ML20205S868
| ML20205S868 | |
| Person / Time | |
|---|---|
| Issue date: | 10/12/1988 |
| From: | Stello V NRC OFFICE OF THE EXECUTIVE DIRECTOR FOR OPERATIONS (EDO) |
| To: | |
| References | |
| FRN-53FR41607, RULE-PR-50 PR-881012, NUDOCS 8811140013 | |
| Download: ML20205S868 (9) | |
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U p' Flow Control Conditions for the Standby Liquid Control in Boiling Water Reactors <
AGENCY: Nuclear Regulatory Commission.
ACTION: Proposed rule.
SUMMARY
- The NRC is propocing to amend its regulations copcerning the flow control conditions for the standby liquid control system in a boil-ing water reactor. The proposed rule would set forth conditions and considerations for determining the reactivity control capacity of a BWR standby liquid control system. The proposed changes are necessary to clarify the existing regulation.
DATE: Comment period expires ( DEC 2 31988 ). Co m wits received after this date will be considered if it is practical to do so, but assurance of consideration cannot be given except as to thoso com-ments received on or before this date.
ADDRESSES: Mail written :omments to the Secretary: U.S. Nuclear Regulatory Commission, Washington, DC 20555; ATTN: Docketing and Service Branch. Deliver comments to 11555 Rockville Pike, Rockville, MO between 7:30 a.m. and 4:15 p.m. weekdays. Copies of comments received may be examined at the NRC Public Document Room (PDR) at 2120 L Street NW. , Washingtors, DC, lower level.
8011140013 001012 I
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FOR FURTHER INFORMATION CONTACT: William R. Pearson, Office of Nuclear Regulatory Research, L'.S. Nuclear Regulatory Commission, Washington, DC 20555, Telephone: (301)492-3764.
SUPPLEMENTARY INFORMATION: On June 26, 1984, the Commission published in the Federal Register (49 FR 26036) a final rule entitled "Reduction of Risk from Anticipated Transients Without Scram (ATVS) Events for Light-Water-Cooled Nuclear Power Plants," which revised the regulations in 10 CFR Part 50. The final rule required, et S 50.62(c)(4), that boil-ing water reactors have a standby liquid control system (SLCS) with a minimum flow rate and boron content equivalent in (reactivity] control capacity to 86 gallons per minute (gpm) of 13 weight percent of sodium pentaborate solution. The rule did not specify the size of the reactor pressurevessel(RPV)intowhichthissolutionshouldbeinjected.
Questions have been raised, especially from licensees with a smaller RPV, concerning the interpretation of the phrase, "equivalent in control capacity." On January 28, 1985, a generic letter that provided clarifi-cation of this phrase was issued to appropriate licen.ees (PDR accession number 8501290633). This letter provided the basis for the flow rate and weight percent of sodium pentaborate decahydrate and described how equiva-1ency could be achieved for a smaller F.PV. The staff confiders the con-tents of this letter, which were derived from the underlying materials considered when the rule was developed, to be technically correct. The letter ir applicable to BWRs with (1) volume of water in the suppression pool per megawatt of core power ratios, (2) reactivity control systems.
and (1,) core designs similar to currently licensed BWR/1-6 designs.
The language used in the existing rule is unclear and subject to differing 2
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interpretations. The staff proposes to clarify the language to more precisely reflect the underlying technical bases.
The standby liquid control system (SLCS) is designed to meet the requirements of general design criterion (G0C) number 26 of Appendix A to Part 50. GDC 26 states, "Two independent reactivity control systems of different design principles shall be provided. One of the systems shall use control rods, preferably including a positive means for inserting the rods, and shall be capable of reliably controlling reactivity changes to assure that under conditions of normal operation, including anticipated operational occurrences, and with appropriate margins for n}alfunctions such as stuck rods, specified acceptable fuel design limits are not exceeded. The second reactivity control system shall be capable of reli-ably controlling the rate of reactivity changes resulting from planned, normal power changes (including xenon burnout) to assure acceptable fuel J design limits are not exceeded. One of the systems shall be capable of holding the reactor core subcritical under cold conditions." In the case
, of a boiling water reactor, the second reactivity control system is the SLCS. In addition, the SLCS is used to reduce risk from ATWS.
