ML20212G394
| ML20212G394 | |
| Person / Time | |
|---|---|
| Site: | Crystal River  |
| Issue date: | 10/28/1997 |
| From: | Raghavan L NRC (Affiliation Not Assigned) |
| To: | Richard Anderson FLORIDA POWER CORP. |
| References | |
| TAC-M96314, NUDOCS 9711060159 | |
| Download: ML20212G394 (10) | |
Text
_
October 28, 1997 Mr. Roy A. Anderson Senior Vice President Nuclear Operations Florida Power Corporation ATTN:
Manager. Nuclear Licensing Crystal River Energy Complex (SA2A) 15760 W. Power Line Street Crystal River. Florida 34428 6708
SUBJECT:
CRYSTAL RIVER NUCLEAR GENERATING PLANT UNIT 3 - BORON PRECIPITATION PREVENTION - SITE VISIT BY NRC STAFF (TAC NO, M96314)
Dear Mr. Anderson:
This is to confirm a site visit by Dr. Warren Lyon Reactor Systems Branch, Office of Nuclear Reactor Regulation, during the week of November 3, 1997.
Dr. Lyon has been assigned to generically review the boron precipitation prevention issue and plans to visit Crystal River 3 to gather plant-specific information.
Enclosed is the plan and objective for his visit.
The site visit was discussed with, and agreed to by your staff.
If you have any questions regarding this matter, please write or call me at (301) 415-1471 Sincerely,
/S/
L. Raghavan, Project Manager Project Directorate 11-3 Division of Reactor Projects - 1/11 Office of Nuclear Reactor Regulation i (fl Docket No, 50-302
Enclosure:
As stated
[d) $ $ g i'{ g g g [ l)/
cc w/ enc 1:
See next page list ribut' on
)ocket Fi e
Public CR3 Reading B. Boger J. Zwolinski OGC ACRS T. Collins W. Lyon J. Jaudon Document Name: G:\\ CRYSTAL \\96314.LTR To receive a copy of this document, indicate in the box:
"C" - Copy without attachment / enclosure "E" - Copy with attachment / enclosure "N" - No copy 0FFICE PDll-3/PM lE PDil-3/LA E
PDil-3/D T
lt l
ll NAME LRaghavan U BClayton $ n o FHebdongef DALE 10/13/97 10/29 /97 10/19/97 0FFIClAL RECORD COPY DM 6
2 P
PDft
5 CtCoq y*
\\
UNITED STATES g
,}
NUCLEAR REGULATORY COMMISSION 3
WASHINGTON, D.C. 3068H001 o,
%.,..4+/g October 28, 1997 Mr. Roy A. Anderson Senior Vice President Nuclear Operations Florida Power Corporation ATIN: Manager. Nuclear Licensing
)
Crystal River Energy Complex (SA2A) 15760 W. Power Line Street Crystal River, Florida 34428-6708
SUBJECT:
CRYSTAL RIVER NUCLEAR GENERATING PLANT UNIT 3 - BORON PRECIPITATION PREVENTION - SITE VISIT BY NRC STAFF (TAC NO. M96314)
Dear Mr. Anderson:
This is to confirm a site visit by Dr. Warren Lyon. Reactor Systems Branch.
Office of Nuclear Reactor Regulation. during the week of November 3. 1997.
Dr. Lyon has been assigned to generically review the boron precipitation prevention issue and plans to visit Crystal River 3 to gather plant-specific information.
Enclosed is the plan and objective for his visit.
The site visit was discussed with, and agreed to by your staff.
If you have any questions regarding this matter, please write or call me at (301) 415 1471.
