ML20202G837
| ML20202G837 | |
| Person / Time | |
|---|---|
| Issue date: | 04/03/1986 |
| From: | Sniezek J Committee To Review Generic Requirements |
| To: | Stello V NRC OFFICE OF THE EXECUTIVE DIRECTOR FOR OPERATIONS (EDO) |
| References | |
| NUDOCS 8604150021 | |
| Download: ML20202G837 (12) | |
Text
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APR 3 1986 MEMORANDUM FOR:
Victor Stello, Jr.
Executive Director for Operations FROM:
James H. Sniezek, Chairman Committee to Review Generic Requirements
SUBJECT:
MINUTES OF CRGR MEETING NUMBER 87 The Connittee to Review Generic Requirements (CRGR) met on Wednesday, March 19, 1986 from 1:00_3:30 p.m.
A list of attendees for this meeting is enclosed (Enclosure 1).
1.
W. Russell continued the presentation for CRGR review of the final rule-making package to revise the regulations for operator licensing,10 CFR 55, conforming amendments, and three associated regulatory guides. This item was discussed, but not completed, at CRGR Meeting No. 86 held on February 26, 1986. Enclosurc 2 Oc:m:ari:cs this matter (Category 2 its).
2.
The CRGR agreed to exempt from CRGR review, NRR's Evaluation of the BWR Owners' Group Request for Relief from NUREG_0737, Item II.E.4.2(7) for BWR Small Vent and Purge Lines for Pilgrim 1, Hatch 1 & 2, Peach Bottom 2 & 3, and Limerick 1.
This matter is discussed in Enclosure 3. contains predecisional information and therefore will not be released to the Public Document Room until the NRC has considered (in a public forum) or decided the matter addressed by the information.
1 In accordance with the ED0's Jul 18, 1983 directive concerning " Feedback and l
Closure on CRGR Reviews," item (y) above requires written response from the 1
l l
cognizant office to report agreement or disagreement with CRGR recommendations l
in these minutes. The response, which is required within 5 working days after receipt of these meeting minutes, is to be forwarded to the CRGR Chairman and if there is disagreement with the CRGR recommendations, to the EDO for decision-naking.
Questions concerning these meeting minutes should be referred to Walt Schwink (492 8639).
Original !!gted by hmes H. Sniezek l.
James H. Sniezek, Chairman Connittee to Review Generic
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l Requirements
Enclosures:
As Stated Ih cc: See next page l
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NAR 171986 MEMORANDUM FOR:
Robert Bernero, NRR Edward L. Jordan, IE Richard E. Cunningham, NMSS Denwood F. Ross, RES Clemens J. Heltemes, Jr., AE00 j
l Joseph Scinto, ELD i
James H. Sniezek, Chairman FROM:
Comittee to Review Generic Requirements EXEMPTION FROM CRGR REVIEW 0F NRR'S EVALUATION OF 4
BWR OWNERS' GROUP REQUEST FOR RELIEF FROM NUREG.0737,
SUBJECT:
ITEM II.E.4.2(7) FOR BWR SMALL VENT AND PURGE LINES FO PILGRIM 1, HATCH 1&2, PEACH BOTTOM 283, AND LIMERICK 1 I
Memorandum H. R. Denton-to J. H. Snfezek dtd
Reference:
March 11, 1986 T
By the reference memorandum with attached safety evaluation and regulatory analysis (Enclosure 1), I was advised by the Director, NRR of his intention to grant partial relief to six BWRs from the current requirements of NUREG-0737, Item II.E.4.2(7) unless there are obje'ctions to the proposed action.
The current requirement calls for automatic isolation of purge and vent valves Based upon NRR's evaluation of the offsite radiological on high radiation.
consequences for accidental releases through 2-inch diameter and smaller lines, NRR concludes that automatic isolation is not required for these valves at the I
4 The safety evaluation and regulatory analysis show that i
six named facilities.
the risk to the public of granting such relief is well below the levels of regulatory concern,(and the costs associated with implementin
-a are moderately high $100K per plant).