The SLCS consists of a tank containing the sodium penteborate decahydrate solution, two pumps, control instrumentation, appropriate piping, and means for testing the system without injecting the borate solution into the RPV. Sodium pentaborate decahydrate (NAaB iop3s.10H 2O) solution is prepared from a mixture of borax and boric acid dissolved in water. The solution nominally is a 13 weight percent solution of sodium pentaborate decahydrate in which the boron-10 isotope is at natural abundance (about 19.78%). A description of the SLCS and its functions is 3
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given in the General Electric Co. document NEDO-24222 (80 NEDO 21, Class I, February 1981), entitled '9ssessment of BWR Mitigation of ATWS, Volume I (NUREG-0406, Alternate No. 3)," sections 3.2, 6.1.3, and 7.2.10.
The important parameters for reactivity control are the concentra-tion of the boron-10 isotope (which has a large thermal neutron capture cross-section) in the RPV cooling water and the time required to achieve this concentration. These parameters are in turn dependent upon the RPV volume (and therefore RPV inside diameter), boron injection flow rate, boron solution concentration, and boron-10 isotopic enrichment level.
The standard that is specified in S 50.62(c)(4), (86 gpm o,f 13 weight percent sodium pentaborate solution) assumes a boron-10 isotopic enrich-ment at the naturally occurring level and was intended to represent the reactivity control achieved for a BWR core design in a RPV with an inside diameter of 251 inches. Safety analyses show however, that equivalent reactivity control is achieved for a given core design in a different size RPV when the same boron-10 isotepe concentration is provided within that RPV. Hence for a given core desir,n, any combinatioa of injection rate, Sejrvn solution concentration level, boron-10 isotopic enrichment level, and RPV volune that resulte in the same boron-10 concentration {
1evel within that RPV will provide reactivity control equivalent to the !
standerd. For example, 16.5 gpm of 26 weight percent sodium pentaborate i L
solution enriched to twice the natural level of boron-10 content injected [
into a 218 inch inside diameter RPV provides reactivity control equivalent to the standard. ;
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If sodium pentaborate decahydrate solution enriched in the boron-10 isotopi is used, procedures should be established to assure proper dis-posal of the non-enriched solution and ensure that the boron-10 isotope concentration in the new solution is sufficient to shut down the reactor.
Environmental Impact: Categorical Exclusion f
The NRC has determined that this proposed rule is the type of action
, described as a categorical exclusion in 10 CFR 51.22(c)(2). Thus, neither an environmental impact statement nor an environmental assessment has been ;
prepared. .
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Paperwork Reduction Act Statement This proposed rule does not contain a new or amended information !
collectionrequiremontsubjecttothePaperworkReductionActof1980 j (44 U.S.C. 3501 et seq.). Existing requirements were approved by the Office of Management and Budget under control number 3150-0011. t Regulatory Analysis L
- Since this proposed rule is of a clarifying nature and does not substantially change existing regulatory requirements, the regulatory analysis prepared for the final rule entitled "Reduction of Risk from Anticipated Transients Without Scram (ATVS) Events for Light-Water-Cooled Nuclear Power Plants," published June 26, 1984 (49 FR 26036) is still
, valid and will be used for this rule. The analysis is available for l i
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inspection in the Public Document Room, 2120 L Street NW., Washington.
DC, Lower level. Single Copies of the analysis may be obtained from William R. Pearson, Office of Nuclear Regulatory Research, U.S. Nuclear Regulatory Commission, Washington, DC 2C555, telephone (301)492-3764.
Regulatory Flexibility Act Certification In accordance with the Regulatory Flexibility Act of 1980 (5 U.S.C.
605(b)), the Commission certifies that this rule, if promulgated, will not have a significant economic impact on a substantial number of small entities and that therefore a regulatory flexibility analysis need not i
be prepared. This rulemaking action would affect only licensees that own and operate nuclear utilization facilities licensed under Sections 103 i and 104 of the Atomic Energy Act of 1954, as amended. These licensees do i not fall within the definition of small businesses set forth in Section 3 l of the Small Business Act (15 U.S.C. 632) or within the Small Business 1
Size Standards set forth in the regulations issued for the Small Business Administration at 13 CFR Part 121. ,
i Backfit Analysis j The NRC has determined that the backfit rule, 10 CFR 50.109, does not apply to this proposed rule, and therefore, that a backfit analysis is not required, because these amendments do not involve any provisions l
which would impose beckfits as defined in 10 CFR 50.109(a)(1).