Sincerely, h
L. Raghavan. Project Manager-ProjectDirectorate11-3 Division of Reactor Projects - 1/II Office of Nuclear Reactor Regulation Docket No. 50-302
Enclosure:
As stated cc w/ enc 1: See next page
1 Hr. Roy A. Anderson CRYSTAL RIVER UNIT NO, 3 Florida Power Corporation cc:
Mr. R. Alexander Glenn Mr. Robert E. Grazio. Director Corporate Counsel Nuclear Regulatory Affairs (SA2A)
Florida Power Corporation Florida Power Corporation MAC ASA Crystal River Energy Complex P.O. Box 14042 15760 W. Power Line Street St. Petersburg, Florida 33733 4042 Crystal River, Florida 34428 6708 Mr. Charles G. Pardee Director Senior Resident Inspector Nuclear Plant Operations (NA2C)
Crystal River Unit 3 Florida Power Corporation U.S. Nuclear Regulatory Commission Crystal River Energy Complex 6745 N. Tallahassee Road 15760 W. Power Line Street Crystal River. Florida 34428 Crystal River. Florida 34428 6708 Mr. John P. Cowan Mr. Bruce J. Hickle. Director Vice President, Nuclear Production Director. Restart (NA2C)
(NA2E)
Florida Power Corporation Florida power Corporation Crystal River Energy Complex Crystal River Energy Complex 15760 W. Power Line Street 15760 W. Power Line Street Crystal River. Florida 34428 6708 Crystal River, Florida 34428 6708 Mr. Robert B. Borsum Mr. James S, Baumstark Framatome lechnologies Inc.
Director. Quality Programs (SA2C) 1700 Rockville Pike. Suite 525 Florida Power Corporation Rockville. Maryland 20852 Crystal River Energy Complex 15760 W. Power Line Street Mr. Bill Passetti Crystal River, Florida 34428 6708 Office of Radiation Control De)artment of Health and Regional Administrator, Region 11 lehabilitative Services U.S. Nuclear Regulatory Commission 1317 Winewood Blvd.
61 Forsyth Street, SW., Suite 23T85 Tallahassee, Florida 32399 0700 Atlanta, GA 30303-3415 Attorney General Mr. Kerry Landis Department of Legal Affairs U.S. Nuclear Regulatory Commission The Capitol 61 Forsyth Street, SW., Suite 23T85 Tallahassee, Florida 32304 Atlanta, GA 30303-3415 Mr. Joe Myers, Director Division of Emergency Preparedr,ess Department of Community Affairs 2740 Centerview Drive Tallahassee, Florida-32399-2100-Chairman Board of County Commissioners Citrus Count 110 North pka Avenue
- Iverness, rida 34450 4245
4 h/g7 11/3 6/9'l VISIT BY WARREN LYON (NRC/NRR) TO CRYSTAL RIVER WITH RESPECT TO CONTROL OF BORON IN THE RCS DURING POSTULATED EVENTS Objectives 1.
Understand licensee's assessment of boron precipitation, its position regarding boron precipitation control, and its proposed solution (s),
2.
Understand licensee assessment of and control of potentialinadvertent boron dilution, 3.
Understand information supporting items 1 and 2, and 4.
Obtain information to:
a.
determine safety significance, b.
assess technical understanding, and support closure of anyissues or questions regarding boron precipitation and c.
boron dilution.
Introduction and Overview Wanen Lyon (NRC/NRR/DSSA/SRXB) has been assigned to generically investigate control of boron (1) to prevent boron precipitation and (2) to prevent boron dilution that could lead to potentialinadvertent criticality. The Crystal River boron precipitation issue is a priority aspect of his assignment that is best addressed by a visit to the Crystal River plant to gather infonnation on boron precipitation pertinent to restart of the Crystal River plant and pertirient to longer term work, if any, that is necessary for complete closure of the Crystal River issue.
While at the site, Mr. Lyon also plans to gather information on boron dilution control with respect to potential inadvertent criticality, a topic that Framatome Technologies has identified as a preliminary safety cuncem (PSC 195).
This communication provides questions and topics we believe should be addressed to facilitate understanding these topics and to facilitate closing the boron precipitation issue at Crystal River No written response is requested at this time.
The following must be accomplished during the site visit in regard to NRC restart approval relevant to the boron precipitation issue:
1.
Briefing on safety significance.
2.
Briefing on licensee plan and schedule to close the issue.
3.
Briefing on supporting analyses and analysis results.
4.