Based upon the apparently insignificant effect on pl. ant safety and the cost l
savings to the industry, I propose to exempt this matter from CRGR review.
' is a copy of the memorandum I am proposing to send to H. Denton.
I Since we have a CRGR meeting scheduled for Wednesday, March 19, I will solicit
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[f your opinions on this matter at the meeting.
Original signed by hmasH.Sr:iczeh.
James H. Sniezek, Chairman Comittee to Review Generic Requirements
Enclosures:
Distribution:
As stated JHSniezek WSchwink RCapra DEDROGR cf cc:
J. Lyons Central File OFC :ROGR
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MAR 111986 MEMORANDUM FOR: James H. Sniezek, Acting Deputy Executive Director for Regional Operations and Generic Requirements FROM:
Harold R. Denton, Director Office of Nuclear Reactor Regulation
SUBJECT:
REVIEW 0F BWR OWNERS GROUP REQUEST FOR RELIEF FROM NUREG-0737, ITEM II.E.4.2(7) FOR BWR SMALL VENT J.iiD PURGE LINES FOR PILGRIM 1, HATCH 1 AND 2 PEACH BOTTOM 2 AND 3, AND LIMERICK 1.
My staff has reviewed a request made in a June 20, 1985 meeting by the BWR Owners Group (BWROG) on behalf of Pilgrim 1. Hatch 1 & 2, Peach Bottom 2 & 3, and Limerick 1 that we review the Boiling Water Reactor Owners Group's (BWROG) i evaluation of offsite radiological consequences for accidental releases through 2-inch diameter vent and purge lines which do not meet the NUREG-0737 Item II.E.4.2(7) requirement for automatic isolation on high radiation, and provide relief from this requirement.
Our Safety Evaluation in Enclosure 1 supports the licensee's analyses, based on conservative confirmatory staff calculations. The results show that for the limiting reactor coolant system break that would not initiate automatic isolation offsite doses are within a small fraction of the dose guideline values of 10 CFR Part 100, and thus are acceptable.
l Our Regulatory Analysis of this request for relief is contained in.
It indicates our conclusion that relief should be provided j
from the NUREG-0737. Item II.E.4.2(7) requirement for automatic isolation on high radiation for 2-inch nominal diameter and smaller vent and purge lines.
J I plan to provide the requested relief and to make notification to the owners of the six units named above.
If I receive no coments within 15 working days of the date of this memo, I will assume there are no objections to the proposed action.
I!
?W k u Harold R. Denton, Director Office of Nuclear Reactor Regulation
Enclosures:
i As stated cc's: See Next Page
Contact:
W. Meinke X29445 46/317d553-app.
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ENCLOSURE 1 EVALUATION OF THE RADIOLOGICAL CONSEQUENCES FOR ACCIDENTAL RELEASES THROUGH BWR 2-INCH VENT AND PURGE LINES INTRODUCTION I
NUREG-0737. Item II.E.4.2(7) required that the containment purge and vent isolation valves must close on a high radiation signal. This position was added to the original NUREG-0578 requirements of Recommendation 2.1.4 as a result of further staff evaluation of features needed to improve containment isolation dependability.
One basis for the implementation of II.E.4.2(7) was the additional protection it would provide against low rates of reactor coolant leakage and releases to the environment which would not initiate the other automatic isolation signals of reactor low water level and high drywell pressure. The BWR Owners Group (BWROG) previously transmitted an evaluation of offsite radiological consequences for accidental releases through BWR vent and purge lines which do i
not meet the requirement of NUREG-0737. Item II.E.4.2(7) in a letter from T. J. Dente of the BWROG to D. G. Eisenhut of the NRC, dated June 14, 1982.
In a June 20, 1985 meeting, the BWROG requested that the staff review its
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evaluation for small (2-inch diameter) vent and purge lines.