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l j List of Subjects in 10 CFR Part 50 Antitrust, Classified information, Fire protection, Incorporation by l
reference, Intergovernmental relations, Nuclear power plants and reactors, Penalty, Radiation protection, Reactor siting criteria, Reporting and recordkeeping requirements.
For the reasons set out in the preamble and under the authority of f the Atomic Energy Act of 1954, as amended, the Energy Reorganization Act of 1974, as amended, and 5 U.S.C. 552 and 553, the NRC is proposing to adopt the following amendment to 10 CFR Part 50. '
PART 50 - DOMESTIC LICENSING OF PRODUCTION AND UTILIZATION FACILITIES
- 1. The authority citation for Part 50 continues to read as follows.
I AUTHORITY: Secs. 102, 103, 104, 105, 161, 182 lei, 186, 189, 68 Stat. t 936, 937, 938, 948, 953, 954, 955, 956, as amended, sec. 234, 83 Stat.
1244, as amended (42 U.S.C. 2132, 2133, 2134, 2135, 2201, 2232, 2233, 2236, 2239, 2282); secs. 201, as amended, 202, 206, 88 Stat. 1242, as amended, 1244, 1246 (42 U.S.C. 5841, 5842, 5846).
Section 50.7 also issued under Pub. L.95-601, sec. 10, 92 Stat.
2951 (42 U.S.C. 5851). Section 50.10 also issued under secs. 101, 185, l
68 Stat. 936, 955, as amended (42 U.S.C. 2131, 2235); sec. 102, Pub. L.91-190, 83 Stat. 853 (42 U.S.C. 4332). Sections 50.23, 50.35, 50.55, and 50.56, also issued under sec. 185, 68 Stat. 955 (42 U.S.C. 2235). Sec- l tions 50.33a, 50.55a, and Appendix Q also issued under sec. 102, Pub. L.91-190, 83 Stat. 853 (42 U.S.C. 4332). Sections 50.34 and 50.54 also i
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issued under sec. 204, 88 Stat. 1245 (42 U.S.C. 5844). Sections 50.58, 50.91, and 50.92 also issued under Pub. L.97-415, 96 Stat. 2073 (42 U.S.C. 2239). Section 50.78 also issued under sec. 122, 68 Stat. 939 (42 U.S.C. 2152). Sections 50.80-50.81 also issued under sec. 184, 68 Stat. 954, as amended (42 U.S.C. 2234). Section 50.103 also issued under sec. 108, 68 Stat. 939, as amended (42 U.S.C. 2138). Appendix F also issued under sec. 187, 68 Stat. 955 (42 U.S.C. 2237).
For the purposes of sec. 223, 68 Stat. 958 as amended (42 U.S.C.
2273); SS 50.10(a), (b), and (c), 50.44, 50.46, 50.48, 50.54 and 50.80(a) are issued under sec.161b, 68 Stat. 948, as amended (42 U,S.C. 2201(b));
$$ 50.10(b) and (c) and 50.54 are issued under sec. 1611, 68 Stat. 949, as amended (42 U.S.C. 2201(i)); and $$ 50.9, 50.55(e), 50.59(b), 50.70, 50.71, 50.72, 50.73, and 50.78 are issued under sec. 161o, 68 Stat. 950, as amended (42 U.S.C. 2201(o)).
- 2. In S 50.62, paragraph (c)(4) is revised to read as follows:
$ 50.62 Requirements for reduction of risk frors anticipated transients without scraw (ATWS) events for light-water-cooled nuclear power plants.
- A
- A A (c) ***
(4) Each boiling water reactor must have a standby liquid control system (SLCS) with the capability of injecting into the reactor pressure vessel a borated water solution at such a fiow rate, level of boron con-centration and boton-10 isotope enrichment, and accounting for reactor r pressure vessel volume, that the resulting reactivity control is at least f equivalent to that resulting from injection of 86 gallons per minute of 8
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13 weight percent sodium pentaborate decahydrate solution at the natural boron-10 isotope abundance into a 251 inch inside diameter reactor pres-sure vessel for a given core design. The SLCS and its injection location must be designed to perform its function in a reliable manner. The SLCS initiation must be automatic and must be designed to perform its function in a reliable manner for plants granted a construction permit after July 26, 1984, and for plants granted a construction permit prior to July 26, 1984, that have already been designed and built to include this feature.
- A A A e A Dated at Rockville, Maryland, this/dbday of Ch 1938.
- J s I A f f Vidor Stellol J Executiv's Direc ,
for Operations 9
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