With respect to dump-to sump and hot leg injection, please provide P&lDs and procedures, review training, and review potential issues or problems regarding the unusuallineups. The last item should include success probability estimates, assessment of the pump experiencing reverse flow with respect to its safety related designation, the probability that establishing the lineups will cause loss of decay heat removal or other detrimental conditions, and should cover the process of initiating decay heat removal via the pump that was experiencing reverse flow.
Enclosure
1 5.
Walkdown of hardware and controls involved in LOCA and post LOCA operations, 6.
Review of operations associated with item 5 (procedures and training) that involve boron control or are influenced by the need for boron control. This should include operations that may be atrimentally affected by boron control measures, such as not bumping RCPs, and an, ppraisal of the overallimpact.
7.
Identincation of any changes in understanding or licensee position regarding boron control since January 1,1993 and appralsal of those changes with respect to the Thadani(NRC) communication of March 3,1993, 8.
Discussion of any other items that will contribute to solution of this issue.
The depth of coverage of these items may be based in part on the closure necessary for Crystal River restar1, At a minimum, the NRC expects an in depth coverage of licensee plans for closure, including an acceptable schedule. Areas that are not fully addressed may require future meetings at NRC headquarters, Similar coverage of boron dilution considerations would be helpful and may alleviate the necessity of future meetings.
Formal meetings with slides and presentations are not necessary, informal (scheduled) meetings with provision of appropriate documentation are suggested.
Questions or discussion of topics to be addressed during the visit should be directed to Warren Lyon at 310-415 3892.
Safety Significance The most significant aspect of potential boron precipitation and related issues is What is the safety significance?" Since the staff must address this as part of its regulatory evaluation, it requires a characterization of safety significance as presently understood, Broadly, the following questions apply:
1.
Does any of the information have significance with respect to the existence of a substantial safety hazard as defined in 10 CFR 21.3(4)?
2.
What is the quantitative risk due to boron precipitation? What probabilistic risk analyses have been accomplished and what were the results? What other techniques are available to characterize safety and have these been applied? If so,
- what were the results?
3.
What is the impact of addressing boron precipitation upon response to other plant events? Do actions taken in response to boron controlincrease the risk associated with other potential accidents and, if so, by how much?
The ste" must also address these questions with respect to boron dilution.
T chnmal Questions and Observations We would appreciate a briefing that provides detailed analysis information, summarizes your findings, and discusses our observations in regard to the following:
i 1.
With respect to acceptability of hot leg noule gaps as a means of limiting boron concentration:
a.
One must either show that water cooling of the exterior of the reactor vesselis not credible or must establish that such cooling will be acceptable. The potentialinfluence of break flow, containment spray, and reactor vessel cavity flooding should be addressed, b.
Consideration of an oval reactor vessel or intemals should be addressed, including sticking of the " seal" at the hot leg nonle gap during cooldown. Item e, immediately above, also applies, Further understanding of potential mechanisms for blocking the " thin" hot leg c.
nonle gaps is needed, including elimination of mechanisms involving impurity deposition (Inch mng boron), corrosion, sticking, and debris.
I d.
The approach appears to base acceptability on analyses of aan behavior with little reliance on experimental or operating data other than gap ;nessurements taken at cold conditions. Do any other data exist? Do gap data exist over the life of the plants? Does any operationalinformation exist that provides insight into gap flow rates?
Can cold leg injection lead to cooling the reactor vessel shell unevenly (both e.
axially arid radially) and, if so, what is the effect upon gap behavior?
2.
Boron solubility; s.
Is boron solubility in steam used to remove some of the boron from the core region. If so, what uncertainty is associated with these data? What substantiation exists to confirm the adequacy of the data for determining compliance with 50.46(b)(5)?
b.
Does solubility of boron in steam lead to conditions where condensate can become saturated followed by boron precipitation due to cooling.
The curvature of the boron solubility in water curve with increasing c.
temperature means that if one mixes equal parts of saturated hot water with non borated coU water, boron will precipitate. The situation is exacerbated if the cold water Wso contains boron. What are the implications for injection?