DISCUSSION The staff has reviewed the BWROG evaluation which provides calculations of the radiological consequences of the limiting reactor coolant system break which 4
I would not initiate automatic isolation with the current design. The limiting event was conservatively modeled as a reactor coolant system break such that the drywell atmosphere would contain saturated steam at a pressure just below the containment isolation setpoint. Steam release thrcugh one vent or purge line was assumed to pass directly to the environn.ent witn no credit given for holdup or dilution, or for filtering by the standby gas treatment system. The fraction of the iodine postulated to become airborne and available for release to the atmosphere, without credit for plateout, was assumed to equal the fraction of the coolant flashing to steam. The BWROG evaluation provided calculations for a typical plant as well as.a generic analytical procedure.
Independent calculations of the radiological consequences of the limiting reactor coolant system break were performed by the staff. The staff conservatively estimated a mass release value of 492 cubic feet per minute of saturated steam at 2 psig over a 30 minute duration until the one purge and vent line would be isolated by other actions.
The assumptions used in this staff analysis were as follows:
1.
Drywell atmosphere is saturated steam and at a pressure equal to the containment isolation setpoint (psig).
2.
Operator action time to close the purge or vent value is assumed to be 30 minutes.
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. 3.
Vent pipe length is conservatively assumed to be 10 ft. for purposes of flow calculations.
4.
Elevation changes have been neglected.
The BWR Owners Group analysis used fomulas described in NEDM-10363-13
" Hydraulic Analyses Procedure for BWR Piping Systems." The staff used similar formulas, which are described in the Crane Flow of Fluid Manual and the above assumptions, and obtained similar results to those provided by the BWR Owners Group.
The staff, using the above release rate, perfonned plant specific calculations of the radiological consequences for Pilgrim Unit 1 Hatch Units 1 and 2, Peach Bottom Units 2 and 3, and Limerick Unit 1.
The staff's calculation of offsite doses differed from the procedure outlined in the BWROG's evaluation in two respects. First, the staff used short tenn diffusion estimates typical of other conservative regulatory evaluations of accidents; the BWROG used annual average relative concentrations typical of a realistic evaluation of doses from routine releases. Second, the staff used conservative reactor coolant iodine concentrations assuming a preaccident iodine spike for those plants with a technical specification iodine spiking limit. For Pilgrim Unit 1, which has no technical specification iodine spiking limit, the staff used the maximum technical specification equilibrium concentration with an accident-initiated spike, modeled by increasing the equilibrium fission product activity release rate from the fuel by a factor of 500. The staff's iodine spiking model is typical of regulatory analyses involving accidental releases of primary coolant, as outlined in Section 15.6.2 of the Standard Review Plan (NUREG-0800). The BWROG's evaluation assumed equilibrium iodine
-e concentrations with an accident-initiated spike using a 95% cumulative probability iodine spiking model.
REStMS The staff estimates of the thyroid and whole body doses at the exclusion area and low population zone outer boundaries for the 6 units are presented in Table I(attached). Although specific acceptance criteria do not exist for this postulated accident, the radiological consequences and frequency of occurrence for this accident would tend to be similar to that of the failure of small lines carrying primary coolant outside containment. The staff concluded that the use of the acceptance criteria for the failure of small lines, which appear in Section 15.6.2 of the Standard Review Plan, would be appropriate for use in this evaluation. Thus, the radiological consequences of this postulated accident would be acceptable if the calculated whole-body and thyroid doses at the exclusion area and low population zone outer boundaries do not exceed a small fraction (10%) of the dose guideline values of 10 CFR Part 100, viz., 2.5 rem and 30 rem respectively, for whole body and thyroid doses. As summarized in Table I, the estimated doses are a small fraction of these dose guideline values of 10 CFR Part 100.
TABLE 1 RADIOLOGICAL CONSEQUENCES FOR ACCIDENTAL RELEASES THROUGH BWR 2-INCH VENT AND PURGE LINES i
Exclusion Area Boundary Low Population Zone (0-2 hr), rems Boundary (0-8 hr). re g.
