermal hydraulics; and (4) the augmented i.
operator capability program has demonstrated the usefulness of computer f
based diagnostic color graphics for the control room and technical
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support center (TSC).
F Mr. B. Tolman (INEL) discussed the results of experiments designed to characterize the LOFT exterior cladding thermocouples. His main I
points were:
(1) external cladding thermocouples can influence rod response under certain hydraulic conditions, (2) nuclear rods cool faster than electric rod simulators, (3) an improved electric rod simulator design is needed for non-nuclear experiments, and (4) con-firmatory nuclear tests are needed to assess conservatism when elect. ic rods do not simulate nuclear rod response.
Dr. McPerson said that the additional conservatism seen in the use of electric rod simclators should be quantified.
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Dr. Plesset commented that while the above infonnation is of val,ue it applies only to the LB LOCA and other a:cidents have now been shown to be of greater safety significance.
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The Semiscale test program and results was discussed by Mr. W. Lyon (RES). The FY 81 program was oescribed. Currently, the natural l
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ECCS Meed ng July 7,1981 l'
l circulation tests have begun and the W liquid level device is being tested. Dr. Plesset asked' how the natural circulation tests will differ from similar tests run at PKL.
RES said Semiscale tests a
should give a better indication of reflux flow and noncondensible l
gas behavior.
In FY 82, additional natural circulation tests are planned; also intermediate break LOCA, loss of offsite power, and steam generator tube rupture (SGTR) tests are scheduled. The loss of offsite power tests will also include tests of the upper head vents being installed in plants as a post-TMI requirement. The FY 83 schedule l
is less clear. The SGTR tests will be complete and it is hoped the MOD-5 (B&W plant design) will be constructed and operating.
Test results noted included:
(1) heat loss tests - M00-2A losses
(/v90 KW) are less than MOD-3 losses (*80-180 KW) but still must be compensated for in slow transients, (2) UHI SB tests - UHI con.-
figuration appears to offer less margin for protection in SB LOCA tt non-UHI due to the use of 400 psi loop accumulators.
In response to questions on this point Mr. Lyon said the tests indicate j I that UHI does aid core cooling if the loop accumulators are set at l l 400 psi, but it is not as effective as having no UHI and setting the l
loop accumulators at 600 psi. Further discussion on this point centered on the fact that there is no ideal accumulator setting for the complete LOCA break spectrum.
The proposed M00-5 test series was discussed. Because of NRR require-ments that the B&W utilities verify with integral test data their SB LOCA model, NRC proposed a joint NRC/B&W Owner's Group effort using Semiscale. The NRC proposal is that the Owner's Group pay the capital costs ($15-20M) and NRC would pay operating costs. Tne Owner's Group response to date has been less than enthusiastic. Negotia-tions are continuing.
8.
The NRC/EPRI/GE BWR research programs were reviewed by N. Beckner (RES). These programs include the TLTA/ FIST facility for the study 1
ECCS Meeting July 7,1981 S
of blowdown ECCS and the 30 steam sector test facility (SSTF) for study of BWR refill /reflood.
The TLTA facility tests have shown that counter current flow limitation (CCFL) at both the top and bottom of k
the test bundle has aided heat transfer and resulted in rapid reflood.
This was' true for both large and small breaks.
The FIST (full integral simulation tcst) facility is a full scale (vertical) single channel facility (Fig. 5). The Phase 1 test series scheduled to start in early FY 83 will focus on small and intermediate break LOCAs.
Phase 1 NRC costs for FY-83 are w$1.617M, but *$1.3M g
of this amount is carryover from the TLTA program.
The refill reflood program was detailed.
The spray distribution
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tests are, complete and a report (NUREG/CR-1707) has been issued.
Single heated bundle reflood heat transfer tests are also complete and a report is due out soon.
In addition to the above, the TRAC BWR code development is coordinated with this program. The 30 SSTF tests (Fig. 6) have begun and preliminary results froa separate effects tests indicate that multi-dimensional effects (3D) were seen, and I
that upon initiation of low-pressure injection-subcooled CCFL breakdown occurred, resulting in large water delivery to the core region.
9.
The 2D/3D Program was reviewed by H. Sullivan (RES). The Program members (and associated facilities) include: Japan (slab core test a
facility ",CTF, and cylindrical core test facility - CCTF), Germany (upper plenum test facility - UPTF), and NRC (advanced instrumentation h
and code (TRAC) analysis). A " fica chart" of the 3D program inter-I actions was described (Fig. 7). Figure 8 shows the entire 2D/3D Program interactions and projects t
i The UPTF facility and its impact on the 2D/3D Program was discussed.
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Because of delays in the start of construction of UPTF, the coordinated Japaneese tests will be delayed and NRC's associated costs will also be impac ted. NRC is attempting to limit its total cost to approximately L>
ECCS Meeting July 7,1981
$91M when contingencies are considered. To date NRC has spent $44M.
Becaase of the delay in constructing UPTF the program will run to 1987 instead of terminating in 1985.
- 10. Dr. Sullivan provided a brief status on other LOCA programs..He k
noted that FLECHT-SEASET will perform 163-rod bundle blockage t(sts and natural circulation tests. These tests and the related analysis will be completed in FY-83, terminating the program. The ECC-bypass work is also complete. The K-star scaling method used by NRR has been supuported by the test results from the BCL and CREARE facilities.
- 11. The meeting was adjourned at 4:55 p.m.
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