For cooldown? For mixing in such locations as the lower plenum, hot leg nonle gaps, downcomer, and core lower plenum interface and mixing region? What uncerialnty is associated with the boron solubility data? What substantiation exists to confirm the adequacy of the data for determining compliance with 50,46(b)(5)?
d.
What is the influence of other solutes on boron behavior? Can other so!utes contribute to a precipitation problem?
3.
Boror. related items:
a.
Part of the boron concentration problem may be addressed if there is sufficient communication between the upper plenum and the upper downcomer
annulus. The same communication may introduce boron dilution problems.
What are these problems and h;.s nave they been addressed?
b.
Please discuss whether boron can plate out on surfaces from water or steam that contains boron. (Potential concems are flow blockage, removal of boron from the system by unrecognized mechanisms leading to boron dilution problems, and sampling of the sump to assess boron concentration.)
Please discuss the behavior of the sump boron concentration with respect to c.
condensation of steam in the steam generator = and filling of previously volded regions of the steam generator tubes, crossover pipes, and RCP bowls.
d.
If one approaches a boron saturated condition while still hot and pressurized, we do not fully understand how one then cools down without encountering j
boron precipitation. Please discuss.
Can boron precipitate cut in the core former region and, if so, what are the e.
implications?
f.
What is the influence of bypass flow in hot leg nozzle gaps during hot leg breaks?
4.
Modeling items:
Do the thermal hydraulle calculations use pure water properties or properties a.
l of a boron solution? Do other solutes cause a change in water properties and have these changes been addressed?
b.
Analyses we have seen appear to be based upon uniform temperatur6/ property nodes, and occurrence of significant phenomena in the boundary areas between volume nodes or within nodes has not been addressed. (For example, what occurs between a coollower plenum node and a hot core node?) is this true of the licensee calculations for Crystal River and, if so, what are the implications?
c.
What temperature variations can occur within the core volume and how does this affect results and conclusions? In other regions of the RCS?
d.
How are interactions in the downcomer and colet leg between ECCS water, steam, and upper head water accounted for in the modeling? (One of *.he concems is dilution and adequate modeling of diluted water as it moves through the RCS.
S.
Questions and observations on other topics:
a.
When crediting pressurizer spray or other methods of " hot leg injection," what fraction of the added water becomes well mixed with core water above the core and enters into core circulation? What fraction is bypassed to the upper downcomer? With respect to the latter, how much of the added water can be carried out of the break so that it does not contribute to boron dilution in the core?
b.
Has consideration been given to steam generator cooldown following a large break LOCA and the potential for filling the crossover pipes and lower parts of the steam generator tubes with water? If this occurs, are there any implications with respect to boron concentration?
Has consideration been given to the effect of temperature below the typical c.
140 F core inlet temperature?
d.
Are the RVWs always predicted to open for all practical, long-term combinations of water levels in the RCS for the smaller breaks? Please
- discuss, Traditional licensing calculations for LOCAs are based upon high decay heat e.
levels to bound behavior. Some aspects of boron concentration behavior would appear to be of more concem at lower decay heat levels, such as a lower froth level and higher density in the core for the same collapsed liquid level and the corresponding effect upon circulation, or droplet carryover. Has this been addressed and shown to be bounded by the work that has been accomplished?
f.
What is the influence of injection flow rate? (Can variation in flow rate cause lower temperatures so that less boron remains in solution?)
With respect to " Preliminary Report to the B&W Owner's Group on WC 1 g5 Investigations,"
Framatome Technologies Inc.,471244436 00, January igg 6, we have sent the following questions and observations to Framatome as part of the basis for a meeting we have requested be held in Lynchburg, VA during November. These are provided here for licensee information and in case there are Crystal River specific aspects that should be covered during the Crystal River meeting.
1.
Why is the pump bump critical concentration based upon 486 F (page g) when page 18 refsrences 300 F and one may be significantly lower than that under some circumstances?
2.
In Table 1 (page 11), why are BWST concentrations sometimes less than refueling concentrations?
3.
The last paragraph on page 1g appears to attempt to justify using a homogeneous reactor model for evaluation of natural circulation conditions, We cannot accept a homogeneous model unless there is in-depth substantiation.