Thyroid Whole Body Thyroid Whole Body Limerick Unit 1 0.4 0.007 0.08 0.002 Peach Bottom Units 2 & 3 0.4 0.004 0.007 0.00006 Hatch Unit 1*
0.08 0.0008 0.04 0.0004 Hatch Unit 2*
0.08 0.002 0.04 0.0008 Pilgrim Unit 1 3.3 0.03 0.2 0.002
- The difference in whole body doses between Hatch Unit I and Unit 2 was a result of different Technical Specification primary coolant activity 7
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. The staff concludes that the offsite doses are within the acceptance criteria.
Furthermore, the magnitudes of these doses calculated by the staff are higher than would realistically be expected because of the many conservative assumptions in the staff's methodology, particularly with respect to iodine spiking behavior For example, coolant iodine concentration levels generally and to meteorology.
are small fractions of equilibrium technical specification levels, iodine spiking does not always occur coincident with the transients, the iodine spiking concentrations assumed to occur are well in excess of any level recorded at an operating boiling water reactor, and the probability of better meteorological conditions is quite high. A more realistic analysis would yield dose estimates about 1/100th or less of the values noted above.
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ENCLOSURE 2 REGULATORY ANALYSIS 1.
Statement of Problem At present, containment isolation is initiated automatically in BWR vent and purge lines upon signals of reactor low water level and high drywell pressure.
Questions have been raised by specific members of a BWR Owners Group (BWROG) regarding the requirement for all BWR vent and purge lines of a third signal of high radiation level to assure diverse isolation signals in the event of an accident.
NUREG-0737. Item II.E.4.2(7) required that the containment purge and vent.
1 solation valves must close on a high radiation signal. This position was added to the original NUREG-0578 requirements of Recommendation 2.1.4 as a result of a staff evaluation of features needed to improve containment l
isolation dependability. One basis for the implementation of II.E.4.2(7) was j
the additional protection it would provide against low rates of reactor 4
coolant leakage and releases to the environment which would not initiate the other automatic isolation signals of reactor low water level and high drywell pressure.
The BWR Owners Group (BWROG) previously transmitted an evaluation of offsite radiological consequences for accidental releases through BWR vent and lines which do not meet the requirement of NUREG-0737 Item II.E.4.2(7) purge in s
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letter from T. J. Dente of the BWROG to D. G. Eisenhut of the NRC, dated June 14, 1982.
In a June 20,1985 meeting, the BWROG on behalf of Pilgrim 1, Hatch 1 & 2 Peach Bottom 2 & 3, and Limerick 1 requested that the staff review its evaluation for small (2-inch diameter) vent and purge lines and provide relief from this requirement.
-e 10 CFR Part 100 sets forth dose reference values for whole bcdy and i
thyroid doses, which can be used in the evaluation of reactor sites with respect to potential reactor accidents of exceedingly low probability of occurrence, and low risk of public exposure.to radiation.
Conservative calculations are used to determine.the anticipated radio-logical consequences of the limiting reactor coolant system break that would not initate automatic isolation of containment with other automatic isolation signals.
If for these kinds of postulated accidents the conservatively calculated whole-body and thyroid doses at the exclusion area and low population zone outer boundaries do not exceed a small fraction (10%) of the dose guideline values of 10 CFR Part 100, the radiological consequences could be considered acceptable and relief from the requirement could be provided.
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Alternatives Two general types of action are possible:
- 1. Permit NUREG-0737. Item II.E.4.2(7) to continue as a requirement for BWRs for all vent and purge lines, including small (2 inch) lines. This would require those plants that had not yet completed installation of radiation monitors with isolation capabilities for all vent and purge lines to continue design and t.onstruction efforts, even though for certain small lines, calculations show that offsite doses from potential accidents nould be acceptably low.
- 2. Provide relief from the NUREG-0737. Item II.E.4.2(7) requirement for nominal 2-inch vent and purge lines for BWRs when conservative staff calculations show that the offsite radiological consequences of a postulated accident is acceptably low.
3.
Decision Rationale Alternative (1) has been implemented for large vent and purge lines for many plants. For small (2-inch) lines, however, realistic calculations by licensees for Pilgrim-1, Hatch 1 & 2. Peach Bottom 2 & 3 and Limerick 1, and conservative calculations by the NRC staff, have shown that in the case of a postulated accident, licensees can rely on manual operator actions, or other means, to isolate the 2-inch diameter vent and purge lines after a DBA in lieu of the radiation signals. Such manual actions occuring within 30 minutes after the LOCA would limit the estimated offsite thyroid and whole body doses to only a small fraction (410%) of the dose guideline values of 10 CFR Part 100, an acceptably low radiological effect.
Further staff analyses using more realistic assumptions yield dose estimates about 1/100th or less of these conservative calculation values.
e The probability that a BWR reactor coolant system break would occur with vent or purge lines in the operating mode without initiating automatic isolation from signals already required of reactor low water level and/or high dry well pressure is exceedingly low. Furthermore, staff calculations with realistic assumptions show that for small (2-inch) vent and purge lines, if such a situation were to develop, the risk to members of the public offsite would be very low.
The costs to licensees of adding a radiation isolation capability to the small lines is estimated at about $100,000 per plant.
In summary, the risk to the public of implementing alternative (2) is well below the levels of regulatory concern, and the costs of implementation are moderately high. Thus, for nominal 2-inch vent and purge lines relief from the requirement as provided by alternative (2) is acceptable.
4.
Implementation Alternative (2) is recommended since conservative staff calculations show that the radiological consequences of such releif would be only a small fraction (<10%) of 10 CFR Part 100 dose guideline values.
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3-Individual notification of this acceptability will be sent to the owners of Pilgrim 1, Hatch 1 & 2, Peach Bottom 2 & 3 and Limerick 1.
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MEMORANDUM FOR:
Harold R. Denton, Director Office of Nuclear Reactor Regulation FROM:
James H. Sniezek Acting Deputy Executive Director Regional Operations and Generic Requirements
SUBJECT:
EXEMPTION FROM CRGR REVIEW OF NRR'S EVALUATION OF BWR OWNERS' GROUP REQUEST FOR RELIEF FROM NUREG-0737, ITEM II.E.4.2(7) FOR BWR SMALL VENT AND PURGE LINES FOR PILGRIM 1, HATCH 1&2, PEACH BOTTOM 2&3, AND LIMERICK 1 Memorandum H. R. Denton to J. H. Sniezek dtd
Reference:
March 11, 1986 By the reference memorandum with attached safety evaluation and regulatory analysis (Enclosure 1), you advised me of your intent to grant partial relief to six BWRs from the current requirements of NUREG-0737 Item II.E.4.2(7) unless there are objections to the proposed action.
The current requirement calls for automatic isolation of purge and vent valves
-e on high radiation. Based upon your evaluation of the offsite radiological consequences for accidental releases through 2-inch diameter and smaller lines, you concluded that automatic isolation is not required for these lines at the six named facilities. The safety evaluation and regulatory analysis show that the risk to the public of granting such relief is well below the levels of regulatory concern, and the costs associated with implementing automatic closure are moderately high ($100K per plant).
It it noted that one of the assumptions used for the analysis was operator action time to close the purge and vent valves is 30 minutes. The exemption from CRGR review is contingent upon NRR ensuring that this assumption is valid for the six identified plants based upon location and accessibility of the valve operators, and i
instrumentation necessary to determine the need for manual closure, and that plant procedures and operator training are sufficient to support the justification.
Based upon the apparently insignificant effect on plant safety and the cost savings to the industry, this item has been determined to be exempt from CRGR review.
It is rqy understanding that you will be informing other licensees of this position and that this position may be applied to other licensees on a plant-specific basis should they apply for such relief.
James H. Sniezek Acting Deputy Executive Director Regional Operations and Generic Requirements
Enclosure:
As stated cc: CRGR Members J. Lyons f
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