4.
The last paragraph on page 23 states that the potential for accumulation of low boron concentration water is nullified unless there is no circulation around the RCS. We do not understand why this is "somewhat obvious" for separa5d flow and bypass conditions. Have these been eliminated? Can one have cuculation in one loop and not another? Can some tubes in a steam generator be active while others simply accumulate cold dilute water? (What is the effect of the difference in density of boron-solution vs. pure water?)
5.
Some of the questions pertinent to boron precipitation apply to the top of page 25 discussion of the solubility of boron in steam. Please provide verification regarding
t boron carryover in steam? Include substantiation that boron cannot be removed by deposition on surfaces before reaching the break.
6.
The bottom of page 25 states 'Because the core is likely to be highly borated, the mixing of core and downcomer fluids willimprove or increase the boron concentration of the water reaching the bottom of the downcomer." We consider steam coming off the top of the core to be a " core fluid.' Does steam not have the potential to dilute downcomer water? How is this statement consistent with the statement on the top of page 26 that downcomer boron concentration is 1600 ppm with a BWST concentration of 2000 ppm?
7.
The bottom of page 28 states that the time duration for which low boration build up occurs is shown to be limited if system controlis restricted to above 650 psla. This appears to be due to decay heat being rejected by the steam generators efter the time duration is this correct? If so, how do later operfaor cooldown actions influence the results? What about intemal effects such as boron dilution due to steam condensation on incoming ECCS water? What about later actions in which circulation is started with dilution that has occurred prior to reaching the time duration?
8.
On page 29, reference is made to evaluation of differing types of events sequentially, with the remainder of the work being discussed here concentrated on SBLOCA concems. What are the other events of interest and how are they being evaluated?
D.
Please provide a briefing of the behavior discussed at the bottom of page 39 top of page 40 on lack of bubble collapse. We do not understand part of the discussion and the conclusions. For example, the walls of the elevated section of hot legs are relatively thin when compared to the top of the reactor vessel. Why would pump bumps that result in cooling of the top of hot legs containing voids not have the end result of expanding an upper head void to provide water to fill the hot legs? Or why would the pref ^ vizer not provide a filled hot leg end state if there was sufficient hot water in the pt.t,urizer initially?
10.
Page 43. What proof exists that cold water does not flow through the downcomer with little mixing?
11.
Page 43. The end of the first paragraph references an assumption that the downcomer coolant is transferred without mixing into the core and occupies the entire j
core. Please discuss the conservatism of this with respect to the respective volumes.
12.
Page 44. Did you mean to omit the effect of buoyance of steam from the table?
13.
Page 46 discusses the LOTUS model, with the flow areas of each column described by a doubling relationship, and this is stated as a preference for the flow to follow the shortest path. Why wouldn't a constant area follow the shortest path? What is the justification of the doubling behavior?
14.
Page 46. The end of the first paragiaph states that each calculational cellis assumed to be completely mixed at each time advancement and the concentration of flow from one cell to another was based on the concentration of the supplying cell.
Please discuss the validity of this modeling with respect to numerical diffusion.
15.
Page 47, bottom. The rate of increase in effective reactivity at the time of criticality
was considered important. How accurate is the identified 3 to 4 seconds from just critical to prompt critical in 1;ght of such modeling considerations as uniformity of boron concentration entering the core with respect to core bottom location? Nuclear modeling? Core boron distribution in the core? With respect to the page 50 conclusion regarding void generation rate fast enough to meaningfully control the transient to a benign prompt critical excursion?
16.
Page 70, it is net rea'nnably obvious to us that the CE calculation results are applicable to the rlTu Jesign nor can we concur with a licensing position that boron dilution should not h a licensing issue at this time. For example, the 'owered loop B&W design can accumulate substantial dilute water in the steam generator with water level at the hot and cold leg elevation. This cannot occur in the CE design.
(We note there are numerous other differencer between the CE and B&W designs, nnd even from one B&W designed plant to another.)
17.
Are the flow rates on page B 2 for licensing calculation (FSAR) purposes or are these expected values?
_